qgsvectorlayertemporalproperties.cpp

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/***************************************************************************
                         qgsvectorlayertemporalproperties.cpp
                         ---------------
    begin                : May 2020
    copyright            : (C) 2020 by Nyall Dawson
    email                : nyall dot dawson at gmail dot com
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   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 "qgsvectorlayertemporalproperties.h"
#include "qgsvectordataprovidertemporalcapabilities.h"
#include "qgsexpression.h"
#include "qgsvectorlayer.h"
#include "qgsfields.h"
#include "qgsexpressioncontextutils.h"
 
QgsVectorLayerTemporalProperties::QgsVectorLayerTemporalProperties( QObject *parent, bool enabled )
  :  QgsMapLayerTemporalProperties( parent, enabled )
{
}
 
bool QgsVectorLayerTemporalProperties::isVisibleInTemporalRange( const QgsDateTimeRange &range ) const
{
  if ( !isActive() )
    return true;
 
  switch ( mMode )
  {
    case ModeFixedTemporalRange:
      return range.isInfinite() || mFixedRange.isInfinite() || mFixedRange.overlaps( range );
 
    case ModeFeatureDateTimeInstantFromField:
    case ModeFeatureDateTimeStartAndEndFromFields:
    case ModeRedrawLayerOnly:
    case ModeFeatureDateTimeStartAndDurationFromFields:
    case ModeFeatureDateTimeStartAndEndFromExpressions:
      return true;
  }
  return true;
}
 
QgsDateTimeRange QgsVectorLayerTemporalProperties::calculateTemporalExtent( QgsMapLayer *layer ) const
{
  QgsVectorLayer *vectorLayer = qobject_cast<QgsVectorLayer *>( layer );
  if ( !layer )
    return QgsDateTimeRange();
 
  switch ( mMode )
  {
    case QgsVectorLayerTemporalProperties::ModeFixedTemporalRange:
      return mFixedRange;
 
    case QgsVectorLayerTemporalProperties::ModeFeatureDateTimeInstantFromField:
    {
      const int fieldIndex = vectorLayer->fields().lookupField( mStartFieldName );
      if ( fieldIndex >= 0 )
      {
        const QDateTime min = vectorLayer->minimumValue( fieldIndex ).toDateTime();
        const QDateTime maxStartTime = vectorLayer->maximumValue( fieldIndex ).toDateTime();
        const QgsInterval eventDuration = QgsInterval( mFixedDuration, mDurationUnit );
        return QgsDateTimeRange( min, maxStartTime + eventDuration );
      }
      break;
    }
 
    case QgsVectorLayerTemporalProperties::ModeFeatureDateTimeStartAndDurationFromFields:
    {
      const int fieldIndex = vectorLayer->fields().lookupField( mStartFieldName );
      const int durationFieldIndex = vectorLayer->fields().lookupField( mDurationFieldName );
      if ( fieldIndex >= 0 && durationFieldIndex >= 0 )
      {
        const QDateTime minTime = vectorLayer->minimumValue( fieldIndex ).toDateTime();
        // no choice here but to loop through all features to calculate max time :(
 
        QgsFeature f;
        QgsFeatureIterator it = vectorLayer->getFeatures( QgsFeatureRequest().setFlags( QgsFeatureRequest::NoGeometry ).setSubsetOfAttributes( QgsAttributeList() << durationFieldIndex << fieldIndex ) );
        QDateTime maxTime;
        while ( it.nextFeature( f ) )
        {
          const QDateTime start = f.attribute( fieldIndex ).toDateTime();
          if ( start.isValid() )
          {
            const QVariant durationValue = f.attribute( durationFieldIndex );
            if ( durationValue.isValid() )
            {
              const double duration = durationValue.toDouble();
              const QDateTime end = start.addMSecs( QgsInterval( duration, mDurationUnit ).seconds() * 1000.0 );
              if ( end.isValid() )
                maxTime = maxTime.isValid() ? std::max( maxTime, end ) : end;
            }
          }
        }
        return QgsDateTimeRange( minTime, maxTime );
      }
      break;
    }
 
