qgsexpressionfunction.cpp

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/***************************************************************************
                               qgsexpressionfunction.cpp
                             -------------------
    begin                : May 2017
    copyright            : (C) 2017 Matthias Kuhn
    email                : [email protected]
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
 
#include <random>
 
#include "qgscoordinateformatter.h"
#include "qgscoordinateutils.h"
#include "qgsexpressionfunction.h"
#include "qgsexpressionutils.h"
#include "qgsexpressionnodeimpl.h"
#include "qgsexiftools.h"
#include "qgsfeaturerequest.h"
#include "qgsgeos.h"
#include "qgsstringutils.h"
#include "qgsmultipoint.h"
#include "qgsgeometryutils.h"
#include "qgshstoreutils.h"
#include "qgsmultilinestring.h"
#include "qgslinestring.h"
#include "qgscurvepolygon.h"
#include "qgsmaptopixelgeometrysimplifier.h"
#include "qgspolygon.h"
#include "qgstriangle.h"
#include "qgscurve.h"
#include "qgsregularpolygon.h"
#include "qgsquadrilateral.h"
#include "qgsvariantutils.h"
#include "qgsogcutils.h"
#include "qgsdistancearea.h"
#include "qgsgeometryengine.h"
#include "qgsexpressionsorter_p.h"
#include "qgssymbollayerutils.h"
#include "qgsstyle.h"
#include "qgsexception.h"
#include "qgsmessagelog.h"
#include "qgsrasterlayer.h"
#include "qgsvectorlayer.h"
#include "qgsvectorlayerutils.h"
#include "qgsrasterbandstats.h"
#include "qgscolorramp.h"
#include "qgsfieldformatterregistry.h"
#include "qgsfieldformatter.h"
#include "qgsvectorlayerfeatureiterator.h"
#include "qgsproviderregistry.h"
#include "sqlite3.h"
#include "qgstransaction.h"
#include "qgsthreadingutils.h"
#include "qgsapplication.h"
#include "qgis.h"
#include "qgsexpressioncontextutils.h"
#include "qgsunittypes.h"
#include "qgsspatialindex.h"
#include "qgscolorrampimpl.h"
 
#include <QMimeDatabase>
#include <QProcessEnvironment>
#include <QCryptographicHash>
#include <QRegularExpression>
#include <QUuid>
#include <QUrlQuery>
 
typedef QList<QgsExpressionFunction *> ExpressionFunctionList;
 
Q_GLOBAL_STATIC( ExpressionFunctionList, sOwnedFunctions )
Q_GLOBAL_STATIC( QStringList, sBuiltinFunctions )
Q_GLOBAL_STATIC( ExpressionFunctionList, sFunctions )
 
Q_DECLARE_METATYPE( QgsSpatialIndex )
Q_DECLARE_METATYPE( QgsExpressionContext )
Q_DECLARE_METATYPE( std::shared_ptr<QgsVectorLayer> )
 
const QString QgsExpressionFunction::helpText() const
{
  return mHelpText.isEmpty() ? QgsExpression::helpText( mName ) : mHelpText;
}
 
QVariant QgsExpressionFunction::run( QgsExpressionNode::NodeList *args, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
  Q_UNUSED( node )
  // evaluate arguments
  QVariantList argValues;
  if ( args )
  {
    int arg = 0;
    const QList< QgsExpressionNode * > argList = args->list();
    for ( QgsExpressionNode *n : argList )
    {
      QVariant v;
      if ( lazyEval() )
      {
        // Pass in the node for the function to eval as it needs.
        v = QVariant::fromValue( n );
      }
      else
      {
        v = n->eval( parent, context );
        ENSURE_NO_EVAL_ERROR
        bool defaultParamIsNull = mParameterList.count() > arg && mParameterList.at( arg ).optional() && !mParameterList.at( arg ).defaultValue().isValid();
        if ( QgsExpressionUtils::isNull( v ) && !defaultParamIsNull && !handlesNull() )
          return QVariant(); // all "normal" functions return NULL, when any QgsExpressionFunction::Parameter is NULL (so coalesce is abnormal)
      }
      argValues.append( v );
      arg++;
    }
  }
 
  return func( argValues, context, parent, node );
}
 
bool QgsExpressionFunction::usesGeometry( const QgsExpressionNodeFunction *node ) const
{
  Q_UNUSED( node )
  return true;
}
 
QStringList QgsExpressionFunction::aliases() const
{
  return QStringList();
}
 
bool QgsExpressionFunction::isStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
  Q_UNUSED( parent )
  Q_UNUSED( context )
  Q_UNUSED( node )
  return false;
}
 
bool QgsExpressionFunction::prepare( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
  Q_UNUSED( parent )
  Q_UNUSED( context )
  Q_UNUSED( node )
  return true;
}
 
QSet<QString> QgsExpressionFunction::referencedColumns( const QgsExpressionNodeFunction *node ) const
{
  Q_UNUSED( node )
  return QSet<QString>() << QgsFeatureRequest::ALL_ATTRIBUTES;
}
 
bool QgsExpressionFunction::isDeprecated() const
{
  return mGroups.isEmpty() ? false : mGroups.contains( QStringLiteral( "deprecated" ) );
}
 
bool QgsExpressionFunction::operator==( const QgsExpressionFunction &other ) const
{
  return ( QString::compare( mName, other.mName, Qt::CaseInsensitive ) == 0 );
}
 
bool QgsExpressionFunction::handlesNull() const
{
  return mHandlesNull;
}
 
// doxygen doesn't like this constructor for some reason (maybe the function arguments?)
QgsStaticExpressionFunction::QgsStaticExpressionFunction( const QString &fnname, const QgsExpressionFunction::ParameterList &params,
    FcnEval fcn,
    const QString &group,
    const QString &helpText,
    const std::function < bool ( const QgsExpressionNodeFunction *node ) > &usesGeometry,
    const std::function < QSet<QString>( const QgsExpressionNodeFunction *node ) > &referencedColumns,
    bool lazyEval,
    const QStringList &aliases,
    bool handlesNull )
  : QgsExpressionFunction( fnname, params, group, helpText, lazyEval, handlesNull, false )
  , mFnc( fcn )
  , mAliases( aliases )
  , mUsesGeometry( false )
  , mUsesGeometryFunc( usesGeometry )
  , mReferencedColumnsFunc( referencedColumns )
{
}
 
QStringList QgsStaticExpressionFunction::aliases() const
{
  return mAliases;
}
 
bool QgsStaticExpressionFunction::usesGeometry( const QgsExpressionNodeFunction *node ) const
{
  if ( mUsesGeometryFunc )
    return mUsesGeometryFunc( node );
  else
    return mUsesGeometry;
}
 
QSet<QString> QgsStaticExpressionFunction::referencedColumns( const QgsExpressionNodeFunction *node ) const
{
  if ( mReferencedColumnsFunc )
    return mReferencedColumnsFunc( node );
  else
    return mReferencedColumns;
}
 
bool QgsStaticExpressionFunction::isStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
  if ( mIsStaticFunc )
    return mIsStaticFunc( node, parent, context );
  else
    return mIsStatic;
}
 
bool QgsStaticExpressionFunction::prepare( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
  if ( mPrepareFunc )
    return mPrepareFunc( node, parent, context );
 
  return true;
}
 
void QgsStaticExpressionFunction::setIsStaticFunction( const std::function<bool ( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * )> &isStatic )
{
  mIsStaticFunc = isStatic;
}
 
void QgsStaticExpressionFunction::setIsStatic( bool isStatic )
{
  mIsStaticFunc = nullptr;
  mIsStatic = isStatic;
}
 
void QgsStaticExpressionFunction::setPrepareFunction( const std::function<bool ( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * )> &prepareFunc )
{
  mPrepareFunc = prepareFunc;
}
 
bool QgsExpressionFunction::allParamsStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context )
{
  if ( node && node->args() )
  {
    const QList< QgsExpressionNode * > argList = node->args()->list();
    for ( QgsExpressionNode *argNode : argList )
    {
      if ( !argNode->isStatic( parent, context ) )
        return false;
    }
  }
 
  return true;
}
 
static QVariant fcnGenerateSeries( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double start = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double stop = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double step = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  if ( step == 0.0  || ( step > 0.0 && start > stop ) || ( step < 0.0 && start < stop ) )
    return QVariant();
 
  QVariantList array;
  int length = 1;
 
  array << start;
  double current = start + step;
  while ( ( ( step > 0.0 && current <= stop ) || ( step < 0.0 && current >= stop ) ) && length <= 1000000 )
  {
    array << current;
    current += step;
    length++;
  }
 
  return array;
}
 
static QVariant fcnGetVariable( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( !context )
    return QVariant();
 
  const QString name = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
 
  if ( name == QLatin1String( "feature" ) )
  {
    return context->hasFeature() ? QVariant::fromValue( context->feature() ) : QVariant();
  }
  else if ( name == QLatin1String( "id" ) )
  {
    return context->hasFeature() ? QVariant::fromValue( context->feature().id() ) : QVariant();
  }
  else if ( name == QLatin1String( "geometry" ) )
  {
    if ( !context->hasFeature() )
      return QVariant();
 
    const QgsFeature feature = context->feature();
    return feature.hasGeometry() ? QVariant::fromValue( feature.geometry() ) : QVariant();
  }
  else
  {
    return context->variable( name );
  }
}
 
static QVariant fcnEvalTemplate( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString templateString = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return QgsExpression::replaceExpressionText( templateString, context );
}
 
static QVariant fcnEval( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( !context )
    return QVariant();
 
  QString expString = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QgsExpression expression( expString );
  return expression.evaluate( context );
}
 
static QVariant fcnSqrt( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::sqrt( x ) );
}
 
static QVariant fcnAbs( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double val = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::fabs( val ) );
}
 
static QVariant fcnRadians( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double deg = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return ( deg * M_PI ) / 180;
}
static QVariant fcnDegrees( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double rad = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return ( 180 * rad ) / M_PI;
}
static QVariant fcnSin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::sin( x ) );
}
static QVariant fcnCos( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::cos( x ) );
}
static QVariant fcnTan( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::tan( x ) );
}
static QVariant fcnAsin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::asin( x ) );
}
static QVariant fcnAcos( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::acos( x ) );
}
static QVariant fcnAtan( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::atan( x ) );
}
static QVariant fcnAtan2( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double y = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double x = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  return QVariant( std::atan2( y, x ) );
}
static QVariant fcnExp( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::exp( x ) );
}
static QVariant fcnLn( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  if ( x <= 0 )
    return QVariant();
  return QVariant( std::log( x ) );
}
static QVariant fcnLog10( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  if ( x <= 0 )
    return QVariant();
  return QVariant( log10( x ) );
}
static QVariant fcnLog( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double b = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double x = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  if ( x <= 0 || b <= 0 )
    return QVariant();
  return QVariant( std::log( x ) / std::log( b ) );
}
static QVariant fcnRndF( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double min = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double max = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  if ( max < min )
    return QVariant();
 
  std::random_device rd;
  std::mt19937_64 generator( rd() );
 
  if ( !QgsExpressionUtils::isNull( values.at( 2 ) ) )
  {
    quint32 seed;
    if ( QgsExpressionUtils::isIntSafe( values.at( 2 ) ) )
    {
      // if seed can be converted to int, we use as is
      seed = QgsExpressionUtils::getIntValue( values.at( 2 ), parent );
    }
    else
    {
      // if not, we hash string representation to int
      QString seedStr = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
      std::hash<std::string> hasher;
      seed = hasher( seedStr.toStdString() );
    }
    generator.seed( seed );
  }
 
  // Return a random double in the range [min, max] (inclusive)
  double f = static_cast< double >( generator() ) / static_cast< double >( std::mt19937_64::max() );
  return QVariant( min + f * ( max - min ) );
}
static QVariant fcnRnd( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  qlonglong min = QgsExpressionUtils::getIntValue( values.at( 0 ), parent );
  qlonglong max = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
  if ( max < min )
    return QVariant();
 
  std::random_device rd;
  std::mt19937_64 generator( rd() );
 
  if ( !QgsExpressionUtils::isNull( values.at( 2 ) ) )
  {
    quint32 seed;
    if ( QgsExpressionUtils::isIntSafe( values.at( 2 ) ) )
    {
      // if seed can be converted to int, we use as is
      seed = QgsExpressionUtils::getIntValue( values.at( 2 ), parent );
    }
    else
    {
      // if not, we hash string representation to int
      QString seedStr = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
      std::hash<std::string> hasher;
      seed = hasher( seedStr.toStdString() );
    }
    generator.seed( seed );
  }
 
  qint64 randomInteger = min + ( generator() % ( max - min + 1 ) );
  if ( randomInteger  > std::numeric_limits<int>::max() || randomInteger < -std::numeric_limits<int>::max() )
    return QVariant( randomInteger );
 
  // Prevent wrong conversion of QVariant. See #36412
  return QVariant( int( randomInteger ) );
}
 
static QVariant fcnLinearScale( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double val = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double domainMin = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double domainMax = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  double rangeMin = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  double rangeMax = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
 
  if ( domainMin >= domainMax )
  {
    parent->setEvalErrorString( QObject::tr( "Domain max must be greater than domain min" ) );
    return QVariant();
  }
 
  // outside of domain?
  if ( val >= domainMax )
  {
    return rangeMax;
  }
  else if ( val <= domainMin )
  {
    return rangeMin;
  }
 
  // calculate linear scale
  double m = ( rangeMax - rangeMin ) / ( domainMax - domainMin );
  double c = rangeMin - ( domainMin * m );
 
  // Return linearly scaled value
  return QVariant( m * val + c );
}
 
static QVariant fcnExpScale( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double val = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double domainMin = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double domainMax = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  double rangeMin = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  double rangeMax = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
  double exponent = QgsExpressionUtils::getDoubleValue( values.at( 5 ), parent );
 
  if ( domainMin >= domainMax )
  {
    parent->setEvalErrorString( QObject::tr( "Domain max must be greater than domain min" ) );
    return QVariant();
  }
  if ( exponent <= 0 )
  {
    parent->setEvalErrorString( QObject::tr( "Exponent must be greater than 0" ) );
    return QVariant();
  }
 
  // outside of domain?
  if ( val >= domainMax )
  {
    return rangeMax;
  }
  else if ( val <= domainMin )
  {
    return rangeMin;
  }
 
  // Return exponentially scaled value
  return QVariant( ( ( rangeMax - rangeMin ) / std::pow( domainMax - domainMin, exponent ) ) * std::pow( val - domainMin, exponent ) + rangeMin );
}
 
static QVariant fcnMax( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant result( QVariant::Double );
  double maxVal = std::numeric_limits<double>::quiet_NaN();
  for ( const QVariant &val : values )
  {
    double testVal = QgsVariantUtils::isNull( val ) ? std::numeric_limits<double>::quiet_NaN() : QgsExpressionUtils::getDoubleValue( val, parent );
    if ( std::isnan( maxVal ) )
    {
      maxVal = testVal;
    }
    else if ( !std::isnan( testVal ) )
    {
      maxVal = std::max( maxVal, testVal );
    }
  }
 
  if ( !std::isnan( maxVal ) )
  {
    result = QVariant( maxVal );
  }
  return result;
}
 
static QVariant fcnMin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant result( QVariant::Double );
  double minVal = std::numeric_limits<double>::quiet_NaN();
  for ( const QVariant &val : values )
  {
    double testVal = QgsVariantUtils::isNull( val ) ? std::numeric_limits<double>::quiet_NaN() : QgsExpressionUtils::getDoubleValue( val, parent );
    if ( std::isnan( minVal ) )
    {
      minVal = testVal;
    }
    else if ( !std::isnan( testVal ) )
    {
      minVal = std::min( minVal, testVal );
    }
  }
 
  if ( !std::isnan( minVal ) )
  {
    result = QVariant( minVal );
  }
  return result;
}
 
static QVariant fcnAggregate( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  //lazy eval, so we need to evaluate nodes now
 
  //first node is layer id or name
  QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 0 ), parent );
  ENSURE_NO_EVAL_ERROR
  QVariant value = node->eval( parent, context );
  ENSURE_NO_EVAL_ERROR
 
  // TODO this expression function is NOT thread safe
  Q_NOWARN_DEPRECATED_PUSH
  QgsVectorLayer *vl = QgsExpressionUtils::getVectorLayer( value, context, parent );
  Q_NOWARN_DEPRECATED_POP
  if ( !vl )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot find layer with name or ID '%1'" ).arg( value.toString() ) );
    return QVariant();
  }
 
  // second node is aggregate type
  node = QgsExpressionUtils::getNode( values.at( 1 ), parent );
  ENSURE_NO_EVAL_ERROR
  value = node->eval( parent, context );
  ENSURE_NO_EVAL_ERROR
  bool ok = false;
  QgsAggregateCalculator::Aggregate aggregate = QgsAggregateCalculator::stringToAggregate( QgsExpressionUtils::getStringValue( value, parent ), &ok );
  if ( !ok )
  {
    parent->setEvalErrorString( QObject::tr( "No such aggregate '%1'" ).arg( value.toString() ) );
    return QVariant();
  }
 
  // third node is subexpression (or field name)
  node = QgsExpressionUtils::getNode( values.at( 2 ), parent );
  ENSURE_NO_EVAL_ERROR
  QString subExpression = node->dump();
 
  QgsAggregateCalculator::AggregateParameters parameters;
  //optional forth node is filter
  if ( values.count() > 3 )
  {
    node = QgsExpressionUtils::getNode( values.at( 3 ), parent );
    ENSURE_NO_EVAL_ERROR
    QgsExpressionNodeLiteral *nl = dynamic_cast< QgsExpressionNodeLiteral * >( node );
    if ( !nl || nl->value().isValid() )
      parameters.filter = node->dump();
  }
 
  //optional fifth node is concatenator
  if ( values.count() > 4 )
  {
    node = QgsExpressionUtils::getNode( values.at( 4 ), parent );
    ENSURE_NO_EVAL_ERROR
    value = node->eval( parent, context );
    ENSURE_NO_EVAL_ERROR
    parameters.delimiter = value.toString();
  }
 
  //optional sixth node is order by
  QString orderBy;
  if ( values.count() > 5 )
  {
    node = QgsExpressionUtils::getNode( values.at( 5 ), parent );
    ENSURE_NO_EVAL_ERROR
    QgsExpressionNodeLiteral *nl = dynamic_cast< QgsExpressionNodeLiteral * >( node );
    if ( !nl || nl->value().isValid() )
    {
      orderBy = node->dump();
      parameters.orderBy << QgsFeatureRequest::OrderByClause( orderBy );
    }
  }
 
