/* This file is part of Clementine.
   Copyright 2009-2012, David Sansome <me@davidsansome.com>
   Copyright 2010-2011, 2014, Arnaud Bienner <arnaud.bienner@gmail.com>
   Copyright 2010-2012, 2014, John Maguire <john.maguire@gmail.com>
   Copyright 2011, Paweł Bara <keirangtp@gmail.com>
   Copyright 2011, Andrea Decorte <adecorte@gmail.com>
   Copyright 2012, Anand <anandtp@live.in>
   Copyright 2012, Arash Abedinzadeh <arash.abedinzadeh@gmail.com>
   Copyright 2013, Andreas <asfa194@gmail.com>
   Copyright 2013, Kevin Cox <kevincox.ca@gmail.com>
   Copyright 2014, Mark Furneaux <mark@romaco.ca>
   Copyright 2014, Krzysztof Sobiecki <sobkas@gmail.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 "player.h"

#include <QSettings>
#include <QSortFilterProxyModel>
#include <QtConcurrentRun>
#include <QtDebug>
#include <memory>

#include "config.h"
#include "core/application.h"
#include "core/logging.h"
#include "core/urlhandler.h"
#include "engines/enginebase.h"
#include "engines/gstengine.h"
#include "library/librarybackend.h"
#include "playlist/playlist.h"
#include "playlist/playlistitem.h"
#include "playlist/playlistmanager.h"

#ifdef HAVE_LIBLASTFM
#include "internet/lastfm/lastfmservice.h"
#endif

using std::shared_ptr;

const char* Player::kSettingsGroup = "Player";

Player::Player(Application* app, QObject* parent)
    : PlayerInterface(parent),
      app_(app),
      lastfm_(nullptr),
      engine_(new GstEngine(app_)),
      stream_change_type_(Engine::First),
      last_state_(Engine::Empty),
      nb_errors_received_(0),
      volume_before_mute_(50),
      last_pressed_previous_(QDateTime::currentDateTime()),
      menu_previousmode_(PreviousBehaviour_DontRestart),
      seek_step_sec_(10) {
  settings_.beginGroup("Player");

  SetVolume(settings_.value("volume", 50).toInt());

  connect(engine_.get(), SIGNAL(Error(QString)), SIGNAL(Error(QString)));

  connect(engine_.get(), SIGNAL(ValidMediaRequested(MediaPlaybackRequest)),
          SLOT(ValidMediaRequested(MediaPlaybackRequest)));
  connect(engine_.get(), SIGNAL(InvalidMediaRequested(MediaPlaybackRequest)),
          SLOT(InvalidMediaRequested(MediaPlaybackRequest)));
}

Player::~Player() {}

void Player::Init() {
  if (!engine_->Init()) qFatal("Error initialising audio engine");

  connect(engine_.get(), SIGNAL(StateChanged(Engine::State)),
          SLOT(EngineStateChanged(Engine::State)));
  connect(engine_.get(), SIGNAL(TrackAboutToEnd()), SLOT(TrackAboutToEnd()));
  connect(engine_.get(), SIGNAL(TrackEnded()), SLOT(TrackEnded()));
  connect(engine_.get(), SIGNAL(MetaData(Engine::SimpleMetaBundle)),
          SLOT(EngineMetadataReceived(Engine::SimpleMetaBundle)));

  engine_->SetVolume(settings_.value("volume", 50).toInt());

  ReloadSettings();

#ifdef HAVE_LIBLASTFM
  lastfm_ = app_->scrobbler();
#endif
}

void Player::ReloadSettings() {
  QSettings s;
  s.beginGroup(kSettingsGroup);

  menu_previousmode_ = PreviousBehaviour(
      s.value("menu_previousmode", PreviousBehaviour_DontRestart).toInt());

  seek_step_sec_ = s.value("seek_step_sec", 10).toInt();

  s.endGroup();

  engine_->ReloadSettings();
}

void Player::HandleLoadResult(const UrlHandler::LoadResult& result) {
  // Might've been an async load, so check we're still on the same item
  shared_ptr<PlaylistItem> item =
      app_->playlist_manager()->active()->current_item();
  if (!item) {
    loading_async_ = QUrl();
    return;
  }

  if (item->Url() != result.original_url_) return;

  switch (result.type_) {
    case UrlHandler::LoadResult::NoMoreTracks:
      qLog(Debug) << "URL handler for" << result.original_url_
                  << "said no more tracks";

      loading_async_ = QUrl();
      NextItem(stream_change_type_);
      break;

    case UrlHandler::LoadResult::TrackAvailable: {
      // The media URL may contain an auth token.
      qLog(Debug) << "URL handler for" << result.original_url_ << "returned"
                  << result.media_url_.toString(QUrl::RemoveQuery)
                  << "(query removed)";