    case QgsVectorLayerTemporalProperties::ModeFeatureDateTimeStartAndEndFromFields:
    {
      const int startFieldIndex = vectorLayer->fields().lookupField( mStartFieldName );
      const int endFieldIndex = vectorLayer->fields().lookupField( mEndFieldName );
      if ( startFieldIndex >= 0 && endFieldIndex >= 0 )
      {
        return QgsDateTimeRange( std::min( vectorLayer->minimumValue( startFieldIndex ).toDateTime(),
                                           vectorLayer->minimumValue( endFieldIndex ).toDateTime() ),
                                 std::max( vectorLayer->maximumValue( startFieldIndex ).toDateTime(),
                                           vectorLayer->maximumValue( endFieldIndex ).toDateTime() ) );
      }
      else if ( startFieldIndex >= 0 )
      {
        return QgsDateTimeRange( vectorLayer->minimumValue( startFieldIndex ).toDateTime(),
                                 vectorLayer->maximumValue( startFieldIndex ).toDateTime() );
      }
      else if ( endFieldIndex >= 0 )
      {
        return QgsDateTimeRange( vectorLayer->minimumValue( endFieldIndex ).toDateTime(),
                                 vectorLayer->maximumValue( endFieldIndex ).toDateTime() );
      }
      break;
    }
 
    case QgsVectorLayerTemporalProperties::ModeFeatureDateTimeStartAndEndFromExpressions:
    {
      bool hasStartExpression = !mStartExpression.isEmpty();
      bool hasEndExpression = !mEndExpression.isEmpty();
      if ( !hasStartExpression && !hasEndExpression )
        return QgsDateTimeRange();
 
      QDateTime minTime;
      QDateTime maxTime;
 
      // no choice here but to loop through all features
      QgsExpressionContext context;
      context.appendScopes( QgsExpressionContextUtils::globalProjectLayerScopes( vectorLayer ) );
 
      QgsExpression startExpression;
      if ( hasStartExpression )
      {
        startExpression.setExpression( mStartExpression );
        startExpression.prepare( &context );
      }
 
      QgsExpression endExpression;
      if ( hasEndExpression )
      {
        endExpression.setExpression( mEndExpression );
        endExpression.prepare( &context );
      }
 
      QSet< QString > fields;
      if ( hasStartExpression )
        fields.unite( startExpression.referencedColumns() );
      if ( hasEndExpression )
        fields.unite( endExpression.referencedColumns() );
 
      const bool needsGeom = startExpression.needsGeometry() || endExpression.needsGeometry();
 
      QgsFeatureRequest req;
      if ( !needsGeom )
        req.setFlags( QgsFeatureRequest::NoGeometry );
 
      req.setSubsetOfAttributes( fields, vectorLayer->fields() );
 
      QgsFeature f;
      QgsFeatureIterator it = vectorLayer->getFeatures( req );
      while ( it.nextFeature( f ) )
      {
        context.setFeature( f );
        const QDateTime start = hasStartExpression ? startExpression.evaluate( &context ).toDateTime() : QDateTime();
        const QDateTime end = hasEndExpression ? endExpression.evaluate( &context ).toDateTime() : QDateTime();
 
        if ( start.isValid() )
        {
          minTime = minTime.isValid() ? std::min( minTime, start ) : start;
          if ( !hasEndExpression )
            maxTime = maxTime.isValid() ? std::max( maxTime, start ) : start;
        }
        if ( end.isValid() )
        {
          maxTime = maxTime.isValid() ? std::max( maxTime, end ) : end;
          if ( !hasStartExpression )
            minTime = minTime.isValid() ? std::min( minTime, end ) : end;
        }
      }
      return QgsDateTimeRange( minTime, maxTime );
    }
 
    case QgsVectorLayerTemporalProperties::ModeRedrawLayerOnly:
      break;
  }
 
  return QgsDateTimeRange();
}
 
QgsVectorLayerTemporalProperties::TemporalMode QgsVectorLayerTemporalProperties::mode() const
{
  return mMode;
}
 
void QgsVectorLayerTemporalProperties::setMode( QgsVectorLayerTemporalProperties::TemporalMode mode )
{
  if ( mMode == mode )
    return;
  mMode = mode;
}
 