  QString aggregateError;
  QVariant result;
  if ( context )
  {
    QString cacheKey;
    QgsExpression subExp( subExpression );
    QgsExpression filterExp( parameters.filter );
 
    bool isStatic = true;
    if ( filterExp.referencedVariables().contains( QStringLiteral( "parent" ) )
         || filterExp.referencedVariables().contains( QString() )
         || subExp.referencedVariables().contains( QStringLiteral( "parent" ) )
         || subExp.referencedVariables().contains( QString() ) )
    {
      isStatic = false;
    }
    else
    {
      const QSet<QString> refVars = filterExp.referencedVariables() + subExp.referencedVariables();
      for ( const QString &varName : refVars )
      {
        const QgsExpressionContextScope *scope = context->activeScopeForVariable( varName );
        if ( scope && !scope->isStatic( varName ) )
        {
          isStatic = false;
          break;
        }
      }
    }
 
    if ( !isStatic )
    {
      cacheKey = QStringLiteral( "aggfcn:%1:%2:%3:%4:%5%6:%7" ).arg( vl->id(), QString::number( aggregate ), subExpression, parameters.filter,
                 QString::number( context->feature().id() ), QString::number( qHash( context->feature() ) ), orderBy );
    }
    else
    {
      cacheKey = QStringLiteral( "aggfcn:%1:%2:%3:%4:%5" ).arg( vl->id(), QString::number( aggregate ), subExpression, parameters.filter, orderBy );
    }
 
    if ( context->hasCachedValue( cacheKey ) )
    {
      return context->cachedValue( cacheKey );
    }
 
    QgsExpressionContext subContext( *context );
    QgsExpressionContextScope *subScope = new QgsExpressionContextScope();
    subScope->setVariable( QStringLiteral( "parent" ), context->feature(), true );
    subContext.appendScope( subScope );
    result = vl->aggregate( aggregate, subExpression, parameters, &subContext, &ok, nullptr, context->feedback(), &aggregateError );
 
    if ( ok )
    {
      // important -- we should only store cached values when the expression is successfully calculated. Otherwise subsequent
      // use of the expression context will happily grab the invalid QVariant cached value without realising that there was actually an error
      // associated with it's calculation!
      context->setCachedValue( cacheKey, result );
    }
  }
  else
  {
    result = vl->aggregate( aggregate, subExpression, parameters, nullptr, &ok, nullptr, nullptr, &aggregateError );
  }
  if ( !ok )
  {
    if ( !aggregateError.isEmpty() )
      parent->setEvalErrorString( QObject::tr( "Could not calculate aggregate for: %1 (%2)" ).arg( subExpression, aggregateError ) );
    else
      parent->setEvalErrorString( QObject::tr( "Could not calculate aggregate for: %1" ).arg( subExpression ) );
    return QVariant();
  }
 
  return result;
}
 
static QVariant fcnAggregateRelation( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( !context )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot use relation aggregate function in this context" ) );
    return QVariant();
  }
 
  // first step - find current layer
 
  // TODO this expression function is NOT thread safe
  Q_NOWARN_DEPRECATED_PUSH
  QgsVectorLayer *vl = QgsExpressionUtils::getVectorLayer( context->variable( QStringLiteral( "layer" ) ), context, parent );
  Q_NOWARN_DEPRECATED_POP
  if ( !vl )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot use relation aggregate function in this context" ) );
    return QVariant();
  }
 
  //lazy eval, so we need to evaluate nodes now
 
  //first node is relation name
  QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 0 ), parent );
  ENSURE_NO_EVAL_ERROR
  QVariant value = node->eval( parent, context );
  ENSURE_NO_EVAL_ERROR
  QString relationId = value.toString();
  // check relation exists
  QgsRelation relation = QgsProject::instance()->relationManager()->relation( relationId );
  if ( !relation.isValid() || relation.referencedLayer() != vl )
  {
    // check for relations by name
    QList< QgsRelation > relations = QgsProject::instance()->relationManager()->relationsByName( relationId );
    if ( relations.isEmpty() || relations.at( 0 ).referencedLayer() != vl )
    {
      parent->setEvalErrorString( QObject::tr( "Cannot find relation with id '%1'" ).arg( relationId ) );
      return QVariant();
    }
    else
    {
      relation = relations.at( 0 );
    }
  }
 
  QgsVectorLayer *childLayer = relation.referencingLayer();
 
  // second node is aggregate type
  node = QgsExpressionUtils::getNode( values.at( 1 ), parent );
  ENSURE_NO_EVAL_ERROR
  value = node->eval( parent, context );
  ENSURE_NO_EVAL_ERROR
  bool ok = false;
  QgsAggregateCalculator::Aggregate aggregate = QgsAggregateCalculator::stringToAggregate( QgsExpressionUtils::getStringValue( value, parent ), &ok );
  if ( !ok )
  {
    parent->setEvalErrorString( QObject::tr( "No such aggregate '%1'" ).arg( value.toString() ) );
    return QVariant();
  }
 
  //third node is subexpression (or field name)
  node = QgsExpressionUtils::getNode( values.at( 2 ), parent );
  ENSURE_NO_EVAL_ERROR
  QString subExpression = node->dump();
 
  //optional fourth node is concatenator
  QgsAggregateCalculator::AggregateParameters parameters;
  if ( values.count() > 3 )
  {
    node = QgsExpressionUtils::getNode( values.at( 3 ), parent );
    ENSURE_NO_EVAL_ERROR
    value = node->eval( parent, context );
    ENSURE_NO_EVAL_ERROR
    parameters.delimiter = value.toString();
  }
 
  //optional fifth node is order by
  QString orderBy;
  if ( values.count() > 4 )
  {
    node = QgsExpressionUtils::getNode( values.at( 4 ), parent );
    ENSURE_NO_EVAL_ERROR
    QgsExpressionNodeLiteral *nl = dynamic_cast< QgsExpressionNodeLiteral * >( node );
    if ( !nl || nl->value().isValid() )
    {
      orderBy = node->dump();
      parameters.orderBy << QgsFeatureRequest::OrderByClause( orderBy );
    }
  }
 
  if ( !context->hasFeature() )
    return QVariant();
  QgsFeature f = context->feature();
 
  parameters.filter = relation.getRelatedFeaturesFilter( f );
 
  QString cacheKey = QStringLiteral( "relagg:%1:%2:%3:%4:%5" ).arg( vl->id(),
                     QString::number( static_cast< int >( aggregate ) ),
                     subExpression,
                     parameters.filter,
                     orderBy );
  if ( context->hasCachedValue( cacheKey ) )
    return context->cachedValue( cacheKey );
 
  QVariant result;
  ok = false;
 
 
  QgsExpressionContext subContext( *context );
  QString error;
  result = childLayer->aggregate( aggregate, subExpression, parameters, &subContext, &ok, nullptr, context->feedback(), &error );
 
  if ( !ok )
  {
    if ( !error.isEmpty() )
      parent->setEvalErrorString( QObject::tr( "Could not calculate aggregate for: %1 (%2)" ).arg( subExpression, error ) );
    else
      parent->setEvalErrorString( QObject::tr( "Could not calculate aggregate for: %1" ).arg( subExpression ) );
    return QVariant();
  }
 
  // cache value
  context->setCachedValue( cacheKey, result );
  return result;
}
 
 
static QVariant fcnAggregateGeneric( QgsAggregateCalculator::Aggregate aggregate, const QVariantList &values, QgsAggregateCalculator::AggregateParameters parameters, const QgsExpressionContext *context, QgsExpression *parent, int orderByPos = -1 )
{
  if ( !context )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot use aggregate function in this context" ) );
    return QVariant();
  }
 
  // first step - find current layer
 
  // TODO this expression function is NOT thread safe
  Q_NOWARN_DEPRECATED_PUSH
  QgsVectorLayer *vl = QgsExpressionUtils::getVectorLayer( context->variable( QStringLiteral( "layer" ) ), context, parent );
  Q_NOWARN_DEPRECATED_POP
  if ( !vl )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot use aggregate function in this context" ) );
    return QVariant();
  }
 
  //lazy eval, so we need to evaluate nodes now
 
  //first node is subexpression (or field name)
  QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 0 ), parent );
  ENSURE_NO_EVAL_ERROR
  QString subExpression = node->dump();
 
  //optional second node is group by
  QString groupBy;
  if ( values.count() > 1 )
  {
    node = QgsExpressionUtils::getNode( values.at( 1 ), parent );
    ENSURE_NO_EVAL_ERROR
    QgsExpressionNodeLiteral *nl = dynamic_cast< QgsExpressionNodeLiteral * >( node );
    if ( !nl || nl->value().isValid() )
      groupBy = node->dump();
  }
 
  //optional third node is filter
  if ( values.count() > 2 )
  {
    node = QgsExpressionUtils::getNode( values.at( 2 ), parent );
    ENSURE_NO_EVAL_ERROR
    QgsExpressionNodeLiteral *nl = dynamic_cast< QgsExpressionNodeLiteral * >( node );
    if ( !nl || nl->value().isValid() )
      parameters.filter = node->dump();
  }
 
  //optional order by node, if supported
  QString orderBy;
  if ( orderByPos >= 0 && values.count() > orderByPos )
  {
    node = QgsExpressionUtils::getNode( values.at( orderByPos ), parent );
    ENSURE_NO_EVAL_ERROR
    QgsExpressionNodeLiteral *nl = dynamic_cast< QgsExpressionNodeLiteral * >( node );
    if ( !nl || nl->value().isValid() )
    {
      orderBy = node->dump();
      parameters.orderBy << QgsFeatureRequest::OrderByClause( orderBy );
    }
  }
 
  // build up filter with group by
 
  // find current group by value
  if ( !groupBy.isEmpty() )
  {
    QgsExpression groupByExp( groupBy );
    QVariant groupByValue = groupByExp.evaluate( context );
    QString groupByClause = QStringLiteral( "%1 %2 %3" ).arg( groupBy,
                            QgsVariantUtils::isNull( groupByValue ) ? QStringLiteral( "is" ) : QStringLiteral( "=" ),
                            QgsExpression::quotedValue( groupByValue ) );
    if ( !parameters.filter.isEmpty() )
      parameters.filter = QStringLiteral( "(%1) AND (%2)" ).arg( parameters.filter, groupByClause );
    else
      parameters.filter = groupByClause;
  }
 
  QgsExpression subExp( subExpression );
  QgsExpression filterExp( parameters.filter );
 
  bool isStatic = true;
  const QSet<QString> refVars = filterExp.referencedVariables() + subExp.referencedVariables();
  for ( const QString &varName : refVars )
  {
    const QgsExpressionContextScope *scope = context->activeScopeForVariable( varName );
    if ( scope && !scope->isStatic( varName ) )
    {
      isStatic = false;
      break;
    }
  }
 
  QString cacheKey;
  if ( !isStatic )
  {
    cacheKey = QStringLiteral( "agg:%1:%2:%3:%4:%5%6:%7" ).arg( vl->id(), QString::number( aggregate ), subExpression, parameters.filter,
               QString::number( context->feature().id() ), QString::number( qHash( context->feature() ) ), orderBy );
  }
  else
  {
    cacheKey = QStringLiteral( "agg:%1:%2:%3:%4:%5" ).arg( vl->id(), QString::number( aggregate ), subExpression, parameters.filter, orderBy );
  }
 
  if ( context->hasCachedValue( cacheKey ) )
    return context->cachedValue( cacheKey );
 
  QVariant result;
  bool ok = false;
 
  QgsExpressionContext subContext( *context );
  QgsExpressionContextScope *subScope = new QgsExpressionContextScope();
  subScope->setVariable( QStringLiteral( "parent" ), context->feature(), true );
  subContext.appendScope( subScope );
  QString error;
  result = vl->aggregate( aggregate, subExpression, parameters, &subContext, &ok, nullptr, context->feedback(), &error );
 
  if ( !ok )
  {
    if ( !error.isEmpty() )
      parent->setEvalErrorString( QObject::tr( "Could not calculate aggregate for: %1 (%2)" ).arg( subExpression, error ) );
    else
      parent->setEvalErrorString( QObject::tr( "Could not calculate aggregate for: %1" ).arg( subExpression ) );
    return QVariant();
  }
 
  // cache value
  context->setCachedValue( cacheKey, result );
  return result;
}
 
 
static QVariant fcnAggregateCount( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Count, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateCountDistinct( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::CountDistinct, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateCountMissing( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::CountMissing, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMin( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Min, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMax( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Max, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateSum( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Sum, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMean( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Mean, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMedian( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Median, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateStdev( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::StDevSample, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateRange( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Range, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMinority( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Minority, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMajority( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::Majority, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateQ1( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::FirstQuartile, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateQ3( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::ThirdQuartile, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateIQR( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::InterQuartileRange, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMinLength( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::StringMinimumLength, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateMaxLength( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::StringMaximumLength, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateCollectGeometry( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::GeometryCollect, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
}
 
static QVariant fcnAggregateStringConcat( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsAggregateCalculator::AggregateParameters parameters;
 
  //fourth node is concatenator
  if ( values.count() > 3 )
  {
    QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 3 ), parent );
    ENSURE_NO_EVAL_ERROR
    QVariant value = node->eval( parent, context );
    ENSURE_NO_EVAL_ERROR
    parameters.delimiter = value.toString();
  }
 
  return fcnAggregateGeneric( QgsAggregateCalculator::StringConcatenate, values, parameters, context, parent, 4 );
}
 
static QVariant fcnAggregateStringConcatUnique( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsAggregateCalculator::AggregateParameters parameters;
 
  //fourth node is concatenator
  if ( values.count() > 3 )
  {
    QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 3 ), parent );
    ENSURE_NO_EVAL_ERROR
    QVariant value = node->eval( parent, context );
    ENSURE_NO_EVAL_ERROR
    parameters.delimiter = value.toString();
  }
 
  return fcnAggregateGeneric( QgsAggregateCalculator::StringConcatenateUnique, values, parameters, context, parent, 4 );
}
 
static QVariant fcnAggregateArray( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnAggregateGeneric( QgsAggregateCalculator::ArrayAggregate, values, QgsAggregateCalculator::AggregateParameters(), context, parent, 3 );
}
 
static QVariant fcnMapScale( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  if ( !context )
    return QVariant();
 
  QVariant scale = context->variable( QStringLiteral( "map_scale" ) );
  bool ok = false;
  if ( QgsVariantUtils::isNull( scale ) )
    return QVariant();
 
  const double v = scale.toDouble( &ok );
  if ( ok )
    return v;
  return QVariant();
}
 
static QVariant fcnClamp( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double minValue = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double testValue = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double maxValue = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  // force testValue to sit inside the range specified by the min and max value
  if ( testValue <= minValue )
  {
    return QVariant( minValue );
  }
  else if ( testValue >= maxValue )
  {
    return QVariant( maxValue );
  }
  else
  {
    return QVariant( testValue );
  }
}
 
static QVariant fcnFloor( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::floor( x ) );
}
 
static QVariant fcnCeil( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  return QVariant( std::ceil( x ) );
}
 
static QVariant fcnToInt( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return QVariant( QgsExpressionUtils::getIntValue( values.at( 0 ), parent ) );
}
static QVariant fcnToReal( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return QVariant( QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent ) );
}
static QVariant fcnToString( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return QVariant( QgsExpressionUtils::getStringValue( values.at( 0 ), parent ) );
}
 
static QVariant fcnToDateTime( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString format = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  QString language = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
  if ( format.isEmpty() && !language.isEmpty() )
  {
    parent->setEvalErrorString( QObject::tr( "A format is required to convert to DateTime when the language is specified" ) );
    return QVariant( QDateTime() );
  }
 
  if ( format.isEmpty() && language.isEmpty() )
    return QVariant( QgsExpressionUtils::getDateTimeValue( values.at( 0 ), parent ) );
 
  QString datetimestring = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QLocale locale = QLocale();
  if ( !language.isEmpty() )
  {
    locale = QLocale( language );
  }
 
  QDateTime datetime = locale.toDateTime( datetimestring, format );
  if ( !datetime.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot convert '%1' to DateTime" ).arg( datetimestring ) );
    datetime = QDateTime();
  }
  return QVariant( datetime );
}
 
static QVariant fcnMakeDate( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const int year = QgsExpressionUtils::getIntValue( values.at( 0 ), parent );
  const int month = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
  const int day = QgsExpressionUtils::getIntValue( values.at( 2 ), parent );
 
  const QDate date( year, month, day );
  if ( !date.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "'%1-%2-%3' is not a valid date" ).arg( year ).arg( month ).arg( day ) );
    return QVariant();
  }
  return QVariant( date );
}
 
static QVariant fcnMakeTime( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const int hours = QgsExpressionUtils::getIntValue( values.at( 0 ), parent );
  const int minutes = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
  const double seconds = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  const QTime time( hours, minutes, std::floor( seconds ), ( seconds - std::floor( seconds ) ) * 1000 );
  if ( !time.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "'%1-%2-%3' is not a valid time" ).arg( hours ).arg( minutes ).arg( seconds ) );
    return QVariant();
  }
  return QVariant( time );
}
 
static QVariant fcnMakeDateTime( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const int year = QgsExpressionUtils::getIntValue( values.at( 0 ), parent );
  const int month = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
  const int day = QgsExpressionUtils::getIntValue( values.at( 2 ), parent );
  const int hours = QgsExpressionUtils::getIntValue( values.at( 3 ), parent );
  const int minutes = QgsExpressionUtils::getIntValue( values.at( 4 ), parent );
  const double seconds = QgsExpressionUtils::getDoubleValue( values.at( 5 ), parent );
 
  const QDate date( year, month, day );
  if ( !date.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "'%1-%2-%3' is not a valid date" ).arg( year ).arg( month ).arg( day ) );
    return QVariant();
  }
  const QTime time( hours, minutes, std::floor( seconds ), ( seconds - std::floor( seconds ) ) * 1000 );
  if ( !time.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "'%1-%2-%3' is not a valid time" ).arg( hours ).arg( minutes ).arg( seconds ) );
    return QVariant();
  }
  return QVariant( QDateTime( date, time ) );
}
 
static QVariant fcnMakeInterval( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const double years = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  const double months = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double weeks = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const double days = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  const double hours = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
  const double minutes = QgsExpressionUtils::getDoubleValue( values.at( 5 ), parent );
  const double seconds = QgsExpressionUtils::getDoubleValue( values.at( 6 ), parent );
 
  return QVariant::fromValue( QgsInterval( years, months, weeks, days, hours, minutes, seconds ) );
}
 
static QVariant fcnCoalesce( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * )
{
  for ( const QVariant &value : values )
  {
    if ( QgsVariantUtils::isNull( value ) )
      continue;
    return value;
  }
  return QVariant();
}
 
static QVariant fcnNullIf( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * )
{
  const QVariant val1 = values.at( 0 );
  const QVariant val2 = values.at( 1 );
 
  if ( val1 == val2 )
    return QVariant();
  else
    return val1;
}
 
static QVariant fcnLower( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return QVariant( str.toLower() );
}
static QVariant fcnUpper( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return QVariant( str.toUpper() );
}
static QVariant fcnTitle( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QStringList elems = str.split( ' ' );
  for ( int i = 0; i < elems.size(); i++ )
  {
    if ( elems[i].size() > 1 )
      elems[i] = elems[i].at( 0 ).toUpper() + elems[i].mid( 1 ).toLower();
  }
  return QVariant( elems.join( QLatin1Char( ' ' ) ) );
}
 
static QVariant fcnTrim( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return QVariant( str.trimmed() );
}
 
static QVariant fcnLevenshtein( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string1 = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString string2 = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  return QVariant( QgsStringUtils::levenshteinDistance( string1, string2, true ) );
}
 
static QVariant fcnLCS( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string1 = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString string2 = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  return QVariant( QgsStringUtils::longestCommonSubstring( string1, string2, true ) );
}
 
static QVariant fcnHamming( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string1 = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString string2 = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  int dist = QgsStringUtils::hammingDistance( string1, string2 );
  return ( dist < 0 ? QVariant() : QVariant( QgsStringUtils::hammingDistance( string1, string2, true ) ) );
}
 
static QVariant fcnSoundex( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return QVariant( QgsStringUtils::soundex( string ) );
}
 
static QVariant fcnChar( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QChar character = QChar( QgsExpressionUtils::getNativeIntValue( values.at( 0 ), parent ) );
  return QVariant( QString( character ) );
}
 
static QVariant fcnAscii( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString value = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
 
  if ( value.isEmpty() )
  {
    return QVariant();
  }
 
  int res = value.at( 0 ).unicode();
  return QVariant( res );
}
 
static QVariant fcnWordwrap( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.length() == 2 || values.length() == 3 )
  {
    QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
    qlonglong wrap = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
 