      // If there was no length info in song's metadata, use the one provided by
      // URL handler, if there is one
      if (item->Metadata().length_nanosec() <= 0 &&
          result.length_nanosec_ != -1) {
        Song song = item->Metadata();
        song.set_length_nanosec(result.length_nanosec_);
        item->SetTemporaryMetadata(song);
        app_->playlist_manager()->active()->InformOfCurrentSongChange();
      }
      MediaPlaybackRequest req(result.original_url_, result.media_url_);
      if (!result.auth_header_.isEmpty())
        req.headers_["Authorization"] = result.auth_header_;
      engine_->Play(req, stream_change_type_, item->Metadata().has_cue(),
                    item->Metadata().beginning_nanosec(),
                    item->Metadata().end_nanosec());

      current_item_ = item;
      loading_async_ = QUrl();
      break;
    }

    case UrlHandler::LoadResult::WillLoadAsynchronously:
      qLog(Debug) << "URL handler for" << result.original_url_
                  << "is loading asynchronously";

      // We'll get called again later with either NoMoreTracks or TrackAvailable
      loading_async_ = result.original_url_;
      break;
  }
}

void Player::Next() { NextInternal(Engine::Manual); }

void Player::NextAlbum() {
  NextInternal(Engine::Manual, NextTrackOrAlbumSelected::SelectNextAlbum);
}

void Player::NextInternal(Engine::TrackChangeFlags change,
                          NextTrackOrAlbumSelected NextTrackOrAlbum) {
  if (HandleStopAfter()) return;

  if (app_->playlist_manager()->active()->current_item()) {
    const QUrl url = app_->playlist_manager()->active()->current_item()->Url();

    if (url_handlers_.contains(url.scheme())) {
      // The next track is already being loaded
      if (url == loading_async_) return;

      stream_change_type_ = change;
      HandleLoadResult(url_handlers_[url.scheme()]->LoadNext(url));
      return;
    }
  }

  NextItem(change, NextTrackOrAlbum);
}

void Player::NextItem(Engine::TrackChangeFlags change,
                      NextTrackOrAlbumSelected NextTrackOrAlbum) {
  Playlist* active_playlist = app_->playlist_manager()->active();

  // If we received too many errors in auto change, with repeat enabled, we stop
  if (change == Engine::Auto) {
    const PlaylistSequence::RepeatMode repeat_mode =
        active_playlist->sequence()->repeat_mode();
    if (repeat_mode != PlaylistSequence::Repeat_Off) {
      if ((repeat_mode == PlaylistSequence::Repeat_Track &&
           nb_errors_received_ >= 3) ||
          (nb_errors_received_ >=
           app_->playlist_manager()->active()->proxy()->rowCount())) {
        // We received too many "Error" state changes: probably looping over a
        // playlist which contains only unavailable elements: stop now.
        nb_errors_received_ = 0;
        Stop();
        return;
      }
    }
  }

  // Manual track changes override "Repeat track"
  const bool ignore_repeat_track = change & Engine::Manual;

  int i = active_playlist->current_row();
  if (NextTrackOrAlbum == SelectNextAlbum && i != -1) {
    if (active_playlist->sequence()->repeat_mode() !=
        PlaylistSequence::Repeat_Track) {
      int original_index = i;
      QString album = active_playlist->current_item_metadata().album();

      i = active_playlist->next_row(ignore_repeat_track);
      while (i != -1 &&
             active_playlist->item_at(i)->Metadata().album() == album &&
             i != original_index) {
        active_playlist->set_current_row(i, true);
        i = active_playlist->next_row(ignore_repeat_track);
      }
    }
  } else {
    i = active_playlist->next_row(ignore_repeat_track);
  }

  if (i == -1) {
    app_->playlist_manager()->active()->set_current_row(i);
    emit PlaylistFinished();
    Stop();
    return;
  }

