/*
 * Copyright 2015 Google Inc. All Rights Reserved.
 *
 * 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
 *
 * 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.
 */

#include "cobalt/dom/font_cache.h"

namespace cobalt {
namespace dom {

namespace {

const int64 kInactiveProcessTimeIntervalMs = 1000;
const int32_t kInactiveFontListPurgeDelayMs = 300000;
const int32_t kInactiveFontPurgeDelayMs = 900000;
const int32_t kTotalFontCountPurgeThreshold = 64;

}  // namespace

FontCache::RequestedRemoteTypefaceInfo::RequestedRemoteTypefaceInfo(
    const scoped_refptr<loader::font::CachedRemoteTypeface>&
        cached_remote_typeface,
    const base::Closure& typeface_load_event_callback)
    : cached_remote_typeface_reference_(
          new loader::font::CachedRemoteTypefaceReferenceWithCallbacks(
              cached_remote_typeface, typeface_load_event_callback,
              typeface_load_event_callback, typeface_load_event_callback)),
      request_timer_(new base::Timer(false, false)) {
  request_timer_->Start(FROM_HERE,
                        base::TimeDelta::FromMilliseconds(kRequestTimerDelay),
                        typeface_load_event_callback);
}

FontCache::FontCache(render_tree::ResourceProvider** resource_provider,
                     loader::font::RemoteTypefaceCache* remote_typeface_cache,
                     const base::Closure& external_typeface_load_event_callback,
                     const std::string& language)
    : resource_provider_(resource_provider),
      remote_typeface_cache_(remote_typeface_cache),
      external_typeface_load_event_callback_(
          external_typeface_load_event_callback),
      language_(language),
      font_face_map_(new FontFaceMap()),
      last_inactive_process_time_(base::TimeTicks::Now()) {}

void FontCache::SetFontFaceMap(scoped_ptr<FontFaceMap> font_face_map) {
  DCHECK(thread_checker_.CalledOnValidThread());
  // If nothing has changed, then there's nothing to update. Just return.
  if (*font_face_map == *font_face_map_) {
    return;
  }

  // Clear out the cached font lists. It may no longer contain valid font
  // mappings as a result of the font face map changing.
  font_list_map_.clear();

  font_face_map_ = font_face_map.Pass();

  // Generate a set of the urls contained within the new font face map.
  std::set<GURL> new_url_set;
  for (FontFaceMap::iterator map_iterator = font_face_map_->begin();
       map_iterator != font_face_map_->end(); ++map_iterator) {
    map_iterator->second.CollectUrlSources(&new_url_set);
  }

  // Iterate through active remote typeface references, verifying that the font
  // face map still contains each remote typeface's url. Any remote typeface
  // with a url that is no longer contained within |font_face_map_| is purged to
  // allow the remote cache to release the memory.
  RequestedRemoteTypefaceMap::iterator requested_remote_typeface_iterator =
      requested_remote_typeface_cache_.begin();
  while (requested_remote_typeface_iterator !=
         requested_remote_typeface_cache_.end()) {
    RequestedRemoteTypefaceMap::iterator current_iterator =
        requested_remote_typeface_iterator++;

    // If the referenced url is not in the new url set, then purge it.
    if (new_url_set.find(current_iterator->first) == new_url_set.end()) {
      requested_remote_typeface_cache_.erase(current_iterator);
    }
  }
}

void FontCache::ProcessInactiveFontListsAndFonts() {
  DCHECK(thread_checker_.CalledOnValidThread());
  base::TimeTicks current_time = base::TimeTicks::Now();
  if ((current_time - last_inactive_process_time_).InMilliseconds() >
      kInactiveProcessTimeIntervalMs) {
    last_inactive_process_time_ = current_time;
    ProcessInactiveFontLists(current_time);
    ProcessInactiveFonts(current_time);
  }
}

