/*=========================================================================

  Library:   CTK

  Copyright (c) Kitware Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0.txt

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

=========================================================================*/

// Qt includes
#include <QApplication>
#include <QDebug>
#include <QEvent>
#include <QLayout>
#include <QMouseEvent>
#include <QPaintEvent>
#include <QStyle>
#include <QStyleOption>
#include <QPainter>

// CTK includes
#include "ctkSizeGrip.h"

//------------------------------------------------------------------------------
class ctkSizeGripPrivate
{
  Q_DECLARE_PUBLIC(ctkSizeGrip)

protected:
  ctkSizeGrip* const q_ptr;

public:
  ctkSizeGripPrivate(ctkSizeGrip& object);
  void init();

  QWidget* WidgetToResize;
  Qt::Orientations Orientations;
  bool Resize;
  bool IgnoreWidgetMinimumSizeHint;

  QSize WidgetSizeHint;

  QRect WidgetGeom;
  QSize WidgetMinSize;
  QSize WidgetMaxSize;
  QPoint StartPos;

  bool Hover;
  bool Pressed;
};

//------------------------------------------------------------------------------
ctkSizeGripPrivate::ctkSizeGripPrivate(ctkSizeGrip& object)
  : q_ptr(&object)
  , WidgetToResize(0)
  , Orientations(Qt::Horizontal | Qt::Vertical)
  , Resize(false)
  , IgnoreWidgetMinimumSizeHint(true)
  , WidgetSizeHint(-1,-1)  ///< the default widget sizeHint should be used.
  , Hover(false)
  , Pressed(false)
{
}

//------------------------------------------------------------------------------
void ctkSizeGripPrivate::init()
{
  Q_Q(ctkSizeGrip);
  q->setOrientations(Qt::Horizontal | Qt::Vertical);
}

//------------------------------------------------------------------------------
ctkSizeGrip::ctkSizeGrip(QWidget* parent)
  : QWidget(parent)
  , d_ptr(new ctkSizeGripPrivate(*this))
{
  Q_D(ctkSizeGrip);
  d->WidgetToResize = parent;
  d->init();
}

//------------------------------------------------------------------------------
ctkSizeGrip::ctkSizeGrip(QWidget* target, QWidget* parent)
  : QWidget(parent)
  , d_ptr(new ctkSizeGripPrivate(*this))
{
  Q_D(ctkSizeGrip);
  d->WidgetToResize = target;
  d->init();
}

//------------------------------------------------------------------------------
ctkSizeGrip::~ctkSizeGrip()
{
}

//------------------------------------------------------------------------------
void ctkSizeGrip::setOrientations(Qt::Orientations newOrientations)
{
  Q_D(ctkSizeGrip);
  d->Orientations = newOrientations;
  QCursor newCursor;
  QSizePolicy newSizePolicy;
  switch(d->Orientations)
    {
    case Qt::Horizontal:
      newCursor = Qt::SizeHorCursor;
      newSizePolicy = QSizePolicy(QSizePolicy::Fixed, QSizePolicy::Minimum);
      break;
    case Qt::Vertical:
      newCursor = Qt::SizeVerCursor;
      newSizePolicy = QSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed);
      break;
    default:
      newCursor = this->isLeftToRight() ?
        Qt::SizeFDiagCursor : Qt::SizeBDiagCursor;
      newSizePolicy = QSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
      break;
    };
  this->setCursor(newCursor);
  this->setSizePolicy(newSizePolicy);
  this->updateGeometry(); // sizeHint might change
}

//------------------------------------------------------------------------------
Qt::Orientations ctkSizeGrip::orientations()const
{
  Q_D(const ctkSizeGrip);
  return d->Orientations;
}

//------------------------------------------------------------------------------
void ctkSizeGrip::setWidgetToResize(QWidget* target)
{
  Q_D(ctkSizeGrip);
  d->WidgetToResize = target;
  d->WidgetSizeHint = QSize();
}

//------------------------------------------------------------------------------
QWidget* ctkSizeGrip::widgetToResize()const
{
  Q_D(const ctkSizeGrip);
  return d->WidgetToResize;
}

//------------------------------------------------------------------------------
void ctkSizeGrip::setResizeWidget(bool resize)
{
  Q_D(ctkSizeGrip);
  d->Resize = resize;
  this->setWidgetSizeHint(d->WidgetSizeHint);
}

//------------------------------------------------------------------------------
bool ctkSizeGrip::resizeWidget()const
{
  Q_D(const ctkSizeGrip);
  return d->Resize;
}

//------------------------------------------------------------------------------
void ctkSizeGrip::setWidgetSizeHint(QSize sizeHint)
{
  Q_D(ctkSizeGrip);
  if (d->Resize && d->WidgetToResize)
    {
    QSize newSize = d->WidgetToResize->size();
    if (sizeHint.width() >= 0)
      {
      newSize.setWidth(sizeHint.width());
      }
    if (sizeHint.height() >= 0)
      {
      newSize.setHeight(sizeHint.height());
      }
    d->WidgetToResize->resize(newSize);
    }
  if (d->WidgetSizeHint != sizeHint)
    {
    d->WidgetSizeHint = sizeHint;
    emit widgetSizeHintChanged(d->WidgetSizeHint);
    }
}

//------------------------------------------------------------------------------
QSize ctkSizeGrip::widgetSizeHint()const
{
  Q_D(const ctkSizeGrip);
  return d->WidgetSizeHint;
}