    QString customdelimiter = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
 
    return QgsStringUtils::wordWrap( str, static_cast< int >( wrap ), wrap > 0, customdelimiter );
  }
 
  return QVariant();
}
 
static QVariant fcnLength( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  // two variants, one for geometry, one for string
  if ( values.at( 0 ).userType() == QMetaType::type( "QgsGeometry" ) )
  {
    //geometry variant
    QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
    if ( geom.type() != QgsWkbTypes::LineGeometry )
      return QVariant();
 
    return QVariant( geom.length() );
  }
 
  //otherwise fall back to string variant
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return QVariant( str.length() );
}
 
static QVariant fcnLength3D( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.type() != QgsWkbTypes::LineGeometry )
    return QVariant();
 
  double totalLength = 0;
  for ( auto it = geom.const_parts_begin(); it != geom.const_parts_end(); ++it )
  {
    if ( const QgsLineString *line = qgsgeometry_cast< const QgsLineString * >( *it ) )
    {
      totalLength += line->length3D();
    }
    else
    {
      std::unique_ptr< QgsLineString > segmentized( qgsgeometry_cast< const QgsCurve * >( *it )->curveToLine() );
      totalLength += segmentized->length3D();
    }
  }
 
  return totalLength;
}
 
static QVariant fcnReplace( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.count() == 2 && values.at( 1 ).type() == QVariant::Map )
  {
    QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
    QVariantMap map = QgsExpressionUtils::getMapValue( values.at( 1 ), parent );
    QVector< QPair< QString, QString > > mapItems;
 
    for ( QVariantMap::const_iterator it = map.constBegin(); it != map.constEnd(); ++it )
    {
      mapItems.append( qMakePair( it.key(), it.value().toString() ) );
    }
 
    // larger keys should be replaced first since they may contain whole smaller keys
    std::sort( mapItems.begin(),
               mapItems.end(),
               []( const QPair< QString, QString > &pair1,
                   const QPair< QString, QString > &pair2 )
    {
      return ( pair1.first.length() > pair2.first.length() );
    } );
 
    for ( auto it = mapItems.constBegin(); it != mapItems.constEnd(); ++it )
    {
      str = str.replace( it->first, it->second );
    }
 
    return QVariant( str );
  }
  else if ( values.count() == 3 )
  {
    QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
    QVariantList before;
    QVariantList after;
    bool isSingleReplacement = false;
 
    if ( !QgsExpressionUtils::isList( values.at( 1 ) ) && values.at( 2 ).type() != QVariant::StringList )
    {
      before = QVariantList() << QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
    }
    else
    {
      before = QgsExpressionUtils::getListValue( values.at( 1 ), parent );
    }
 
    if ( !QgsExpressionUtils::isList( values.at( 2 ) ) )
    {
      after = QVariantList() << QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
      isSingleReplacement = true;
    }
    else
    {
      after = QgsExpressionUtils::getListValue( values.at( 2 ), parent );
    }
 
    if ( !isSingleReplacement && before.length() != after.length() )
    {
      parent->setEvalErrorString( QObject::tr( "Invalid pair of array, length not identical" ) );
      return QVariant();
    }
 
    for ( int i = 0; i < before.length(); i++ )
    {
      str = str.replace( before.at( i ).toString(), after.at( isSingleReplacement ? 0 : i ).toString() );
    }
 
    return QVariant( str );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function replace requires 2 or 3 arguments" ) );
    return QVariant();
  }
}
 
static QVariant fcnRegexpReplace( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString regexp = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  QString after = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
 
  QRegularExpression re( regexp, QRegularExpression::UseUnicodePropertiesOption );
  if ( !re.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Invalid regular expression '%1': %2" ).arg( regexp, re.errorString() ) );
    return QVariant();
  }
  return QVariant( str.replace( re, after ) );
}
 
static QVariant fcnRegexpMatch( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString regexp = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
 
  QRegularExpression re( regexp, QRegularExpression::UseUnicodePropertiesOption );
  if ( !re.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Invalid regular expression '%1': %2" ).arg( regexp, re.errorString() ) );
    return QVariant();
  }
  return QVariant( ( str.indexOf( re ) + 1 ) );
}
 
static QVariant fcnRegexpMatches( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString regexp = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  QString empty = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
 
  QRegularExpression re( regexp, QRegularExpression::UseUnicodePropertiesOption );
  if ( !re.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Invalid regular expression '%1': %2" ).arg( regexp, re.errorString() ) );
    return QVariant();
  }
 
  QRegularExpressionMatch matches = re.match( str );
  if ( matches.hasMatch() )
  {
    QVariantList array;
    QStringList list = matches.capturedTexts();
 
    // Skip the first string to only return captured groups
    for ( QStringList::const_iterator it = ++list.constBegin(); it != list.constEnd(); ++it )
    {
      array += ( !( *it ).isEmpty() ) ? *it : empty;
    }
 
    return QVariant( array );
  }
  else
  {
    return QVariant();
  }
}
 
static QVariant fcnRegexpSubstr( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QString regexp = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
 
  QRegularExpression re( regexp, QRegularExpression::UseUnicodePropertiesOption );
  if ( !re.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Invalid regular expression '%1': %2" ).arg( regexp, re.errorString() ) );
    return QVariant();
  }
 
  // extract substring
  QRegularExpressionMatch match = re.match( str );
  if ( match.hasMatch() )
  {
    // return first capture
    if ( match.lastCapturedIndex() > 0 )
    {
      // a capture group was present, so use that
      return QVariant( match.captured( 1 ) );
    }
    else
    {
      // no capture group, so using all match
      return QVariant( match.captured( 0 ) );
    }
  }
  else
  {
    return QVariant( "" );
  }
}
 
static QVariant fcnUuid( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * )
{
  QString uuid = QUuid::createUuid().toString();
  if ( values.at( 0 ).toString().compare( QStringLiteral( "WithoutBraces" ), Qt::CaseInsensitive ) == 0 )
    uuid = QUuid::createUuid().toString( QUuid::StringFormat::WithoutBraces );
  else if ( values.at( 0 ).toString().compare( QStringLiteral( "Id128" ), Qt::CaseInsensitive ) == 0 )
    uuid = QUuid::createUuid().toString( QUuid::StringFormat::Id128 );
  return uuid;
}
 
static QVariant fcnSubstr( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( !values.at( 0 ).isValid() || !values.at( 1 ).isValid() )
    return QVariant();
 
  QString str = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  int from = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
 
  int len = 0;
  if ( values.at( 2 ).isValid() )
    len = QgsExpressionUtils::getNativeIntValue( values.at( 2 ), parent );
  else
    len = str.size();
 
  if ( from < 0 )
  {
    from = str.size() + from;
    if ( from < 0 )
    {
      from = 0;
    }
  }
  else if ( from > 0 )
  {
    //account for the fact that substr() starts at 1
    from -= 1;
  }
 
  if ( len < 0 )
  {
    len = str.size() + len - from;
    if ( len < 0 )
    {
      len = 0;
    }
  }
 
  return QVariant( str.mid( from, len ) );
}
static QVariant fcnFeatureId( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  // TODO: handling of 64-bit feature ids?
  return QVariant( static_cast< int >( f.id() ) );
}
 
static QVariant fcnRasterValue( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const int bandNb = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 2 ), parent );
  bool foundLayer = false;
  const QVariant res = QgsExpressionUtils::runMapLayerFunctionThreadSafe( values.at( 0 ), context, parent, [parent, bandNb, geom]( QgsMapLayer * mapLayer )
  {
    QgsRasterLayer *layer = qobject_cast< QgsRasterLayer * >( mapLayer );
    if ( !layer || !layer->dataProvider() )
    {
      parent->setEvalErrorString( QObject::tr( "Function `raster_value` requires a valid raster layer." ) );
      return QVariant();
    }
 
    if ( bandNb < 1 || bandNb > layer->bandCount() )
    {
      parent->setEvalErrorString( QObject::tr( "Function `raster_value` requires a valid raster band number." ) );
      return QVariant();
    }
 
    if ( geom.isNull() || geom.type() != QgsWkbTypes::PointGeometry )
    {
      parent->setEvalErrorString( QObject::tr( "Function `raster_value` requires a valid point geometry." ) );
      return QVariant();
    }
 
    QgsPointXY point = geom.asPoint();
    if ( geom.isMultipart() )
    {
      QgsMultiPointXY multiPoint = geom.asMultiPoint();
      if ( multiPoint.count() == 1 )
      {
        point = multiPoint[0];
      }
      else
      {
        // if the geometry contains more than one part, return an undefined value
        return QVariant();
      }
    }
 
    double value = layer->dataProvider()->sample( point, bandNb );
    return std::isnan( value ) ? QVariant() : value;
  },
  foundLayer );
 
  if ( !foundLayer )
  {
    parent->setEvalErrorString( QObject::tr( "Function `raster_value` requires a valid raster layer." ) );
    return QVariant();
  }
  else
  {
    return res;
  }
}
 
static QVariant fcnRasterAttributes( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const int bandNb = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  const double value = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  bool foundLayer = false;
  const QVariant res = QgsExpressionUtils::runMapLayerFunctionThreadSafe( values.at( 0 ), context, parent, [parent, bandNb, value]( QgsMapLayer * mapLayer )-> QVariant
  {
    QgsRasterLayer *layer = qobject_cast< QgsRasterLayer *>( mapLayer );
    if ( !layer || !layer->dataProvider() )
    {
      parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster layer." ) );
      return QVariant();
    }
 
    if ( bandNb < 1 || bandNb > layer->bandCount() )
    {
      parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster band number." ) );
      return QVariant();
    }
 
    if ( std::isnan( value ) )
    {
      parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster value." ) );
      return QVariant();
    }
 
    if ( ! layer->dataProvider()->attributeTable( bandNb ) )
    {
      return QVariant();
    }
 
    const QVariantList data = layer->dataProvider()->attributeTable( bandNb )->row( value );
    if ( data.isEmpty() )
    {
      return QVariant();
    }
 
    QVariantMap result;
    const QList<QgsRasterAttributeTable::Field> fields { layer->dataProvider()->attributeTable( bandNb )->fields() };
    for ( int idx = 0; idx < static_cast<int>( fields.count( ) ) && idx < static_cast<int>( data.count() ); ++idx )
    {
      const QgsRasterAttributeTable::Field field { fields.at( idx ) };
      if ( field.isColor() || field.isRamp() )
      {
        continue;
      }
      result.insert( fields.at( idx ).name, data.at( idx ) );
    }
 
    return result;
  }, foundLayer );
 
  if ( !foundLayer )
  {
    parent->setEvalErrorString( QObject::tr( "Function `raster_attributes` requires a valid raster layer." ) );
    return QVariant();
  }
  else
  {
    return res;
  }
}
 
static QVariant fcnFeature( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  if ( !context )
    return QVariant();
 
  return context->feature();
}
 
static QVariant fcnAttribute( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsFeature feature;
  QString attr;
  if ( values.size() == 1 )
  {
    attr = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
    feature = context->feature();
  }
  else if ( values.size() == 2 )
  {
    feature = QgsExpressionUtils::getFeature( values.at( 0 ), parent );
    attr = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function `attribute` requires one or two parameters. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
 
  return feature.attribute( attr );
}
 
static QVariant fcnMapToHtmlTable( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString table { R"html(
  <table>
    <thead>
      <th>%1</th>
    </thead>
    <tbody>
      <tr><td>%2</td></tr>
    </tbody>
  </table>)html" };
  QVariantMap dict;
  if ( values.size() == 1 )
  {
    dict = QgsExpressionUtils::getMapValue( values.at( 0 ), parent );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function `map_to_html_table` requires one parameter. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
 
  if ( dict.isEmpty() )
  {
    return QVariant();
  }
 
  QStringList headers;
  QStringList cells;
 
  for ( auto it = dict.cbegin(); it != dict.cend(); ++it )
  {
    headers.push_back( it.key().toHtmlEscaped() );
    cells.push_back( it.value().toString( ).toHtmlEscaped() );
  }
 
  return table.arg( headers.join( QLatin1String( "</th><th>" ) ), cells.join( QLatin1String( "</td><td>" ) ) );
}
 
static QVariant fcnMapToHtmlDefinitionList( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString table { R"html(
  <dl>
    %1
  </dl>)html" };
  QVariantMap dict;
  if ( values.size() == 1 )
  {
    dict = QgsExpressionUtils::getMapValue( values.at( 0 ), parent );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function `map_to_html_dl` requires one parameter. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
 
  if ( dict.isEmpty() )
  {
    return QVariant();
  }
 
  QString rows;
 
  for ( auto it = dict.cbegin(); it != dict.cend(); ++it )
  {
    rows.append( QStringLiteral( "<dt>%1</dt><dd>%2</dd>" ).arg( it.key().toHtmlEscaped(), it.value().toString().toHtmlEscaped() ) );
  }
 
  return table.arg( rows );
}
 
static QVariant fcnValidateFeature( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant layer;
  if ( values.size() < 1 || QgsVariantUtils::isNull( values.at( 0 ) ) )
  {
    layer = context->variable( QStringLiteral( "layer" ) );
  }
  else
  {
    //first node is layer id or name
    QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 0 ), parent );
    ENSURE_NO_EVAL_ERROR
    layer = node->eval( parent, context );
    ENSURE_NO_EVAL_ERROR
  }
 
  QgsFeature feature;
  if ( values.size() < 2 || QgsVariantUtils::isNull( values.at( 1 ) ) )
  {
    feature = context->feature();
  }
  else
  {
    feature = QgsExpressionUtils::getFeature( values.at( 1 ), parent );
  }
 
  QgsFieldConstraints::ConstraintStrength constraintStrength = QgsFieldConstraints::ConstraintStrengthNotSet;
  const QString strength = QgsExpressionUtils::getStringValue( values.at( 2 ), parent ).toLower();
  if ( strength == QLatin1String( "hard" ) )
  {
    constraintStrength = QgsFieldConstraints::ConstraintStrengthHard;
  }
  else if ( strength == QLatin1String( "soft" ) )
  {
    constraintStrength = QgsFieldConstraints::ConstraintStrengthSoft;
  }
 
  bool foundLayer = false;
  const QVariant res = QgsExpressionUtils::runMapLayerFunctionThreadSafe( layer, context, parent, [parent, feature, constraintStrength]( QgsMapLayer * mapLayer ) -> QVariant
  {
    QgsVectorLayer *layer = qobject_cast< QgsVectorLayer * >( mapLayer );
    if ( !layer )
    {
      parent->setEvalErrorString( QObject::tr( "No layer provided to conduct constraints checks" ) );
      return QVariant();
    }
 
    const QgsFields fields = layer->fields();
    bool valid = true;
    for ( int i = 0; i < fields.size(); i++ )
    {
      QStringList errors;
      valid = QgsVectorLayerUtils::validateAttribute( layer, feature, i, errors, constraintStrength );
      if ( !valid )
      {
        break;
      }
    }
 
    return valid;
  }, foundLayer );
 
  if ( !foundLayer )
  {
    parent->setEvalErrorString( QObject::tr( "No layer provided to conduct constraints checks" ) );
    return QVariant();
  }
 
  return res;
}
 
static QVariant fcnValidateAttribute( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant layer;
  if ( values.size() < 2 || QgsVariantUtils::isNull( values.at( 1 ) ) )
  {
    layer = context->variable( QStringLiteral( "layer" ) );
  }
  else
  {
    //first node is layer id or name
    QgsExpressionNode *node = QgsExpressionUtils::getNode( values.at( 1 ), parent );
    ENSURE_NO_EVAL_ERROR
    layer = node->eval( parent, context );
    ENSURE_NO_EVAL_ERROR
  }
 
  QgsFeature feature;
  if ( values.size() < 3 || QgsVariantUtils::isNull( values.at( 2 ) ) )
  {
    feature = context->feature();
  }
  else
  {
    feature = QgsExpressionUtils::getFeature( values.at( 2 ), parent );
  }
 
  QgsFieldConstraints::ConstraintStrength constraintStrength = QgsFieldConstraints::ConstraintStrengthNotSet;
  const QString strength = QgsExpressionUtils::getStringValue( values.at( 3 ), parent ).toLower();
  if ( strength == QLatin1String( "hard" ) )
  {
    constraintStrength = QgsFieldConstraints::ConstraintStrengthHard;
  }
  else if ( strength == QLatin1String( "soft" ) )
  {
    constraintStrength = QgsFieldConstraints::ConstraintStrengthSoft;
  }
 
  const QString attributeName = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
 
  bool foundLayer = false;
  const QVariant res = QgsExpressionUtils::runMapLayerFunctionThreadSafe( layer, context, parent, [parent, feature, attributeName, constraintStrength]( QgsMapLayer * mapLayer ) -> QVariant
  {
    QgsVectorLayer *layer = qobject_cast< QgsVectorLayer * >( mapLayer );
    if ( !layer )
    {
      return QVariant();
    }
 
    const int fieldIndex = layer->fields().indexFromName( attributeName );
    if ( fieldIndex == -1 )
    {
      parent->setEvalErrorString( QObject::tr( "The attribute name did not match any field for the given feature" ) );
      return QVariant();
    }
 
    QStringList errors;
    bool valid = QgsVectorLayerUtils::validateAttribute( layer, feature, fieldIndex, errors, constraintStrength );
    return valid;
  }, foundLayer );
 
  if ( !foundLayer )
  {
    parent->setEvalErrorString( QObject::tr( "No layer provided to conduct constraints checks" ) );
    return QVariant();
  }
 
  return res;
}
 
static QVariant fcnAttributes( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsFeature feature;
  if ( values.size() == 0 || QgsVariantUtils::isNull( values.at( 0 ) ) )
  {
    feature = context->feature();
  }
  else
  {
    feature = QgsExpressionUtils::getFeature( values.at( 0 ), parent );
  }
 
  const QgsFields fields = feature.fields();
  QVariantMap result;
  for ( int i = 0; i < fields.count(); ++i )
  {
    result.insert( fields.at( i ).name(), feature.attribute( i ) );
  }
  return result;
}
 
static QVariant fcnRepresentAttributes( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsVectorLayer *layer = nullptr;
  QgsFeature feature;
 
