add LrcLib as a fallback lyric provider

backend/config.go

@@ -45,6 +45,7 @@ type AppConfig struct {
 	SaveQueueToServer           bool
 	DefaultPlaylistID           string
 	ShowTrackChangeNotification bool
+	EnableLrcLib                bool
 
 	// Experimental - may be removed in future
 	FontNormalTTF string
@@ -159,6 +160,7 @@ func DefaultConfig(appVersionTag string) *Config {
 			SavePlayQueue:               true,
 			SaveQueueToServer:           false,
 			ShowTrackChangeNotification: false,
+			EnableLrcLib:                true,
 		},
 		AlbumPage: AlbumPageConfig{
 			TracklistColumns: []string{"Artist", "Time", "Plays", "Favorite", "Rating"},

backend/lrclib.go

@@ -0,0 +1,107 @@
+package backend
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/dweymouth/supersonic/backend/mediaprovider"
+)
+
+// FetchLrcLibLyrics is a static function to search and fetch lyrics from lrclib.net
+func FetchLrcLibLyrics(name, artist, album string, durationSecs int) (*mediaprovider.Lyrics, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "https://lrclib.net/api/get", nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Add("Accept", "application/json")
+	req.Header.Add("User-Agent", "Supersonic")
+
+	q := req.URL.Query()
+	q.Add("track_name", name)
+	q.Add("artist_name", artist)
+	q.Add("album_name", album)
+	q.Add("duration", strconv.Itoa(durationSecs))
+	req.URL.RawQuery = q.Encode()
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	return parseLrcLibResponse(resp)
+}
+
+func parseLrcLibResponse(resp *http.Response) (*mediaprovider.Lyrics, error) {
+	if resp.StatusCode == http.StatusNotFound {
+		return nil, errors.New("lrclib lyrics not found")
+	} else if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("error from lrclib: status %d", resp.StatusCode)
+	}
+
+	var parsedResponse lrcLibResponse
+	if err := json.NewDecoder(resp.Body).Decode(&parsedResponse); err != nil {
+		return nil, fmt.Errorf("failed to decode lrclib response: %w", err)
+	}
+	lrcs := &mediaprovider.Lyrics{
+		Title:  parsedResponse.TrackName,
+		Artist: parsedResponse.ArtistName,
+	}
+	if parsedResponse.SyncedLyrics != "" {
+		lines, err := parseSyncedLyrics(parsedResponse.SyncedLyrics)
+		if err != nil {
+			return nil, err
+		}
+		lrcs.Synced = true
+		lrcs.Lines = lines
+	} else {
+		for _, line := range strings.Split(parsedResponse.PlainLyrics, "\n") {
+			lrcs.Lines = append(lrcs.Lines, mediaprovider.LyricLine{Text: line})
+		}
+	}
+	return lrcs, nil
+}
+
+var syncedRegex = regexp.MustCompile(`^\[(\d\d):(\d\d\.\d\d\d?)\] ?(.+)$`)
+
+func parseSyncedLyrics(synced string) ([]mediaprovider.LyricLine, error) {
+	var lines []mediaprovider.LyricLine
+	for _, line := range strings.Split(synced, "\n") {
+		matches := syncedRegex.FindStringSubmatch(line)
+		if len(matches) != 4 {
+			continue // malformed lyric line, attempt to continue
+		}
+		min, _ := strconv.Atoi(matches[1])
+		sec, _ := strconv.ParseFloat(matches[2], 64)
+		lines = append(lines, mediaprovider.LyricLine{
+			Start: float64(min)*60 + sec,
+			Text:  matches[3],
+		})
+	}
+	var err error
+	if len(lines) == 0 {
+		err = errors.New("failed to parse synced lyrics")
+	}
+	return lines, err
+}
+
+type lrcLibResponse struct {
+	ID           int     `json:"id"`
+	TrackName    string  `json:"trackName"`
+	ArtistName   string  `json:"artistName"`
+	AlbumName    string  `json:"albumName"`
+	Duration     float64 `json:"duration"`
+	Instrumental bool    `json:"instrumental"`
+	PlainLyrics  string  `json:"plainLyrics"`
+	SyncedLyrics string  `json:"syncedLyrics"`
+}