// Copyright 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 "cc/resources/picture_layer_tiling.h"

#include <algorithm>
#include <cmath>

#include "base/debug/trace_event.h"
#include "cc/base/math_util.h"
#include "ui/gfx/point_conversions.h"
#include "ui/gfx/rect_conversions.h"
#include "ui/gfx/safe_integer_conversions.h"
#include "ui/gfx/size_conversions.h"

namespace cc {

scoped_ptr<PictureLayerTiling> PictureLayerTiling::Create(
    float contents_scale) {
  return make_scoped_ptr(new PictureLayerTiling(contents_scale));
}

scoped_ptr<PictureLayerTiling> PictureLayerTiling::Clone() const {
  return make_scoped_ptr(new PictureLayerTiling(*this));
}

PictureLayerTiling::PictureLayerTiling(float contents_scale)
    : client_(NULL),
      contents_scale_(contents_scale),
      tiling_data_(gfx::Size(), gfx::Size(), true),
      resolution_(NON_IDEAL_RESOLUTION),
      last_source_frame_number_(0),
      last_impl_frame_time_(0) {
}

PictureLayerTiling::~PictureLayerTiling() {
}

void PictureLayerTiling::SetClient(PictureLayerTilingClient* client) {
  client_ = client;
}

gfx::Rect PictureLayerTiling::ContentRect() const {
  return gfx::Rect(tiling_data_.total_size());
}

gfx::SizeF PictureLayerTiling::ContentSizeF() const {
  return gfx::ScaleSize(layer_bounds_, contents_scale_);
}

Tile* PictureLayerTiling::TileAt(int i, int j) const {
  TileMap::const_iterator iter = tiles_.find(TileMapKey(i, j));
  if (iter == tiles_.end())
    return NULL;
  return iter->second.get();
}

void PictureLayerTiling::CreateTile(int i, int j) {
  gfx::Rect tile_rect = tiling_data_.TileBoundsWithBorder(i, j);
  tile_rect.set_size(tiling_data_.max_texture_size());
  TileMapKey key(i, j);
  DCHECK(tiles_.find(key) == tiles_.end());
  scoped_refptr<Tile> tile = client_->CreateTile(this, tile_rect);
  if (tile)
    tiles_[key] = tile;
}

Region PictureLayerTiling::OpaqueRegionInContentRect(
    const gfx::Rect& content_rect) const {
  Region opaque_region;
  // TODO(enne): implement me
  return opaque_region;
}

void PictureLayerTiling::SetLayerBounds(gfx::Size layer_bounds) {
  if (layer_bounds_ == layer_bounds)
    return;

  gfx::Size old_layer_bounds = layer_bounds_;
  layer_bounds_ = layer_bounds;
  gfx::Size old_content_bounds = tiling_data_.total_size();
  gfx::Size content_bounds =
      gfx::ToCeiledSize(gfx::ScaleSize(layer_bounds_, contents_scale_));

  tiling_data_.SetTotalSize(content_bounds);
  if (layer_bounds_.IsEmpty()) {
    tiles_.clear();
    return;
  }

  gfx::Size tile_size = client_->CalculateTileSize(
      tiling_data_.max_texture_size(),
      content_bounds);
  if (tile_size != tiling_data_.max_texture_size()) {
    tiling_data_.SetMaxTextureSize(tile_size);
    tiles_.clear();
    CreateTilesFromLayerRect(gfx::Rect(layer_bounds_));
    return;
  }

  // Any tiles outside our new bounds are invalid and should be dropped.
  if (old_content_bounds.width() > content_bounds.width() ||
      old_content_bounds.height() > content_bounds.height()) {
    int right =
        tiling_data_.TileXIndexFromSrcCoord(content_bounds.width() - 1);
    int bottom =
        tiling_data_.TileYIndexFromSrcCoord(content_bounds.height() - 1);

    std::vector<TileMapKey> invalid_tile_keys;
    for (TileMap::const_iterator it = tiles_.begin();
         it != tiles_.end(); ++it) {
      if (it->first.first > right || it->first.second > bottom)
        invalid_tile_keys.push_back(it->first);
    }
    for (size_t i = 0; i < invalid_tile_keys.size(); ++i)
      tiles_.erase(invalid_tile_keys[i]);
  }

