/***

  Olive - Non-Linear Video Editor
  Copyright (C) 2022 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/>.

***/

#include "viewersizer.h"

#include <QApplication>
#include <QEvent>
#include <QMatrix4x4>
#include <QWheelEvent>

#include "widget/handmovableview/handmovableview.h"

namespace olive {

ViewerSizer::ViewerSizer(QWidget *parent) :
  QWidget(parent),
  widget_(nullptr),
  width_(0),
  height_(0),
  pixel_aspect_(1),
  zoom_(-1),
  current_widget_scale_(0)
{
  horiz_scrollbar_ = new QScrollBar(Qt::Horizontal, this);
  horiz_scrollbar_->setVisible(false);
  connect(horiz_scrollbar_, &QScrollBar::valueChanged, this, &ViewerSizer::ScrollBarMoved);

  vert_scrollbar_ = new QScrollBar(Qt::Vertical, this);
  vert_scrollbar_->setVisible(false);
  connect(vert_scrollbar_, &QScrollBar::valueChanged, this, &ViewerSizer::ScrollBarMoved);

  setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
}

void ViewerSizer::SetWidget(QWidget *widget)
{
  // Delete any previous widgets occupying this space
  delete widget_;

  widget_ = widget;

  if (widget_ != nullptr) {
    widget_->setParent(this);
    widget_->installEventFilter(this);

    UpdateSize();
  }
}

QSize ViewerSizer::GetContainerSize() const
{
  double s = GetRealCurrentZoom();
  return QSize(std::min(this->width(), int(width_ * s)) - vert_scrollbar_->width(), std::min(int(height_ * s), this->height()) - horiz_scrollbar_->height());
}

void ViewerSizer::SetChildSize(int width, int height)
{
  width_ = width;
  height_ = height;

  UpdateSize();
}

void ViewerSizer::SetPixelAspectRatio(const rational &pixel_aspect)
{
  pixel_aspect_ = pixel_aspect;

  UpdateSize();
}

void ViewerSizer::SetZoom(double percent)
{
  zoom_ = percent;

  UpdateSize();
}

void ViewerSizer::SetZoomAnchored(double next_scale, double cursor_x, double cursor_y)
{
  if (next_scale > 0) {
    double cur_scale = GetRealCurrentZoom();

    // Clamp scale within safe values
    next_scale = std::clamp(next_scale, kZoomLevels[0], kZoomLevels[kZoomLevelCount-1]);

    int anchor_x = qRound(double(cursor_x + horiz_scrollbar_->value()) / cur_scale * next_scale - cursor_x);
    int anchor_y = qRound(double(cursor_y + vert_scrollbar_->value()) / cur_scale * next_scale - cursor_y);

    SetZoom(next_scale);

    horiz_scrollbar_->setValue(anchor_x);
    vert_scrollbar_->setValue(anchor_y);
  } else {
    SetZoom(-1);

    horiz_scrollbar_->setValue(0);
    vert_scrollbar_->setValue(0);
  }
}

void ViewerSizer::HandDragMove(int x, int y)
{
  if (horiz_scrollbar_->isVisible()) {
    horiz_scrollbar_->setValue(horiz_scrollbar_->value() - x);
  }

  if (vert_scrollbar_->isVisible()) {
    vert_scrollbar_->setValue(vert_scrollbar_->value() - y);
  }
}

bool ViewerSizer::eventFilter(QObject *watched, QEvent *event)
{
  if (watched == widget_) {
    if (event->type() == QEvent::Wheel) {
      QWheelEvent *w = static_cast<QWheelEvent*>(event);

      if (HandMovableView::WheelEventIsAZoomEvent(w)) {
        double next_scale = GetRealCurrentZoom() * HandMovableView::GetScrollZoomMultiplier(w);
        QPointF cursor_pos = w->position();
        SetZoomAnchored(next_scale, cursor_pos.x(), cursor_pos.y());
      } else {
        // Pass scroll values to scrollbars
        QPoint p = w->pixelDelta();
        horiz_scrollbar_->setValue(horiz_scrollbar_->value() - p.x());
        vert_scrollbar_->setValue(vert_scrollbar_->value() - p.y());
      }
      return true;
    }
  }

  return QWidget::eventFilter(watched, event);
}

void ViewerSizer::resizeEvent(QResizeEvent *event)
{
  QWidget::resizeEvent(event);

