// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/views/layout/box_layout.h"

#include "ui/gfx/geometry/rect.h"
#include "ui/views/view.h"

namespace views {

BoxLayout::BoxLayout(BoxLayout::Orientation orientation,
                     int inside_border_horizontal_spacing,
                     int inside_border_vertical_spacing,
                     int between_child_spacing)
    : orientation_(orientation),
      inside_border_insets_(inside_border_vertical_spacing,
                            inside_border_horizontal_spacing,
                            inside_border_vertical_spacing,
                            inside_border_horizontal_spacing),
      between_child_spacing_(between_child_spacing),
      main_axis_alignment_(MAIN_AXIS_ALIGNMENT_START),
      cross_axis_alignment_(CROSS_AXIS_ALIGNMENT_STRETCH),
      default_flex_(0),
      minimum_cross_axis_size_(0),
      host_(NULL) {
}

BoxLayout::~BoxLayout() {
}

void BoxLayout::SetFlexForView(const View* view, int flex_weight) {
  DCHECK(host_);
  DCHECK(view);
  DCHECK_EQ(host_, view->parent());
  DCHECK_GE(flex_weight, 0);
  flex_map_[view] = flex_weight;
}

void BoxLayout::ClearFlexForView(const View* view) {
  DCHECK(view);
  flex_map_.erase(view);
}

void BoxLayout::SetDefaultFlex(int default_flex) {
  DCHECK_GE(default_flex, 0);
  default_flex_ = default_flex;
}

void BoxLayout::Layout(View* host) {
  DCHECK_EQ(host_, host);
  gfx::Rect child_area(host->GetLocalBounds());
  child_area.Inset(host->GetInsets());
  child_area.Inset(inside_border_insets_);

  int total_main_axis_size = 0;
  int num_visible = 0;
  int flex_sum = 0;
  // Calculate the total size of children in the main axis.
  for (int i = 0; i < host->child_count(); ++i) {
    View* child = host->child_at(i);
    if (!child->visible())
      continue;
    total_main_axis_size +=
        MainAxisSizeForView(child, child_area.width()) + between_child_spacing_;
    ++num_visible;
    flex_sum += GetFlexForView(child);
  }

  if (!num_visible)
    return;

  total_main_axis_size -= between_child_spacing_;
  // Free space can be negative indicating that the views want to overflow.
  int main_free_space = MainAxisSize(child_area) - total_main_axis_size;
  {
    int position = MainAxisPosition(child_area);
    int size = MainAxisSize(child_area);
    if (!flex_sum) {
      switch (main_axis_alignment_) {
        case MAIN_AXIS_ALIGNMENT_START:
          break;
        case MAIN_AXIS_ALIGNMENT_CENTER:
          position += main_free_space / 2;
          size = total_main_axis_size;
          break;
        case MAIN_AXIS_ALIGNMENT_END:
          position += main_free_space;
          size = total_main_axis_size;
          break;
        default:
          NOTREACHED();
          break;
      }
    }
    gfx::Rect new_child_area(child_area);
    SetMainAxisPosition(position, &new_child_area);
    SetMainAxisSize(size, &new_child_area);
    child_area.Intersect(new_child_area);
  }

  int main_position = MainAxisPosition(child_area);
  int total_padding = 0;
  int current_flex = 0;
  for (int i = 0; i < host->child_count(); ++i) {
    View* child = host->child_at(i);
    if (!child->visible())
      continue;

    // Calculate cross axis size.
    gfx::Rect bounds(child_area);
    SetMainAxisPosition(main_position, &bounds);
    if (cross_axis_alignment_ != CROSS_AXIS_ALIGNMENT_STRETCH) {
      int free_space = CrossAxisSize(bounds) - CrossAxisSizeForView(child);
      int position = CrossAxisPosition(bounds);
      if (cross_axis_alignment_ == CROSS_AXIS_ALIGNMENT_CENTER) {
        position += free_space / 2;
      } else if (cross_axis_alignment_ == CROSS_AXIS_ALIGNMENT_END) {
        position += free_space;
      }
      SetCrossAxisPosition(position, &bounds);
      SetCrossAxisSize(CrossAxisSizeForView(child), &bounds);
    }

    // Calculate flex padding.
    int current_padding = 0;
    if (GetFlexForView(child) > 0) {
      current_flex += GetFlexForView(child);
      int quot = (main_free_space * current_flex) / flex_sum;
      int rem = (main_free_space * current_flex) % flex_sum;
      current_padding = quot - total_padding;
      // Use the current remainder to round to the nearest pixel.
      if (std::abs(rem) * 2 >= flex_sum)
        current_padding += main_free_space > 0 ? 1 : -1;
      total_padding += current_padding;
    }

    // Set main axis size.
    int child_main_axis_size = MainAxisSizeForView(child, child_area.width());
    SetMainAxisSize(child_main_axis_size + current_padding, &bounds);
    if (MainAxisSize(bounds) > 0 || GetFlexForView(child) > 0)
      main_position += MainAxisSize(bounds) + between_child_spacing_;

    // Clamp child view bounds to |child_area|.
    bounds.Intersect(child_area);
    child->SetBoundsRect(bounds);
  }