  // Create tiles for newly exposed areas.
  Region layer_region((gfx::Rect(layer_bounds_)));
  layer_region.Subtract(gfx::Rect(old_layer_bounds));
  for (Region::Iterator iter(layer_region); iter.has_rect(); iter.next()) {
    Invalidate(iter.rect());
    CreateTilesFromLayerRect(iter.rect());
  }
}

void PictureLayerTiling::Invalidate(const Region& layer_invalidation) {
  std::vector<TileMapKey> new_tiles;

  for (Region::Iterator region_iter(layer_invalidation);
       region_iter.has_rect();
       region_iter.next()) {
    gfx::Rect layer_invalidation = region_iter.rect();
    layer_invalidation.Intersect(gfx::Rect(layer_bounds_));
    gfx::Rect rect =
        gfx::ToEnclosingRect(ScaleRect(layer_invalidation, contents_scale_));

    for (PictureLayerTiling::Iterator tile_iter(this, contents_scale_, rect);
         tile_iter;
         ++tile_iter) {
      TileMapKey key(tile_iter.tile_i_, tile_iter.tile_j_);
      TileMap::iterator found = tiles_.find(key);
      if (found == tiles_.end())
        continue;

      tiles_.erase(found);
      new_tiles.push_back(key);
    }
  }

  for (size_t i = 0; i < new_tiles.size(); ++i)
    CreateTile(new_tiles[i].first, new_tiles[i].second);
}

void PictureLayerTiling::CreateTilesFromLayerRect(gfx::Rect layer_rect) {
  gfx::Rect content_rect =
      gfx::ToEnclosingRect(ScaleRect(layer_rect, contents_scale_));
  CreateTilesFromContentRect(content_rect);
}

void PictureLayerTiling::CreateTilesFromContentRect(gfx::Rect content_rect) {
  for (TilingData::Iterator iter(&tiling_data_, content_rect); iter; ++iter) {
    TileMap::iterator found =
        tiles_.find(TileMapKey(iter.index_x(), iter.index_y()));
    // Ignore any tiles that already exist.
    if (found != tiles_.end())
      continue;
    CreateTile(iter.index_x(), iter.index_y());
  }
}

PictureLayerTiling::Iterator::Iterator()
    : tiling_(NULL),
      current_tile_(NULL),
      tile_i_(0),
      tile_j_(0),
      left_(0),
      top_(0),
      right_(-1),
      bottom_(-1) {
}

PictureLayerTiling::Iterator::Iterator(const PictureLayerTiling* tiling,
                                       float dest_scale,
                                       gfx::Rect dest_rect)
    : tiling_(tiling),
      dest_rect_(dest_rect),
      dest_to_content_scale_(0),
      current_tile_(NULL),
      tile_i_(0),
      tile_j_(0),
      left_(0),
      top_(0),
      right_(-1),
      bottom_(-1) {
  DCHECK(tiling_);
  if (dest_rect_.IsEmpty())
    return;

  dest_to_content_scale_ = tiling_->contents_scale_ / dest_scale;
  // This is the maximum size that the dest rect can be, given the content size.
  gfx::Size dest_content_size = gfx::ToCeiledSize(gfx::ScaleSize(
      tiling_->ContentRect().size(),
      1 / dest_to_content_scale_,
      1 / dest_to_content_scale_));

  gfx::Rect content_rect =
      gfx::ToEnclosingRect(gfx::ScaleRect(dest_rect_,
                                          dest_to_content_scale_,
                                          dest_to_content_scale_));
  // IndexFromSrcCoord clamps to valid tile ranges, so it's necessary to
  // check for non-intersection first.
  content_rect.Intersect(gfx::Rect(tiling_->tiling_data_.total_size()));
  if (content_rect.IsEmpty())
    return;

  left_ = tiling_->tiling_data_.TileXIndexFromSrcCoord(content_rect.x());
  top_ = tiling_->tiling_data_.TileYIndexFromSrcCoord(content_rect.y());
  right_ = tiling_->tiling_data_.TileXIndexFromSrcCoord(
      content_rect.right() - 1);
  bottom_ = tiling_->tiling_data_.TileYIndexFromSrcCoord(
      content_rect.bottom() - 1);

  tile_i_ = left_ - 1;
  tile_j_ = top_;
  ++(*this);
}

PictureLayerTiling::Iterator::~Iterator() {
}

PictureLayerTiling::Iterator& PictureLayerTiling::Iterator::operator++() {
  if (tile_j_ > bottom_)
    return *this;

  bool first_time = tile_i_ < left_;
  bool new_row = false;
  tile_i_++;
  if (tile_i_ > right_) {
    tile_i_ = left_;
    tile_j_++;
    new_row = true;
    if (tile_j_ > bottom_) {
      current_tile_ = NULL;
      return *this;
    }
  }

  current_tile_ = tiling_->TileAt(tile_i_, tile_j_);