QgsTemporalProperty::Flags QgsVectorLayerTemporalProperties::flags() const
{
  return mode() == ModeFixedTemporalRange ? QgsTemporalProperty::FlagDontInvalidateCachedRendersWhenRangeChanges : QgsTemporalProperty::Flags();
}
 
void  QgsVectorLayerTemporalProperties::setFixedTemporalRange( const QgsDateTimeRange &range )
{
  mFixedRange = range;
}
 
const QgsDateTimeRange &QgsVectorLayerTemporalProperties::fixedTemporalRange() const
{
  return mFixedRange;
}
 
bool QgsVectorLayerTemporalProperties::readXml( const QDomElement &element, const QgsReadWriteContext &context )
{
  Q_UNUSED( context )
 
  QDomElement temporalNode = element.firstChildElement( QStringLiteral( "temporal" ) );
 
  setIsActive( temporalNode.attribute( QStringLiteral( "enabled" ), QStringLiteral( "0" ) ).toInt() );
 
  mMode = static_cast< TemporalMode >( temporalNode.attribute( QStringLiteral( "mode" ), QStringLiteral( "0" ) ). toInt() );
 
  mStartFieldName = temporalNode.attribute( QStringLiteral( "startField" ) );
  mEndFieldName = temporalNode.attribute( QStringLiteral( "endField" ) );
  mStartExpression = temporalNode.attribute( QStringLiteral( "startExpression" ) );
  mEndExpression = temporalNode.attribute( QStringLiteral( "endExpression" ) );
  mDurationFieldName = temporalNode.attribute( QStringLiteral( "durationField" ) );
  mDurationUnit = QgsUnitTypes::decodeTemporalUnit( temporalNode.attribute( QStringLiteral( "durationUnit" ), QgsUnitTypes::encodeUnit( QgsUnitTypes::TemporalMinutes ) ) );
  mFixedDuration = temporalNode.attribute( QStringLiteral( "fixedDuration" ) ).toDouble();
  mAccumulateFeatures = temporalNode.attribute( QStringLiteral( "accumulate" ), QStringLiteral( "0" ) ).toInt();
 
  QDomNode rangeElement = temporalNode.namedItem( QStringLiteral( "fixedRange" ) );
 
  QDomNode begin = rangeElement.namedItem( QStringLiteral( "start" ) );
  QDomNode end = rangeElement.namedItem( QStringLiteral( "end" ) );
 
  QDateTime beginDate = QDateTime::fromString( begin.toElement().text(), Qt::ISODate );
  QDateTime endDate = QDateTime::fromString( end.toElement().text(), Qt::ISODate );
 
  QgsDateTimeRange range = QgsDateTimeRange( beginDate, endDate );
  setFixedTemporalRange( range );
 
  return true;
}
 
QDomElement QgsVectorLayerTemporalProperties::writeXml( QDomElement &element, QDomDocument &document, const QgsReadWriteContext &context )
{
  Q_UNUSED( context )
  if ( element.isNull() )
    return QDomElement();
 
  QDomElement temporalElement = document.createElement( QStringLiteral( "temporal" ) );
  temporalElement.setAttribute( QStringLiteral( "enabled" ), isActive() ? QStringLiteral( "1" ) : QStringLiteral( "0" ) );
  temporalElement.setAttribute( QStringLiteral( "mode" ), QString::number( mMode ) );
 
  temporalElement.setAttribute( QStringLiteral( "startField" ), mStartFieldName );
  temporalElement.setAttribute( QStringLiteral( "endField" ), mEndFieldName );
  temporalElement.setAttribute( QStringLiteral( "startExpression" ), mStartExpression );
  temporalElement.setAttribute( QStringLiteral( "endExpression" ), mEndExpression );
  temporalElement.setAttribute( QStringLiteral( "durationField" ), mDurationFieldName );
  temporalElement.setAttribute( QStringLiteral( "durationUnit" ), QgsUnitTypes::encodeUnit( mDurationUnit ) );
  temporalElement.setAttribute( QStringLiteral( "fixedDuration" ), qgsDoubleToString( mFixedDuration ) );
  temporalElement.setAttribute( QStringLiteral( "accumulate" ), mAccumulateFeatures ? QStringLiteral( "1" ) : QStringLiteral( "0" ) );
 
  QDomElement rangeElement = document.createElement( QStringLiteral( "fixedRange" ) );
 
  QDomElement startElement = document.createElement( QStringLiteral( "start" ) );
  QDomElement endElement = document.createElement( QStringLiteral( "end" ) );
 