const scoped_refptr<dom::FontList>& FontCache::GetFontList(
    const FontListKey& font_list_key) {
  DCHECK(thread_checker_.CalledOnValidThread());
  FontListInfo& font_list_info = font_list_map_[font_list_key];
  if (font_list_info.font_list == NULL) {
    font_list_info.font_list = new FontList(this, font_list_key);
  }
  return font_list_info.font_list;
}

const scoped_refptr<render_tree::Font>& FontCache::GetFontFromTypefaceAndSize(
    const scoped_refptr<render_tree::Typeface>& typeface, float size) {
  DCHECK(thread_checker_.CalledOnValidThread());
  FontKey font_key(typeface->GetId(), size);
  // Check to see if the font is already in the cache. If it is not, then
  // create it from the typeface and size and add it to the cache.
  FontInfo& cached_font_info = font_map_[font_key];
  if (cached_font_info.font == NULL) {
    cached_font_info.font = typeface->CreateFontWithSize(size);
  }
  return cached_font_info.font;
}

scoped_refptr<render_tree::Font> FontCache::TryGetFont(
    const std::string& family, render_tree::FontStyle style, float size,
    FontListFont::State* state) {
  DCHECK(thread_checker_.CalledOnValidThread());
  FontFaceMap::iterator font_face_map_iterator = font_face_map_->find(family);
  if (font_face_map_iterator != font_face_map_->end()) {
    // Retrieve the font face style set entry that most closely matches the
    // desired style. Given that a font face was found for this family, it
    // should never be NULL.
    // https://www.w3.org/TR/css3-fonts/#font-prop-desc
    const FontFaceStyleSet::Entry* style_set_entry =
        font_face_map_iterator->second.MatchStyle(style);
    DCHECK(style_set_entry != NULL);

    // Walk the entry's sources:
    // - If a remote source is encountered, always return the results of its
    //   attempted retrieval, regardless of its success.
    // - If a local source is encountered, only return the local font if it is
    //   successfully retrieved. In the case where the font is not locally
    //   available, the next font in the source list should be attempted
    //   instead.
    // https://www.w3.org/TR/css3-fonts/#src-desc
    for (FontFaceSources::const_iterator source_iterator =
             style_set_entry->sources.begin();
         source_iterator != style_set_entry->sources.end(); ++source_iterator) {
      if (source_iterator->IsUrlSource()) {
        return TryGetRemoteFont(source_iterator->GetUrl(), size, state);
      } else {
        scoped_refptr<render_tree::Font> font =
            TryGetLocalFont(source_iterator->GetName(), style, size, state);
        if (font != NULL) {
          return font;
        }
      }
    }

    *state = FontListFont::kUnavailableState;
    return NULL;
  } else {
    return TryGetLocalFont(family, style, size, state);
  }
}

FontCache::CharacterFallbackTypefaceMap&
FontCache::GetCharacterFallbackTypefaceMap(
    const render_tree::FontStyle& style) {
  DCHECK(thread_checker_.CalledOnValidThread());
  return character_fallback_typeface_maps_[CharacterFallbackKey(style)];
}

const scoped_refptr<render_tree::Typeface>&
FontCache::GetCharacterFallbackTypeface(int32 utf32_character,
                                        const render_tree::FontStyle& style) {
  DCHECK(thread_checker_.CalledOnValidThread());
  DCHECK(resource_provider());
  return GetCachedLocalTypeface(
      resource_provider()->GetCharacterFallbackTypeface(utf32_character, style,
                                                        language_));
}

scoped_refptr<render_tree::GlyphBuffer> FontCache::CreateGlyphBuffer(
    const char16* text_buffer, int32 text_length, bool is_rtl,
    FontList* font_list) {
  DCHECK(resource_provider());
  return resource_provider()->CreateGlyphBuffer(
      text_buffer, static_cast<size_t>(text_length), language_, is_rtl,
      font_list);
}

float FontCache::GetTextWidth(const char16* text_buffer, int32 text_length,
                              bool is_rtl, FontList* font_list,
                              render_tree::FontVector* maybe_used_fonts) {
  DCHECK(resource_provider());
  return resource_provider()->GetTextWidth(
      text_buffer, static_cast<size_t>(text_length), language_, is_rtl,
      font_list, maybe_used_fonts);
}

void FontCache::ProcessInactiveFontLists(const base::TimeTicks& current_time) {
  for (FontListMap::iterator font_list_iterator = font_list_map_.begin();
       font_list_iterator != font_list_map_.end();) {
    FontListInfo& font_list_info = font_list_iterator->second;