  // Calculate the current geometry rect.  Due to floating point rounding
  // and ToEnclosingRect, tiles might overlap in destination space on the
  // edges.
  gfx::Rect last_geometry_rect = current_geometry_rect_;

  gfx::Rect content_rect = tiling_->tiling_data_.TileBounds(tile_i_, tile_j_);

  current_geometry_rect_ = gfx::ToEnclosingRect(
      gfx::ScaleRect(content_rect, 1 / dest_to_content_scale_,
                                   1 / dest_to_content_scale_));

  current_geometry_rect_.Intersect(dest_rect_);

  if (first_time)
    return *this;

  // Iteration happens left->right, top->bottom.  Running off the bottom-right
  // edge is handled by the intersection above with dest_rect_.  Here we make
  // sure that the new current geometry rect doesn't overlap with the last.
  int min_left;
  int min_top;
  if (new_row) {
    min_left = dest_rect_.x();
    min_top = last_geometry_rect.bottom();
  } else {
    min_left = last_geometry_rect.right();
    min_top = last_geometry_rect.y();
  }

  int inset_left = std::max(0, min_left - current_geometry_rect_.x());
  int inset_top = std::max(0, min_top - current_geometry_rect_.y());
  current_geometry_rect_.Inset(inset_left, inset_top, 0, 0);

  if (!new_row) {
    DCHECK_EQ(last_geometry_rect.right(), current_geometry_rect_.x());
    DCHECK_EQ(last_geometry_rect.bottom(), current_geometry_rect_.bottom());
    DCHECK_EQ(last_geometry_rect.y(), current_geometry_rect_.y());
  }

  return *this;
}

gfx::Rect PictureLayerTiling::Iterator::geometry_rect() const {
  return current_geometry_rect_;
}

gfx::Rect PictureLayerTiling::Iterator::full_tile_geometry_rect() const {
  gfx::Rect rect = tiling_->tiling_data_.TileBoundsWithBorder(tile_i_, tile_j_);
  rect.set_size(tiling_->tiling_data_.max_texture_size());
  return rect;
}

gfx::RectF PictureLayerTiling::Iterator::texture_rect() const {
  gfx::PointF tex_origin =
      tiling_->tiling_data_.TileBoundsWithBorder(tile_i_, tile_j_).origin();

  // Convert from dest space => content space => texture space.
  gfx::RectF texture_rect(current_geometry_rect_);
  texture_rect.Scale(dest_to_content_scale_,
                     dest_to_content_scale_);
  texture_rect.Offset(-tex_origin.OffsetFromOrigin());
  texture_rect.Intersect(tiling_->ContentRect());

  return texture_rect;
}

gfx::Size PictureLayerTiling::Iterator::texture_size() const {
  return tiling_->tiling_data_.max_texture_size();
}

void PictureLayerTiling::UpdateTilePriorities(
    WhichTree tree,
    gfx::Size device_viewport,
    const gfx::RectF& viewport_in_layer_space,
    gfx::Size last_layer_bounds,
    gfx::Size current_layer_bounds,
    float last_layer_contents_scale,
    float current_layer_contents_scale,
    const gfx::Transform& last_screen_transform,
    const gfx::Transform& current_screen_transform,
    int current_source_frame_number,
    double current_frame_time,
    bool store_screen_space_quads_on_tiles) {
  if (ContentRect().IsEmpty())
    return;

  bool first_update_in_new_source_frame =
      current_source_frame_number != last_source_frame_number_;

  bool first_update_in_new_impl_frame =
      current_frame_time != last_impl_frame_time_;

  // In pending tree, this is always called. We update priorities:
  // - Immediately after a commit (first_update_in_new_source_frame).
  // - On animation ticks after the first frame in the tree
  //   (first_update_in_new_impl_frame).
  // In active tree, this is only called during draw. We update priorities:
  // - On draw if properties were not already computed by the pending tree
  //   and activated for the frame (first_update_in_new_impl_frame).
  if (!first_update_in_new_impl_frame && !first_update_in_new_source_frame)
    return;

  double time_delta = 0;
  if (last_impl_frame_time_ != 0 && last_layer_bounds == current_layer_bounds)
    time_delta = current_frame_time - last_impl_frame_time_;

  gfx::Rect viewport_in_content_space =
      gfx::ToEnclosingRect(gfx::ScaleRect(viewport_in_layer_space,
                                          contents_scale_));

  gfx::Size tile_size = tiling_data_.max_texture_size();
  int64 prioritized_rect_area =
      TilePriority::kNumTilesToCoverWithInflatedViewportRectForPrioritization *
      tile_size.width() * tile_size.height();

  gfx::Rect prioritized_rect = ExpandRectEquallyToAreaBoundedBy(
      viewport_in_content_space,
      prioritized_rect_area,
      ContentRect());
  DCHECK(ContentRect().Contains(prioritized_rect));