  QDomText startText = document.createTextNode( mFixedRange.begin().toTimeSpec( Qt::OffsetFromUTC ).toString( Qt::ISODate ) );
  QDomText endText = document.createTextNode( mFixedRange.end().toTimeSpec( Qt::OffsetFromUTC ).toString( Qt::ISODate ) );
  startElement.appendChild( startText );
  endElement.appendChild( endText );
  rangeElement.appendChild( startElement );
  rangeElement.appendChild( endElement );
 
  temporalElement.appendChild( rangeElement );
 
  element.appendChild( temporalElement );
 
  return element;
}
 
void QgsVectorLayerTemporalProperties::setDefaultsFromDataProviderTemporalCapabilities( const QgsDataProviderTemporalCapabilities *capabilities )
{
  if ( const QgsVectorDataProviderTemporalCapabilities *vectorCaps = dynamic_cast< const QgsVectorDataProviderTemporalCapabilities *>( capabilities ) )
  {
    setIsActive( vectorCaps->hasTemporalCapabilities() );
    setFixedTemporalRange( vectorCaps->availableTemporalRange() );
    setStartField( vectorCaps->startField() );
    setEndField( vectorCaps->endField() );
    switch ( vectorCaps->mode() )
    {
      case QgsVectorDataProviderTemporalCapabilities::ProviderHasFixedTemporalRange:
        setMode( ModeFixedTemporalRange );
        break;
      case QgsVectorDataProviderTemporalCapabilities::ProviderStoresFeatureDateTimeInstantInField:
        setMode( ModeFeatureDateTimeInstantFromField );
        break;
      case QgsVectorDataProviderTemporalCapabilities::ProviderStoresFeatureDateTimeStartAndEndInSeparateFields:
        setMode( ModeFeatureDateTimeStartAndEndFromFields );
        break;
    }
  }
}
 
QString QgsVectorLayerTemporalProperties::startExpression() const
{
  return mStartExpression;
}
 
void QgsVectorLayerTemporalProperties::setStartExpression( const QString &startExpression )
{
  mStartExpression = startExpression;
}
 
QString QgsVectorLayerTemporalProperties::endExpression() const
{
  return mEndExpression;
}
 
void QgsVectorLayerTemporalProperties::setEndExpression( const QString &endExpression )
{
  mEndExpression = endExpression;
}
 
bool QgsVectorLayerTemporalProperties::accumulateFeatures() const
{
  return mAccumulateFeatures;
}
 
void QgsVectorLayerTemporalProperties::setAccumulateFeatures( bool accumulateFeatures )
{
  mAccumulateFeatures = accumulateFeatures;
}
 
double QgsVectorLayerTemporalProperties::fixedDuration() const
{
  return mFixedDuration;
}
 
void QgsVectorLayerTemporalProperties::setFixedDuration( double fixedDuration )
{
  mFixedDuration = fixedDuration;
}
 
QString QgsVectorLayerTemporalProperties::startField() const
{
  return mStartFieldName;
}
 
void QgsVectorLayerTemporalProperties::setStartField( const QString &startFieldName )
{
  mStartFieldName = startFieldName;
}
 
QString QgsVectorLayerTemporalProperties::endField() const
{
  return mEndFieldName;
}
 
void QgsVectorLayerTemporalProperties::setEndField( const QString &field )
{
  mEndFieldName = field;
}
 
QString QgsVectorLayerTemporalProperties::durationField() const
{
  return mDurationFieldName;
}
 
void QgsVectorLayerTemporalProperties::setDurationField( const QString &field )
{
  mDurationFieldName = field;
}
 
QgsUnitTypes::TemporalUnit QgsVectorLayerTemporalProperties::durationUnits() const
{
  return mDurationUnit;
}
 
void QgsVectorLayerTemporalProperties::setDurationUnits( QgsUnitTypes::TemporalUnit units )
{
  mDurationUnit = units;
}
 
QString dateTimeExpressionLiteral( const QDateTime &datetime )
{
  return QStringLiteral( "make_datetime(%1,%2,%3,%4,%5,%6)" ).arg( datetime.date().year() )
         .arg( datetime.date().month() )
         .arg( datetime.date().day() )
         .arg( datetime.time().hour() )
         .arg( datetime.time().minute() )
         .arg( datetime.time().second() + datetime.time().msec() / 1000.0 );
}
 