  PlayAt(i, change, false);
}

void Player::PlayPlaylist(const QString& playlistName) {
  PlayPlaylistInternal(Engine::Manual, playlistName);
}

void Player::PlayPlaylistInternal(Engine::TrackChangeFlags change,
                                  const QString& playlistName) {
  Playlist* playlist = nullptr;
  for (Playlist* p : app_->playlist_manager()->GetAllPlaylists()) {
    if (playlistName == app_->playlist_manager()->GetPlaylistName(p->id())) {
      playlist = p;
      break;
    }
  }

  if (playlist == NULL) {
    qLog(Warning) << "Playlist '" << playlistName << "' not found.";
    return;
  }

  app_->playlist_manager()->SetActivePlaylist(playlist->id());
  app_->playlist_manager()->SetCurrentPlaylist(playlist->id());
  if (playlist->rowCount() == 0) return;

  int i = app_->playlist_manager()->active()->current_row();
  if (i == -1) i = app_->playlist_manager()->active()->last_played_row();
  if (i == -1) i = 0;

  PlayAt(i, Engine::First, true);
}

bool Player::HandleStopAfter() {
  if (app_->playlist_manager()->active()->stop_after_current()) {
    // Find what the next track would've been, and mark that one as current
    // so it plays next time the user presses Play.
    const int next_row = app_->playlist_manager()->active()->next_row();
    if (next_row != -1) {
      app_->playlist_manager()->active()->set_current_row(next_row, true);
    }

    app_->playlist_manager()->active()->StopAfter(-1);

    Stop(true);
    return true;
  }
  return false;
}

void Player::TrackEnded() {
  if (HandleStopAfter()) return;

  if (current_item_ && current_item_->IsLocalLibraryItem() &&
      current_item_->Metadata().id() != -1 &&
      !app_->playlist_manager()->active()->have_incremented_playcount() &&
      app_->playlist_manager()->active()->get_lastfm_status() !=
          Playlist::LastFM_Seeked) {
    // The track finished before its scrobble point (30 seconds), so increment
    // the play count now.
    app_->playlist_manager()->library_backend()->IncrementPlayCountAsync(
        current_item_->Metadata().id());
  }

  NextInternal(Engine::Auto);
}

void Player::PlayPause() {
  switch (engine_->state()) {
    case Engine::Paused:
      engine_->Unpause();
      break;

    case Engine::Playing: {
      // We really shouldn't pause last.fm streams
      // Stopping seems like a reasonable thing to do (especially on mac where
      // there
      // is no media key for stop).
      if (current_item_->options() & PlaylistItem::PauseDisabled) {
        Stop();
      } else {
        engine_->Pause();
      }
      break;
    }

    case Engine::Empty:
    case Engine::Error:
    case Engine::Idle: {
      app_->playlist_manager()->SetActivePlaylist(
          app_->playlist_manager()->current_id());
      if (app_->playlist_manager()->active()->rowCount() == 0) break;

      int i = app_->playlist_manager()->active()->current_row();
      if (i == -1) i = app_->playlist_manager()->active()->last_played_row();
      if (i == -1) i = 0;

      PlayAt(i, Engine::First, true);
      break;
    }
  }
}

void Player::RestartOrPrevious() {
  if (engine_->position_nanosec() < 8 * kNsecPerSec) return Previous();

  SeekTo(0);
}

void Player::Stop(bool stop_after) {
#ifdef HAVE_LIBLASTFM
  lastfm_->Scrobble();
#endif

  engine_->Stop(stop_after);
  app_->playlist_manager()->active()->set_current_row(-1);
  current_item_.reset();
}

void Player::StopAfterCurrent() {
  app_->playlist_manager()->active()->StopAfter(
      app_->playlist_manager()->active()->current_row());
}

bool Player::PreviousWouldRestartTrack() const {
  // Check if it has been over two seconds since previous button was pressed
  return menu_previousmode_ == PreviousBehaviour_Restart &&
         last_pressed_previous_.isValid() &&
         last_pressed_previous_.secsTo(QDateTime::currentDateTime()) >= 2;
}

