/* This file is part of Clementine.
   Copyright 2010, David Sansome <me@davidsansome.com>

   Clementine 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.

   Clementine 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 Clementine.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "stretchheaderview.h"
#include "core/logging.h"

#include <QDataStream>

#include <algorithm>
#include <cmath>
#include <numeric>

const int StretchHeaderView::kMinimumColumnWidth = 10;
const int StretchHeaderView::kMagicNumber = 0x502c950f;

StretchHeaderView::StretchHeaderView(Qt::Orientation orientation, QWidget* parent)
  : QHeaderView(orientation, parent),
    stretch_enabled_(false),
    in_mouse_move_event_(false)
{
  connect(this, SIGNAL(sectionResized(int,int,int)), SLOT(SectionResized(int,int,int)));
}

void StretchHeaderView::setModel(QAbstractItemModel* model) {
  QHeaderView::setModel(model);

  if (stretch_enabled_) {
    column_widths_.resize(count());
    std::fill(column_widths_.begin(), column_widths_.end(), 1.0 / count());
  }
}

void StretchHeaderView::NormaliseWidths(const QList<int>& sections) {
  if (!stretch_enabled_)
    return;

  const ColumnWidthType total_sum =
      std::accumulate(column_widths_.begin(), column_widths_.end(), 0.0);
  ColumnWidthType selected_sum = total_sum;

  if (!sections.isEmpty()) {
    selected_sum = 0.0;
    for (int i=0 ; i<count() ; ++i)
      if (sections.contains(i))
        selected_sum += column_widths_[i];
  }

  if (total_sum != 0.0 && !qFuzzyCompare(total_sum, 1.0)) {
    const ColumnWidthType mult = (selected_sum + (1.0 - total_sum)) / selected_sum;
    for (int i=0 ; i<column_widths_.count() ; ++i) {
      if (sections.isEmpty() || sections.contains(i))
        column_widths_[i] *= mult;
    }
  }
}

void StretchHeaderView::UpdateWidths(const QList<int>& sections) {
  if (!stretch_enabled_)
    return;

  ColumnWidthType total_w = 0.0;

  for (int i=0 ; i<column_widths_.count() ; ++i) {
    const ColumnWidthType w = column_widths_[i];
    int pixels = w * width();

    if (pixels != 0 && total_w - int(total_w) > 0.5)
      pixels ++;

    total_w += w;

    if (!sections.isEmpty() && !sections.contains(i))
      continue;

    if (pixels == 0 && !isSectionHidden(i))
      hideSection(i);
    else if (pixels != 0 && isSectionHidden(i)) {
      showSection(i);
      AssertMinimalColumnWidth(i);
    }

    if (pixels != 0)
      resizeSection(i, pixels);
  }
}

void StretchHeaderView::HideSection(int logical) {
  // Would this hide the last section?
  bool all_hidden = true;
  for (int i=0 ; i<count() ; ++i) {
    if (i != logical && !isSectionHidden(i) && sectionSize(i) > 0) {
      all_hidden = false;
      break;
    }
  }
  if (all_hidden) {
    return;
  }

  if (!stretch_enabled_) {
    hideSection(logical);
    return;
  }

  column_widths_[logical] = 0.0;
  NormaliseWidths();
  UpdateWidths();
}

void StretchHeaderView::ShowSection(int logical) {
  if (!stretch_enabled_) {
    showSection(logical);
    return;
  }

  // How many sections are visible already?
  int visible_count = 0;
  for (int i=0 ; i<count() ; ++i) {
    if (!isSectionHidden(i))
      visible_count ++;
  }

  column_widths_[logical] =
      visible_count == 0 ? 1.0 : 1.0 / visible_count;
  NormaliseWidths();
  UpdateWidths();
}

void StretchHeaderView::SetSectionHidden(int logical, bool hidden) {
  if(hidden) {
    HideSection(logical);
  } else {
    ShowSection(logical);
    AssertMinimalColumnWidth(logical);
  }
}

void StretchHeaderView::resizeEvent(QResizeEvent* event) {
  QHeaderView::resizeEvent(event);

  if (!stretch_enabled_)
    return;

  UpdateWidths();
}

void StretchHeaderView::mouseMoveEvent(QMouseEvent* e) {
  in_mouse_move_event_ = true;
  QHeaderView::mouseMoveEvent(e);
  in_mouse_move_event_ = false;
}

void StretchHeaderView::SectionResized(int logical, int, int new_size) {
  if (!stretch_enabled_)
    return;

  if (in_mouse_move_event_) {
    // Update this section's proportional width
    column_widths_[logical] = ColumnWidthType(new_size) / width();

