qgsalgorithmsplitvectorlayer.cpp

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/***************************************************************************
                         qgsalgorithmsplitvectorlayer.cpp
                         ---------------------
    begin                : May 2020
    copyright            : (C) 2020 by Alexander Bruy
    email                : alexander dot bruy 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 "qgsalgorithmsplitvectorlayer.h"
#include "qgsvectorfilewriter.h"
 
 
QString QgsSplitVectorLayerAlgorithm::name() const
{
  return QStringLiteral( "splitvectorlayer" );
}
 
QString QgsSplitVectorLayerAlgorithm::displayName() const
{
  return QObject::tr( "Split vector layer" );
}
 
QStringList QgsSplitVectorLayerAlgorithm::tags() const
{
  return QObject::tr( "vector,split,field,unique" ).split( ',' );
}
 
QString QgsSplitVectorLayerAlgorithm::group() const
{
  return QObject::tr( "Vector general" );
}
 
QString QgsSplitVectorLayerAlgorithm::groupId() const
{
  return QStringLiteral( "vectorgeneral" );
}
 
QString QgsSplitVectorLayerAlgorithm::shortHelpString() const
{
  return QObject::tr( "Splits input vector layer into multiple layers by specified unique ID field." )
         + QStringLiteral( "\n\n" )
         + QObject::tr( "Each of the layers created in the output folder contains all features from "
                        "the input layer with the same value for the specified attribute. The number "
                        "of files generated is equal to the number of different values found for the "
                        "specified attribute." );
}
 
QgsSplitVectorLayerAlgorithm *QgsSplitVectorLayerAlgorithm::createInstance() const
{
  return new QgsSplitVectorLayerAlgorithm();
}
 
void QgsSplitVectorLayerAlgorithm::initAlgorithm( const QVariantMap & )
{
  addParameter( new QgsProcessingParameterFeatureSource( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ) ) );
  addParameter( new QgsProcessingParameterField( QStringLiteral( "FIELD" ), QObject::tr( "Unique ID field" ),
                QVariant(), QStringLiteral( "INPUT" ) ) );
 
  QStringList options = QgsVectorFileWriter::supportedFormatExtensions();
  auto fileTypeParam = qgis::make_unique < QgsProcessingParameterEnum >( QStringLiteral( "FILE_TYPE" ), QObject::tr( "Output file type" ), options, false, QVariantList() << 0, true );
  fileTypeParam->setFlags( QgsProcessingParameterDefinition::FlagAdvanced );
  addParameter( fileTypeParam.release() );
 
  addParameter( new QgsProcessingParameterFolderDestination( QStringLiteral( "OUTPUT" ), QObject::tr( "Output directory" ) ) );
  addOutput( new QgsProcessingOutputMultipleLayers( QStringLiteral( "OUTPUT_LAYERS" ), QObject::tr( "Output layers" ) ) );
}
 
QVariantMap QgsSplitVectorLayerAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
{
  std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
  if ( !source )
    throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
 
  QString fieldName = parameterAsString( parameters, QStringLiteral( "FIELD" ), context );
  QString outputDir = parameterAsString( parameters, QStringLiteral( "OUTPUT" ), context );
  QString outputFormat;
  if ( parameters.value( QStringLiteral( "FILE_TYPE" ) ).isValid() )
  {
    int idx = parameterAsEnum( parameters, QStringLiteral( "FILE_TYPE" ), context );
    outputFormat = QgsVectorFileWriter::supportedFormatExtensions().at( idx );
  }
  else
  {
    outputFormat = context.preferredVectorFormat();
    if ( !QgsVectorFileWriter::supportedFormatExtensions().contains( outputFormat, Qt::CaseInsensitive ) )
      outputFormat = QStringLiteral( "gpkg" );
  }
 
  if ( !QDir().mkpath( outputDir ) )
    throw QgsProcessingException( QStringLiteral( "Failed to create output directory." ) );
 
  QgsFields fields = source->fields();
  QgsCoordinateReferenceSystem crs = source->sourceCrs();
  QgsWkbTypes::Type geometryType = source->wkbType();
  int fieldIndex = fields.lookupField( fieldName );
  QSet< QVariant > uniqueValues = source->uniqueValues( fieldIndex );
  QString baseName = outputDir + QDir::separator() + fieldName;
 
  int current = 0;
  double step = uniqueValues.size() > 0 ? 100.0 / uniqueValues.size() : 1;
 
  int count = 0;
  QgsFeature feat;
  QStringList outputLayers;
  std::unique_ptr< QgsFeatureSink > sink;
 
  for ( auto it = uniqueValues.constBegin(); it != uniqueValues.constEnd(); ++it )
  {
    if ( feedback->isCanceled() )
      break;
 
    QString fileName = QStringLiteral( "%1_%2.%3" ).arg( baseName ).arg( current ).arg( outputFormat );
    feedback->pushInfo( QObject::tr( "Creating layer: %1" ).arg( fileName ) );
 
    sink.reset( QgsProcessingUtils::createFeatureSink( fileName, context, fields, geometryType, crs ) );
    QString expr = QgsExpression::createFieldEqualityExpression( fieldName, *it );
    QgsFeatureIterator features = source->getFeatures( QgsFeatureRequest().setFilterExpression( expr ) );
    while ( features.nextFeature( feat ) )
    {
      if ( feedback->isCanceled() )
        break;
 
      sink->addFeature( feat, QgsFeatureSink::FastInsert );
      count += 1;
    }
 
    feedback->pushInfo( QObject::tr( "Added %1 features to layer" ).arg( count ) );
    outputLayers << fileName;
 
    current += 1;
    feedback->setProgress( current * step );
  }
 
  QVariantMap outputs;
  outputs.insert( QStringLiteral( "OUTPUT" ), outputDir );
  outputs.insert( QStringLiteral( "OUTPUT_LAYERS" ), outputLayers );
  return outputs;
}