feat(subsonic): implement getSimilarSongs.view

closes #195

server/ctrlsubsonic/handlers_by_tags.go

@@ -449,3 +449,66 @@ func (c *Controller) ServeGetTopSongs(r *http.Request) *spec.Response {
 	}
 	return sub
 }
+
+func (c *Controller) ServeGetSimilarSongs(r *http.Request) *spec.Response {
+	params := r.Context().Value(CtxParams).(params.Params)
+	count := params.GetOrInt("count", 10)
+	id, err := params.GetID("id")
+	if err != nil || id.Type != specid.Track {
+		return spec.NewError(10, "please provide an track `id` parameter")
+	}
+	apiKey, _ := c.DB.GetSetting("lastfm_api_key")
+	if apiKey == "" {
+		return spec.NewResponse()
+	}
+
+	var track db.Track
+	err = c.DB.
+		Preload("Artist").
+		Preload("Album").
+		Where("id=?", id.Value).
+		First(&track).
+		Error
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return spec.NewError(10, "couldn't find a track with that id")
+	}
+
+	similarTracks, err := lastfm.TrackGetSimilarTracks(apiKey, track.Artist.Name, track.TagTitle)
+	if err != nil {
+		return spec.NewError(0, "fetching track similar tracks: %v", err)
+	}
+	if len(similarTracks.Tracks) == 0 {
+		return spec.NewError(70, "no similar songs found for track: %v", track.TagTitle)
+	}
+
+	similarTrackNames := make([]string, len(similarTracks.Tracks))
+	for i, t := range similarTracks.Tracks {
+		similarTrackNames[i] = t.Name
+	}
+
+	var tracks []*db.Track
+	err = c.DB.
+		Preload("Artist").
+		Preload("Album").
+		Select("tracks.*").
+		Where("tracks.tag_title IN (?)", similarTrackNames).
+		Order(gorm.Expr("random()")).
+		Limit(count).
+		Find(&tracks).
+		Error
+	if err != nil {
+		return spec.NewError(0, "error finding tracks: %v", err)
+	}
+	if len(tracks) == 0 {
+		return spec.NewError(70, "no similar song could be match with collection in database: %v", track.TagTitle)
+	}
+
+	sub := spec.NewResponse()
+	sub.SimilarSongs = &spec.SimilarSongs{
+		Tracks: make([]*spec.TrackChild, len(tracks)),
+	}
+	for i, track := range tracks {
+		sub.SimilarSongs.Tracks[i] = spec.NewTrackByTags(track, track.Album)
+	}
+	return sub
+}

server/ctrlsubsonic/spec/spec.go

@@ -48,6 +48,7 @@ type Response struct {
 	Starred           *Starred           `xml:"starred"           json:"starred,omitempty"`
 	StarredTwo        *StarredTwo        `xml:"starred2"          json:"starred2,omitempty"`
 	TopSongs          *TopSongs          `xml:"topSongs"          json:"topSongs,omitempty"`
+	SimilarSongs      *SimilarSongs      `xml:"similarSongs"      json:"similarSongs,omitempty"`
 }
 
 func NewResponse() *Response {
@@ -357,3 +358,7 @@ type StarredTwo struct {
 type TopSongs struct {
 	Tracks []*TrackChild `xml:"song,omitempty" json:"song,omitempty"`
 }
+
+type SimilarSongs struct {
+	Tracks []*TrackChild `xml:"song,omitempty" json:"song,omitempty"`
+}

server/scrobble/lastfm/lastfm.go

@@ -31,6 +31,7 @@ type LastFM struct {
 	Error          Error          `xml:"error"`
 	Artist         Artist         `xml:"artist"`
 	TopTracks      TopTracks      `xml:"toptracks"`
+	SimilarTracks  SimilarTracks  `xml:"similartracks"`
 }
 
 type Session struct {
@@ -84,6 +85,13 @@ type TopTracks struct {
 	Tracks  []Track  `xml:"track"`
 }
 
+type SimilarTracks struct {
+	XMLName xml.Name `xml:"similartracks"`
+	Artist  string   `xml:"artist,attr"`
+	Track   string   `xml:"track,attr"`
+	Tracks  []Track  `xml:"track"`
+}
+
 type Track struct {
 	Rank      int     `xml:"rank,attr"`
 	Tracks    []Track `xml:"track"`
@@ -158,6 +166,18 @@ func ArtistGetTopTracks(apiKey, artistName string) (TopTracks, error) {
 	return resp.TopTracks, nil
 }
 
+func TrackGetSimilarTracks(apiKey string, artistName, trackName string) (SimilarTracks, error) {
+	params := url.Values{}
+	params.Add("method", "track.getSimilar")
+	params.Add("api_key", apiKey)
+	params.Add("track", trackName)
+	params.Add("artist", artistName)
+	resp, err := makeRequest("GET", params)
+	if err != nil {
+		return SimilarTracks{}, fmt.Errorf("making track GET: %w", err)
+	}
+	return resp.SimilarTracks, nil
+}
 func GetSession(apiKey, secret, token string) (string, error) {
 	params := url.Values{}
 	params.Add("method", "auth.getSession")

server/server.go

@@ -218,6 +218,7 @@ func setupSubsonic(r *mux.Router, ctrl *ctrlsubsonic.Controller) {
 	r.Handle("/createBookmark{_:(?:\\.view)?}", ctrl.H(ctrl.ServeCreateBookmark))
 	r.Handle("/deleteBookmark{_:(?:\\.view)?}", ctrl.H(ctrl.ServeDeleteBookmark))
 	r.Handle("/getTopSongs{_:(?:\\.view)?}", ctrl.H(ctrl.ServeGetTopSongs))
+	r.Handle("/getSimilarSongs{_:(?:\\.view)?}", ctrl.H(ctrl.ServeGetSimilarSongs))
 
 	// raw
 	r.Handle("/download{_:(?:\\.view)?}", ctrl.HR(ctrl.ServeDownload))