iTunes file util and data provider for media galleries

chrome/browser/media_galleries/fileapi/itunes_data_provider.cc

+// Copyright 2013 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 "chrome/browser/media_galleries/fileapi/itunes_data_provider.h"
+
+#include "base/format_macros.h"
+#include "base/logging.h"
+#include "base/platform_file.h"
+#include "base/stl_util.h"
+#include "base/stringprintf.h"
+#include "base/threading/thread_restrictions.h"
+#include "chrome/browser/media_galleries/fileapi/itunes_library_parser.h"
+
+namespace itunes {
+
+namespace {
+
+// A "reasonable" artificial limit.
+const int64 kMaxLibraryFileSize = 50 * 1024 * 1024;

[Lei Zhang, 2013/06/06 09:58:54]

If you search, you will find users reporting having xml files bigger than this.
People love their music. I'd double it for now and add a TODO to add a UMA.

[vandebo (ex-Chrome), 2013/06/06 19:49:18]

Done.

+
+std::string ReadFile(const base::FilePath& path) {
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  base::PlatformFile file = base::CreatePlatformFile(
+      path, base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ, NULL, NULL);
+  if (file == base::kInvalidPlatformFileValue)
+    return std::string();
+
+  base::PlatformFileInfo file_info;
+  if (!base::GetPlatformFileInfo(file, &file_info) ||
+      file_info.size > kMaxLibraryFileSize) {
+    base::ClosePlatformFile(file);
+    return std::string();
+  }
+
+  std::string result(file_info.size, 0);
+  if (base::ReadPlatformFile(file, 0, string_as_array(&result),
+        file_info.size) != file_info.size) {
+    result.clear();
+  }
+
+  base::ClosePlatformFile(file);
+  return result;
+}
+
+}  // namespace
+
+ITunesDataProvider::ITunesDataProvider(const base::FilePath& library_path)
+    : library_path_(library_path),
+      needs_refresh_(true) {
+}
+
+ITunesDataProvider::~ITunesDataProvider() {}
+
+// TODO(vandebo): add a file watch that resets |needs_refresh_| when the
+// file changes.
+void ITunesDataProvider::RefreshData(const base::Closure& ready_callback) {
+  if (!needs_refresh_) {

[Lei Zhang, 2013/06/06 09:58:54]

If you write this the other way around, it's only 5 lines:

  if (needs_refresh_) {
    ParseLibrary();
    needs_refresh_ = false;
  }
  ready_callback.Run();

[vandebo (ex-Chrome), 2013/06/06 19:49:18]

Done.

+    ready_callback.Run();
+    return;
+  }
+
+  ParseLibrary();
+  needs_refresh_ = false;
+  ready_callback.Run();
+}
+
+base::FilePath ITunesDataProvider::library_path() const {
+  return library_path_;
+}
+
+bool ITunesDataProvider::KnownArtist(const ArtistName& artist) const {
+  DCHECK(!needs_refresh_);
+  return ContainsKey(library_, artist);
+}
+
+bool ITunesDataProvider::KnownAlbum(const ArtistName& artist,
+                                    const AlbumName& album) const {
+  DCHECK(!needs_refresh_);
+  Library::const_iterator library_it = library_.find(artist);
+  if (library_it == library_.end())
+    return false;
+  return ContainsKey(library_it->second, album);
+
+}
+
+bool ITunesDataProvider::GetTrackLocation(const ArtistName& artist,
+                                          const AlbumName& album,
+                                          const TrackName& track,
+                                          base::FilePath* result) const {
+  DCHECK(!needs_refresh_);
+  Library::const_iterator library_it = library_.find(artist);
+  if (library_it == library_.end())
+    return false;
+
+  Artist::const_iterator artist_it = library_it->second.find(album);
+  if (artist_it == library_it->second.end())
+    return false;
+
+  Album::const_iterator album_it = artist_it->second.find(track);
+  if (album_it == artist_it->second.end())
+    return false;
+
+  if (result)
+    *result = album_it->second;
+  return true;
+}
+
+std::set<ITunesDataProvider::ArtistName>
+ITunesDataProvider::GetArtists() const {
+  DCHECK(!needs_refresh_);
+  std::set<ArtistName> result;
+  Library::const_iterator it;
+  for (it = library_.begin(); it != library_.end(); ++it) {
+    result.insert(it->first);
+  }
+  return result;
+}
+
+std::set<ITunesDataProvider::AlbumName> ITunesDataProvider::GetAlbums(
+    const ArtistName& artist) const {
+  DCHECK(!needs_refresh_);
+  std::set<AlbumName> result;
+  Library::const_iterator artist_lookup = library_.find(artist);
+  if (artist_lookup == library_.end())
+    return result;
+
+  const Artist& artist_entry = artist_lookup->second;
+  Artist::const_iterator it;
+  for (it = artist_entry.begin(); it != artist_entry.end(); ++it) {
+    result.insert(it->first);
+  }
+  return result;
+}
+
+std::map<ITunesDataProvider::TrackName, base::FilePath>
+ITunesDataProvider::GetTracks(const ArtistName& artist,
+                              const AlbumName& album) const {
+  DCHECK(!needs_refresh_);
+  std::map<TrackName, base::FilePath> empty_result;
+  Library::const_iterator artist_lookup = library_.find(artist);
+  if (artist_lookup == library_.end())
+    return empty_result;
+
+  Artist::const_iterator album_lookup = artist_lookup->second.find(album);
+  if (album_lookup == artist_lookup->second.end())
+    return empty_result;
+
+  return album_lookup->second;
+}
+
+// static
+ITunesDataProvider::Album ITunesDataProvider::MakeUniqueTrackNames(
+    const ITunesLibraryParser::Album& album) {
+  // TODO(vandebo): It would be nice to ensure that names returned from here
+  // are stable, but aside from persisting every name returned, it's not
+  // obvious how to do that (without including the track id in every name).
+  typedef std::set<const ITunesLibraryParser::Track*> TrackRefs;