  // TODO this expression function is NOT thread safe
  Q_NOWARN_DEPRECATED_PUSH
  if ( values.isEmpty() )
  {
    feature = context->feature();
    layer = QgsExpressionUtils::getVectorLayer( context->variable( QStringLiteral( "layer" ) ), context, parent );
  }
  else if ( values.size() == 1 )
  {
    layer = QgsExpressionUtils::getVectorLayer( context->variable( QStringLiteral( "layer" ) ), context, parent );
    feature = QgsExpressionUtils::getFeature( values.at( 0 ), parent );
  }
  else if ( values.size() == 2 )
  {
    layer = QgsExpressionUtils::getVectorLayer( values.at( 0 ), context,  parent );
    feature = QgsExpressionUtils::getFeature( values.at( 1 ), parent );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function `represent_attributes` requires no more than two parameters. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
  Q_NOWARN_DEPRECATED_POP
 
  if ( !layer )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot use represent attributes function: layer could not be resolved." ) );
    return QVariant();
  }
 
  if ( !feature.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot use represent attributes function: feature could not be resolved." ) );
    return QVariant();
  }
 
  const QgsFields fields = feature.fields();
  QVariantMap result;
  for ( int fieldIndex = 0; fieldIndex < fields.count(); ++fieldIndex )
  {
    const QString fieldName { fields.at( fieldIndex ).name() };
    const QVariant attributeVal = feature.attribute( fieldIndex );
    const QString cacheValueKey = QStringLiteral( "repvalfcnval:%1:%2:%3" ).arg( layer->id(), fieldName, attributeVal.toString() );
    if ( context && context->hasCachedValue( cacheValueKey ) )
    {
      result.insert( fieldName, context->cachedValue( cacheValueKey ) );
    }
    else
    {
      const QgsEditorWidgetSetup setup = layer->editorWidgetSetup( fieldIndex );
      QgsFieldFormatter *fieldFormatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );
      QVariant cache;
      if ( context )
      {
        const QString cacheKey = QStringLiteral( "repvalfcn:%1:%2" ).arg( layer->id(), fieldName );
 
        if ( !context->hasCachedValue( cacheKey ) )
        {
          cache = fieldFormatter->createCache( layer, fieldIndex, setup.config() );
          context->setCachedValue( cacheKey, cache );
        }
        else
        {
          cache = context->cachedValue( cacheKey );
        }
      }
      QString value( fieldFormatter->representValue( layer, fieldIndex, setup.config(), cache, attributeVal ) );
 
      result.insert( fields.at( fieldIndex ).name(), value );
 
      if ( context )
      {
        context->setCachedValue( cacheValueKey, value );
      }
 
    }
  }
  return result;
}
 
static QVariant fcnCoreFeatureMaptipDisplay( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const bool isMaptip )
{
  QgsVectorLayer *layer = nullptr;
  QgsFeature feature;
  bool evaluate = true;
 
  // TODO this expression function is NOT thread safe
  Q_NOWARN_DEPRECATED_PUSH
  if ( values.isEmpty() )
  {
    feature = context->feature();
    layer = QgsExpressionUtils::getVectorLayer( context->variable( QStringLiteral( "layer" ) ), context, parent );
  }
  else if ( values.size() == 1 )
  {
    layer = QgsExpressionUtils::getVectorLayer( context->variable( QStringLiteral( "layer" ) ), context, parent );
    feature = QgsExpressionUtils::getFeature( values.at( 0 ), parent );
  }
  else if ( values.size() == 2 )
  {
    layer = QgsExpressionUtils::getVectorLayer( values.at( 0 ), context, parent );
    feature = QgsExpressionUtils::getFeature( values.at( 1 ), parent );
  }
  else if ( values.size() == 3 )
  {
    layer = QgsExpressionUtils::getVectorLayer( values.at( 0 ), context, parent );
    feature = QgsExpressionUtils::getFeature( values.at( 1 ), parent );
    evaluate = values.value( 2 ).toBool();
  }
  else
  {
    if ( isMaptip )
    {
      parent->setEvalErrorString( QObject::tr( "Function `maptip` requires no more than three parameters. %n given.", nullptr, values.length() ) );
    }
    else
    {
      parent->setEvalErrorString( QObject::tr( "Function `display` requires no more than three parameters. %n given.", nullptr, values.length() ) );
    }
    return QVariant();
  }
 
  if ( !layer )
  {
    parent->setEvalErrorString( QObject::tr( "The layer is not valid." ) );
    return QVariant( );
  }
  Q_NOWARN_DEPRECATED_POP
 
  if ( !feature.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "The feature is not valid." ) );
    return QVariant( );
  }
 
  if ( ! evaluate )
  {
    if ( isMaptip )
    {
      return layer->mapTipTemplate();
    }
    else
    {
      return layer->displayExpression();
    }
  }
 
  QgsExpressionContext subContext( *context );
  subContext.appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( layer ) );
  subContext.setFeature( feature );
 
  if ( isMaptip )
  {
    return QgsExpression::replaceExpressionText( layer->mapTipTemplate(), &subContext );
  }
  else
  {
    QgsExpression exp( layer->displayExpression() );
    exp.prepare( &subContext );
    return exp.evaluate( &subContext ).toString();
  }
}
 
static QVariant fcnFeatureDisplayExpression( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnCoreFeatureMaptipDisplay( values, context, parent, false );
}
 
static QVariant fcnFeatureMaptip( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return fcnCoreFeatureMaptipDisplay( values, context, parent, true );
}
 
static QVariant fcnIsSelected( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsFeature feature;
  QVariant layer;
  if ( values.isEmpty() )
  {
    feature = context->feature();
    layer = context->variable( QStringLiteral( "layer" ) );
  }
  else if ( values.size() == 1 )
  {
    feature = QgsExpressionUtils::getFeature( values.at( 0 ), parent );
    layer = context->variable( QStringLiteral( "layer" ) );
  }
  else if ( values.size() == 2 )
  {
    feature = QgsExpressionUtils::getFeature( values.at( 1 ), parent );
    layer = values.at( 0 );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function `is_selected` requires no more than two parameters. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
 
  bool foundLayer = false;
  const QVariant res = QgsExpressionUtils::runMapLayerFunctionThreadSafe( layer, context, parent, [feature]( QgsMapLayer * mapLayer ) -> QVariant
  {
    QgsVectorLayer *layer = qobject_cast< QgsVectorLayer * >( mapLayer );
    if ( !layer || !feature.isValid() )
    {
      return QVariant( QVariant::Bool );
    }
 
    return layer->selectedFeatureIds().contains( feature.id() );
  }, foundLayer );
  if ( !foundLayer )
    return  QVariant( QVariant::Bool );
  else
    return res;
}
 
static QVariant fcnNumSelected( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant layer;
 
  if ( values.isEmpty() )
    layer = context->variable( QStringLiteral( "layer" ) );
  else if ( values.count() == 1 )
    layer = values.at( 0 );
  else
  {
    parent->setEvalErrorString( QObject::tr( "Function `num_selected` requires no more than one parameter. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
 
  bool foundLayer = false;
  const QVariant res = QgsExpressionUtils::runMapLayerFunctionThreadSafe( layer, context, parent, []( QgsMapLayer * mapLayer ) -> QVariant
  {
    QgsVectorLayer *layer = qobject_cast< QgsVectorLayer * >( mapLayer );
    if ( !layer )
    {
      return QVariant( QVariant::LongLong );
    }
 
    return layer->selectedFeatureCount();
  }, foundLayer );
  if ( !foundLayer )
    return  QVariant( QVariant::LongLong );
  else
    return res;
}
 
static QVariant fcnSqliteFetchAndIncrement( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  static QMap<QString, qlonglong> counterCache;
  QVariant functionResult;
 
  auto fetchAndIncrementFunc = [ values, parent, &functionResult ]( QgsMapLayer * mapLayer, const QString & databaseArgument )
  {
    QString database;
 
    const QgsVectorLayer *layer = qobject_cast< QgsVectorLayer *>( mapLayer );
 
    if ( layer )
    {
      const QVariantMap decodedUri = QgsProviderRegistry::instance()->decodeUri( layer->providerType(), layer->dataProvider()->dataSourceUri() );
      database = decodedUri.value( QStringLiteral( "path" ) ).toString();
      if ( database.isEmpty() )
      {
        parent->setEvalErrorString( QObject::tr( "Could not extract file path from layer `%1`." ).arg( layer->name() ) );
      }
    }
    else
    {
      database = databaseArgument;
    }
 
    const QString table = values.at( 1 ).toString();
    const QString idColumn = values.at( 2 ).toString();
    const QString filterAttribute = values.at( 3 ).toString();
    const QVariant filterValue = values.at( 4 ).toString();
    const QVariantMap defaultValues = values.at( 5 ).toMap();
 
    // read from database
    sqlite3_database_unique_ptr sqliteDb;
    sqlite3_statement_unique_ptr sqliteStatement;
 
    if ( sqliteDb.open_v2( database, SQLITE_OPEN_READWRITE, nullptr ) != SQLITE_OK )
    {
      parent->setEvalErrorString( QObject::tr( "Could not open sqlite database %1. Error %2. " ).arg( database, sqliteDb.errorMessage() ) );
      functionResult = QVariant();
      return;
    }
 
    QString errorMessage;
    QString currentValSql;
 
    qlonglong nextId = 0;
    bool cachedMode = false;
    bool valueRetrieved = false;
 
    QString cacheString = QStringLiteral( "%1:%2:%3:%4:%5" ).arg( database, table, idColumn, filterAttribute, filterValue.toString() );
 
    // Running in transaction mode, check for cached value first
    if ( layer && layer->dataProvider() && layer->dataProvider()->transaction() )
    {
      cachedMode = true;
 
      auto cachedCounter = counterCache.find( cacheString );
 
      if ( cachedCounter != counterCache.end() )
      {
        qlonglong &cachedValue = cachedCounter.value();
        nextId = cachedValue;
        nextId += 1;
        cachedValue = nextId;
        valueRetrieved = true;
      }
    }
 
    // Either not in cached mode or no cached value found, obtain from DB
    if ( !cachedMode || !valueRetrieved )
    {
      int result = SQLITE_ERROR;
 
      currentValSql = QStringLiteral( "SELECT %1 FROM %2" ).arg( QgsSqliteUtils::quotedIdentifier( idColumn ), QgsSqliteUtils::quotedIdentifier( table ) );
      if ( !filterAttribute.isNull() )
      {
        currentValSql += QStringLiteral( " WHERE %1 = %2" ).arg( QgsSqliteUtils::quotedIdentifier( filterAttribute ), QgsSqliteUtils::quotedValue( filterValue ) );
      }
 
      sqliteStatement = sqliteDb.prepare( currentValSql, result );
 
      if ( result == SQLITE_OK )
      {
        nextId = 0;
        if ( sqliteStatement.step() == SQLITE_ROW )
        {
          nextId = sqliteStatement.columnAsInt64( 0 ) + 1;
        }
 
        // If in cached mode: add value to cache and connect to transaction
        if ( cachedMode && result == SQLITE_OK )
        {
          counterCache.insert( cacheString, nextId );
 
          QObject::connect( layer->dataProvider()->transaction(), &QgsTransaction::destroyed, [cacheString]()
          {
            counterCache.remove( cacheString );
          } );
        }
        valueRetrieved = true;
      }
    }
 
    if ( valueRetrieved )
    {
      QString upsertSql;
      upsertSql = QStringLiteral( "INSERT OR REPLACE INTO %1" ).arg( QgsSqliteUtils::quotedIdentifier( table ) );
      QStringList cols;
      QStringList vals;
      cols << QgsSqliteUtils::quotedIdentifier( idColumn );
      vals << QgsSqliteUtils::quotedValue( nextId );
 
      if ( !filterAttribute.isNull() )
      {
        cols << QgsSqliteUtils::quotedIdentifier( filterAttribute );
        vals << QgsSqliteUtils::quotedValue( filterValue );
      }
 
      for ( QVariantMap::const_iterator iter = defaultValues.constBegin(); iter != defaultValues.constEnd(); ++iter )
      {
        cols << QgsSqliteUtils::quotedIdentifier( iter.key() );
        vals << iter.value().toString();
      }
 
      upsertSql += QLatin1String( " (" ) + cols.join( ',' ) + ')';
      upsertSql += QLatin1String( " VALUES " );
      upsertSql += '(' + vals.join( ',' ) + ')';
 
      int result = SQLITE_ERROR;
      if ( layer && layer->dataProvider() && layer->dataProvider()->transaction() )
      {
        QgsTransaction *transaction = layer->dataProvider()->transaction();
        if ( transaction->executeSql( upsertSql, errorMessage ) )
        {
          result = SQLITE_OK;
        }
      }
      else
      {
        result = sqliteDb.exec( upsertSql, errorMessage );
      }
      if ( result == SQLITE_OK )
      {
        functionResult = QVariant( nextId );
        return;
      }
      else
      {
        parent->setEvalErrorString( QStringLiteral( "Could not increment value: SQLite error: \"%1\" (%2)." ).arg( errorMessage, QString::number( result ) ) );
        functionResult = QVariant();
        return;
      }
    }
 
    functionResult = QVariant();
  };
 
  bool foundLayer = false;
  QgsExpressionUtils::executeLambdaForMapLayer( values.at( 0 ), context, parent, [&fetchAndIncrementFunc]( QgsMapLayer * layer )
  {
    fetchAndIncrementFunc( layer, QString() );
  }, foundLayer );
  if ( !foundLayer )
  {
    const QString databasePath = values.at( 0 ).toString();
    QgsThreadingUtils::runOnMainThread( [&fetchAndIncrementFunc, databasePath]
    {
      fetchAndIncrementFunc( nullptr, databasePath );
    } );
  }
 
  return functionResult;
}
 
static QVariant fcnConcat( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString concat;
  for ( const QVariant &value : values )
  {
    if ( !QgsVariantUtils::isNull( value ) )
      concat += QgsExpressionUtils::getStringValue( value, parent );
  }
  return concat;
}
 
static QVariant fcnStrpos( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  return string.indexOf( QgsExpressionUtils::getStringValue( values.at( 1 ), parent ) ) + 1;
}
 
static QVariant fcnRight( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  int pos = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  return string.right( pos );
}
 
static QVariant fcnLeft( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  int pos = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  return string.left( pos );
}
 
static QVariant fcnRPad( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  int length = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  QString fill = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
  return string.leftJustified( length, fill.at( 0 ), true );
}
 
static QVariant fcnLPad( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  int length = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  QString fill = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
  return string.rightJustified( length, fill.at( 0 ), true );
}
 
static QVariant fcnFormatString( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.size() < 1 )
  {
    parent->setEvalErrorString( QObject::tr( "Function format requires at least 1 argument" ) );
    return QVariant();
  }
 
  QString string = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  for ( int n = 1; n < values.length(); n++ )
  {
    string = string.arg( QgsExpressionUtils::getStringValue( values.at( n ), parent ) );
  }
  return string;
}
 
 
static QVariant fcnNow( const QVariantList &, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * )
{
  return QVariant( QDateTime::currentDateTime() );
}
 
static QVariant fcnToDate( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString format = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  QString language = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
  if ( format.isEmpty() && !language.isEmpty() )
  {
    parent->setEvalErrorString( QObject::tr( "A format is required to convert to Date when the language is specified" ) );
    return QVariant( QDate() );
  }
 
  if ( format.isEmpty() && language.isEmpty() )
    return QVariant( QgsExpressionUtils::getDateValue( values.at( 0 ), parent ) );
 
  QString datestring = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QLocale locale = QLocale();
  if ( !language.isEmpty() )
  {
    locale = QLocale( language );
  }
 
  QDate date = locale.toDate( datestring, format );
  if ( !date.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot convert '%1' to Date" ).arg( datestring ) );
    date = QDate();
  }
  return QVariant( date );
}
 
static QVariant fcnToTime( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString format = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  QString language = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
  if ( format.isEmpty() && !language.isEmpty() )
  {
    parent->setEvalErrorString( QObject::tr( "A format is required to convert to Time when the language is specified" ) );
    return QVariant( QTime() );
  }
 
  if ( format.isEmpty() && language.isEmpty() )
    return QVariant( QgsExpressionUtils::getTimeValue( values.at( 0 ), parent ) );
 
  QString timestring = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QLocale locale = QLocale();
  if ( !language.isEmpty() )
  {
    locale = QLocale( language );
  }
 
  QTime time = locale.toTime( timestring, format );
  if ( !time.isValid() )
  {
    parent->setEvalErrorString( QObject::tr( "Cannot convert '%1' to Time" ).arg( timestring ) );
    time = QTime();
  }
  return QVariant( time );
}
 
static QVariant fcnToInterval( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  return QVariant::fromValue( QgsExpressionUtils::getInterval( values.at( 0 ), parent ) );
}
 
/*
 * DMS functions
 */
 
static QVariant floatToDegreeFormat( const QgsCoordinateFormatter::Format format, const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double value = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  QString axis = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  int precision = QgsExpressionUtils::getNativeIntValue( values.at( 2 ), parent );
 
  QString formatString;
  if ( values.count() > 3 )
    formatString = QgsExpressionUtils::getStringValue( values.at( 3 ), parent );
 
  QgsCoordinateFormatter::FormatFlags flags = QgsCoordinateFormatter::FormatFlags();
  if ( formatString.compare( QLatin1String( "suffix" ), Qt::CaseInsensitive ) == 0 )
  {
    flags = QgsCoordinateFormatter::FlagDegreesUseStringSuffix;
  }
  else if ( formatString.compare( QLatin1String( "aligned" ), Qt::CaseInsensitive ) == 0 )
  {
    flags = QgsCoordinateFormatter::FlagDegreesUseStringSuffix | QgsCoordinateFormatter::FlagDegreesPadMinutesSeconds;
  }
  else if ( ! formatString.isEmpty() )
  {
    parent->setEvalErrorString( QObject::tr( "Invalid formatting parameter: '%1'. It must be empty, or 'suffix' or 'aligned'." ).arg( formatString ) );
    return QVariant();
  }
 
  if ( axis.compare( QLatin1String( "x" ), Qt::CaseInsensitive ) == 0 )
  {
    return QVariant::fromValue( QgsCoordinateFormatter::formatX( value, format, precision, flags ) );
  }
  else if ( axis.compare( QLatin1String( "y" ), Qt::CaseInsensitive ) == 0 )
  {
    return QVariant::fromValue( QgsCoordinateFormatter::formatY( value, format, precision, flags ) );
  }
  else
  {
    parent->setEvalErrorString( QObject::tr( "Invalid axis name: '%1'. It must be either 'x' or 'y'." ).arg( axis ) );
    return QVariant();
  }
}
 
static QVariant fcnToDegreeMinute( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
  QgsCoordinateFormatter::Format format = QgsCoordinateFormatter::FormatDegreesMinutes;
  return floatToDegreeFormat( format, values, context, parent, node );
}
 
static QVariant fcnToDecimal( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double value = 0.0;
  bool ok = false;
  value = QgsCoordinateUtils::dmsToDecimal( QgsExpressionUtils::getStringValue( values.at( 0 ), parent ), &ok );
 
  return ok ? QVariant( value ) : QVariant();
}
 
static QVariant fcnToDegreeMinuteSecond( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
  QgsCoordinateFormatter::Format format = QgsCoordinateFormatter::FormatDegreesMinutesSeconds;
  return floatToDegreeFormat( format, values, context, parent, node );
}
 
static QVariant fcnAge( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QDateTime d1 = QgsExpressionUtils::getDateTimeValue( values.at( 0 ), parent );
  QDateTime d2 = QgsExpressionUtils::getDateTimeValue( values.at( 1 ), parent );
  qint64 seconds = d2.secsTo( d1 );
  return QVariant::fromValue( QgsInterval( seconds ) );
}
 
static QVariant fcnDayOfWeek( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( !values.at( 0 ).canConvert<QDate>() )
    return QVariant();
 