void Player::Previous() { PreviousItem(Engine::Manual); }

void Player::PreviousItem(Engine::TrackChangeFlags change) {
  const bool ignore_repeat_track = change & Engine::Manual;

  if (menu_previousmode_ == PreviousBehaviour_Restart) {
    // Check if it has been over two seconds since previous button was pressed
    QDateTime now = QDateTime::currentDateTime();
    if (last_pressed_previous_.isValid() &&
        last_pressed_previous_.secsTo(now) >= 2) {
      last_pressed_previous_ = now;
      PlayAt(app_->playlist_manager()->active()->current_row(), change, false);
      return;
    }
    last_pressed_previous_ = now;
  }

  int i = app_->playlist_manager()->active()->previous_row(ignore_repeat_track);
  app_->playlist_manager()->active()->set_current_row(i);
  if (i == -1) {
    Stop();
    PlayAt(i, change, true);
    return;
  }

  PlayAt(i, change, false);
}

void Player::EngineStateChanged(Engine::State state) {
  if (Engine::Error == state) {
    nb_errors_received_++;
  } else {
    nb_errors_received_ = 0;
  }

  switch (state) {
    case Engine::Paused:
      emit Paused();
      break;
    case Engine::Playing:
      emit Playing();
      break;
    case Engine::Error:
    case Engine::Empty:
    case Engine::Idle:
      emit Stopped();
      break;
  }
  last_state_ = state;
}

void Player::SetVolume(int value) {
  int old_volume = engine_->volume();

  int volume = qBound(0, value, 100);
  settings_.setValue("volume", volume);
  engine_->SetVolume(volume);

  if (volume != old_volume) {
    emit VolumeChanged(volume);
  }
}

int Player::GetVolume() const { return engine_->volume(); }

void Player::PlayAt(int index, Engine::TrackChangeFlags change,
                    bool reshuffle) {
  if (change == Engine::Manual &&
      engine_->position_nanosec() != engine_->length_nanosec()) {
    emit TrackSkipped(current_item_);
    const QUrl& url = current_item_->Url();
    if (url_handlers_.contains(url.scheme())) {
      url_handlers_[url.scheme()]->TrackSkipped();
    }
  }

  if (current_item_ && app_->playlist_manager()->active()->has_item_at(index) &&
      current_item_->Metadata().IsOnSameAlbum(
          app_->playlist_manager()->active()->item_at(index)->Metadata())) {
    change |= Engine::SameAlbum;
  }

  if (reshuffle) app_->playlist_manager()->active()->ReshuffleIndices();
  app_->playlist_manager()->active()->set_current_row(index);

  if (app_->playlist_manager()->active()->current_row() == -1) {
    // Maybe index didn't exist in the playlist.
    return;
  }

  current_item_ = app_->playlist_manager()->active()->current_item();
  const QUrl url = current_item_->Url();

  if (url_handlers_.contains(url.scheme())) {
    // It's already loading
    if (url == loading_async_) return;

    stream_change_type_ = change;
    HandleLoadResult(url_handlers_[url.scheme()]->StartLoading(url));
  } else {
    loading_async_ = QUrl();
    MediaPlaybackRequest req(current_item_->Url());
    engine_->Play(req, change, current_item_->Metadata().has_cue(),
                  current_item_->Metadata().beginning_nanosec(),
                  current_item_->Metadata().end_nanosec());

#ifdef HAVE_LIBLASTFM
    if (lastfm_->IsScrobblingEnabled())
      lastfm_->NowPlaying(current_item_->Metadata());
#endif
  }
}

void Player::CurrentMetadataChanged(const Song& metadata) {
  // those things might have changed (especially when a previously invalid
  // song was reloaded) so we push the latest version into Engine
  engine_->RefreshMarkers(metadata.beginning_nanosec(), metadata.end_nanosec());

#ifdef HAVE_LIBLASTFM
  lastfm_->Scrobble();
  lastfm_->NowPlaying(metadata);
#endif
}

void Player::SeekTo(int seconds) {
  const qint64 length_nanosec = engine_->length_nanosec();