    // Find the visible sections to the right of the section that's being resized
    int visual = visualIndex(logical);
    QList<int> logical_sections_to_resize;
    for (int i=0 ; i<count() ; ++i) {
      if (!isSectionHidden(i) && visualIndex(i) > visual)
        logical_sections_to_resize << i;
    }

    // Resize just those columns
    if (!logical_sections_to_resize.isEmpty()) {
      in_mouse_move_event_ = false;
      UpdateWidths(logical_sections_to_resize);
      NormaliseWidths(logical_sections_to_resize);
      in_mouse_move_event_ = true;
    }
  }
}

void StretchHeaderView::ToggleStretchEnabled() {
  SetStretchEnabled(!is_stretch_enabled());
}

void StretchHeaderView::SetStretchEnabled(bool enabled) {
  stretch_enabled_ = enabled;

  if (enabled) {
    // Initialise the list of widths from the current state of the widget
    column_widths_.resize(count());
    for (int i=0 ; i<count() ; ++i) {
      column_widths_[i] = ColumnWidthType(sectionSize(i)) / width();
    }

    // Stretch the columns to fill the widget
    NormaliseWidths();
    UpdateWidths();
  }

  emit StretchEnabledChanged(enabled);
}

void StretchHeaderView::SetColumnWidth(int logical, ColumnWidthType width) {
  if (!stretch_enabled_)
    return;

  column_widths_[logical] = width;

  QList<int> other_columns;
  for (int i=0 ; i<count() ; ++i)
    if (!isSectionHidden(i) && i != logical)
      other_columns << i;
  NormaliseWidths(other_columns);
}

// makes sure the column will apear no matter what
void StretchHeaderView::AssertMinimalColumnWidth(int logical) {
  if (sectionSize(logical) < kMinimumColumnWidth) {
    resizeSection(logical, kMinimumColumnWidth);
  }
}

bool StretchHeaderView::RestoreState(const QByteArray& data) {
  QDataStream s(data);
  s.setVersion(QDataStream::Qt_4_6);

  int magic_number = 0;
  s >> magic_number;

  if (magic_number != kMagicNumber || s.atEnd()) {
    return false;
  }

  QList<int> pixel_widths;
  QList<int> visual_indices;
  int sort_indicator_order = Qt::AscendingOrder;
  int sort_indicator_section = 0;

  s >> stretch_enabled_;
  s >> pixel_widths;
  s >> visual_indices;
  s >> column_widths_;
  s >> sort_indicator_order;
  s >> sort_indicator_section;

  setSortIndicator(sort_indicator_section, Qt::SortOrder(sort_indicator_order));

  const int persisted_column_count =
      qMin(qMin(visual_indices.count(), pixel_widths.count()), column_widths_.count());

  // Set column visible state, visual indices and, if we're not in stretch mode,
  // pixel widths.
  for (int i=0 ; i<count() && i<persisted_column_count ; ++i) {
    setSectionHidden(i, pixel_widths[i] <= kMinimumColumnWidth);
    moveSection(visualIndex(visual_indices[i]), i);

    if (!stretch_enabled_) {
      resizeSection(i, pixel_widths[i]);
    }
  }
  
  // Have we added more columns since the last time?
  while (column_widths_.count() < count()) {
    column_widths_ << 0;
  }

  if (stretch_enabled_) {
    // In stretch mode, we've already set the proportional column widths so apply
    // them now.
    UpdateWidths();
  }

  emit StretchEnabledChanged(stretch_enabled_);

  return true;
}

QByteArray StretchHeaderView::SaveState() const {
  QByteArray ret;
  QDataStream s(&ret, QIODevice::WriteOnly);

  QList<int> pixel_widths;
  QList<int> visual_indices;

  for (int i=0 ; i<count() ; ++i) {
    pixel_widths << sectionSize(i);
    visual_indices << logicalIndex(i);
  }

  s.setVersion(QDataStream::Qt_4_6);
  s << kMagicNumber;

  s << stretch_enabled_;
  s << pixel_widths;
  s << visual_indices;
  s << column_widths_;
  s << int(sortIndicatorOrder());
  s << sortIndicatorSection();

  return ret;
}