  QDate date = QgsExpressionUtils::getDateValue( values.at( 0 ), parent );
  if ( !date.isValid() )
    return QVariant();
 
  // return dayOfWeek() % 7 so that values range from 0 (sun) to 6 (sat)
  // (to match PostgreSQL behavior)
  return date.dayOfWeek() % 7;
}
 
static QVariant fcnDay( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.days() );
  }
  else
  {
    QDateTime d1 = QgsExpressionUtils::getDateTimeValue( value, parent );
    return QVariant( d1.date().day() );
  }
}
 
static QVariant fcnYear( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.years() );
  }
  else
  {
    QDateTime d1 = QgsExpressionUtils::getDateTimeValue( value, parent );
    return QVariant( d1.date().year() );
  }
}
 
static QVariant fcnMonth( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.months() );
  }
  else
  {
    QDateTime d1 = QgsExpressionUtils::getDateTimeValue( value, parent );
    return QVariant( d1.date().month() );
  }
}
 
static QVariant fcnWeek( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.weeks() );
  }
  else
  {
    QDateTime d1 = QgsExpressionUtils::getDateTimeValue( value, parent );
    return QVariant( d1.date().weekNumber() );
  }
}
 
static QVariant fcnHour( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.hours() );
  }
  else
  {
    QTime t1 = QgsExpressionUtils::getTimeValue( value, parent );
    return QVariant( t1.hour() );
  }
}
 
static QVariant fcnMinute( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.minutes() );
  }
  else
  {
    QTime t1 = QgsExpressionUtils::getTimeValue( value, parent );
    return QVariant( t1.minute() );
  }
}
 
static QVariant fcnSeconds( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariant value = values.at( 0 );
  QgsInterval inter = QgsExpressionUtils::getInterval( value, parent, false );
  if ( inter.isValid() )
  {
    return QVariant( inter.seconds() );
  }
  else
  {
    QTime t1 = QgsExpressionUtils::getTimeValue( value, parent );
    return QVariant( t1.second() );
  }
}
 
static QVariant fcnEpoch( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QDateTime dt = QgsExpressionUtils::getDateTimeValue( values.at( 0 ), parent );
  if ( dt.isValid() )
  {
    return QVariant( dt.toMSecsSinceEpoch() );
  }
  else
  {
    return QVariant();
  }
}
 
static QVariant fcnDateTimeFromEpoch( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  long long millisecs_since_epoch = QgsExpressionUtils::getIntValue( values.at( 0 ), parent );
  // no sense to check for strange values, as Qt behavior is undefined anyway (see docs)
  return QVariant( QDateTime::fromMSecsSinceEpoch( millisecs_since_epoch ) );
}
 
static QVariant fcnExif( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QString filepath = QgsExpressionUtils::getFilePathValue( values.at( 0 ), context, parent );
  if ( parent->hasEvalError() )
  {
    parent->setEvalErrorString( QObject::tr( "Function `%1` requires a value which represents a possible file path" ).arg( QLatin1String( "exif" ) ) );
    return QVariant();
  }
  QString tag = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  return !tag.isNull() ? QgsExifTools::readTag( filepath, tag ) : QVariant( QgsExifTools::readTags( filepath ) );
}
 
static QVariant fcnExifGeoTag( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QString filepath = QgsExpressionUtils::getFilePathValue( values.at( 0 ), context, parent );
  if ( parent->hasEvalError() )
  {
    parent->setEvalErrorString( QObject::tr( "Function `%1` requires a value which represents a possible file path" ).arg( QLatin1String( "exif_geotag" ) ) );
    return QVariant();
  }
  bool ok;
  return QVariant::fromValue( QgsGeometry( new QgsPoint( QgsExifTools::getGeoTag( filepath, ok ) ) ) );
}
 
#define ENSURE_GEOM_TYPE(f, g, geomtype) \
  if ( !(f).hasGeometry() ) \
    return QVariant(); \
  QgsGeometry g = (f).geometry(); \
  if ( (g).type() != (geomtype) ) \
    return QVariant();
 
static QVariant fcnX( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  ENSURE_GEOM_TYPE( f, g, QgsWkbTypes::PointGeometry )
  if ( g.isMultipart() )
  {
    return g.asMultiPoint().at( 0 ).x();
  }
  else
  {
    return g.asPoint().x();
  }
}
 
static QVariant fcnY( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  ENSURE_GEOM_TYPE( f, g, QgsWkbTypes::PointGeometry )
  if ( g.isMultipart() )
  {
    return g.asMultiPoint().at( 0 ).y();
  }
  else
  {
    return g.asPoint().y();
  }
}
 
static QVariant fcnZ( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  ENSURE_GEOM_TYPE( f, g, QgsWkbTypes::PointGeometry )
 
  if ( g.isEmpty() )
    return QVariant();
 
  const QgsAbstractGeometry *abGeom = g.constGet();
 
  if ( g.isEmpty() || !abGeom->is3D() )
    return QVariant();
 
  if ( g.type() == QgsWkbTypes::PointGeometry && !g.isMultipart() )
  {
    const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( g.constGet() );
    if ( point )
      return point->z();
  }
  else if ( g.type() == QgsWkbTypes::PointGeometry && g.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( g.constGet() ) )
    {
      if ( collection->numGeometries() > 0 )
      {
        if ( const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) ) )
          return point->z();
      }
    }
  }
 
  return QVariant();
}
 
static QVariant fcnGeomIsValid( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  bool isValid = geom.isGeosValid();
 
  return QVariant( isValid );
}
 
static QVariant fcnGeomMakeValid( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  const QString methodString = QgsExpressionUtils::getStringValue( values.at( 1 ), parent ).trimmed();
#if GEOS_VERSION_MAJOR==3 && GEOS_VERSION_MINOR<10
  Qgis::MakeValidMethod method = Qgis::MakeValidMethod::Linework;
#else
  Qgis::MakeValidMethod method = Qgis::MakeValidMethod::Structure;
#endif
  if ( methodString.compare( QLatin1String( "linework" ), Qt::CaseInsensitive ) == 0 )
    method = Qgis::MakeValidMethod::Linework;
  else if ( methodString.compare( QLatin1String( "structure" ), Qt::CaseInsensitive ) == 0 )
    method = Qgis::MakeValidMethod::Structure;
 
  const bool keepCollapsed = values.value( 2 ).toBool();
 
  QgsGeometry valid;
  try
  {
    valid = geom.makeValid( method, keepCollapsed );
  }
  catch ( QgsNotSupportedException & )
  {
    parent->setEvalErrorString( QObject::tr( "The make_valid parameters require a newer GEOS library version" ) );
    return QVariant();
  }
 
  return QVariant::fromValue( valid );
}
 
static QVariant fcnGeometryCollectionAsArray( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  QVector<QgsGeometry> multiGeom = geom.asGeometryCollection();
  QVariantList array;
  for ( int i = 0; i < multiGeom.size(); ++i )
  {
    array += QVariant::fromValue( multiGeom.at( i ) );
  }
 
  return array;
}
 
static QVariant fcnGeomX( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  //if single point, return the point's x coordinate
  if ( geom.type() == QgsWkbTypes::PointGeometry && !geom.isMultipart() )
  {
    return geom.asPoint().x();
  }
 
  //otherwise return centroid x
  QgsGeometry centroid = geom.centroid();
  QVariant result( centroid.asPoint().x() );
  return result;
}
 
static QVariant fcnGeomY( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  //if single point, return the point's y coordinate
  if ( geom.type() == QgsWkbTypes::PointGeometry && !geom.isMultipart() )
  {
    return geom.asPoint().y();
  }
 
  //otherwise return centroid y
  QgsGeometry centroid = geom.centroid();
  QVariant result( centroid.asPoint().y() );
  return result;
}
 
static QVariant fcnGeomZ( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant(); //or 0?
 
  if ( !geom.constGet()->is3D() )
    return QVariant();
 
  //if single point, return the point's z coordinate
  if ( geom.type() == QgsWkbTypes::PointGeometry && !geom.isMultipart() )
  {
    const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( geom.constGet() );
    if ( point )
      return point->z();
  }
  else if ( geom.type() == QgsWkbTypes::PointGeometry && geom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        if ( const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) ) )
          return point->z();
      }
    }
  }
 
  return QVariant();
}
 
static QVariant fcnGeomM( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant(); //or 0?
 
  if ( !geom.constGet()->isMeasure() )
    return QVariant();
 
  //if single point, return the point's m value
  if ( geom.type() == QgsWkbTypes::PointGeometry && !geom.isMultipart() )
  {
    const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( geom.constGet() );
    if ( point )
      return point->m();
  }
  else if ( geom.type() == QgsWkbTypes::PointGeometry && geom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        if ( const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) ) )
          return point->m();
      }
    }
  }
 
  return QVariant();
}
 
static QVariant fcnPointN( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  int idx = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
 
  if ( idx < 0 )
  {
    //negative idx
    int count = geom.constGet()->nCoordinates();
    idx = count + idx;
  }
  else
  {
    //positive idx is 1 based
    idx -= 1;
  }
 
  QgsVertexId vId;
  if ( idx < 0 || !geom.vertexIdFromVertexNr( idx, vId ) )
  {
    parent->setEvalErrorString( QObject::tr( "Point index is out of range" ) );
    return QVariant();
  }
 
  QgsPoint point = geom.constGet()->vertexAt( vId );
  return QVariant::fromValue( QgsGeometry( new QgsPoint( point ) ) );
}
 
static QVariant fcnStartPoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  QgsVertexId vId;
  if ( !geom.vertexIdFromVertexNr( 0, vId ) )
  {
    return QVariant();
  }
 
  QgsPoint point = geom.constGet()->vertexAt( vId );
  return QVariant::fromValue( QgsGeometry( new QgsPoint( point ) ) );
}
 
static QVariant fcnEndPoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  QgsVertexId vId;
  if ( !geom.vertexIdFromVertexNr( geom.constGet()->nCoordinates() - 1, vId ) )
  {
    return QVariant();
  }
 
  QgsPoint point = geom.constGet()->vertexAt( vId );
  return QVariant::fromValue( QgsGeometry( new QgsPoint( point ) ) );
}
 
static QVariant fcnNodesToPoints( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  bool ignoreClosing = false;
  if ( values.length() > 1 )
  {
    ignoreClosing = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
  }
 
  QgsMultiPoint *mp = new QgsMultiPoint();
 
  const QgsCoordinateSequence sequence = geom.constGet()->coordinateSequence();
  for ( const QgsRingSequence &part : sequence )
  {
    for ( const QgsPointSequence &ring : part )
    {
      bool skipLast = false;
      if ( ignoreClosing && ring.count() > 2 && ring.first() == ring.last() )
      {
        skipLast = true;
      }
 
      for ( int i = 0; i < ( skipLast ? ring.count() - 1 : ring.count() ); ++ i )
      {
        mp->addGeometry( ring.at( i ).clone() );
      }
    }
  }
 
  return QVariant::fromValue( QgsGeometry( mp ) );
}
 
static QVariant fcnSegmentsToLines( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const QVector< QgsLineString * > linesToProcess = QgsGeometryUtils::extractLineStrings( geom.constGet() );
 
  //OK, now we have a complete list of segmentized lines from the geometry
  QgsMultiLineString *ml = new QgsMultiLineString();
  for ( QgsLineString *line : linesToProcess )
  {
    for ( int i = 0; i < line->numPoints() - 1; ++i )
    {
      QgsLineString *segment = new QgsLineString();
      segment->setPoints( QgsPointSequence()
                          << line->pointN( i )
                          << line->pointN( i + 1 ) );
      ml->addGeometry( segment );
    }
    delete line;
  }
 
  return QVariant::fromValue( QgsGeometry( ml ) );
}
 
static QVariant fcnInteriorRingN( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const QgsCurvePolygon *curvePolygon = qgsgeometry_cast< const QgsCurvePolygon * >( geom.constGet() );
  if ( !curvePolygon && geom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        curvePolygon = qgsgeometry_cast< const QgsCurvePolygon * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( !curvePolygon )
    return QVariant();
 
  //idx is 1 based
  qlonglong idx = QgsExpressionUtils::getIntValue( values.at( 1 ), parent ) - 1;
 
  if ( idx >= curvePolygon->numInteriorRings() || idx < 0 )
    return QVariant();
 
  QgsCurve *curve = static_cast< QgsCurve * >( curvePolygon->interiorRing( static_cast< int >( idx ) )->clone() );
  QVariant result = curve ? QVariant::fromValue( QgsGeometry( curve ) ) : QVariant();
  return result;
}
 
static QVariant fcnGeometryN( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() );
  if ( !collection )
    return QVariant();
 
  //idx is 1 based
  qlonglong idx = QgsExpressionUtils::getIntValue( values.at( 1 ), parent ) - 1;
 
  if ( idx < 0 || idx >= collection->numGeometries() )
    return QVariant();
 
  QgsAbstractGeometry *part = collection->geometryN( static_cast< int >( idx ) )->clone();
  QVariant result = part ? QVariant::fromValue( QgsGeometry( part ) ) : QVariant();
  return result;
}
 
static QVariant fcnBoundary( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  QgsAbstractGeometry *boundary = geom.constGet()->boundary();
  if ( !boundary )
    return QVariant();
 
  return QVariant::fromValue( QgsGeometry( boundary ) );
}
 
static QVariant fcnLineMerge( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  QgsGeometry merged = geom.mergeLines();
  if ( merged.isNull() )
    return QVariant();
 
  return QVariant::fromValue( merged );
}
 
static QVariant fcnSharedPaths( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  const QgsGeometry geom2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  if ( geom2.isNull() )
    return QVariant();
 
  const QgsGeometry sharedPaths = geom.sharedPaths( geom2 );
  if ( sharedPaths.isNull() )
    return QVariant();
 
  return QVariant::fromValue( sharedPaths );
}
 
 
static QVariant fcnSimplify( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  double tolerance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
 
  QgsGeometry simplified = geom.simplify( tolerance );
  if ( simplified.isNull() )
    return QVariant();
 
  return simplified;
}
 
static QVariant fcnSimplifyVW( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  double tolerance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
 
  QgsMapToPixelSimplifier simplifier( QgsMapToPixelSimplifier::SimplifyGeometry, tolerance, QgsMapToPixelSimplifier::Visvalingam );
 
  QgsGeometry simplified = simplifier.simplify( geom );
  if ( simplified.isNull() )
    return QVariant();
 
  return simplified;
}
 
static QVariant fcnSmooth( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  int iterations = std::min( QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent ), 10 );
  double offset = std::clamp( QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent ), 0.0, 0.5 );
  double minLength = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  double maxAngle = std::clamp( QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent ), 0.0, 180.0 );
 
  QgsGeometry smoothed = geom.smooth( static_cast<unsigned int>( iterations ), offset, minLength, maxAngle );
  if ( smoothed.isNull() )
    return QVariant();
 
  return smoothed;
}
 
static QVariant fcnTriangularWave( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double wavelength = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double amplitude = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const bool strict = QgsExpressionUtils::getIntValue( values.at( 3 ), parent );
 
  const QgsGeometry waved = geom.triangularWaves( wavelength, amplitude, strict );
  if ( waved.isNull() )
    return QVariant();
 
  return waved;
}
 
static QVariant fcnTriangularWaveRandomized( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double minWavelength = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double maxWavelength = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const double minAmplitude = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  const double maxAmplitude = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
  const long long seed = QgsExpressionUtils::getIntValue( values.at( 5 ), parent );
 
  const QgsGeometry waved = geom.triangularWavesRandomized( minWavelength, maxWavelength,
                            minAmplitude, maxAmplitude, seed );
  if ( waved.isNull() )
    return QVariant();
 
  return waved;
}
 
static QVariant fcnSquareWave( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double wavelength = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double amplitude = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const bool strict = QgsExpressionUtils::getIntValue( values.at( 3 ), parent );
 
  const QgsGeometry waved = geom.squareWaves( wavelength, amplitude, strict );
  if ( waved.isNull() )
    return QVariant();
 
  return waved;
}
 
static QVariant fcnSquareWaveRandomized( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double minWavelength = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double maxWavelength = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const double minAmplitude = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  const double maxAmplitude = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
  const long long seed = QgsExpressionUtils::getIntValue( values.at( 5 ), parent );
 
  const QgsGeometry waved = geom.squareWavesRandomized( minWavelength, maxWavelength,
                            minAmplitude, maxAmplitude, seed );
  if ( waved.isNull() )
    return QVariant();
 
  return waved;
}
 
static QVariant fcnRoundWave( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double wavelength = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double amplitude = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const bool strict = QgsExpressionUtils::getIntValue( values.at( 3 ), parent );
 
  const QgsGeometry waved = geom.roundWaves( wavelength, amplitude, strict );
  if ( waved.isNull() )
    return QVariant();
 
  return waved;
}
 
static QVariant fcnRoundWaveRandomized( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double minWavelength = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double maxWavelength = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const double minAmplitude = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  const double maxAmplitude = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
  const long long seed = QgsExpressionUtils::getIntValue( values.at( 5 ), parent );
 
  const QgsGeometry waved = geom.roundWavesRandomized( minWavelength, maxWavelength,
                            minAmplitude, maxAmplitude, seed );
  if ( waved.isNull() )
    return QVariant();
 
  return waved;
}
 
static QVariant fcnApplyDashPattern( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const QVariantList pattern = QgsExpressionUtils::getListValue( values.at( 1 ), parent );
  QVector< double > dashPattern;
  dashPattern.reserve( pattern.size() );
  for ( const QVariant &value : std::as_const( pattern ) )
  {
    bool ok = false;
    double v = value.toDouble( &ok );
    if ( ok )
    {
      dashPattern << v;
    }
    else
    {
      parent->setEvalErrorString( QStringLiteral( "Dash pattern must be an array of numbers" ) );
      return QgsGeometry();
    }
  }
 
