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 "qgsstatisticalsummary.h"
#include "qgsdatetimestatisticalsummary.h"
#include "qgsstringstatisticalsummary.h"
#include <QVariant>


class QgsFeatureIterator;
class QgsExpression;
class QgsVectorLayer;
class QgsExpressionContext;

class CORE_EXPORT QgsAggregateCalculator
{
  public:

    struct AggregateInfo
    {
      QString function; 
      QString name; 
      QSet<QVariant::Type> supportedTypes; 
    };

    enum Aggregate
    {
      Count,  
      CountDistinct,  
      CountMissing,  
      Min,  
      Max,  
      Sum,  
      Mean,  
      Median, 
      StDev, 
      StDevSample, 
      Range, 
      Minority, 
      Majority, 
      FirstQuartile, 
      ThirdQuartile, 
      InterQuartileRange, 
      StringMinimumLength, 
      StringMaximumLength, 
      StringConcatenate, 
      GeometryCollect, 
      ArrayAggregate 
    };

    struct AggregateParameters
    {

      QString filter;

      QString delimiter;
    };

    QgsAggregateCalculator( const QgsVectorLayer *layer );

    const QgsVectorLayer *layer() const;

    void setParameters( const AggregateParameters &parameters );

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

    QString filter() const { return mFilterExpression; }

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

    QString delimiter() const { return mDelimiter; }

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

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

    static QList< QgsAggregateCalculator::AggregateInfo > aggregates();

  private:

    const QgsVectorLayer *mLayer = nullptr;

    QString mFilterExpression;

    QString mDelimiter;

    static QgsStatisticalSummary::Statistic numericStatFromAggregate( Aggregate aggregate, bool *ok = nullptr );
    static QgsStringStatisticalSummary::Statistic stringStatFromAggregate( Aggregate aggregate, bool *ok = nullptr );
    static QgsDateTimeStatisticalSummary::Statistic dateTimeStatFromAggregate( Aggregate aggregate, bool *ok = nullptr );

    static QVariant calculateNumericAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context, QgsStatisticalSummary::Statistic stat );

    static QVariant calculateStringAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context, QgsStringStatisticalSummary::Statistic stat );

    static QVariant calculateDateTimeAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context, QgsDateTimeStatisticalSummary::Statistic stat );
    static QVariant calculateGeometryAggregate( QgsFeatureIterator &fit, QgsExpression *expression, QgsExpressionContext *context );

    static QVariant calculateArrayAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
        QgsExpressionContext *context );

    static QVariant calculate( Aggregate aggregate, QgsFeatureIterator &fit, QVariant::Type resultType,
                               int attr, QgsExpression *expression,
                               const QString &delimiter,
                               QgsExpressionContext *context, bool *ok = nullptr );
    static QVariant concatenateStrings( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
                                        QgsExpressionContext *context, const QString &delimiter );

    QVariant defaultValue( Aggregate aggregate ) const;
};

#endif //QGSAGGREGATECALCULATOR_H