QString QgsVectorLayerTemporalProperties::createFilterString( const QgsVectorLayerTemporalContext &, const QgsDateTimeRange &range ) const
{
  if ( !isActive() )
    return QString();
 
  switch ( mMode )
  {
    case ModeFixedTemporalRange:
    case ModeRedrawLayerOnly:
      return QString();
 
    case ModeFeatureDateTimeInstantFromField:
    {
      if ( mAccumulateFeatures )
      {
        return QStringLiteral( "(%1 %2 %3) OR %1 IS NULL" ).arg( QgsExpression::quotedColumnRef( mStartFieldName ),
               range.includeEnd() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ) );
      }
      else if ( qgsDoubleNear( mFixedDuration, 0.0 ) )
      {
        return QStringLiteral( "(%1 %2 %3 AND %1 %4 %5) OR %1 IS NULL" ).arg( QgsExpression::quotedColumnRef( mStartFieldName ),
               range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
               dateTimeExpressionLiteral( range.begin() ),
               range.includeEnd() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ) );
      }
      else
      {
        return QStringLiteral( "(%1 %2 %3 AND %1 %4 %5) OR %1 IS NULL" ).arg( QgsExpression::quotedColumnRef( mStartFieldName ),
               range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
               dateTimeExpressionLiteral( range.begin() + QgsInterval( -mFixedDuration, mDurationUnit ) ),
               range.includeEnd() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ) );
      }
    }
 
    case ModeFeatureDateTimeStartAndDurationFromFields:
    {
      QString intervalExpression;
      switch ( mDurationUnit )
      {
        case QgsUnitTypes::TemporalMilliseconds:
          intervalExpression = QStringLiteral( "make_interval(0,0,0,0,0,0,%1/1000)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalSeconds:
          intervalExpression = QStringLiteral( "make_interval(0,0,0,0,0,0,%1)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalMinutes:
          intervalExpression = QStringLiteral( "make_interval(0,0,0,0,0,%1,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalHours:
          intervalExpression = QStringLiteral( "make_interval(0,0,0,0,%1,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalDays:
          intervalExpression = QStringLiteral( "make_interval(0,0,0,%1,0,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalWeeks:
          intervalExpression = QStringLiteral( "make_interval(0,0,%1,0,0,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalMonths:
          intervalExpression = QStringLiteral( "make_interval(0,%1,0,0,0,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalYears:
          intervalExpression = QStringLiteral( "make_interval(%1,0,0,0,0,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalDecades:
          intervalExpression = QStringLiteral( "make_interval(10 * %1,0,0,0,0,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalCenturies:
          intervalExpression = QStringLiteral( "make_interval(100 * %1,0,0,0,0,0,0)" ).arg( QgsExpression::quotedColumnRef( mDurationFieldName ) );
          break;
 
        case QgsUnitTypes::TemporalUnknownUnit:
          return QString();
      }
      return QStringLiteral( "(%1 %2 %3 OR %1 IS NULL) AND ((%1 + %4 %5 %6) OR %7 IS NULL)" ).arg( QgsExpression::quotedColumnRef( mStartFieldName ),
             range.includeEnd() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
             dateTimeExpressionLiteral( range.end() ),
             intervalExpression,
             range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
             dateTimeExpressionLiteral( range.begin() ),
             QgsExpression::quotedColumnRef( mDurationFieldName ) );
      break;
    }
 
    case ModeFeatureDateTimeStartAndEndFromFields:
    {
      if ( !mStartFieldName.isEmpty() && !mEndFieldName.isEmpty() )
      {
        return QStringLiteral( "(%1 %2 %3 OR %1 IS NULL) AND (%4 %5 %6 OR %4 IS NULL)" ).arg( QgsExpression::quotedColumnRef( mStartFieldName ),
               range.includeEnd() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ),
               QgsExpression::quotedColumnRef( mEndFieldName ),
               range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
               dateTimeExpressionLiteral( range.begin() ) );
      }
      else if ( !mStartFieldName.isEmpty() )
      {
        return QStringLiteral( "%1 %2 %3 OR %1 IS NULL" ).arg( QgsExpression::quotedColumnRef( mStartFieldName ),
               range.includeBeginning() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ) );
      }
      else if ( !mEndFieldName.isEmpty() )
      {
        return QStringLiteral( "%1 %2 %3 OR %1 IS NULL" ).arg( QgsExpression::quotedColumnRef( mEndFieldName ),
               range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
               dateTimeExpressionLiteral( range.begin() ) );
      }
      break;
    }
 
