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 /*
  * This file is part of KQuickCharts
  * SPDX-FileCopyrightText: 2019 Arjen Hiemstra <ahiemstra@heimr.nl>
  *
  * SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
  */
 
 #ifndef HISTORYPROXYSOURCE_H
 #define HISTORYPROXYSOURCE_H
 
 #include <QTimer>
 #include <QVariant>
 #include <QVector>
 #include <memory>
 
 #include "ChartDataSource.h"
 
 /**
  * A data source that provides a history of a single item of a different data source.
  *
  * This data source will monitor a single item of another data source for changes
  * and record them, exposing historical values as
  */
 class HistoryProxySource : public ChartDataSource
 {
     Q_OBJECT
 
     /**
      * The data source to read data from.
      *
      * This will use the item at \ref item from the provided source and use that
      * to fill the history of this source.
      *
      * \note Changing this property will clear the existing history.
      */
     Q_PROPERTY(ChartDataSource *source READ source WRITE setSource NOTIFY sourceChanged)
     /**
      * The item of the data source to read data from.
      *
      * This item will be read either when the source's dataChanged has been
      * emitted or on an interval if \ref interval has been set.
      *
      * The default is 0.
      *
      * \note Changing this property will clear the existing history.
      */
     Q_PROPERTY(int item READ item WRITE setItem NOTIFY itemChanged)
     /**
      * The maximum amount of history to keep.
      *
      * The default is 10.
      */
     Q_PROPERTY(int maximumHistory READ maximumHistory WRITE setMaximumHistory NOTIFY maximumHistoryChanged)
     /**
      * The interval, in milliseconds, with which to query the data source.
      *
      * If set to a value <= 0, a new item will be added whenever \ref source
      * changes. Otherwise, source will be sampled every interval milliseconds
      * and a new item will be added with whatever value it has at that point,
      * even if it did not change.
      *
      * The default is 0.
      */
     Q_PROPERTY(int interval READ interval WRITE setInterval NOTIFY intervalChanged)
     /**
      * The fill mode.
      *
      * This determines what happens when there is not enough history yet. See
      * \ref FillMode for which modes are available.
      *
      * The default is DoNotFill.
      *
      * \note Changing this property will clear the existing history.
      */
     Q_PROPERTY(FillMode fillMode READ fillMode WRITE setFillMode NOTIFY fillModeChanged)
 
 public:
     /**
      * The different fill modes.
      *
      * These determine the value returned by \ref itemCount and what happens
      * when requesting an item that does not have a value in the history.
      */
     enum FillMode {
         /**
          * Do not fill with any items. The source's \ref itemCount will be equal
          * to the number of items in the history.
          */
         DoNotFill,
         /**
          * Fill with empty values, starting at 0. The source's \ref itemCount
          * will be equal to \ref maximumHistory. Items that do not have a value
          * in the history will return a default-constructed value based on the
          * first item of the source.
          */
         FillFromStart,
         /**
          * Fill with empty values, placing partial history at the end. This
          * means that the first recorded history item will be shown at position
          * `maximumHistory - 1`, the second at `maximumHistory - 2` and so on,
          * until \ref maximumHistory is reached, after which items will be
          * discarded normally.
          */
         FillFromEnd
     };
     Q_ENUM(FillMode)
 
     explicit HistoryProxySource(QObject *parent = nullptr);
 
     int itemCount() const override;
     QVariant item(int index) const override;
     QVariant minimum() const override;
     QVariant maximum() const override;
 
     QVariant first() const override;
 
     ChartDataSource *source() const;
     void setSource(ChartDataSource *newSource);
     Q_SIGNAL void sourceChanged();
 
     int item() const;
     void setItem(int newItem);
     Q_SIGNAL void itemChanged();
 
     int maximumHistory() const;
     void setMaximumHistory(int maximumHistory);
     Q_SIGNAL void maximumHistoryChanged();
 
     int interval() const;
     void setInterval(int newInterval);
     Q_SIGNAL void intervalChanged();
 
     FillMode fillMode() const;
     void setFillMode(FillMode newFillMode);
     Q_SIGNAL void fillModeChanged();
 
     /**
      * Clear the entire history of this source.
      */
     Q_INVOKABLE void clear();
 
 private:
     void update();
 
     ChartDataSource *m_dataSource = nullptr;
     int m_item = 0;
     int m_maximumHistory = 10;
     FillMode m_fillMode = DoNotFill;
     std::unique_ptr<QTimer> m_updateTimer;
     QVector<QVariant> m_history;
 };
 
 #endif // HISTORYPROXYSOURCE_H