    // Any font list that has a single ref is unreferenced outside of the font
    // cache and is no longer active.
    if (font_list_info.font_list->HasOneRef()) {
      // If there is no inactive time set, then the font list has just become
      // inactive, so set the time now.
      if (font_list_info.inactive_time.is_null()) {
        font_list_info.inactive_time = current_time;
        // Otherwise, check to see if the purge delay has been reached.
      } else if ((current_time - font_list_info.inactive_time)
                     .InMilliseconds() >= kInactiveFontListPurgeDelayMs) {
        font_list_map_.erase(font_list_iterator++);
        continue;
      }
      // Otherwise, if there's an inactive time set on this font list, clear it.
    } else if (!font_list_info.inactive_time.is_null()) {
      font_list_info.inactive_time = base::TimeTicks();
    }

    ++font_list_iterator;
  }
}

void FontCache::ProcessInactiveFonts(const base::TimeTicks& current_time) {
  for (FontMap::iterator font_iterator = font_map_.begin();
       font_iterator != font_map_.end();) {
    FontInfo& font_info = font_iterator->second;

    // Any font that has a single ref is unreferenced outside of the font cache
    // and is no longer active.
    if (font_info.font->HasOneRef()) {
      // If there is no inactive time set, then the font has just become
      // inactive, so set the time now and insert it into the inactive font set.
      if (font_info.inactive_time.is_null()) {
        font_info.inactive_time = current_time;
        inactive_font_set_.insert(
            InactiveFontKey(font_info.inactive_time, font_iterator->first));
      }
      // Otherwise, if there's an inactive time set on this font, clear it and
      // remove the font from the inactive font set.
    } else if (!font_info.inactive_time.is_null()) {
      inactive_font_set_.erase(
          InactiveFontKey(font_info.inactive_time, font_iterator->first));
      font_info.inactive_time = base::TimeTicks();
    }

    ++font_iterator;
  }

  // Continue looping until the total font count drops to the purge threshold or
  // there are no more inactive fonts to purge.
  while (font_map_.size() > kTotalFontCountPurgeThreshold &&
         inactive_font_set_.size() > 0) {
    // Grab the first inactive font in the set. They are ordered by the time
    // they became inactive, so the first inactive font in the set is the
    // oldest.
    InactiveFontSet::iterator inactive_font_iterator =
        inactive_font_set_.begin();
    // Check to see if the oldest inactive font is old enough to be purged. If
    // it is not, simply break out. None of the other inactive fonts will be
    // purgeable either.
    if ((current_time - inactive_font_iterator->inactive_time)
            .InMilliseconds() < kInactiveFontPurgeDelayMs) {
      break;
    }

    // The inactive font is old enough to be purged. Remove it from both the
    // font map and the inactive font set.
    font_map_.erase(inactive_font_iterator->font_key);
    inactive_font_set_.erase(inactive_font_iterator);
  }
}

const scoped_refptr<render_tree::Typeface>& FontCache::GetCachedLocalTypeface(
    const scoped_refptr<render_tree::Typeface>& typeface) {
  // Check to see if a typeface with a matching id is already in the cache. If
  // it is not, then add the passed in typeface to the cache.
  scoped_refptr<render_tree::Typeface>& cached_typeface =
      local_typeface_map_[typeface->GetId()];
  if (cached_typeface == NULL) {
    cached_typeface = typeface;
  }
  return cached_typeface;
}

scoped_refptr<render_tree::Font> FontCache::TryGetRemoteFont(
    const GURL& url, float size, FontListFont::State* state) {
  // Retrieve the font from the remote typeface cache, potentially triggering a
  // load.
  scoped_refptr<loader::font::CachedRemoteTypeface> cached_remote_typeface =
      remote_typeface_cache_->CreateCachedResource(url);