  if ( dashPattern.size() % 2 != 0 )
  {
    parent->setEvalErrorString( QStringLiteral( "Dash pattern must contain an even number of elements" ) );
    return QgsGeometry();
  }
 
  const QString startRuleString = QgsExpressionUtils::getStringValue( values.at( 2 ), parent ).trimmed();
  Qgis::DashPatternLineEndingRule startRule = Qgis::DashPatternLineEndingRule::NoRule;
  if ( startRuleString.compare( QLatin1String( "no_rule" ), Qt::CaseInsensitive ) == 0 )
    startRule = Qgis::DashPatternLineEndingRule::NoRule;
  else if ( startRuleString.compare( QLatin1String( "full_dash" ), Qt::CaseInsensitive ) == 0 )
    startRule = Qgis::DashPatternLineEndingRule::FullDash;
  else if ( startRuleString.compare( QLatin1String( "half_dash" ), Qt::CaseInsensitive ) == 0 )
    startRule = Qgis::DashPatternLineEndingRule::HalfDash;
  else if ( startRuleString.compare( QLatin1String( "full_gap" ), Qt::CaseInsensitive ) == 0 )
    startRule = Qgis::DashPatternLineEndingRule::FullGap;
  else if ( startRuleString.compare( QLatin1String( "half_gap" ), Qt::CaseInsensitive ) == 0 )
    startRule = Qgis::DashPatternLineEndingRule::HalfGap;
  else
  {
    parent->setEvalErrorString( QStringLiteral( "'%1' is not a valid dash pattern rule" ).arg( startRuleString ) );
    return QgsGeometry();
  }
 
  const QString endRuleString = QgsExpressionUtils::getStringValue( values.at( 3 ), parent ).trimmed();
  Qgis::DashPatternLineEndingRule endRule = Qgis::DashPatternLineEndingRule::NoRule;
  if ( endRuleString.compare( QLatin1String( "no_rule" ), Qt::CaseInsensitive ) == 0 )
    endRule = Qgis::DashPatternLineEndingRule::NoRule;
  else if ( endRuleString.compare( QLatin1String( "full_dash" ), Qt::CaseInsensitive ) == 0 )
    endRule = Qgis::DashPatternLineEndingRule::FullDash;
  else if ( endRuleString.compare( QLatin1String( "half_dash" ), Qt::CaseInsensitive ) == 0 )
    endRule = Qgis::DashPatternLineEndingRule::HalfDash;
  else if ( endRuleString.compare( QLatin1String( "full_gap" ), Qt::CaseInsensitive ) == 0 )
    endRule = Qgis::DashPatternLineEndingRule::FullGap;
  else if ( endRuleString.compare( QLatin1String( "half_gap" ), Qt::CaseInsensitive ) == 0 )
    endRule = Qgis::DashPatternLineEndingRule::HalfGap;
  else
  {
    parent->setEvalErrorString( QStringLiteral( "'%1' is not a valid dash pattern rule" ).arg( endRuleString ) );
    return QgsGeometry();
  }
 
  const QString adjustString = QgsExpressionUtils::getStringValue( values.at( 4 ), parent ).trimmed();
  Qgis::DashPatternSizeAdjustment adjustment = Qgis::DashPatternSizeAdjustment::ScaleBothDashAndGap;
  if ( adjustString.compare( QLatin1String( "both" ), Qt::CaseInsensitive ) == 0 )
    adjustment = Qgis::DashPatternSizeAdjustment::ScaleBothDashAndGap;
  else if ( adjustString.compare( QLatin1String( "dash" ), Qt::CaseInsensitive ) == 0 )
    adjustment = Qgis::DashPatternSizeAdjustment::ScaleDashOnly;
  else if ( adjustString.compare( QLatin1String( "gap" ), Qt::CaseInsensitive ) == 0 )
    adjustment = Qgis::DashPatternSizeAdjustment::ScaleGapOnly;
  else
  {
    parent->setEvalErrorString( QStringLiteral( "'%1' is not a valid dash pattern size adjustment" ).arg( adjustString ) );
    return QgsGeometry();
  }
 
  const double patternOffset = QgsExpressionUtils::getDoubleValue( values.at( 5 ), parent );
 
  const QgsGeometry result = geom.applyDashPattern( dashPattern, startRule, endRule, adjustment, patternOffset );
  if ( result.isNull() )
    return QVariant();
 
  return result;
}
 
static QVariant fcnDensifyByCount( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const long long count = QgsExpressionUtils::getIntValue( values.at( 1 ), parent );
  const QgsGeometry densified = geom.densifyByCount( static_cast< int >( count ) );
  if ( densified.isNull() )
    return QVariant();
 
  return densified;
}
 
static QVariant fcnDensifyByDistance( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const double distance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const QgsGeometry densified = geom.densifyByDistance( distance );
  if ( densified.isNull() )
    return QVariant();
 
  return densified;
}
 
static QVariant fcnCollectGeometries( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QVariantList list;
  if ( values.size() == 1 && QgsExpressionUtils::isList( values.at( 0 ) ) )
  {
    list = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
  }
  else
  {
    list = values;
  }
 
  QVector< QgsGeometry > parts;
  parts.reserve( list.size() );
  for ( const QVariant &value : std::as_const( list ) )
  {
    if ( value.userType() == QMetaType::type( "QgsGeometry" ) )
    {
      parts << value.value<QgsGeometry>();
    }
    else
    {
      parent->setEvalErrorString( QStringLiteral( "Cannot convert to geometry" ) );
      return QgsGeometry();
    }
  }
 
  return QgsGeometry::collectGeometry( parts );
}
 
static QVariant fcnMakePoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.count() < 2 || values.count() > 4 )
  {
    parent->setEvalErrorString( QObject::tr( "Function make_point requires 2-4 arguments" ) );
    return QVariant();
  }
 
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double y = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double z = values.count() >= 3 ? QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent ) : 0.0;
  double m = values.count() >= 4 ? QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent ) : 0.0;
  switch ( values.count() )
  {
    case 2:
      return QVariant::fromValue( QgsGeometry( new QgsPoint( x, y ) ) );
    case 3:
      return QVariant::fromValue( QgsGeometry( new QgsPoint( QgsWkbTypes::PointZ, x, y, z ) ) );
    case 4:
      return QVariant::fromValue( QgsGeometry( new QgsPoint( QgsWkbTypes::PointZM, x, y, z, m ) ) );
  }
  return QVariant(); //avoid warning
}
 
static QVariant fcnMakePointM( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  double x = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
  double y = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double m = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  return QVariant::fromValue( QgsGeometry( new QgsPoint( QgsWkbTypes::PointM, x, y, 0.0, m ) ) );
}
 
static QVariant fcnMakeLine( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.empty() )
  {
    return QVariant();
  }
 
  QVector<QgsPoint> points;
  points.reserve( values.count() );
 
  auto addPoint = [&points]( const QgsGeometry & geom )
  {
    if ( geom.isNull() )
      return;
 
    if ( geom.type() != QgsWkbTypes::PointGeometry || geom.isMultipart() )
      return;
 
    const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( geom.constGet() );
    if ( !point )
      return;
 
    points << *point;
  };
 
  for ( const QVariant &value : values )
  {
    if ( value.type() == QVariant::List )
    {
      const QVariantList list = value.toList();
      for ( const QVariant &v : list )
      {
        addPoint( QgsExpressionUtils::getGeometry( v, parent ) );
      }
    }
    else
    {
      addPoint( QgsExpressionUtils::getGeometry( value, parent ) );
    }
  }
 
  if ( points.count() < 2 )
    return QVariant();
 
  return QgsGeometry( new QgsLineString( points ) );
}
 
static QVariant fcnMakePolygon( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.count() < 1 )
  {
    parent->setEvalErrorString( QObject::tr( "Function make_polygon requires an argument" ) );
    return QVariant();
  }
 
  QgsGeometry outerRing = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( outerRing.type() == QgsWkbTypes::PolygonGeometry )
    return outerRing; // if it's already a polygon we have nothing to do
 
  if ( outerRing.type() != QgsWkbTypes::LineGeometry || outerRing.isNull() )
    return QVariant();
 
  std::unique_ptr< QgsPolygon > polygon = std::make_unique< QgsPolygon >();
 
  const QgsCurve *exteriorRing = qgsgeometry_cast< QgsCurve * >( outerRing.constGet() );
  if ( !exteriorRing && outerRing.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( outerRing.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        exteriorRing = qgsgeometry_cast< QgsCurve * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( !exteriorRing )
    return QVariant();
 
  polygon->setExteriorRing( exteriorRing->segmentize() );
 
 
  for ( int i = 1; i < values.count(); ++i )
  {
    QgsGeometry ringGeom = QgsExpressionUtils::getGeometry( values.at( i ), parent );
    if ( ringGeom.isNull() )
      continue;
 
    if ( ringGeom.type() != QgsWkbTypes::LineGeometry || ringGeom.isNull() )
      continue;
 
    const QgsCurve *ring = qgsgeometry_cast< QgsCurve * >( ringGeom.constGet() );
    if ( !ring && ringGeom.isMultipart() )
    {
      if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( ringGeom.constGet() ) )
      {
        if ( collection->numGeometries() == 1 )
        {
          ring = qgsgeometry_cast< QgsCurve * >( collection->geometryN( 0 ) );
        }
      }
    }
 
    if ( !ring )
      continue;
 
    polygon->addInteriorRing( ring->segmentize() );
  }
 
  return QVariant::fromValue( QgsGeometry( std::move( polygon ) ) );
}
 
static QVariant fcnMakeTriangle( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  std::unique_ptr<QgsTriangle> tr( new QgsTriangle() );
  std::unique_ptr<QgsLineString> lineString( new QgsLineString() );
  lineString->clear();
 
  for ( const QVariant &value : values )
  {
    QgsGeometry geom = QgsExpressionUtils::getGeometry( value, parent );
    if ( geom.isNull() )
      return QVariant();
 
    if ( geom.type() != QgsWkbTypes::PointGeometry || geom.isMultipart() )
      return QVariant();
 
    const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( geom.constGet() );
    if ( !point && geom.isMultipart() )
    {
      if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() ) )
      {
        if ( collection->numGeometries() == 1 )
        {
          point = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
        }
      }
    }
 
    if ( !point )
      return QVariant();
 
    lineString->addVertex( *point );
  }
 
  tr->setExteriorRing( lineString.release() );
 
  return QVariant::fromValue( QgsGeometry( tr.release() ) );
}
 
static QVariant fcnMakeCircle( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  if ( geom.type() != QgsWkbTypes::PointGeometry || geom.isMultipart() )
    return QVariant();
 
  double radius = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  int segment = QgsExpressionUtils::getNativeIntValue( values.at( 2 ), parent );
 
  if ( segment < 3 )
  {
    parent->setEvalErrorString( QObject::tr( "Segment must be greater than 2" ) );
    return QVariant();
  }
  const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( geom.constGet() );
  if ( !point && geom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        point = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
  if ( !point )
    return QVariant();
 
  QgsCircle circ( *point, radius );
  return QVariant::fromValue( QgsGeometry( circ.toPolygon( static_cast<unsigned int>( segment ) ) ) );
}
 
static QVariant fcnMakeEllipse( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  if ( geom.type() != QgsWkbTypes::PointGeometry || geom.isMultipart() )
    return QVariant();
 
  double majorAxis = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double minorAxis = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  double azimuth = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  int segment = QgsExpressionUtils::getNativeIntValue( values.at( 4 ), parent );
  if ( segment < 3 )
  {
    parent->setEvalErrorString( QObject::tr( "Segment must be greater than 2" ) );
    return QVariant();
  }
  const QgsPoint *point = qgsgeometry_cast< const QgsPoint * >( geom.constGet() );
  if ( !point && geom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        point = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
  if ( !point )
    return QVariant();
 
  QgsEllipse elp( *point, majorAxis,  minorAxis, azimuth );
  return QVariant::fromValue( QgsGeometry( elp.toPolygon( static_cast<unsigned int>( segment ) ) ) );
}
 
static QVariant fcnMakeRegularPolygon( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
 
  QgsGeometry pt1 = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( pt1.isNull() )
    return QVariant();
 
  if ( pt1.type() != QgsWkbTypes::PointGeometry || pt1.isMultipart() )
    return QVariant();
 
  QgsGeometry pt2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  if ( pt2.isNull() )
    return QVariant();
 
  if ( pt2.type() != QgsWkbTypes::PointGeometry || pt2.isMultipart() )
    return QVariant();
 
  unsigned int nbEdges = static_cast<unsigned int>( QgsExpressionUtils::getIntValue( values.at( 2 ), parent ) );
  if ( nbEdges < 3 )
  {
    parent->setEvalErrorString( QObject::tr( "Number of edges/sides must be greater than 2" ) );
    return QVariant();
  }
 
  QgsRegularPolygon::ConstructionOption option = static_cast< QgsRegularPolygon::ConstructionOption >( QgsExpressionUtils::getIntValue( values.at( 3 ), parent ) );
  if ( ( option < QgsRegularPolygon::InscribedCircle ) || ( option > QgsRegularPolygon::CircumscribedCircle ) )
  {
    parent->setEvalErrorString( QObject::tr( "Option can be 0 (inscribed) or 1 (circumscribed)" ) );
    return QVariant();
  }
 
  const QgsPoint *center = qgsgeometry_cast< const QgsPoint * >( pt1.constGet() );
  if ( !center && pt1.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( pt1.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        center = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
  if ( !center )
    return QVariant();
 
  const QgsPoint *corner = qgsgeometry_cast< const QgsPoint * >( pt2.constGet() );
  if ( !corner && pt2.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( pt2.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        corner = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
  if ( !corner )
    return QVariant();
 
  QgsRegularPolygon rp = QgsRegularPolygon( *center, *corner, nbEdges, option );
 
  return QVariant::fromValue( QgsGeometry( rp.toPolygon() ) );
 
}
 
static QVariant fcnMakeSquare( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry pt1 = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( pt1.isNull() )
    return QVariant();
  if ( pt1.type() != QgsWkbTypes::PointGeometry || pt1.isMultipart() )
    return QVariant();
 
  QgsGeometry pt2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  if ( pt2.isNull() )
    return QVariant();
  if ( pt2.type() != QgsWkbTypes::PointGeometry || pt2.isMultipart() )
    return QVariant();
 
  const QgsPoint *point1 = qgsgeometry_cast< const QgsPoint *>( pt1.constGet() );
  const QgsPoint *point2 = qgsgeometry_cast< const QgsPoint *>( pt2.constGet() );
  QgsQuadrilateral square = QgsQuadrilateral::squareFromDiagonal( *point1, *point2 );
 
  return QVariant::fromValue( QgsGeometry( square.toPolygon() ) );
}
 
static QVariant fcnMakeRectangleFrom3Points( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry pt1 = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( pt1.isNull() )
    return QVariant();
  if ( pt1.type() != QgsWkbTypes::PointGeometry || pt1.isMultipart() )
    return QVariant();
 
  QgsGeometry pt2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  if ( pt2.isNull() )
    return QVariant();
  if ( pt2.type() != QgsWkbTypes::PointGeometry || pt2.isMultipart() )
    return QVariant();
 
  QgsGeometry pt3 = QgsExpressionUtils::getGeometry( values.at( 2 ), parent );
  if ( pt3.isNull() )
    return QVariant();
  if ( pt3.type() != QgsWkbTypes::PointGeometry || pt3.isMultipart() )
    return QVariant();
 
  QgsQuadrilateral::ConstructionOption option = static_cast< QgsQuadrilateral::ConstructionOption >( QgsExpressionUtils::getIntValue( values.at( 3 ), parent ) );
  if ( ( option < QgsQuadrilateral::Distance ) || ( option > QgsQuadrilateral::Projected ) )
  {
    parent->setEvalErrorString( QObject::tr( "Option can be 0 (distance) or 1 (projected)" ) );
    return QVariant();
  }
  const QgsPoint *point1 = qgsgeometry_cast< const QgsPoint *>( pt1.constGet() );
  const QgsPoint *point2 = qgsgeometry_cast< const QgsPoint *>( pt2.constGet() );
  const QgsPoint *point3 = qgsgeometry_cast< const QgsPoint *>( pt3.constGet() );
  QgsQuadrilateral rect = QgsQuadrilateral::rectangleFrom3Points( *point1, *point2, *point3, option );
  return QVariant::fromValue( QgsGeometry( rect.toPolygon() ) );
}
 
static QVariant pointAt( const QgsGeometry &geom, int idx, QgsExpression *parent ) // helper function
{
  if ( geom.isNull() )
    return QVariant();
 
  if ( idx < 0 )
  {
    idx += geom.constGet()->nCoordinates();
  }
  if ( idx < 0 || idx >= geom.constGet()->nCoordinates() )
  {
    parent->setEvalErrorString( QObject::tr( "Index is out of range" ) );
    return QVariant();
  }
  return QVariant::fromValue( geom.vertexAt( idx ) );
}
 
// function used for the old $ style
static QVariant fcnOldXat( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, feature )
  const QgsGeometry geom = feature.geometry();
  const int idx = QgsExpressionUtils::getNativeIntValue( values.at( 0 ), parent );
 
  const QVariant v = pointAt( geom, idx, parent );
 
  if ( !v.isNull() )
    return QVariant( v.value<QgsPoint>().x() );
  else
    return QVariant();
}
static QVariant fcnXat( const QVariantList &values, const QgsExpressionContext *f, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
  if ( values.at( 1 ).isNull() && !values.at( 0 ).isNull() ) // the case where the alias x_at function is called like a $ function (x_at(i))
  {
    return fcnOldXat( values, f, parent, node );
  }
  else if ( values.at( 0 ).isNull() && !values.at( 1 ).isNull() ) // same as above with x_at(i:=0) (vertex value is at the second position)
  {
    return fcnOldXat( QVariantList() << values[1], f, parent, node );
  }
 
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
  {
    return QVariant();
  }
 
  const int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
 
  const QVariant v = pointAt( geom, vertexNumber, parent );
  if ( !v.isNull() )
    return QVariant( v.value<QgsPoint>().x() );
  else
    return QVariant();
}
 
// function used for the old $ style
static QVariant fcnOldYat( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, feature )
  const QgsGeometry geom = feature.geometry();
  const int idx = QgsExpressionUtils::getNativeIntValue( values.at( 0 ), parent );
 
  const QVariant v = pointAt( geom, idx, parent );
 
  if ( !v.isNull() )
    return QVariant( v.value<QgsPoint>().y() );
  else
    return QVariant();
}
static QVariant fcnYat( const QVariantList &values, const QgsExpressionContext *f, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
  if ( values.at( 1 ).isNull() && !values.at( 0 ).isNull() ) // the case where the alias y_at function is called like a $ function (y_at(i))
  {
    return fcnOldYat( values, f, parent, node );
  }
  else if ( values.at( 0 ).isNull() && !values.at( 1 ).isNull() ) // same as above with x_at(i:=0) (vertex value is at the second position)
  {
    return fcnOldYat( QVariantList() << values[1], f, parent, node );
  }
 
