#pragma once

#include <QtNodes/GraphicsView>
#include <QtNodes/StyleCollection>

#include <QGraphicsProxyWidget>
#include <QMouseEvent>
#include <QPainter>
#include <QScrollBar>
#include <QWheelEvent>

#include <cmath>

class ZoomGraphicsView : public QtNodes::GraphicsView {
public:
  explicit ZoomGraphicsView(QtNodes::BasicGraphicsScene *scene,
                            QWidget *parent = nullptr)
      : QtNodes::GraphicsView(scene, parent) {
    setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);
    setCacheMode(QGraphicsView::CacheNone);
  }

  void setZoomSensitivity(double sensitivity) {
    m_sensitivity = sensitivity;
  }
  double zoomSensitivity() const { return m_sensitivity; }

  void updateProxyCacheMode() {
    if (!scene())
      return;

    const double zoom = transform().m11();
    const bool highZoom = zoom > 1.4;

    if (highZoom == m_proxiesCached)
      return;
    m_proxiesCached = highZoom;

    auto cacheMode = highZoom ? QGraphicsItem::DeviceCoordinateCache
                              : QGraphicsItem::NoCache;
    for (QGraphicsItem *item : scene()->items()) {
      if (item->type() == QGraphicsProxyWidget::Type)
        item->setCacheMode(cacheMode);
    }
  }

protected:
  void wheelEvent(QWheelEvent *event) override {
    const double dy = event->angleDelta().y();
    if (dy == 0.0) {
      event->ignore();
      return;
    }

    static constexpr double kTickUnits = 120.0;
    const double exponent = dy / kTickUnits;
    const double factor = std::pow(m_sensitivity, exponent);
    const double proposed = transform().m11() * factor;
    setupScale(proposed);
  }

  void mousePressEvent(QMouseEvent *event) override {
    if (event->button() == Qt::LeftButton) {
      m_panActive = true;
      m_panStart = event->pos();
    }
    QGraphicsView::mousePressEvent(event);
  }

  void mouseMoveEvent(QMouseEvent *event) override {
    if (m_panActive && (event->buttons() & Qt::LeftButton) &&
        !(event->modifiers() & Qt::ShiftModifier) &&
        !scene()->mouseGrabberItem()) {
      QPoint delta = event->pos() - m_panStart;
      m_panStart = event->pos();
      horizontalScrollBar()->setValue(horizontalScrollBar()->value() - delta.x());
      verticalScrollBar()->setValue(verticalScrollBar()->value() - delta.y());
      return;
    }
    QGraphicsView::mouseMoveEvent(event);
  }

  void mouseReleaseEvent(QMouseEvent *event) override {
    if (event->button() == Qt::LeftButton)
      m_panActive = false;
    QGraphicsView::mouseReleaseEvent(event);
  }

  void drawBackground(QPainter *painter, const QRectF &r) override {
    QGraphicsView::drawBackground(painter, r);

    const double zoom = transform().m11();
    auto const &style =
        QtNodes::StyleCollection::flowViewStyle();

    static constexpr double kBaseFine = 15.0;
    static constexpr double kBaseCoarse = 150.0;
    static constexpr double kMinPixelSpacing = 10.0;

    double fineStep = kBaseFine;
    while (fineStep * zoom < kMinPixelSpacing)
      fineStep *= 2.0;

    double coarseStep = kBaseCoarse;
    while (coarseStep * zoom < kMinPixelSpacing * 5.0)
      coarseStep *= 2.0;

    auto drawGrid = [&](double gridStep) {
      QRect windowRect = rect();
      QPointF tl = mapToScene(windowRect.topLeft());
      QPointF br = mapToScene(windowRect.bottomRight());

      double left = std::floor(tl.x() / gridStep - 0.5);
      double right = std::floor(br.x() / gridStep + 1.0);
      double bottom = std::floor(tl.y() / gridStep - 0.5);
      double top = std::floor(br.y() / gridStep + 1.0);

      for (int xi = int(left); xi <= int(right); ++xi)
        painter->drawLine(QLineF(xi * gridStep, bottom * gridStep,
                                 xi * gridStep, top * gridStep));

      for (int yi = int(bottom); yi <= int(top); ++yi)
        painter->drawLine(QLineF(left * gridStep, yi * gridStep,
                                 right * gridStep, yi * gridStep));
    };

    painter->setPen(QPen(style.FineGridColor, 1.0));
    drawGrid(fineStep);

    painter->setPen(QPen(style.CoarseGridColor, 1.0));
    drawGrid(coarseStep);
  }

private:
  double m_sensitivity = 1.2;
  bool m_proxiesCached = false;
  bool m_panActive = false;
  QPoint m_panStart;
};