[Lei Zhang, 2013/06/06 09:58:54]

What about a std::multimap instead of these two structures? Code will instead
look roughly like:

typedef std::multimap<TrackName, const ITunesLibraryParser::Track*> AlbumInfo;
AlbumInfo info;
Album result;

ITunesLibraryParser::Album::const_iterator album_it;
for (album_it = album.begin(); album_it != album.end(); ++album_it) {
  const ITunesLibraryParser::Track& track = *album_it;
  std::string name = track.location.BaseName().AsUTF8Unsafe();
  info.insert(std::make_pair(name, &track);
}

for (AlbumInfo::iterator it = info.begin();
     it != info.end();
     it = info.upper_bound(it->first)) {
  if (info.count(it->first) == 1) {
    result[it->first] = it->second->location;
  } else {
    std::pair<AlbumInfo::iterator, AlbumInfo::iterator> dups =
      info.equal_range(it->first);
    for (AlbumInfo::iterator dup_it = dups.first;
         dup_it != dups.second;
         ++dup_it) {
      std::string id =
          base::StringPrintf(" (%" PRId64 ")", (*dup_it)->id);
      base::FilePath unique_name =
          (*dup_it)->location.BaseName().InsertBeforeExtensionASCII(id);
      result[unique_name.AsUTF8Unsafe()] = (*dup_it)->location;
    }
  }
}

[vandebo (ex-Chrome), 2013/06/06 19:49:18]

multimap is an interesting idea, but to me, it looks like the existing code is
simpler.

+  typedef std::map<TrackName, TrackRefs> AlbumInfo;
+
+  Album result;
+  AlbumInfo duped_tracks;
+
+  ITunesLibraryParser::Album::const_iterator album_it;
+  for (album_it = album.begin(); album_it != album.end(); ++album_it) {

[Lei Zhang, 2013/06/06 09:58:54]

a "const ITunesLibraryParser::Track& track = *album_it;" can help readability
and avoid "&*album_it"

[vandebo (ex-Chrome), 2013/06/06 19:49:18]

Done.

+    std::string name = album_it->location.BaseName().AsUTF8Unsafe();
+    duped_tracks[name].insert(&*album_it);
+  }
+
+  for (AlbumInfo::const_iterator name_it = duped_tracks.begin();
+       name_it != duped_tracks.end();
+       ++name_it) {
+    if (name_it->second.size() == 1) {

[Lei Zhang, 2013/06/06 09:58:54]

name_it->second can also use a const ref alias inside this loop for readability.

[vandebo (ex-Chrome), 2013/06/06 19:49:18]

Done.

+      result[name_it->first] = (*name_it->second.begin())->location;
+    } else {
+      for (TrackRefs::const_iterator track_it = name_it->second.begin();
+           track_it != name_it->second.end(); ++track_it) {
+        std::string id =
+            base::StringPrintf(" (%" PRId64 ")", (*track_it)->id);
+        base::FilePath unique_name =
+            (*track_it)->location.BaseName().InsertBeforeExtensionASCII(id);
+        result[unique_name.AsUTF8Unsafe()] = (*track_it)->location;
+      }
+    }
+  }
+
+  return result;
+}
+
+void ITunesDataProvider::ParseLibrary() {
+  std::string xml = ReadFile(library_path_);
+
+  library_.clear();
+  ITunesLibraryParser parser;
+  if (!parser.Parse(xml))
+    return;
+
+  ITunesLibraryParser::Library::const_iterator artist_it;
+  ITunesLibraryParser::Albums::const_iterator album_it;
+  for (artist_it = parser.library().begin();
+       artist_it != parser.library().end();
+       ++artist_it) {
+    for (album_it = artist_it->second.begin();
+         album_it != artist_it->second.end();
+         ++album_it) {
+      library_[artist_it->first][album_it->first] =
+          ITunesDataProvider::MakeUniqueTrackNames(album_it->second);
+    }
+  }
+};
+
+}  // namespace itunes