[rhythmbox] lyrics: fetch lyrics from metadata tags

[Jonathan Matthew <jmatthew src gnome org>]

commit 1416e4cbeb751acb92d2008d9e4afe9e4967a2be
Author: Christian Weiske <cweiske cweiske de>
Date:   Sat Jul 15 20:48:39 2017 +1000

    lyrics: fetch lyrics from metadata tags
    
    Only works with ogg tags for now.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=463978

 plugins/lyrics/lyrics.py |   95 ++++++++++++++++++++++++++++++++++++++-------
 1 files changed, 80 insertions(+), 15 deletions(-)
---
diff --git a/plugins/lyrics/lyrics.py b/plugins/lyrics/lyrics.py
index 13124b3..c0f8de1 100644
--- a/plugins/lyrics/lyrics.py
+++ b/plugins/lyrics/lyrics.py
@@ -32,6 +32,7 @@ import urllib.request
 import rb
 from gi.repository import Gtk, Gio, GObject, Peas
 from gi.repository import RB
+from gi.repository import Gst, GstPbutils
 
 import LyricsParse
 from LyricsConfigureDialog import LyricsConfigureDialog
@@ -132,22 +133,33 @@ def build_cache_path(artist, title):
        return os.path.join(artist_folder, title[:128] + '.lyric')
 
 class LyricGrabber(object):
+       """
+       Fetch lyrics from several sources.
+
+       1. Local cache file
+       2. Lyric tags in file meta data
+       3. Online services
+       """
        def __init__(self, db, entry):
                self.db = db
                self.entry = entry
-               
+
                (self.artist, self.title) = parse_song_data(self.db, self.entry)
 
                self.cache_path = build_cache_path(self.artist, self.title)
 
        def verify_lyric(self):
                return os.path.exists(self.cache_path)
-         
+
        def search_lyrics(self, callback, cache_only=False):
+               """
+               Fetch lyrics from cache.
+
+               If no cache file exist, tag extraction is tried next.
+               """
                self.callback = callback
-               
+
                status = self.verify_lyric()
-               
                if status:
                        f = open(self.cache_path, 'rt')
                        text = f.read()
@@ -155,20 +167,73 @@ class LyricGrabber(object):
                        self.callback(text)
                elif cache_only:
                        self.callback(_("No lyrics found"))
-               elif self.artist == "" and self.title == "":
-                       self.callback(_("No lyrics found"))
                else:
-                       def lyric_callback (text):
-                               if text is not None:
-                                       f = open(self.cache_path, 'wt')
-                                       f.write (text)
-                                       f.close ()
-                                       self.callback(text)
-                               else:
-                                       self.callback(_("No lyrics found"))
+                       self.search_tags()
+
+       def search_tags(self):
+               """
+               Initiate fetching meta tags.
+
+               Result will be handled in search_tags_result
+               """
+               location = self.entry.get_playback_uri()
+               self.discoverer = GstPbutils.Discoverer(timeout=Gst.SECOND*3)
+               self.discoverer.connect('discovered', self.search_tags_result)
+               self.discoverer.start()
+               self.discoverer.discover_uri_async(location)
+
+       def search_tags_result(self, discoverer, info, error):
+               """
+               Extract lyrics from the file meta data (tags).
+
+               If no lyrics tags are found, online services are tried next.
+
+               Supported file formats and lyrics tags:
+               - ogg/vorbis files with "LYRICS" and "SYNCLYRICS" tag
+               """
+               tags = info.get_tags()
+               if tags is None:
+                       self.search_online()
+                       return
 
+               for i in range(tags.get_tag_size("extended-comment")):
+                       (exists, value) = tags.get_string_index("extended-comment", i)
+                       #ogg/vorbis unsynchronized lyrics
+                       if exists and value.startswith("LYRICS"):
+                               text = value.replace("LYRICS=", "")
+                               self.lyrics_found(text)
+                               return
+                       #ogg/vorbis synchronized lyrics
+                       elif exists and value.startswith("SYNCLYRICS"):
+                               text = value.replace("SYNCLYRICS=", "")
+                               self.lyrics_found(text)
+                               return
+
+               self.search_online()
+
+       def search_online(self):
+               """Initiate searching the online lyrics services"""
+               if self.artist == "" and self.title == "":
+                       self.callback(_("No lyrics found"))
+               else:
                        parser = LyricsParse.Parser(self.artist, self.title)
-                       parser.get_lyrics(lyric_callback)
+                       parser.get_lyrics(self.search_online_result)
+
+       def search_online_result(self, text):
+               """Handle the result of searching online lyrics services"""
+               if text is not None:
+                       self.lyrics_found(text)
+               else:
+                       self.callback(_("No lyrics found"))
+
+
+       def lyrics_found(self, text):
+               f = open(self.cache_path, 'wt')
+               f.write(text)
+               f.close()
+
+               self.callback(text)
+
 
 class LyricPane(object):
        def __init__(self, db, song_info):