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
  {
    return QVariant();
  }
 
  const int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
 
  const QVariant v = pointAt( geom, vertexNumber, parent );
  if ( !v.isNull() )
    return QVariant( v.value<QgsPoint>().y() );
  else
    return QVariant();
}
 
static QVariant fcnZat( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
  {
    return QVariant();
  }
 
  const int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
 
  const QVariant v = pointAt( geom, vertexNumber, parent );
  if ( !v.isNull() && v.value<QgsPoint>().is3D() )
    return QVariant( v.value<QgsPoint>().z() );
  else
    return QVariant();
}
 
static QVariant fcnMat( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
  {
    return QVariant();
  }
 
  const int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
 
  const QVariant v = pointAt( geom, vertexNumber, parent );
  if ( !v.isNull() && v.value<QgsPoint>().isMeasure() )
    return QVariant( v.value<QgsPoint>().m() );
  else
    return QVariant();
}
 
 
static QVariant fcnGeometry( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
{
  if ( !context )
    return QVariant();
 
  // prefer geometry from context if it's present, otherwise fallback to context's feature's geometry
  if ( context->hasGeometry() )
    return context->geometry();
  else
  {
    FEAT_FROM_CONTEXT( context, f )
    QgsGeometry geom = f.geometry();
    if ( !geom.isNull() )
      return  QVariant::fromValue( geom );
    else
      return QVariant();
  }
}
 
static QVariant fcnGeomFromWKT( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString wkt = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QgsGeometry geom = QgsGeometry::fromWkt( wkt );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnGeomFromWKB( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QByteArray wkb = QgsExpressionUtils::getBinaryValue( values.at( 0 ), parent );
  if ( wkb.isNull() )
    return QVariant();
 
  QgsGeometry geom;
  geom.fromWkb( wkb );
  return !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
}
 
static QVariant fcnGeomFromGML( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QString gml = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
  QgsOgcUtils::Context ogcContext;
  if ( context )
  {
    QgsWeakMapLayerPointer mapLayerPtr {context->variable( QStringLiteral( "layer" ) ).value<QgsWeakMapLayerPointer>() };
    if ( mapLayerPtr )
    {
      ogcContext.layer = mapLayerPtr.data();
      ogcContext.transformContext = context->variable( QStringLiteral( "_project_transform_context" ) ).value<QgsCoordinateTransformContext>();
    }
  }
  QgsGeometry geom = QgsOgcUtils::geometryFromGML( gml, ogcContext );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnGeomArea( const QVariantList &, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  ENSURE_GEOM_TYPE( f, g, QgsWkbTypes::PolygonGeometry )
  QgsDistanceArea *calc = parent->geomCalculator();
  if ( calc )
  {
    double area = calc->measureArea( f.geometry() );
    area = calc->convertAreaMeasurement( area, parent->areaUnits() );
    return QVariant( area );
  }
  else
  {
    return QVariant( f.geometry().area() );
  }
}
 
static QVariant fcnArea( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.type() != QgsWkbTypes::PolygonGeometry )
    return QVariant();
 
  return QVariant( geom.area() );
}
 
static QVariant fcnGeomLength( const QVariantList &, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  ENSURE_GEOM_TYPE( f, g, QgsWkbTypes::LineGeometry )
  QgsDistanceArea *calc = parent->geomCalculator();
  if ( calc )
  {
    double len = calc->measureLength( f.geometry() );
    len = calc->convertLengthMeasurement( len, parent->distanceUnits() );
    return QVariant( len );
  }
  else
  {
    return QVariant( f.geometry().length() );
  }
}
 
static QVariant fcnGeomPerimeter( const QVariantList &, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  FEAT_FROM_CONTEXT( context, f )
  ENSURE_GEOM_TYPE( f, g, QgsWkbTypes::PolygonGeometry )
  QgsDistanceArea *calc = parent->geomCalculator();
  if ( calc )
  {
    double len = calc->measurePerimeter( f.geometry() );
    len = calc->convertLengthMeasurement( len, parent->distanceUnits() );
    return QVariant( len );
  }
  else
  {
    return f.geometry().isNull() ? QVariant( 0 ) : QVariant( f.geometry().constGet()->perimeter() );
  }
}
 
static QVariant fcnPerimeter( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.type() != QgsWkbTypes::PolygonGeometry )
    return QVariant();
 
  //length for polygons = perimeter
  return QVariant( geom.length() );
}
 
static QVariant fcnGeomNumPoints( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant( geom.isNull() ? 0 : geom.constGet()->nCoordinates() );
}
 
static QVariant fcnGeomNumGeometries( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  return QVariant( geom.constGet()->partCount() );
}
 
static QVariant fcnGeomIsMultipart( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  return QVariant( geom.isMultipart() );
}
 
static QVariant fcnGeomNumInteriorRings( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const QgsCurvePolygon *curvePolygon = qgsgeometry_cast< const QgsCurvePolygon * >( geom.constGet() );
  if ( curvePolygon )
    return QVariant( curvePolygon->numInteriorRings() );
 
  const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() );
  if ( collection )
  {
    //find first CurvePolygon in collection
    for ( int i = 0; i < collection->numGeometries(); ++i )
    {
      curvePolygon = qgsgeometry_cast< const QgsCurvePolygon *>( collection->geometryN( i ) );
      if ( !curvePolygon )
        continue;
 
      return QVariant( curvePolygon->isEmpty() ? 0 : curvePolygon->numInteriorRings() );
    }
  }
 
  return QVariant();
}
 
static QVariant fcnGeomNumRings( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  const QgsCurvePolygon *curvePolygon = qgsgeometry_cast< const QgsCurvePolygon * >( geom.constGet() );
  if ( curvePolygon )
    return QVariant( curvePolygon->ringCount() );
 
  bool foundPoly = false;
  int ringCount = 0;
  const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( geom.constGet() );
  if ( collection )
  {
    //find CurvePolygons in collection
    for ( int i = 0; i < collection->numGeometries(); ++i )
    {
      curvePolygon = qgsgeometry_cast< QgsCurvePolygon *>( collection->geometryN( i ) );
      if ( !curvePolygon )
        continue;
 
      foundPoly = true;
      ringCount += curvePolygon->ringCount();
    }
  }
 
  if ( !foundPoly )
    return QVariant();
 
  return QVariant( ringCount );
}
 
static QVariant fcnBounds( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry geomBounds = QgsGeometry::fromRect( geom.boundingBox() );
  QVariant result = !geomBounds.isNull() ? QVariant::fromValue( geomBounds ) : QVariant();
  return result;
}
 
static QVariant fcnBoundsWidth( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( geom.boundingBox().width() );
}
 
static QVariant fcnBoundsHeight( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( geom.boundingBox().height() );
}
 
static QVariant fcnGeometryType( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  return QgsWkbTypes::geometryDisplayString( geom.type() );
}
 
static QVariant fcnXMin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( geom.boundingBox().xMinimum() );
}
 
static QVariant fcnXMax( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( geom.boundingBox().xMaximum() );
}
 
static QVariant fcnYMin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( geom.boundingBox().yMinimum() );
}
 
static QVariant fcnYMax( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( geom.boundingBox().yMaximum() );
}
 
static QVariant fcnZMax( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() || geom.isEmpty( ) )
    return QVariant();
 
  if ( !geom.constGet()->is3D() )
    return QVariant();
 
  double max = std::numeric_limits< double >::lowest();
 
  for ( auto it = geom.vertices_begin(); it != geom.vertices_end(); ++it )
  {
    double z = ( *it ).z();
 
    if ( max < z )
      max = z;
  }
 
  if ( max == std::numeric_limits< double >::lowest() )
    return QVariant( QVariant::Double );
 
  return QVariant( max );
}
 
static QVariant fcnZMin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() || geom.isEmpty() )
    return QVariant();
 
  if ( !geom.constGet()->is3D() )
    return QVariant();
 
  double min = std::numeric_limits< double >::max();
 
  for ( auto it = geom.vertices_begin(); it != geom.vertices_end(); ++it )
  {
    double z = ( *it ).z();
 
    if ( z < min )
      min = z;
  }
 
  if ( min == std::numeric_limits< double >::max() )
    return QVariant( QVariant::Double );
 
  return QVariant( min );
}
 
static QVariant fcnMMin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() || geom.isEmpty() )
    return QVariant();
 
  if ( !geom.constGet()->isMeasure() )
    return QVariant();
 
  double min = std::numeric_limits< double >::max();
 
  for ( auto it = geom.vertices_begin(); it != geom.vertices_end(); ++it )
  {
    double m = ( *it ).m();
 
    if ( m < min )
      min = m;
  }
 
  if ( min == std::numeric_limits< double >::max() )
    return QVariant( QVariant::Double );
 
  return QVariant( min );
}
 
static QVariant fcnMMax( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() || geom.isEmpty() )
    return QVariant();
 
  if ( !geom.constGet()->isMeasure() )
    return QVariant();
 
  double max = std::numeric_limits< double >::lowest();
 
  for ( auto it = geom.vertices_begin(); it != geom.vertices_end(); ++it )
  {
    double m = ( *it ).m();
 
    if ( max < m )
      max = m;
  }
 
  if ( max == std::numeric_limits< double >::lowest() )
    return QVariant( QVariant::Double );
 
  return QVariant( max );
}
 
static QVariant fcnSinuosity( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsCurve *curve = qgsgeometry_cast< const QgsCurve * >( geom.constGet() );
  if ( !curve )
  {
    parent->setEvalErrorString( QObject::tr( "Function `sinuosity` requires a line geometry." ) );
    return QVariant();
  }
 
  return QVariant( curve->sinuosity() );
}
 
static QVariant fcnStraightDistance2d( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsCurve *curve = geom.constGet() ? qgsgeometry_cast< const QgsCurve * >( geom.constGet()->simplifiedTypeRef() ) : nullptr;
  if ( !curve )
  {
    parent->setEvalErrorString( QObject::tr( "Function `straight_distance_2d` requires a line geometry or a multi line geometry with a single part." ) );
    return QVariant();
  }
 
  return QVariant( curve->straightDistance2d() );
}
 
static QVariant fcnRoundness( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsCurvePolygon *poly = geom.constGet() ? qgsgeometry_cast< const QgsCurvePolygon * >( geom.constGet()->simplifiedTypeRef() ) : nullptr;
 
  if ( !poly )
  {
    parent->setEvalErrorString( QObject::tr( "Function `roundness` requires a polygon geometry or a multi polygon geometry with a single part." ) );
    return QVariant();
  }
 
  return QVariant( poly->roundness() );
}
 
 
 
static QVariant fcnFlipCoordinates( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( geom.isNull() )
    return QVariant();
 
  std::unique_ptr< QgsAbstractGeometry > flipped( geom.constGet()->clone() );
  flipped->swapXy();
  return QVariant::fromValue( QgsGeometry( std::move( flipped ) ) );
}
 
static QVariant fcnIsClosed( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.isNull() )
    return QVariant();
 
  const QgsCurve *curve = qgsgeometry_cast< const QgsCurve * >( fGeom.constGet() );
  if ( !curve && fGeom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        curve = qgsgeometry_cast< const QgsCurve * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( !curve )
    return QVariant();
 
  return QVariant::fromValue( curve->isClosed() );
}
 
static QVariant fcnCloseLine( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( geom.isNull() )
    return QVariant();
 
  QVariant result;
  if ( !geom.isMultipart() )
  {
    const QgsLineString *line = qgsgeometry_cast<const QgsLineString * >( geom.constGet() );
 
    if ( !line )
      return QVariant();
 
    std::unique_ptr< QgsLineString > closedLine( line->clone() );
    closedLine->close();
 
    result = QVariant::fromValue( QgsGeometry( std::move( closedLine ) ) );
  }
  else
  {
    const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection *>( geom.constGet() );
 
    std::unique_ptr< QgsGeometryCollection > closed( collection->createEmptyWithSameType() );
 
    for ( int i = 0; i < collection->numGeometries(); ++i )
    {
      if ( const QgsLineString *line = qgsgeometry_cast<const QgsLineString * >( collection->geometryN( i ) ) )
      {
        std::unique_ptr< QgsLineString > closedLine( line->clone() );
        closedLine->close();
 
        closed->addGeometry( closedLine.release() );
      }
    }
    result = QVariant::fromValue( QgsGeometry( std::move( closed ) ) );
  }
 
  return result;
}
 
static QVariant fcnIsEmpty( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.isNull() )
    return QVariant();
 
  return QVariant::fromValue( fGeom.isEmpty() );
}
 
static QVariant fcnIsEmptyOrNull( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( QgsVariantUtils::isNull( values.at( 0 ) ) )
    return QVariant::fromValue( true );
 
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return QVariant::fromValue( fGeom.isNull() || fGeom.isEmpty() );
}
 
static QVariant fcnRelate( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.length() < 2 || values.length() > 3 )
    return QVariant();
 
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
 
  if ( fGeom.isNull() || sGeom.isNull() )
    return QVariant();
 
  std::unique_ptr<QgsGeometryEngine> engine( QgsGeometry::createGeometryEngine( fGeom.constGet() ) );
 
  if ( values.length() == 2 )
  {
    //two geometry arguments, return relation
    QString result = engine->relate( sGeom.constGet() );
    return QVariant::fromValue( result );
  }
  else
  {
    //three arguments, test pattern
    QString pattern = QgsExpressionUtils::getStringValue( values.at( 2 ), parent );
    bool result = engine->relatePattern( sGeom.constGet(), pattern );
    return QVariant::fromValue( result );
  }
}
 
static QVariant fcnBbox( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.intersects( sGeom.boundingBox() ) ? TVL_True : TVL_False;
}
static QVariant fcnDisjoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.disjoint( sGeom ) ? TVL_True : TVL_False;
}
static QVariant fcnIntersects( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.intersects( sGeom ) ? TVL_True : TVL_False;
}
static QVariant fcnTouches( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.touches( sGeom ) ? TVL_True : TVL_False;
}
static QVariant fcnCrosses( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.crosses( sGeom ) ? TVL_True : TVL_False;
}
static QVariant fcnContains( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.contains( sGeom ) ? TVL_True : TVL_False;
}
static QVariant fcnOverlaps( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.overlaps( sGeom ) ? TVL_True : TVL_False;
}
static QVariant fcnWithin( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return fGeom.within( sGeom ) ? TVL_True : TVL_False;
}
 
static QVariant fcnBuffer( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const double dist = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const int seg = QgsExpressionUtils::getNativeIntValue( values.at( 2 ), parent );
  const QString endCapString = QgsExpressionUtils::getStringValue( values.at( 3 ), parent ).trimmed();
  const QString joinString = QgsExpressionUtils::getStringValue( values.at( 4 ), parent ).trimmed();
  const double miterLimit = QgsExpressionUtils::getDoubleValue( values.at( 5 ), parent );
 
  Qgis::EndCapStyle capStyle = Qgis::EndCapStyle::Round;
  if ( endCapString.compare( QLatin1String( "flat" ), Qt::CaseInsensitive ) == 0 )
    capStyle = Qgis::EndCapStyle::Flat;
  else if ( endCapString.compare( QLatin1String( "square" ), Qt::CaseInsensitive ) == 0 )
    capStyle = Qgis::EndCapStyle::Square;
 
  Qgis::JoinStyle joinStyle = Qgis::JoinStyle::Round;
  if ( joinString.compare( QLatin1String( "miter" ), Qt::CaseInsensitive ) == 0 )
    joinStyle = Qgis::JoinStyle::Miter;
  else if ( joinString.compare( QLatin1String( "bevel" ), Qt::CaseInsensitive ) == 0 )
    joinStyle = Qgis::JoinStyle::Bevel;
 
  QgsGeometry geom = fGeom.buffer( dist, seg, capStyle, joinStyle, miterLimit );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnForceRHR( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsGeometry reoriented = fGeom.forceRHR();
  return !reoriented.isNull() ? QVariant::fromValue( reoriented ) : QVariant();
}
 
static QVariant fcnForcePolygonCW( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsGeometry reoriented = fGeom.forcePolygonClockwise();
  return !reoriented.isNull() ? QVariant::fromValue( reoriented ) : QVariant();
}
 
static QVariant fcnForcePolygonCCW( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsGeometry reoriented = fGeom.forcePolygonCounterClockwise();
  return !reoriented.isNull() ? QVariant::fromValue( reoriented ) : QVariant();
}
 
static QVariant fcnWedgeBuffer( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const QgsPoint *pt = qgsgeometry_cast<const QgsPoint *>( fGeom.constGet() );
  if ( !pt && fGeom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        pt = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( !pt )
  {
    parent->setEvalErrorString( QObject::tr( "Function `wedge_buffer` requires a point value for the center." ) );
    return QVariant();
  }
 
  double azimuth = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double width = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  double outerRadius = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
  double innerRadius = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
 
  QgsGeometry geom = QgsGeometry::createWedgeBuffer( *pt, azimuth, width, outerRadius, innerRadius );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnTaperedBuffer( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.type() != QgsWkbTypes::LineGeometry )
  {
    parent->setEvalErrorString( QObject::tr( "Function `tapered_buffer` requires a line geometry." ) );
    return QVariant();
  }
 
  double startWidth = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double endWidth = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  int segments = static_cast< int >( QgsExpressionUtils::getIntValue( values.at( 3 ), parent ) );
 
  QgsGeometry geom = fGeom.taperedBuffer( startWidth, endWidth, segments );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnBufferByM( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.type() != QgsWkbTypes::LineGeometry )
  {
    parent->setEvalErrorString( QObject::tr( "Function `buffer_by_m` requires a line geometry." ) );
    return QVariant();
  }
 
  int segments = static_cast< int >( QgsExpressionUtils::getIntValue( values.at( 1 ), parent ) );
 