  // Iterate through all of the tiles that were live last frame but will
  // not be live this frame, and mark them as being dead.
  for (TilingData::DifferenceIterator iter(&tiling_data_,
                                           last_prioritized_rect_,
                                           prioritized_rect);
       iter;
       ++iter) {
    TileMap::iterator find = tiles_.find(iter.index());
    if (find == tiles_.end())
      continue;

    TilePriority priority;
    DCHECK(!priority.is_live);
    Tile* tile = find->second.get();
    tile->SetPriority(tree, priority);
  }
  last_prioritized_rect_ = prioritized_rect;

  gfx::Rect view_rect(device_viewport);
  float current_scale = current_layer_contents_scale / contents_scale_;
  float last_scale = last_layer_contents_scale / contents_scale_;

  // Fast path tile priority calculation when both transforms are translations.
  if (last_screen_transform.IsIdentityOrTranslation() &&
      current_screen_transform.IsIdentityOrTranslation()) {
    gfx::Vector2dF current_offset(
        current_screen_transform.matrix().get(0, 3),
        current_screen_transform.matrix().get(1, 3));
    gfx::Vector2dF last_offset(
        last_screen_transform.matrix().get(0, 3),
        last_screen_transform.matrix().get(1, 3));

    for (TilingData::Iterator iter(&tiling_data_, prioritized_rect);
         iter; ++iter) {
      TileMap::iterator find = tiles_.find(iter.index());
      if (find == tiles_.end())
        continue;
      Tile* tile = find->second.get();

      gfx::Rect tile_bounds =
          tiling_data_.TileBounds(iter.index_x(), iter.index_y());
      gfx::RectF current_screen_rect = gfx::ScaleRect(
          tile_bounds,
          current_scale,
          current_scale) + current_offset;
      gfx::RectF last_screen_rect = gfx::ScaleRect(
          tile_bounds,
          last_scale,
          last_scale) + last_offset;

      float distance_to_visible_in_pixels =
          TilePriority::manhattanDistance(current_screen_rect, view_rect);

      float time_to_visible_in_seconds =
          TilePriority::TimeForBoundsToIntersect(
              last_screen_rect, current_screen_rect, time_delta, view_rect);
      TilePriority priority(
          resolution_,
          time_to_visible_in_seconds,
          distance_to_visible_in_pixels);
      if (store_screen_space_quads_on_tiles)
        priority.set_current_screen_quad(gfx::QuadF(current_screen_rect));
      tile->SetPriority(tree, priority);
    }
  } else {
    for (TilingData::Iterator iter(&tiling_data_, prioritized_rect);
         iter; ++iter) {
      TileMap::iterator find = tiles_.find(iter.index());
      if (find == tiles_.end())
        continue;
      Tile* tile = find->second.get();

      gfx::Rect tile_bounds =
          tiling_data_.TileBounds(iter.index_x(), iter.index_y());
      gfx::RectF current_layer_content_rect = gfx::ScaleRect(
          tile_bounds,
          current_scale,
          current_scale);
      gfx::RectF current_screen_rect = MathUtil::MapClippedRect(
          current_screen_transform, current_layer_content_rect);
      gfx::RectF last_layer_content_rect = gfx::ScaleRect(
          tile_bounds,
          last_scale,
          last_scale);
      gfx::RectF last_screen_rect  = MathUtil::MapClippedRect(
          last_screen_transform, last_layer_content_rect);

      float distance_to_visible_in_pixels =
          TilePriority::manhattanDistance(current_screen_rect, view_rect);

      float time_to_visible_in_seconds =
          TilePriority::TimeForBoundsToIntersect(
              last_screen_rect, current_screen_rect, time_delta, view_rect);

      TilePriority priority(
          resolution_,
          time_to_visible_in_seconds,
          distance_to_visible_in_pixels);
      if (store_screen_space_quads_on_tiles) {
          bool clipped;
          priority.set_current_screen_quad(
            MathUtil::MapQuad(current_screen_transform,
                              gfx::QuadF(current_layer_content_rect),
                              &clipped));
      }
      tile->SetPriority(tree, priority);
    }
  }

  last_source_frame_number_ = current_source_frame_number;
  last_impl_frame_time_ = current_frame_time;
}

void PictureLayerTiling::DidBecomeActive() {
  for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it) {
    it->second->SetPriority(ACTIVE_TREE, it->second->priority(PENDING_TREE));
    it->second->SetPriority(PENDING_TREE, TilePriority());

