/***

  Olive - Non-Linear Video Editor
  Copyright (C) 2021 Olive Team

  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 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.

***/

#ifndef TIMEBASEDVIEWSELECTIONMANAGER_H
#define TIMEBASEDVIEWSELECTIONMANAGER_H

#include <QGraphicsView>
#include <QMouseEvent>
#include <QToolTip>

#include "common/rational.h"
#include "common/timecodefunctions.h"
#include "timebasedview.h"

namespace olive {

template <typename T>
class TimeBasedViewSelectionManager
{
public:
  TimeBasedViewSelectionManager(TimeBasedView *view) :
    view_(view)
  {}

  void ClearDrawnObjects()
  {
    drawn_objects_.clear();
  }

  void DeclareDrawnObject(T *object, const QRectF &pos)
  {
    drawn_objects_.append({object, pos});
  }

  bool Select(T *key)
  {
    if (!IsSelected(key)) {
      selected_.append(key);
      return true;
    }

    return false;
  }

  bool Deselect(T *key)
  {
    return selected_.removeOne(key);
  }

  void ClearSelection()
  {
    selected_.clear();
  }

  bool IsSelected(T *key) const
  {
    return selected_.contains(key);
  }

  const QVector<T*> &GetSelectedObjects() const
  {
    return selected_;
  }

  void SetTimebase(const rational &tb)
  {
    timebase_ = tb;
  }

  T *MousePress(QMouseEvent *event)
  {
    T *key_under_cursor = nullptr;

    if (event->button() == Qt::LeftButton) {
      // See if there's a keyframe in this position
      QPointF scene_pos = view_->mapToScene(event->pos());
      foreach (const DrawnObject &kp, drawn_objects_) {
        if (kp.second.contains(scene_pos)) {
          key_under_cursor = kp.first;
          break;
        }
      }

      bool holding_shift = event->modifiers() & Qt::ShiftModifier;

      if (IsSelected(key_under_cursor)) {
        if (holding_shift) {
          // If selected and holding shift, de-select this item but do nothing else
          Deselect(key_under_cursor);
        }
      } else {
        if (!holding_shift) {
          // If not already selecting and not holding shift, clear the current selection
          ClearSelection();
        }

        // Add item to selection, either nothing if shift wasn't held, or the existing selection
        Select(key_under_cursor);
      }
    }

    return key_under_cursor;
  }

  bool IsDragging() const
  {
    return !dragging_.isEmpty();
  }

  void DragStart(T *initial_item, QMouseEvent *event)
  {
    initial_drag_item_ = initial_item;

    dragging_.clear();

    dragging_.resize(selected_.size());
    for (int i=0; i<selected_.size(); i++) {
      T *obj = selected_.at(i);

      dragging_[i] = {obj->time()};
    }

    drag_mouse_start_ = view_->mapToScene(event->pos());
  }

  void DragMove(QMouseEvent *event, const QString &tip_format)
  {
    QPointF diff = view_->mapToScene(event->pos()) - drag_mouse_start_;

    for (int i=0; i<selected_.size(); i++) {
      const rational &old_time = dragging_.at(i).time;
      rational proposed_time = old_time + view_->SceneToTimeNoGrid(diff.x());
      T *sel = selected_.at(i);

      // Magic number: use interval of 1ms to avoid collisions
      rational adj(1, 1000);
      if (old_time < proposed_time) {
        adj = -adj;
      }
      while (true) {
        NodeKeyframe *key_at_time = sel->parent()->GetKeyframeAtTimeOnTrack(sel->input(), proposed_time, sel->track(), sel->element());
        if (!key_at_time || key_at_time == sel) {
          break;
        }

        proposed_time += adj;
      }

      sel->set_time(proposed_time);
    }

    // Show information about this keyframe
    QString tip = Timecode::time_to_timecode(initial_drag_item_->time(), timebase_,
                                             Core::instance()->GetTimecodeDisplay(), false);

    if (!tip_format.isEmpty()) {
      tip = tip_format.arg(tip);
    }

    QToolTip::hideText();
    QToolTip::showText(QCursor::pos(), tip);
  }

  void DragStop(MultiUndoCommand *command)
  {
    QToolTip::hideText();

    for (int i=0; i<selected_.size(); i++) {
      command->add_child(new SetTimeCommand(selected_.at(i), selected_.at(i)->time(), dragging_.at(i).time));
    }
  }

private:
  class SetTimeCommand : public UndoCommand
  {
  public:
    SetTimeCommand(T* key, const rational& time)
    {
      key_ = key;
      new_time_ = time;
      old_time_ = key_->time();
    }

    SetTimeCommand(T* key, const rational& new_time, const rational& old_time)
    {
      key_ = key;
      new_time_ = new_time;
      old_time_ = old_time;
    }

    virtual Project* GetRelevantProject() const override
    {
      return key_->parent()->project();
    }

  protected:
    virtual void redo() override
    {
      key_->set_time(new_time_);
    }

    virtual void undo() override
    {
      key_->set_time(old_time_);
    }

  private:
    T* key_;

    rational old_time_;
    rational new_time_;

  };

  TimeBasedView *view_;

  using DrawnObject = QPair<T*, QRectF>;
  QVector<DrawnObject> drawn_objects_;

  QVector<T*> selected_;

  struct DragObject
  {
    rational time;
  };

  QVector<DragObject> dragging_;

  T *initial_drag_item_;

  QPointF drag_mouse_start_;

  rational timebase_;

};

}

#endif // TIMEBASEDVIEWSELECTIONMANAGER_H