  // Flex views should have grown/shrunk to consume all free space.
  if (flex_sum)
    DCHECK_EQ(total_padding, main_free_space);
}

gfx::Size BoxLayout::GetPreferredSize(const View* host) const {
  DCHECK_EQ(host_, host);
  // Calculate the child views' preferred width.
  int width = 0;
  if (orientation_ == kVertical) {
    for (int i = 0; i < host->child_count(); ++i) {
      const View* child = host->child_at(i);
      if (!child->visible())
        continue;

      width = std::max(width, child->GetPreferredSize().width());
    }
    width = std::max(width, minimum_cross_axis_size_);
  }

  return GetPreferredSizeForChildWidth(host, width);
}

int BoxLayout::GetPreferredHeightForWidth(const View* host, int width) const {
  DCHECK_EQ(host_, host);
  int child_width = width - NonChildSize(host).width();
  return GetPreferredSizeForChildWidth(host, child_width).height();
}

void BoxLayout::Installed(View* host) {
  DCHECK(!host_);
  host_ = host;
}

void BoxLayout::Uninstalled(View* host) {
  DCHECK_EQ(host_, host);
  host_ = NULL;
  flex_map_.clear();
}

void BoxLayout::ViewRemoved(View* host, View* view) {
  ClearFlexForView(view);
}

int BoxLayout::GetFlexForView(const View* view) const {
  std::map<const View*, int>::const_iterator it = flex_map_.find(view);
  if (it == flex_map_.end())
    return default_flex_;

  return it->second;
}

int BoxLayout::MainAxisSize(const gfx::Rect& rect) const {
  return orientation_ == kHorizontal ? rect.width() : rect.height();
}

int BoxLayout::MainAxisPosition(const gfx::Rect& rect) const {
  return orientation_ == kHorizontal ? rect.x() : rect.y();
}

void BoxLayout::SetMainAxisSize(int size, gfx::Rect* rect) const {
  if (orientation_ == kHorizontal)
    rect->set_width(size);
  else
    rect->set_height(size);
}

void BoxLayout::SetMainAxisPosition(int position, gfx::Rect* rect) const {
  if (orientation_ == kHorizontal)
    rect->set_x(position);
  else
    rect->set_y(position);
}

int BoxLayout::CrossAxisSize(const gfx::Rect& rect) const {
  return orientation_ == kVertical ? rect.width() : rect.height();
}

int BoxLayout::CrossAxisPosition(const gfx::Rect& rect) const {
  return orientation_ == kVertical ? rect.x() : rect.y();
}

void BoxLayout::SetCrossAxisSize(int size, gfx::Rect* rect) const {
  if (orientation_ == kVertical)
    rect->set_width(size);
  else
    rect->set_height(size);
}

void BoxLayout::SetCrossAxisPosition(int position, gfx::Rect* rect) const {
  if (orientation_ == kVertical)
    rect->set_x(position);
  else
    rect->set_y(position);
}

int BoxLayout::MainAxisSizeForView(const View* view,
                                   int child_area_width) const {
  return orientation_ == kHorizontal
             ? view->GetPreferredSize().width()
             : view->GetHeightForWidth(cross_axis_alignment_ ==
                                               CROSS_AXIS_ALIGNMENT_STRETCH
                                           ? child_area_width
                                           : view->GetPreferredSize().width());
}

int BoxLayout::CrossAxisSizeForView(const View* view) const {
  return orientation_ == kVertical
             ? view->GetPreferredSize().width()
             : view->GetHeightForWidth(view->GetPreferredSize().width());
}

gfx::Size BoxLayout::GetPreferredSizeForChildWidth(const View* host,
                                                   int child_area_width) const {
  gfx::Rect child_area_bounds;

  if (orientation_ == kHorizontal) {
    // Horizontal layouts ignore |child_area_width|, meaning they mimic the
    // default behavior of GridLayout::GetPreferredHeightForWidth().
    // TODO(estade): fix this if it ever becomes a problem.
    int position = 0;
    for (int i = 0; i < host->child_count(); ++i) {
      const View* child = host->child_at(i);
      if (!child->visible())
        continue;

      gfx::Size size(child->GetPreferredSize());
      if (size.IsEmpty())
        continue;

      gfx::Rect child_bounds(position, 0, size.width(), size.height());
      child_area_bounds.Union(child_bounds);
      position += size.width() + between_child_spacing_;
    }
    child_area_bounds.set_height(
        std::max(child_area_bounds.height(), minimum_cross_axis_size_));
  } else {
    int height = 0;
    for (int i = 0; i < host->child_count(); ++i) {
      const View* child = host->child_at(i);
      if (!child->visible())
        continue;

      // Use the child area width for getting the height if the child is
      // supposed to stretch. Use its preferred size otherwise.
      int extra_height = MainAxisSizeForView(child, child_area_width);
      // Only add |between_child_spacing_| if this is not the only child.
      if (height != 0 && extra_height > 0)
        height += between_child_spacing_;
      height += extra_height;
    }

    child_area_bounds.set_width(child_area_width);
    child_area_bounds.set_height(height);
  }

  gfx::Size non_child_size = NonChildSize(host);
  return gfx::Size(child_area_bounds.width() + non_child_size.width(),
                   child_area_bounds.height() + non_child_size.height());
}

gfx::Size BoxLayout::NonChildSize(const View* host) const {
  gfx::Insets insets(host->GetInsets());
  return gfx::Size(insets.width() + inside_border_insets_.width(),
                   insets.height() + inside_border_insets_.height());
}

} // namespace views