    case ModeFeatureDateTimeStartAndEndFromExpressions:
    {
      if ( !mStartExpression.isEmpty() && !mEndExpression.isEmpty() )
      {
        return QStringLiteral( "((%1) %2 %3) AND ((%4) %5 %6)" ).arg( mStartExpression,
               range.includeEnd() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ),
               mEndExpression,
               range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
               dateTimeExpressionLiteral( range.begin() ) );
      }
      else if ( !mStartExpression.isEmpty() )
      {
        return QStringLiteral( "(%1) %2 %3" ).arg( mStartExpression,
               range.includeBeginning() ? QStringLiteral( "<=" ) : QStringLiteral( "<" ),
               dateTimeExpressionLiteral( range.end() ) );
      }
      else if ( !mEndExpression.isEmpty() )
      {
        return QStringLiteral( "(%1) %2 %3" ).arg( mEndExpression,
               range.includeBeginning() ? QStringLiteral( ">=" ) : QStringLiteral( ">" ),
               dateTimeExpressionLiteral( range.begin() ) );
      }
      break;
    }
  }
 
  return QString();
}
 
void QgsVectorLayerTemporalProperties::guessDefaultsFromFields( const QgsFields &fields )
{
 
  // Check the fields and keep the first one that matches.
  // We assume that the user has organized the data with the
  // more "interesting" field names first.
  // This candidates list is a prioritized list of candidates ranked by "interestingness"!
  // See discussion at https://github.com/qgis/QGIS/pull/30245 - this list must NOT be translated,
  // but adding hardcoded localized variants of the strings is encouraged.
  static QStringList sStartCandidates{ QStringLiteral( "start" ),
                                       QStringLiteral( "begin" ),
                                       QStringLiteral( "from" )};
 
  static QStringList sEndCandidates{ QStringLiteral( "end" ),
                                     QStringLiteral( "last" ),
                                     QStringLiteral( "to" )};
 
  static QStringList sSingleFieldCandidates{ QStringLiteral( "event" ) };
 
 
  bool foundStart = false;
  bool foundEnd = false;
 
  for ( const QgsField &field : fields )
  {
    if ( field.type() != QVariant::Date && field.type() != QVariant::DateTime )
      continue;
 
    if ( !foundStart )
    {
      for ( const QString &candidate : sStartCandidates )
      {
        QString fldName = field.name();
        if ( fldName.indexOf( candidate, 0, Qt::CaseInsensitive ) > -1 )
        {
          mStartFieldName = fldName;
          foundStart = true;
        }
      }
    }
 
    if ( !foundEnd )
    {
      for ( const QString &candidate : sEndCandidates )
      {
        QString fldName = field.name();
        if ( fldName.indexOf( candidate, 0, Qt::CaseInsensitive ) > -1 )
        {
          mEndFieldName = fldName;
          foundEnd = true;
        }
      }
    }
 
    if ( foundStart && foundEnd )
      break;
  }
 
  if ( !foundStart )
  {
    // loop again, looking for likely "single field" candidates
    for ( const QgsField &field : fields )
    {
      if ( field.type() != QVariant::Date && field.type() != QVariant::DateTime )
        continue;
 
      for ( const QString &candidate : sSingleFieldCandidates )
      {
        QString fldName = field.name();
        if ( fldName.indexOf( candidate, 0, Qt::CaseInsensitive ) > -1 )
        {
          mStartFieldName = fldName;
          foundStart = true;
        }
      }
 
      if ( foundStart )
        break;
    }
  }
 
  if ( foundStart && foundEnd )
    mMode = ModeFeatureDateTimeStartAndEndFromFields;
  else if ( foundStart )
    mMode = ModeFeatureDateTimeInstantFromField;
 
  // note -- NEVER auto enable temporal properties here! It's just a helper designed
  // to shortcut the initial field selection
}
 
QgsVectorLayer *QgsVectorLayerTemporalContext::layer() const
{
  return mLayer;
}
 
void QgsVectorLayerTemporalContext::setLayer( QgsVectorLayer *layer )
{
  mLayer = layer;
}