126 lines
2.9 KiB
Go
126 lines
2.9 KiB
Go
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// Package mbz extracts MusicBrainz Picard-specific tags from general tag metadata.
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// See https://picard.musicbrainz.org/docs/mappings/ for more information.
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package mbz
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import (
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"strings"
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"github.com/dhowden/tag"
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)
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// Info is a structure which contains MusicBrainz identifier information.
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type Info struct {
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AcoustID string
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Album string
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AlbumArtist string
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Artist string
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ReleaseGroup string
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Track string
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}
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// Supported MusicBrainz tag names
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const (
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TagAcoustID = "acoustid_id"
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TagAlbum = "musicbrainz_albumid"
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TagAlbumArtist = "musicbrainz_albumartistid"
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TagArtist = "musicbrainz_artistid"
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TagReleaseGroup = "musicbrainz_releasegroupid"
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TagTrack = "musicbrainz_recordingid"
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)
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// UFIDProviderURL is the URL that we match inside a UFID tag.
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const UFIDProviderURL = "http://musicbrainz.org"
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// Mapping between the internal picard tag names and aliases.
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var tags = map[string]string{
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TagAcoustID: "Acoustid Id",
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TagAlbum: "MusicBrainz Album Id",
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TagAlbumArtist: "MusicBrainz Album Artist Id",
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TagArtist: "MusicBrainz Artist Id",
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TagReleaseGroup: "MusicBrainz Release Group Id",
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TagTrack: "MusicBrainz Track Id",
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}
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func (i *Info) set(t, v string) {
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switch t {
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case TagAcoustID:
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i.AcoustID = v
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case TagAlbum:
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i.Album = v
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case TagAlbumArtist:
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i.AlbumArtist = v
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case TagArtist:
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i.Artist = v
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case TagReleaseGroup:
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i.ReleaseGroup = v
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case TagTrack:
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i.Track = v
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}
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}
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// Set the MusicBrainz tag to the given value.
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func (i *Info) Set(t, v string) {
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if _, ok := tags[t]; ok {
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i.set(t, v)
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return
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}
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for k, tt := range tags {
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if tt == t {
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i.set(k, v)
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return
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}
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}
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}
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// extractID3 attempts to extract MusicBrainz Picard tags from m.Raw(), where m.Format
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// is assumed to be a supported version of ID3.
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func extractID3(m tag.Metadata) *Info {
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var txxx, ufid string
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switch m.Format() {
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case tag.ID3v2_2:
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txxx, ufid = "TXX", "UFI"
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case tag.ID3v2_3, tag.ID3v2_4:
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txxx, ufid = "TXXX", "UFID"
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}
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i := &Info{}
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for k, v := range m.Raw() {
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switch {
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case strings.HasPrefix(k, txxx):
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if str, ok := v.(*tag.Comm); ok {
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i.Set(str.Description, str.Text)
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}
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case strings.HasPrefix(k, ufid):
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if id, ok := v.(*tag.UFID); ok {
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if id.Provider == UFIDProviderURL {
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i.Set(TagTrack, string(id.Identifier))
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}
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}
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}
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}
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return i
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}
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// extractMP4Vorbis attempts to extract MusicBrainz Picard tags from m.Raw(), where m.Format
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// is assumed to be MP4 or VORBIS.
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func extractMP4Vorbis(m tag.Metadata) *Info {
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i := &Info{}
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for t, v := range m.Raw() {
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if s, ok := v.(string); ok {
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i.Set(t, s)
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}
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}
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return i
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}
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// Extract tags created by MusicBrainz Picard which can be used with with the MusicBrainz and LastFM APIs.
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// See https://picard.musicbrainz.org/docs/mappings/ for more information.
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func Extract(m tag.Metadata) *Info {
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switch m.Format() {
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case tag.ID3v2_2, tag.ID3v2_3, tag.ID3v2_4:
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return extractID3(m)
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}
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return extractMP4Vorbis(m)
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}
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