qgsaggregatecalculator.h

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/***************************************************************************
                             qgsaggregatecalculator.h
                             ------------------------
    begin                : May 2016
    copyright            : (C) 2016 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 QGSAGGREGATECALCULATOR_H
#define QGSAGGREGATECALCULATOR_H
 
#include "qgis_core.h"
#include "qgsfeatureid.h"
#include "qgsfeaturerequest.h"
#include "qgsstatisticalsummary.h"
 
#include <QVariant>
 
class QgsFeatureIterator;
class QgsExpression;
class QgsVectorLayer;
class QgsExpressionContext;

class CORE_EXPORT QgsAggregateCalculator
{
  public:
    struct AggregateInfo
    {
        QString function;
        QString name;
        QSet<QMetaType::Type> supportedTypes;
    };

    struct AggregateParameters
    {
        QString filter;

        QString delimiter;

        QgsFeatureRequest::OrderBy orderBy;
    };

    QgsAggregateCalculator( const QgsVectorLayer *layer );

    QString lastError() const { return mLastError; }

    const QgsVectorLayer *layer() const;

    void setParameters( const AggregateParameters &parameters );

    void setFilter( const QString &filterExpression ) { mFilterExpression = filterExpression; }

    void setFidsFilter( const QgsFeatureIds &fids );

    QString filter() const { return mFilterExpression; }

    void setDelimiter( const QString &delimiter ) { mDelimiter = delimiter; }

    QString delimiter() const { return mDelimiter; }

    QVariant calculate( Qgis::Aggregate aggregate, const QString &fieldOrExpression, QgsExpressionContext *context = nullptr, bool *ok = nullptr, QgsFeedback *feedback = nullptr ) const;

    static Qgis::Aggregate stringToAggregate( const QString &string, bool *ok = nullptr );

    static QString displayName( Qgis::Aggregate aggregate );

    static QList< QgsAggregateCalculator::AggregateInfo > aggregates();
 
  private:
    const QgsVectorLayer *mLayer = nullptr;

    QString mFilterExpression;

    QgsFeatureRequest::OrderBy mOrderBy;

    QString mDelimiter;

    QgsFeatureIds mFidsFilter;
 
    //trigger variable
    bool mFidsSet = false;
 
    mutable QString mLastError;
 
    static Qgis::Statistic numericStatFromAggregate( Qgis::Aggregate aggregate, bool *ok = nullptr );
    static Qgis::StringStatistic stringStatFromAggregate( Qgis::Aggregate aggregate, bool *ok = nullptr );
    static Qgis::DateTimeStatistic dateTimeStatFromAggregate( Qgis::Aggregate aggregate, bool *ok = nullptr );
 
    static QVariant calculateNumericAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression, QgsExpressionContext *context, Qgis::Statistic stat );
 
    static QVariant calculateStringAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression, QgsExpressionContext *context, Qgis::StringStatistic stat );
 
    static QVariant calculateDateTimeAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression, QgsExpressionContext *context, Qgis::DateTimeStatistic stat );
    static QVariant calculateGeometryAggregate( QgsFeatureIterator &fit, QgsExpression *expression, QgsExpressionContext *context );
 
    static QVariant calculateArrayAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression, QgsExpressionContext *context );
 
    static QVariant calculate(
      Qgis::Aggregate aggregate,
      QgsFeatureIterator &fit,
      QMetaType::Type resultType,
      int attr,
      QgsExpression *expression,
      const QString &delimiter,
      QgsExpressionContext *context,
      bool *ok = nullptr,
      QString *error = nullptr
    );
    static QVariant concatenateStrings( QgsFeatureIterator &fit, int attr, QgsExpression *expression, QgsExpressionContext *context, const QString &delimiter, bool unique = false );
 
    QVariant defaultValue( Qgis::Aggregate aggregate ) const;
};
 
#endif //QGSAGGREGATECALCULATOR_H