  // If the length is 0 then either there is no song playing, or the song isn't
  // seekable.
  if (length_nanosec <= 0) {
    return;
  }

  const qint64 nanosec =
      qBound(0ll, qint64(seconds) * kNsecPerSec, length_nanosec);
  engine_->Seek(nanosec);

  // If we seek the track we need to move the scrobble point
  qLog(Info) << "Track seeked to" << nanosec << "ns - updating scrobble point";
  app_->playlist_manager()->active()->UpdateScrobblePoint(nanosec);

  emit Seeked(nanosec / 1000);
}

void Player::SeekForward() {
  SeekTo(engine()->position_nanosec() / kNsecPerSec + seek_step_sec_);
}

void Player::SeekBackward() {
  SeekTo(engine()->position_nanosec() / kNsecPerSec - seek_step_sec_);
}

void Player::EngineMetadataReceived(const Engine::SimpleMetaBundle& bundle) {
  PlaylistItemPtr item = app_->playlist_manager()->active()->current_item();
  if (!item) return;

  Engine::SimpleMetaBundle bundle_copy = bundle;

  // Maybe the metadata is from icycast and has "Artist - Title" shoved
  // together in the title field.
  const int dash_pos = bundle_copy.title.indexOf('-');
  if (dash_pos != -1 && bundle_copy.artist.isEmpty()) {
    // Split on " - " if it exists, otherwise split on "-".
    const int space_dash_pos = bundle_copy.title.indexOf(" - ");
    if (space_dash_pos != -1) {
      bundle_copy.artist = bundle_copy.title.left(space_dash_pos).trimmed();
      bundle_copy.title = bundle_copy.title.mid(space_dash_pos + 3).trimmed();
    } else {
      bundle_copy.artist = bundle_copy.title.left(dash_pos).trimmed();
      bundle_copy.title = bundle_copy.title.mid(dash_pos + 1).trimmed();
    }
  }

  Song song = item->Metadata();
  song.MergeFromSimpleMetaBundle(bundle_copy);

  // Ignore useless metadata
  if (song.title().isEmpty() && song.artist().isEmpty()) return;

  app_->playlist_manager()->active()->SetStreamMetadata(item->Url(), song);
}

PlaylistItemPtr Player::GetItemAt(int pos) const {
  if (pos < 0 || pos >= app_->playlist_manager()->active()->rowCount())
    return PlaylistItemPtr();
  return app_->playlist_manager()->active()->item_at(pos);
}

void Player::Mute() {
  const int current_volume = engine_->volume();

  if (current_volume == 0) {
    SetVolume(volume_before_mute_);
  } else {
    volume_before_mute_ = current_volume;
    SetVolume(0);
  }
}

void Player::Pause() { engine_->Pause(); }

void Player::Play() {
  switch (GetState()) {
    case Engine::Playing:
      SeekTo(0);
      break;
    case Engine::Paused:
      engine_->Unpause();
      break;
    default:
      PlayPause();
      break;
  }
}

void Player::ShowOSD() {
  if (current_item_) emit ForceShowOSD(current_item_->Metadata(), false);
}

void Player::TogglePrettyOSD() {
  if (current_item_) emit ForceShowOSD(current_item_->Metadata(), true);
}

void Player::TrackAboutToEnd() {
  // If the current track was from a URL handler then it might have special
  // behaviour to queue up a subsequent track.  We don't want to preload (and
  // scrobble) the next item in the playlist if it's just going to be stopped
  // again immediately after.
  if (app_->playlist_manager()->active()->current_item()) {
    const QUrl url = app_->playlist_manager()->active()->current_item()->Url();
    if (url_handlers_.contains(url.scheme())) {
      url_handlers_[url.scheme()]->TrackAboutToEnd();
      return;
    }
  }

  const bool has_next_row =
      app_->playlist_manager()->active()->next_row() != -1;
  PlaylistItemPtr next_item;

  if (has_next_row) {
    next_item = app_->playlist_manager()->active()->item_at(
        app_->playlist_manager()->active()->next_row());
  }

  if (engine_->is_autocrossfade_enabled()) {
    // Crossfade is on, so just start playing the next track.  The current one
    // will fade out, and the new one will fade in

    // But, if there's no next track and we don't want to fade out, then do
    // nothing and just let the track finish to completion.
    if (!engine_->is_fadeout_enabled() && !has_next_row) return;