  RequestedRemoteTypefaceMap::iterator requested_remote_typeface_iterator =
      requested_remote_typeface_cache_.find(url);

  // If the requested url is not currently cached, then create a cached
  // reference and request timer, providing callbacks for when the load is
  // completed or the timer expires.
  if (requested_remote_typeface_iterator ==
      requested_remote_typeface_cache_.end()) {
    // Create the remote typeface load event's callback. This callback occurs on
    // successful loads, failed loads, and when the request's timer expires.
    base::Closure typeface_load_event_callback = base::Bind(
        &FontCache::OnRemoteTypefaceLoadEvent, base::Unretained(this), url);

    // Insert the newly requested remote typeface's info into the cache, and set
    // the iterator from the return value of the map insertion.
    requested_remote_typeface_iterator =
        requested_remote_typeface_cache_
            .insert(std::make_pair(
                url, new RequestedRemoteTypefaceInfo(
                         cached_remote_typeface, typeface_load_event_callback)))
            .first;
  }

  scoped_refptr<render_tree::Typeface> typeface =
      cached_remote_typeface->TryGetResource();
  if (typeface != NULL) {
    *state = FontListFont::kLoadedState;
    return GetFontFromTypefaceAndSize(typeface, size);
  } else {
    if (cached_remote_typeface->IsLoading()) {
      if (requested_remote_typeface_iterator->second->HasActiveRequestTimer()) {
        *state = FontListFont::kLoadingWithTimerActiveState;
      } else {
        *state = FontListFont::kLoadingWithTimerExpiredState;
      }
    } else {
      *state = FontListFont::kUnavailableState;
    }
    return NULL;
  }
}

scoped_refptr<render_tree::Font> FontCache::TryGetLocalFont(
    const std::string& family, render_tree::FontStyle style, float size,
    FontListFont::State* state) {
  DCHECK(resource_provider());
  // Only request the local font from the resource provider if the family is
  // empty or the resource provider actually has the family. The reason for this
  // is that the resource provider's |GetLocalTypeface()| is guaranteed to
  // return a non-NULL value, and in the case where a family is not supported,
  // the subsequent fonts in the font list need to be attempted. An empty family
  // signifies using the default font.
  if (!family.empty() &&
      !resource_provider()->HasLocalFontFamily(family.c_str())) {
    *state = FontListFont::kUnavailableState;
    return NULL;
  } else {
    *state = FontListFont::kLoadedState;
    return GetFontFromTypefaceAndSize(
        GetCachedLocalTypeface(
            resource_provider()->GetLocalTypeface(family.c_str(), style)),
        size);
  }
}

void FontCache::OnRemoteTypefaceLoadEvent(const GURL& url) {
  DCHECK(thread_checker_.CalledOnValidThread());
  RequestedRemoteTypefaceMap::iterator requested_remote_typeface_iterator =
      requested_remote_typeface_cache_.find(url);
  if (requested_remote_typeface_iterator !=
      requested_remote_typeface_cache_.end()) {
    // NOTE: We can potentially track the exact font list fonts that are
    // impacted by each load event and only reset them. However, as a result of
    // the minimal amount of processing required to update the loading status of
    // a font, the small number of fonts involved, and the fact that this is an
    // infrequent event, adding this additional layer of tracking complexity
    // doesn't appear to offer any meaningful benefits.
    for (FontListMap::iterator font_list_iterator = font_list_map_.begin();
         font_list_iterator != font_list_map_.end(); ++font_list_iterator) {
      FontListInfo& font_list_info = font_list_iterator->second;
      font_list_info.font_list->ResetLoadingFonts();
    }

    // Clear the request timer. It only runs until the first load event occurs.
    requested_remote_typeface_iterator->second->ClearRequestTimer();

    external_typeface_load_event_callback_.Run();
  }
}

}  // namespace dom
}  // namespace cobalt