//------------------------------------------------------------------------------
QSize ctkSizeGrip::sizeHint() const
{
  Q_D(const ctkSizeGrip);
  QSize minSize;
  QStyle::ContentsType contents;
  switch (d->Orientations)
    {
    case Qt::Horizontal:
    case Qt::Vertical:
      {
      contents = QStyle::CT_Splitter;
      int splitterWidth = this->style()->pixelMetric(QStyle::PM_SplitterWidth, 0, this);
      minSize = QSize(splitterWidth, splitterWidth);
      break;
      }
    default:
      contents = QStyle::CT_SizeGrip;
      minSize = QSize(13, 13);
      break;
    };
  QStyleOption opt(0);
  opt.init(this);
  return (this->style()->sizeFromContents(contents, &opt, minSize, this).
          expandedTo(QApplication::globalStrut()));
}

//------------------------------------------------------------------------------
void ctkSizeGrip::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event);
  Q_D(ctkSizeGrip);
  QPainter painter(this);
  switch (d->Orientations)
    {
    case Qt::Horizontal:
    case Qt::Vertical:
      {
      QStyleOption opt(0);
      opt.rect = rect();
      opt.palette = palette();
      opt.state = (d->Orientations == Qt::Horizontal) ?
        QStyle::State_Horizontal : QStyle::State_None;
      if (d->Hover)
        {
        opt.state |= QStyle::State_MouseOver;
        }
      if (d->Pressed)
        {
        opt.state |= QStyle::State_Sunken;
        }
      if (isEnabled())
        {
        opt.state |= QStyle::State_Enabled;
        }
      this->style()->drawControl(QStyle::CE_Splitter, &opt, &painter, this);
      break;
      }
    default:
      {
      QStyleOptionSizeGrip opt;
      opt.init(this);
      opt.corner = this->isLeftToRight() ? Qt::BottomRightCorner : Qt::BottomLeftCorner;
      style()->drawControl(QStyle::CE_SizeGrip, &opt, &painter, this);
      break;
      }
    };
}

//------------------------------------------------------------------------------
bool ctkSizeGrip::event(QEvent *event)
{
  Q_D(ctkSizeGrip);
  switch(event->type())
    {
    case QEvent::HoverEnter:
      d->Hover = true;
      update();
      break;
    case QEvent::HoverLeave:
      d->Hover = false;
      update();
      break;
    default:
      break;
    }
  return this->Superclass::event(event);
}

//------------------------------------------------------------------------------
void ctkSizeGrip::mousePressEvent(QMouseEvent * e)
{
  if (e->button() != Qt::LeftButton)
    {
    QWidget::mousePressEvent(e);
    return;
    }

  Q_D(ctkSizeGrip);
  d->StartPos = e->globalPos();
  d->Pressed = true;
  d->WidgetGeom = d->WidgetToResize->geometry();
  d->WidgetMinSize = d->WidgetToResize->minimumSize();
  d->WidgetMaxSize = d->WidgetToResize->maximumSize();
}


//------------------------------------------------------------------------------
void ctkSizeGrip::mouseMoveEvent(QMouseEvent * e)
{
  if (e->buttons() != Qt::LeftButton)
    {
    this->Superclass::mouseMoveEvent(e);
    return;
    }

  Q_D(ctkSizeGrip);
  if (!d->Pressed || d->WidgetToResize->testAttribute(Qt::WA_WState_ConfigPending))
    {
    return;
    }

  QPoint newPos(e->globalPos());
  QSize offset(newPos.x() - d->StartPos.x(), newPos.y() - d->StartPos.y());

  QSize widgetSizeHint = d->WidgetGeom.size();
  if (d->Orientations & Qt::Vertical)
    {
    widgetSizeHint.rheight() = d->WidgetGeom.height() + offset.height();
    }

  if (d->Orientations & Qt::Horizontal)
    {
    widgetSizeHint.rwidth() = d->WidgetGeom.width() + offset.width() * (this->isLeftToRight() ? 1 : -1);
    }
  // Make sure we don't allow "unreasonable" sizes.
  widgetSizeHint = widgetSizeHint.expandedTo(d->WidgetMinSize).boundedTo(d->WidgetMaxSize);

  if (!d->IgnoreWidgetMinimumSizeHint)
    {
    widgetSizeHint = QLayout::closestAcceptableSize(d->WidgetToResize, widgetSizeHint);
    }
  else
    {
    // Here we can't use QLayout::closestAcceptableSize as it internally uses
    // the widget minimumSizeHint to expand the size.
    // This usually allows only enlarging the widget but prevent shrinking the
    // widget.
    // Manually assess the closest acceptable size
    // Respect the heightForWidth ratio
    if (d->WidgetToResize->heightForWidth(widgetSizeHint.width()) != -1)
      {
      widgetSizeHint.rheight() = d->WidgetToResize->heightForWidth(widgetSizeHint.width());
      }
    }

  widgetSizeHint = widgetSizeHint.expandedTo(QApplication::globalStrut());

  this->setWidgetSizeHint(
    QSize(d->Orientations & Qt::Horizontal ? widgetSizeHint.width() : -1,
          d->Orientations & Qt::Vertical ? widgetSizeHint.height() : -1));
}

//------------------------------------------------------------------------------
void ctkSizeGrip::mouseReleaseEvent(QMouseEvent *mouseEvent)
{
  if (mouseEvent->button() != Qt::LeftButton)
    {
    this->Superclass::mouseReleaseEvent(mouseEvent);
    return;
    }
  Q_D(ctkSizeGrip);
  d->Pressed = false;
  d->StartPos = QPoint();
}

//------------------------------------------------------------------------------
void ctkSizeGrip::mouseDoubleClickEvent(QMouseEvent *mouseEvent)
{
  if (mouseEvent->button() != Qt::LeftButton)
    {
    this->Superclass::mouseDoubleClickEvent(mouseEvent);
    return;
    }
  this->setWidgetSizeHint(QSize(-1, -1));
}