  UpdateSize();
}

void ViewerSizer::UpdateSize()
{
  if (widget_ == nullptr) {
    return;
  }

  // If the aspect ratio is 0, default to taking all space
  if (!width_ || !height_) {
    widget_->move(0, 0);
    widget_->resize(width(), height());
    return;
  }

  // Calculate how much UI space is available (it will be less if we have to show scrollbars)
  int available_width = width();
  int available_height = height();

  // Determine if we need scrollbars for the zoom we want
  horiz_scrollbar_->setVisible(zoom_ > 0 && GetZoomedValue(width_) > available_width);
  vert_scrollbar_->setVisible(zoom_ > 0 && GetZoomedValue(height_) > available_height);

  // Horizontal scrollbar will reduce the available height
  if (horiz_scrollbar_->isVisible()) {
    available_height -= horiz_scrollbar_->sizeHint().height();
  }

  // Vertical scrollbar will reduce the available width
  if (vert_scrollbar_->isVisible()) {
    available_width -= vert_scrollbar_->sizeHint().width();
  }

  // Set correct values on horizontal scrollbar
  if (horiz_scrollbar_->isVisible()) {
    horiz_scrollbar_->resize(available_width, horiz_scrollbar_->sizeHint().height());
    horiz_scrollbar_->move(0, this->height() - horiz_scrollbar_->height() - 1);
    horiz_scrollbar_->setMaximum(GetZoomedValue(width_) - available_width);
    horiz_scrollbar_->setPageStep(available_width);
  }

  // Set correct values on vertical scrollbar
  if (vert_scrollbar_->isVisible()) {
    vert_scrollbar_->resize(vert_scrollbar_->sizeHint().width(), available_height);
    vert_scrollbar_->move(this->width() - vert_scrollbar_->width() - 1, 0);
    vert_scrollbar_->setMaximum(GetZoomedValue(height_) - available_height);
    vert_scrollbar_->setPageStep(available_height);
  }

  // Size widget to the UI space we've calculated
  widget_->resize(available_width, available_height);

  // Adjust to aspect ratio
  double sequence_aspect_ratio = double(width_) / double(height_)
      * pixel_aspect_.toDouble();
  double our_aspect_ratio = double(available_width) / double(available_height);

  QMatrix4x4 child_matrix;
  double current_scale;

  if (our_aspect_ratio > sequence_aspect_ratio) {

    // This container is wider than the image, scale by height
    child_matrix.scale(sequence_aspect_ratio / our_aspect_ratio, 1.0);
    current_scale = double(available_height) / double(height_);

  } else {

    // This container is taller than the image, scale by width
    child_matrix.scale(1.0, our_aspect_ratio / sequence_aspect_ratio);
    current_scale = double(available_width) / double(width_);

  }

  current_widget_scale_ = current_scale;

  if (zoom_ > 0) {

    // Scale to get to the requested zoom
    double zoom_diff = zoom_ / current_scale;
    child_matrix.scale(zoom_diff, zoom_diff, 1.0);

  }

  emit RequestScale(child_matrix);

  ScrollBarMoved();
}

int ViewerSizer::GetZoomedValue(int value)
{
  return qRound(value * zoom_);
}

double ViewerSizer::GetRealCurrentZoom() const
{
  if (zoom_ < 0) {
    // Currently set to "fit"
    return current_widget_scale_;
  } else {
    // Explicit zoom set
    return zoom_;
  }
}

void ViewerSizer::ScrollBarMoved()
{
  QMatrix4x4 mat;

  float x_scroll, y_scroll;

  if (horiz_scrollbar_->isVisible()) {
    int zoomed_width = GetZoomedValue(width_);
    x_scroll = (zoomed_width/2 - horiz_scrollbar_->value() - widget_->width() / 2) * (2.0 / zoomed_width);
  } else {
    x_scroll = 0;
  }

  if (vert_scrollbar_->isVisible()) {
    int zoomed_height = GetZoomedValue(height_);
    y_scroll = (zoomed_height/2 - vert_scrollbar_->value() - widget_->height() / 2) * (2.0 / zoomed_height);
  } else {
    y_scroll = 0;
  }

  // Zero translate is centered, so we need to determine how much "off center" we are
  mat.translate(x_scroll, y_scroll);

  emit RequestTranslate(mat);
}

}