    // If the next track is on the same album (or same cue file), and the
    // user doesn't want to crossfade between tracks on the same album, then
    // don't do this automatic crossfading.
    if (engine_->crossfade_same_album() || !has_next_row || !next_item ||
        !current_item_->Metadata().IsOnSameAlbum(next_item->Metadata())) {
      TrackEnded();
      return;
    }
  }

  // Crossfade is off, so start preloading the next track so we don't get a
  // gap between songs.
  if (!has_next_row || !next_item) return;

  MediaPlaybackRequest req(next_item->Url());

  // Get the actual track URL rather than the stream URL.
  UrlHandler* handler = url_handlers_.value(req.RequestUrl().scheme(), nullptr);
  if (handler != nullptr) {
    UrlHandler::LoadResult result = handler->LoadNext(req.RequestUrl());
    switch (result.type_) {
      case UrlHandler::LoadResult::NoMoreTracks:
        return;

      case UrlHandler::LoadResult::WillLoadAsynchronously:
        loading_async_ = req.RequestUrl();
        return;

      case UrlHandler::LoadResult::TrackAvailable:
        req.SetMediaUrl(result.media_url_);
        break;
    }
  }
  engine_->StartPreloading(req, next_item->Metadata().has_cue(),
                           next_item->Metadata().beginning_nanosec(),
                           next_item->Metadata().end_nanosec());
}

void Player::IntroPointReached() { NextInternal(Engine::Intro); }

void Player::ValidMediaRequested(const MediaPlaybackRequest& req) {
  emit SongChangeRequestProcessed(req.RequestUrl(), true);
}

void Player::InvalidMediaRequested(const MediaPlaybackRequest& req) {
  // first send the notification to others...
  emit SongChangeRequestProcessed(req.RequestUrl(), false);
  // ... and now when our listeners have completed their processing of the
  // current item we can change the current item by skipping to the next song

  QSettings s;
  s.beginGroup(kSettingsGroup);

  bool stop_playback = s.value("stop_play_if_fail", 0).toBool();
  s.endGroup();

  if (stop_playback) {
    Stop();
  } else {
    NextItem(Engine::Auto);
  }
}

void Player::RegisterUrlHandler(UrlHandler* handler) {
  const QString scheme = handler->scheme();

  if (url_handlers_.contains(scheme)) {
    qLog(Warning) << "Tried to register a URL handler for" << scheme
                  << "but one was already registered";
    return;
  }

  qLog(Info) << "Registered URL handler for" << scheme;
  url_handlers_.insert(scheme, handler);
  connect(handler, SIGNAL(destroyed(QObject*)),
          SLOT(UrlHandlerDestroyed(QObject*)));
  connect(handler, SIGNAL(AsyncLoadComplete(UrlHandler::LoadResult)),
          SLOT(HandleLoadResult(UrlHandler::LoadResult)));
}

void Player::UnregisterUrlHandler(UrlHandler* handler) {
  const QString scheme = url_handlers_.key(handler);
  if (scheme.isEmpty()) {
    qLog(Warning) << "Tried to unregister a URL handler for"
                  << handler->scheme() << "that wasn't registered";
    return;
  }

  qLog(Info) << "Unregistered URL handler for" << scheme;
  url_handlers_.remove(scheme);
  disconnect(handler, SIGNAL(destroyed(QObject*)), this,
             SLOT(UrlHandlerDestroyed(QObject*)));
  disconnect(handler, SIGNAL(AsyncLoadComplete(UrlHandler::LoadResult)), this,
             SLOT(HandleLoadResult(UrlHandler::LoadResult)));
}

const UrlHandler* Player::HandlerForUrl(const QUrl& url) const {
  QMap<QString, UrlHandler*>::const_iterator it =
      url_handlers_.constFind(url.scheme());
  if (it == url_handlers_.constEnd()) {
    return nullptr;
  }
  return *it;
}

void Player::UrlHandlerDestroyed(QObject* object) {
  UrlHandler* handler = static_cast<UrlHandler*>(object);
  const QString scheme = url_handlers_.key(handler);
  if (!scheme.isEmpty()) {
    url_handlers_.remove(scheme);
  }
}
