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


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

class CORE_EXPORT QgsAggregateCalculator
{
  public:

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

    struct AggregateParameters
    {
      QString filter;

      QString delimiter;
    };

    QgsAggregateCalculator( QgsVectorLayer* layer );

    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 );

  private:

    QgsVectorLayer* mLayer;

    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 );

    QgsExpressionContext* createContext() const;

    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