#ifndef HISTOGRAMCHART_H
#define HISTOGRAMCHART_H

#include <cmath>

#include <QQuickItem>
#include <QtQuick/QQuickPaintedItem>
#include <QColor>


struct Statistics {
  qreal sum = 0;
  qreal sumSquares = 0;
  int count = 0;

  void add(qreal v) {
      sum += v;
      sumSquares += v*v;
      count++;
  }

  void clear() {
    sum = 0;
    sumSquares = 0;
    count = 0;
  }

  int getCount() const {
      return count;
  }

  qreal getMean() const {
    return sum / static_cast<qreal>(count);
  }

  qreal getStdDev() const {
    const qreal x = sumSquares / static_cast<qreal>(count);
    const qreal e = getMean();
    return std::sqrt(x - (e*e));
  }
};

class HistogramChart : public QQuickPaintedItem
{
    Q_OBJECT
    Q_PROPERTY(QString name READ name WRITE setName)
    Q_PROPERTY(QColor color READ color WRITE setColor)
    Q_PROPERTY(qreal  binWidth    READ binWidth WRITE setBinWidth)
    Q_PROPERTY(qreal  mean        READ mean)
    Q_PROPERTY(qreal  stdDev      READ stdDev)
    Q_PROPERTY(int    totalCount  READ totalCount)
    Q_PROPERTY(qreal  maxBinValue READ maxBinValue)

public:
    HistogramChart(QQuickItem* parent = nullptr);

    QString name() const { return m_name; }
    void setName(const QString &name) { m_name = name; }

    QColor color() const { return m_color; }
    void setColor(const QColor& color) { m_color = color; }

    qreal binWidth() const { return _binWidth; }
    void setBinWidth(qreal newBinWidth) { _binWidth = newBinWidth; reset(); }

    qreal mean()        const { return stats.getMean();   }
    qreal stdDev()      const { return stats.getStdDev(); }
    int   totalCount()  const { return stats.getCount();  }
    qreal maxBinValue() const { return minValue + (maxBinIndex * binWidth()); }

    void paint(QPainter *painter);

    Q_INVOKABLE void pushData(qreal value);

    Q_INVOKABLE void clear();  // soft reset
    Q_INVOKABLE void reset();  // hard reset

public:
    int numberOfBins() const;
    int binIndex(qreal value) const;


private:
    QString m_name;
    QColor m_color;

    std::vector<int> _histogram;
    qreal _binWidth = 100;
    qreal minValue = std::numeric_limits<qreal>::quiet_NaN();
    qreal maxValue = std::numeric_limits<qreal>::quiet_NaN();

    size_t lastUpdatedBinIndex = 0;
    int maxBinCount = 0;
    int maxBinIndex = 0;

    // Satistics
    Statistics stats;
};

#endif // HISTOGRAMCHART_H