    // Tile holds a ref onto a picture pile. If the tile never gets invalidated
    // and recreated, then that picture pile ref could exist indefinitely.  To
    // prevent this, ask the client to update the pile to its own ref.  This
    // will cause PicturePileImpls and their clones to get deleted once the
    // corresponding PictureLayerImpl and any in flight raster jobs go out of
    // scope.
    client_->UpdatePile(it->second);
  }
}

scoped_ptr<base::Value> PictureLayerTiling::AsValue() const {
  scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
  state->SetInteger("num_tiles", tiles_.size());
  state->SetDouble("content_scale", contents_scale_);
  state->Set("content_bounds",
             MathUtil::AsValue(ContentRect().size()).release());
  return state.PassAs<base::Value>();
}

// This struct represents an event at which the expending rect intersects
// one of its boundaries.  4 intersection events will occur during expansion.
struct EdgeEvent {
  enum { BOTTOM, TOP, LEFT, RIGHT } edge;
  int* num_edges;
  int distance;
};

gfx::Rect PictureLayerTiling::ExpandRectEquallyToAreaBoundedBy(
    gfx::Rect starting_rect,
    int64 target_area,
    gfx::Rect bounding_rect) {
  DCHECK(!starting_rect.IsEmpty());
  DCHECK(!bounding_rect.IsEmpty());
  DCHECK_GT(target_area, 0);

  gfx::Rect rect = IntersectRects(starting_rect, bounding_rect);
  if (rect.IsEmpty())
    return rect;

  // These values will be updated by the loop and uses as the output.
  int origin_x = rect.x();
  int origin_y = rect.y();
  int width = rect.width();
  int height = rect.height();

  // In the beginning we will consider 2 edges in each dimension.
  int num_y_edges = 2;
  int num_x_edges = 2;

  // Create an event list.
  EdgeEvent events[] = {
    { EdgeEvent::BOTTOM, &num_y_edges, rect.y() - bounding_rect.y() },
    { EdgeEvent::TOP, &num_y_edges, bounding_rect.bottom() - rect.bottom() },
    { EdgeEvent::LEFT, &num_x_edges, rect.x() - bounding_rect.x() },
    { EdgeEvent::RIGHT, &num_x_edges, bounding_rect.right() - rect.right() }
  };

  // Sort the events by distance (closest first).
  if (events[0].distance > events[1].distance) std::swap(events[0], events[1]);
  if (events[2].distance > events[3].distance) std::swap(events[2], events[3]);
  if (events[0].distance > events[2].distance) std::swap(events[0], events[2]);
  if (events[1].distance > events[3].distance) std::swap(events[1], events[3]);
  if (events[1].distance > events[2].distance) std::swap(events[1], events[2]);

  for (int event_index = 0; event_index < 4; event_index++) {
    const EdgeEvent& event = events[event_index];

    // Early out if our distance to event is 0.
    // This optimization is not required for correctness.
    if (event.distance == 0) {
      --*event.num_edges;
      continue;
    }

    // Compute coefficients for the quadraic equation.
    int a = num_y_edges * num_x_edges;
    int b = num_y_edges * width + num_x_edges * height;
    int c = width * height - target_area;

    // Compute the delta for our edges using the quadratic equation.
    int delta = a == 0 ? -c / b :
       (-b + static_cast<int>(std::sqrt(b * b - 4.0 * a * c))) / (2 * a);

    // Clamp delta to our event distance.
    if (delta > event.distance)
      delta = event.distance;

    // Adjust the edge count for this kind of edge.
    --*event.num_edges;

    // Apply the delta to the edges and edge events.
    for (int i = event_index; i < 4; i++) {
      switch (events[i].edge) {
        case EdgeEvent::BOTTOM:
            origin_y -= delta;
            height += delta;
            break;
        case EdgeEvent::TOP:
            height += delta;
            break;
        case EdgeEvent::LEFT:
            origin_x -= delta;
            width += delta;
            break;
        case EdgeEvent::RIGHT:
            width += delta;
            break;
      }
      events[i].distance -= delta;
    }

    // If our delta is less then our event distance, we're done.
    if (delta < event.distance)
      break;
  }

  return gfx::Rect(origin_x, origin_y, width, height);
}

}  // namespace cc