/***************************************************************************
                         qgsremappingproxyfeaturesink.h
                         ----------------------
    begin                : April 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.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QGSREMAPPINGPROXYFEATURESINK_H
#define QGSREMAPPINGPROXYFEATURESINK_H

#include "qgis_core.h"
#include "qgis.h"
#include "qgsfeaturesink.h"
#include "qgsproperty.h"

/**
 * \class QgsRemappingSinkDefinition
 * \ingroup core
 * Defines the parameters used to remap features when creating a QgsRemappingProxyFeatureSink.
 *
 * The definition includes parameters required to correctly map incoming features to the structure
 * of the destination sink, e.g. information about how to create output field values and how to transform
 * geometries to match the destination CRS.
 *
 * \since QGIS 3.14
 */
class CORE_EXPORT QgsRemappingSinkDefinition
{
  public:

    /**
     * Returns the field mapping, which defines how to map the values from incoming features to destination
     * field values.
     *
     * Field values are mapped using a QgsProperty source object, which allows either direct field value to field value
     * mapping or use of QgsExpression expressions to transform values to the destination field.
     *
     * \see setFieldMap()
     * \see addMappedField()
     */
    QMap< QString, QgsProperty > fieldMap() const { return mFieldMap; }

    /**
     * Sets the field mapping, which defines how to map the values from incoming features to destination
     * field values.
     *
     * Field values are mapped using a QgsProperty source object, which allows either direct field value to field value
     * mapping or use of QgsExpression expressions to transform values to the destination field.
     *
     * \see fieldMap()
     * \see addMappedField()
     */
    void setFieldMap( const QMap< QString, QgsProperty > &map ) { mFieldMap = map; }

    /**
     * Adds a mapping for a destination field.
     *
     * Field values are mapped using a QgsProperty source object, which allows either direct field value to field value
     * mapping or use of QgsExpression expressions to transform values to the destination field.
     *
     * \see setFieldMap()
     * \see fieldMap()
     */
    void addMappedField( const QString &destinationField, const QgsProperty &property ) { mFieldMap.insert( destinationField, property ); }

    /**
     * Returns the transform used for reprojecting incoming features to the sink's destination CRS.
     *
     * \see setTransform()
     */
    QgsCoordinateTransform transform() const { return mTransform; }

    /**
     * Sets the \a transform used for reprojecting incoming features to the sink's destination CRS.
     *
     * \see transform()
     */
    void setTransform( const QgsCoordinateTransform &transform )  { mTransform = transform; }

    /**
     * Returns the WKB geometry type for the destination.
     *
     * \see setDestinationWkbType()
     */
    QgsWkbTypes::Type destinationWkbType() const { return mDestinationWkbType; }

    /**
     * Sets the WKB geometry \a type for the destination.
     *
     * \see setDestinationWkbType()
     */
    void setDestinationWkbType( QgsWkbTypes::Type type ) { mDestinationWkbType = type; }

    /**
     * Returns the fields for the destination sink.
     *
     * \see setDestinationFields()
     */
    QgsFields destinationFields() const { return mDestinationFields; }

    /**
     * Sets the \a fields for the destination sink.
     *
     * \see destinationFields()
     */
    void setDestinationFields( const QgsFields &fields ) { mDestinationFields = fields; }

  private:

    QMap< QString, QgsProperty > mFieldMap;

    QgsCoordinateTransform mTransform;

    QgsWkbTypes::Type mDestinationWkbType = QgsWkbTypes::Unknown;

    QgsFields mDestinationFields;

};


/**
 * \class QgsRemappingProxyFeatureSink
 * \ingroup core
 * A QgsFeatureSink which proxies incoming features to a destination feature sink, after applying
 * transformations and field value mappings.
 *
 * This sink allows for transformation of incoming features to match the requirements of storing
 * in an existing destination layer, e.g. by reprojecting the features to the destination's CRS
 * and by coercing geometries to the format required by the destination sink.
 *
 * \since QGIS 3.14
 */
class CORE_EXPORT QgsRemappingProxyFeatureSink : public QgsFeatureSink
{
  public:

    /**
     * Constructor for QgsRemappingProxyFeatureSink, using the specified \a mappingDefinition
     * to manipulate features before sending them to the destination \a sink.
     */
    QgsRemappingProxyFeatureSink( const QgsRemappingSinkDefinition &mappingDefinition, QgsFeatureSink *sink );

    /**
     * Sets the expression \a context to use when evaluating mapped field values.
     */
    void setExpressionContext( const QgsExpressionContext &context );

    /**
     * Remaps a \a feature to a set of features compatible with the destination sink.
     */
    QgsFeatureList remapFeature( const QgsFeature &feature ) const;

    bool addFeature( QgsFeature &feature, QgsFeatureSink::Flags flags = nullptr ) override;
    bool addFeatures( QgsFeatureList &features, QgsFeatureSink::Flags flags = nullptr ) override;
    bool addFeatures( QgsFeatureIterator &iterator, QgsFeatureSink::Flags flags = nullptr ) override;

    /**
     * Returns the destination QgsFeatureSink which the proxy will forward features to.
     */
    QgsFeatureSink *destinationSink() { return mSink; }

  private:

    QgsRemappingSinkDefinition mDefinition;
    QgsFeatureSink *mSink = nullptr;
    mutable QgsExpressionContext mContext;
};

#endif // QGSREMAPPINGPROXYFEATURESINK_H