  QgsGeometry geom = fGeom.variableWidthBufferByM( segments );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnOffsetCurve( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double dist = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  int segments = QgsExpressionUtils::getNativeIntValue( values.at( 2 ), parent );
  const int joinInt = QgsExpressionUtils::getIntValue( values.at( 3 ), parent );
  if ( joinInt < 1 || joinInt > 3 )
    return QVariant();
  const Qgis::JoinStyle join = static_cast< Qgis::JoinStyle >( joinInt );
 
  double miterLimit = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
 
  QgsGeometry geom = fGeom.offsetCurve( dist, segments, join, miterLimit );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnSingleSidedBuffer( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double dist = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  int segments = QgsExpressionUtils::getNativeIntValue( values.at( 2 ), parent );
 
  const int joinInt = QgsExpressionUtils::getIntValue( values.at( 3 ), parent );
  if ( joinInt < 1 || joinInt > 3 )
    return QVariant();
  const Qgis::JoinStyle join = static_cast< Qgis::JoinStyle >( joinInt );
 
  double miterLimit = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
 
  QgsGeometry geom = fGeom.singleSidedBuffer( dist, segments, Qgis::BufferSide::Left, join, miterLimit );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnExtend( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double distStart = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double distEnd = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  QgsGeometry geom = fGeom.extendLine( distStart, distEnd );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnTranslate( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double dx = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double dy = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  fGeom.translate( dx, dy );
  return QVariant::fromValue( fGeom );
}
 
static QVariant fcnRotate( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const double rotation = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const QgsGeometry center = values.at( 2 ).isValid() ? QgsExpressionUtils::getGeometry( values.at( 2 ), parent )
                             : QgsGeometry();
  const bool perPart = values.value( 3 ).toBool();
 
  if ( center.isNull() && perPart && fGeom.isMultipart() )
  {
    // no explicit center, rotating per part
    // (note that we only do this branch for multipart geometries -- for singlepart geometries
    // the result is equivalent to setting perPart as false anyway)
    std::unique_ptr< QgsGeometryCollection > collection( qgsgeometry_cast< QgsGeometryCollection * >( fGeom.constGet()->clone() ) );
    for ( auto it = collection->parts_begin(); it != collection->parts_end(); ++it )
    {
      const QgsPointXY partCenter = ( *it )->boundingBox().center();
      QTransform t = QTransform::fromTranslate( partCenter.x(), partCenter.y() );
      t.rotate( -rotation );
      t.translate( -partCenter.x(), -partCenter.y() );
      ( *it )->transform( t );
    }
    return QVariant::fromValue( QgsGeometry( std::move( collection ) ) );
  }
  else
  {
    QgsPointXY pt;
    if ( center.isEmpty() )
    {
      // if center wasn't specified, use bounding box centroid
      pt = fGeom.boundingBox().center();
    }
    else if ( QgsWkbTypes::flatType( center.constGet()->simplifiedTypeRef()->wkbType() ) != QgsWkbTypes::Point )
    {
      parent->setEvalErrorString( QObject::tr( "Function 'rotate' requires a point value for the center" ) );
      return QVariant();
    }
    else
    {
      pt = QgsPointXY( *qgsgeometry_cast< const QgsPoint * >( center.constGet()->simplifiedTypeRef() ) );
    }
 
    fGeom.rotate( rotation, pt );
    return QVariant::fromValue( fGeom );
  }
}
 
static QVariant fcnScale( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  const double xScale = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double yScale = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  const QgsGeometry center = values.at( 3 ).isValid() ? QgsExpressionUtils::getGeometry( values.at( 3 ), parent )
                             : QgsGeometry();
 
  QgsPointXY pt;
  if ( center.isNull() )
  {
    // if center wasn't specified, use bounding box centroid
    pt = fGeom.boundingBox().center();
  }
  else if ( QgsWkbTypes::flatType( center.constGet()->simplifiedTypeRef()->wkbType() ) != QgsWkbTypes::Point )
  {
    parent->setEvalErrorString( QObject::tr( "Function 'scale' requires a point value for the center" ) );
    return QVariant();
  }
  else
  {
    pt = center.asPoint();
  }
 
  QTransform t = QTransform::fromTranslate( pt.x(), pt.y() );
  t.scale( xScale, yScale );
  t.translate( -pt.x(), -pt.y() );
  fGeom.transform( t );
  return QVariant::fromValue( fGeom );
}
 
static QVariant fcnAffineTransform( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.isNull() )
  {
    return QVariant();
  }
 
  const double deltaX = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  const double deltaY = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  const double rotationZ = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
 
  const double scaleX = QgsExpressionUtils::getDoubleValue( values.at( 4 ), parent );
  const double scaleY = QgsExpressionUtils::getDoubleValue( values.at( 5 ), parent );
 
  const double deltaZ = QgsExpressionUtils::getDoubleValue( values.at( 6 ), parent );
  const double deltaM = QgsExpressionUtils::getDoubleValue( values.at( 7 ), parent );
  const double scaleZ = QgsExpressionUtils::getDoubleValue( values.at( 8 ), parent );
  const double scaleM = QgsExpressionUtils::getDoubleValue( values.at( 9 ), parent );
 
  if ( deltaZ != 0.0 && !fGeom.constGet()->is3D() )
  {
    fGeom.get()->addZValue( 0 );
  }
  if ( deltaM != 0.0 && !fGeom.constGet()->isMeasure() )
  {
    fGeom.get()->addMValue( 0 );
  }
 
  QTransform transform;
  transform.translate( deltaX, deltaY );
  transform.rotate( rotationZ );
  transform.scale( scaleX, scaleY );
  fGeom.transform( transform, deltaZ, scaleZ, deltaM, scaleM );
 
  return QVariant::fromValue( fGeom );
}
 
 
static QVariant fcnCentroid( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry geom = fGeom.centroid();
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
static QVariant fcnPointOnSurface( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry geom = fGeom.pointOnSurface();
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnPoleOfInaccessibility( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double tolerance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  QgsGeometry geom = fGeom.poleOfInaccessibility( tolerance );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnConvexHull( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry geom = fGeom.convexHull();
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
#if GEOS_VERSION_MAJOR>3 || ( GEOS_VERSION_MAJOR == 3 && GEOS_VERSION_MINOR>=11 )
static QVariant fcnConcaveHull( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  try
  {
    QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
    const double targetPercent = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
    const bool allowHoles = values.value( 2 ).toBool();
    QgsGeometry geom = fGeom.concaveHull( targetPercent, allowHoles );
    QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
    return result;
  }
  catch ( QgsCsException &cse )
  {
    QgsMessageLog::logMessage( QObject::tr( "Error caught in concave_hull() function: %1" ).arg( cse.what() ) );
    return QVariant();
  }
}
#endif
 
static QVariant fcnMinimalCircle( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  int segments = 36;
  if ( values.length() == 2 )
    segments = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  if ( segments < 0 )
  {
    parent->setEvalErrorString( QObject::tr( "Parameter can not be negative." ) );
    return QVariant();
  }
 
  QgsGeometry geom = fGeom.minimalEnclosingCircle( static_cast<unsigned int>( segments ) );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnOrientedBBox( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry geom = fGeom.orientedMinimumBoundingBox( );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnMainAngle( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  const QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  // we use the angle of the oriented minimum bounding box to calculate the polygon main angle.
  // While ArcGIS uses a different approach ("the angle of longest collection of segments that have similar orientation"), this
  // yields similar results to OMBB approach under the same constraints ("this tool is meant for primarily orthogonal polygons rather than organically shaped ones.")
 
  double area, angle, width, height;
  const QgsGeometry geom = fGeom.orientedMinimumBoundingBox( area, angle, width, height );
 
  if ( geom.isNull() )
  {
    parent->setEvalErrorString( QObject::tr( "Error calculating polygon main angle: %1" ).arg( geom.lastError() ) );
    return QVariant();
  }
  return angle;
}
 
static QVariant fcnDifference( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  QgsGeometry geom = fGeom.difference( sGeom );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnReverse( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.isNull() )
    return QVariant();
 
  QVariant result;
  if ( !fGeom.isMultipart() )
  {
    const QgsCurve *curve = qgsgeometry_cast<const QgsCurve * >( fGeom.constGet() );
    if ( !curve )
      return QVariant();
 
    QgsCurve *reversed = curve->reversed();
    result = reversed ? QVariant::fromValue( QgsGeometry( reversed ) ) : QVariant();
  }
  else
  {
    const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection *>( fGeom.constGet() );
    std::unique_ptr< QgsGeometryCollection > reversed( collection->createEmptyWithSameType() );
    for ( int i = 0; i < collection->numGeometries(); ++i )
    {
      if ( const QgsCurve *curve = qgsgeometry_cast<const QgsCurve * >( collection->geometryN( i ) ) )
      {
        reversed->addGeometry( curve->reversed() );
      }
      else
      {
        reversed->addGeometry( collection->geometryN( i )->clone() );
      }
    }
    result = reversed ? QVariant::fromValue( QgsGeometry( std::move( reversed ) ) ) : QVariant();
  }
  return result;
}
 
static QVariant fcnExteriorRing( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( fGeom.isNull() )
    return QVariant();
 
  const QgsCurvePolygon *curvePolygon = qgsgeometry_cast< const QgsCurvePolygon * >( fGeom.constGet() );
  if ( !curvePolygon && fGeom.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        curvePolygon = qgsgeometry_cast< const QgsCurvePolygon * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( !curvePolygon || !curvePolygon->exteriorRing() )
    return QVariant();
 
  QgsCurve *exterior = static_cast< QgsCurve * >( curvePolygon->exteriorRing()->clone() );
  QVariant result = exterior ? QVariant::fromValue( QgsGeometry( exterior ) ) : QVariant();
  return result;
}
 
static QVariant fcnDistance( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  return QVariant( fGeom.distance( sGeom ) );
}
 
static QVariant fcnHausdorffDistance( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry g1 = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry g2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
 
  double res = -1;
  if ( values.length() == 3 && values.at( 2 ).isValid() )
  {
    double densify = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
    densify = std::clamp( densify, 0.0, 1.0 );
    res = g1.hausdorffDistanceDensify( g2, densify );
  }
  else
  {
    res = g1.hausdorffDistance( g2 );
  }
 
  return res > -1 ? QVariant( res ) : QVariant();
}
 
static QVariant fcnIntersection( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  QgsGeometry geom = fGeom.intersection( sGeom );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
static QVariant fcnSymDifference( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  QgsGeometry geom = fGeom.symDifference( sGeom );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
static QVariant fcnCombine( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry sGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
  QgsGeometry geom = fGeom.combine( sGeom );
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnGeomToWKT( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.length() < 1 || values.length() > 2 )
    return QVariant();
 
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  int prec = 8;
  if ( values.length() == 2 )
    prec = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  QString wkt = fGeom.asWkt( prec );
  return QVariant( wkt );
}
 
static QVariant fcnGeomToWKB( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  return fGeom.isNull() ? QVariant() : QVariant( fGeom.asWkb() );
}
 
static QVariant fcnAzimuth( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.length() != 2 )
  {
    parent->setEvalErrorString( QObject::tr( "Function `azimuth` requires exactly two parameters. %n given.", nullptr, values.length() ) );
    return QVariant();
  }
 
  QgsGeometry fGeom1 = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry fGeom2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
 
  const QgsPoint *pt1 = qgsgeometry_cast<const QgsPoint *>( fGeom1.constGet() );
  if ( !pt1 && fGeom1.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom1.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        pt1 = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  const QgsPoint *pt2 = qgsgeometry_cast<const QgsPoint *>( fGeom2.constGet() );
  if ( !pt2 && fGeom2.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom2.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        pt2 = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( !pt1 || !pt2 )
  {
    parent->setEvalErrorString( QObject::tr( "Function `azimuth` requires two points as arguments." ) );
    return QVariant();
  }
 
  // Code from PostGIS
  if ( qgsDoubleNear( pt1->x(), pt2->x() ) )
  {
    if ( pt1->y() < pt2->y() )
      return 0.0;
    else if ( pt1->y() > pt2->y() )
      return M_PI;
    else
      return 0;
  }
 
  if ( qgsDoubleNear( pt1->y(), pt2->y() ) )
  {
    if ( pt1->x() < pt2->x() )
      return M_PI_2;
    else if ( pt1->x() > pt2->x() )
      return M_PI + ( M_PI_2 );
    else
      return 0;
  }
 
  if ( pt1->x() < pt2->x() )
  {
    if ( pt1->y() < pt2->y() )
    {
      return std::atan( std::fabs( pt1->x() - pt2->x() ) / std::fabs( pt1->y() - pt2->y() ) );
    }
    else /* ( pt1->y() > pt2->y() )  - equality case handled above */
    {
      return std::atan( std::fabs( pt1->y() - pt2->y() ) / std::fabs( pt1->x() - pt2->x() ) )
             + ( M_PI_2 );
    }
  }
 
  else /* ( pt1->x() > pt2->x() ) - equality case handled above */
  {
    if ( pt1->y() > pt2->y() )
    {
      return std::atan( std::fabs( pt1->x() - pt2->x() ) / std::fabs( pt1->y() - pt2->y() ) )
             + M_PI;
    }
    else /* ( pt1->y() < pt2->y() )  - equality case handled above */
    {
      return std::atan( std::fabs( pt1->y() - pt2->y() ) / std::fabs( pt1->x() - pt2->x() ) )
             + ( M_PI + ( M_PI_2 ) );
    }
  }
}
 
static QVariant fcnProject( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( ! geom.constGet() || QgsWkbTypes::flatType( geom.constGet()->simplifiedTypeRef( )->wkbType() ) != QgsWkbTypes::Type::Point )
  {
    parent->setEvalErrorString( QStringLiteral( "'project' requires a point geometry" ) );
    return QVariant();
  }
 
  double distance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double azimuth = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
  double inclination = QgsExpressionUtils::getDoubleValue( values.at( 3 ), parent );
 
  const QgsPoint *p = static_cast<const QgsPoint *>( geom.constGet()->simplifiedTypeRef( ) );
  QgsPoint newPoint = p->project( distance,  180.0 * azimuth / M_PI, 180.0 * inclination / M_PI );
 
  return QVariant::fromValue( QgsGeometry( new QgsPoint( newPoint ) ) );
}
 
static QVariant fcnInclination( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fGeom1 = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry fGeom2 = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
 
  const QgsPoint *pt1 = qgsgeometry_cast<const QgsPoint *>( fGeom1.constGet() );
  if ( !pt1 && fGeom1.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom1.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        pt1 = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
  const QgsPoint *pt2 = qgsgeometry_cast<const QgsPoint *>( fGeom2.constGet() );
  if ( !pt2 && fGeom2.isMultipart() )
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( fGeom2.constGet() ) )
    {
      if ( collection->numGeometries() == 1 )
      {
        pt2 = qgsgeometry_cast< const QgsPoint * >( collection->geometryN( 0 ) );
      }
    }
  }
 
  if ( ( fGeom1.type() != QgsWkbTypes::PointGeometry ) || ( fGeom2.type() != QgsWkbTypes::PointGeometry ) ||
       !pt1 || !pt2 )
  {
    parent->setEvalErrorString( QStringLiteral( "Function 'inclination' requires two points as arguments." ) );
    return QVariant();
  }
 
  return pt1->inclination( *pt2 );
 
}
 
static QVariant fcnExtrude( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.length() != 3 )
    return QVariant();
 
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double x = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double y = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  QgsGeometry geom = fGeom.extrude( x, y );
 
  QVariant result = geom.constGet() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnOrderParts( const QVariantList &values, const QgsExpressionContext *ctx, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( values.length() < 2 )
    return QVariant();
 
  QgsGeometry fGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
 
  if ( !fGeom.isMultipart() )
    return values.at( 0 );
 
  QString expString = QgsExpressionUtils::getStringValue( values.at( 1 ), parent );
  QVariant cachedExpression;
  if ( ctx )
    cachedExpression = ctx->cachedValue( expString );
  QgsExpression expression;
 
  if ( cachedExpression.isValid() )
  {
    expression = cachedExpression.value<QgsExpression>();
  }
  else
    expression = QgsExpression( expString );
 
  bool asc = values.value( 2 ).toBool();
 
  QgsExpressionContext *unconstedContext = nullptr;
  QgsFeature f;
  if ( ctx )
  {
    // ExpressionSorter wants a modifiable expression context, but it will return it in the same shape after
    // so no reason to worry
    unconstedContext = const_cast<QgsExpressionContext *>( ctx );
    f = ctx->feature();
  }
  else
  {
    // If there's no context provided, create a fake one
    unconstedContext = new QgsExpressionContext();
  }
 
  const QgsGeometryCollection *collection = qgsgeometry_cast<const QgsGeometryCollection *>( fGeom.constGet() );
  Q_ASSERT( collection ); // Should have failed the multipart check above
 
  QgsFeatureRequest::OrderBy orderBy;
  orderBy.append( QgsFeatureRequest::OrderByClause( expression, asc ) );
  QgsExpressionSorter sorter( orderBy );
 
  QList<QgsFeature> partFeatures;
  partFeatures.reserve( collection->partCount() );
  for ( int i = 0; i < collection->partCount(); ++i )
  {
    f.setGeometry( QgsGeometry( collection->geometryN( i )->clone() ) );
    partFeatures << f;
  }
 
  sorter.sortFeatures( partFeatures, unconstedContext );
 
  QgsGeometryCollection *orderedGeom = qgsgeometry_cast<QgsGeometryCollection *>( fGeom.constGet()->clone() );
 
  Q_ASSERT( orderedGeom );
 
  while ( orderedGeom->partCount() )
    orderedGeom->removeGeometry( 0 );
 
  for ( const QgsFeature &feature : std::as_const( partFeatures ) )
  {
    orderedGeom->addGeometry( feature.geometry().constGet()->clone() );
  }
 
  QVariant result = QVariant::fromValue( QgsGeometry( orderedGeom ) );
 
  if ( !ctx )
    delete unconstedContext;
 
  return result;
}
 
static QVariant fcnClosestPoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fromGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry toGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
 
  QgsGeometry geom = fromGeom.nearestPoint( toGeom );
 
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnShortestLine( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry fromGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  QgsGeometry toGeom = QgsExpressionUtils::getGeometry( values.at( 1 ), parent );
 
  QgsGeometry geom = fromGeom.shortestLine( toGeom );
 
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnLineInterpolatePoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry lineGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double distance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
 
  QgsGeometry geom = lineGeom.interpolate( distance );
 
  QVariant result = !geom.isNull() ? QVariant::fromValue( geom ) : QVariant();
  return result;
}
 
static QVariant fcnLineSubset( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry lineGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  if ( lineGeom.type() != QgsWkbTypes::LineGeometry )
  {
    parent->setEvalErrorString( QObject::tr( "line_substring requires a curve geometry input" ) );
    return QVariant();
  }
 
  const QgsCurve *curve = nullptr;
  if ( !lineGeom.isMultipart() )
    curve = qgsgeometry_cast< const QgsCurve * >( lineGeom.constGet() );
  else
  {
    if ( const QgsGeometryCollection *collection = qgsgeometry_cast< const QgsGeometryCollection * >( lineGeom.constGet() ) )
    {
      if ( collection->numGeometries() > 0 )
      {
        curve = qgsgeometry_cast< const QgsCurve * >( collection->geometryN( 0 ) );
      }
    }
  }
  if ( !curve )
    return QVariant();
 
  double startDistance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
  double endDistance = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );
 
  std::unique_ptr< QgsCurve > substring( curve->curveSubstring( startDistance, endDistance ) );
  QgsGeometry result( std::move( substring ) );
  return !result.isNull() ? QVariant::fromValue( result ) : QVariant();
}
 
static QVariant fcnLineInterpolateAngle( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry lineGeom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  double distance = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
 
  return lineGeom.interpolateAngle( distance ) * 180.0 / M_PI;
}
 
static QVariant fcnAngleAtVertex( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  int vertex = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  if ( vertex < 0 )
  {
    //negative idx
    int count = geom.constGet()->nCoordinates();
    vertex = count + vertex;
  }
 
  return geom.angleAtVertex( vertex ) * 180.0 / M_PI;
}
 
static QVariant fcnDistanceToVertex( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
  int vertex = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
  if ( vertex < 0 )
  {
    //negative idx
    int count = geom.constGet()->nCoordinates();
    vertex = count + vertex;
  }
 
  return geom.distanceToVertex( vertex );
}
 
static QVariant fcnLineLocatePoint( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent,