[sound-juicer] Skip data tracks at the start of disc

[Phillip Wood <pwood src gnome org>]

commit 4a1c231562901124b53c9494fca0ed026916ae88
Author: Phillip Wood <phillip wood dunelm org uk>
Date:   Wed Jul 13 10:53:57 2016 +0100

    Skip data tracks at the start of disc
    
    MusicBrainz ignores data tracks at the end of the disc so they never
    appear but those at the start of the disc (typically on PlayStation CDs)
    are labelled ‘[data track]’¹. Adjust the track numbers to start at ‘1’
    so they make sense and also GStreamer automatically skips the data
    tracks so this ensures the correct tracks are played/extracted.
    
    ¹ https://musicbrainz.org/doc/Style/Unknown_and_untitled/Special_purpose_track_title
    
    https://bugzilla.gnome.org/show_bug.cgi?id=768596

 libjuicer/sj-metadata-musicbrainz5.c |   35 ++++++++++++++++++++++++++++-----
 1 files changed, 29 insertions(+), 6 deletions(-)
---
diff --git a/libjuicer/sj-metadata-musicbrainz5.c b/libjuicer/sj-metadata-musicbrainz5.c
index 9c3f80b..b06d1a9 100644
--- a/libjuicer/sj-metadata-musicbrainz5.c
+++ b/libjuicer/sj-metadata-musicbrainz5.c
@@ -696,6 +696,7 @@ fill_tracks_from_medium (SjMetadataMusicbrainz5  *self,
   Mb5TrackList track_list;
   GList *tracks;
   unsigned int i;
+  gboolean skip_data_tracks;
   char buffer[512]; /* for the GET() macro */
 
   track_list = mb5_medium_get_tracklist (medium);
@@ -705,31 +706,55 @@ fill_tracks_from_medium (SjMetadataMusicbrainz5  *self,
   album->number = mb5_track_list_size (track_list);
 
   tracks = NULL;
+  skip_data_tracks = TRUE;
 
   for (i = 0; i < mb5_track_list_size (track_list); i++) {
     Mb5Track mbt;
     Mb5ArtistCredit credit;
     Mb5Recording recording;
     TrackDetails *track;
+    gchar *title;
+    gint track_offset;
 
     mbt = mb5_track_list_item (track_list, i);
     if (!mbt)
       continue;
 
-    track = g_new0 (TrackDetails, 1);
+    recording = mb5_track_get_recording (mbt);
+    /*
+     * title points to a string on the stack so set it to NULL to
+     * prevent the GET macro from trying to free it
+     */
+    title = NULL;
+    GET (title, mb5_track_get_title, mbt);
+    if (title == NULL && recording != NULL)
+      GET (title, mb5_recording_get_title, recording);
+
+    /*
+     * Skip data tracks at the start of the disc
+     * https://musicbrainz.org/doc/Style/Unknown_and_untitled/Special_purpose_track_title
+     */
+    if (skip_data_tracks) {
+      if (g_strcmp0 (title, "[data track]") == 0) {
+        continue;
+      } else {
+        skip_data_tracks = FALSE;
+        track_offset = mb5_track_get_position (mbt) - 1;
+      }
+    }
 
+    track = g_new0 (TrackDetails, 1);
+    track->title = g_strdup (title);
     track->album = album;
 
-    track->number = mb5_track_get_position (mbt);
+    track->number = mb5_track_get_position (mbt) - track_offset;
 
     /* Prefer metadata from Mb5Track over metadata from Mb5Recording
      * https://bugzilla.gnome.org/show_bug.cgi?id=690903#c8
      */
     track->duration = mb5_track_get_length (mbt) / 1000;
-    GET (track->title, mb5_track_get_title, mbt);
     credit = mb5_track_get_artistcredit (mbt);
 
-    recording = mb5_track_get_recording (mbt);
     if (recording != NULL) {
       GET (track->track_id, mb5_recording_get_id, recording);
       fill_recording_relations (self, recording, track, cancellable, error);
@@ -740,8 +765,6 @@ fill_tracks_from_medium (SjMetadataMusicbrainz5  *self,
 
       if (track->duration == 0)
         track->duration = mb5_recording_get_length (recording) / 1000;
-      if (track->title == NULL)
-        GET (track->title, mb5_recording_get_title, recording);
       if (credit == NULL)
           credit = mb5_recording_get_artistcredit (recording);
     }