Add lyrics: paste, fetch, and read them while reviewing
Lyrics are suggested at submission and never imposed. The conversion worker makes one LRCLIB lookup with whatever metadata exists, and the waiting page has a Hae sanoitukset button that re-queries with whatever title and artist are currently typed — which is the case that matters, since our metadata comes from ID3 tags and YouTube uploaders. Neither path overwrites typed text. - lyrics text on both submissions and songs, copied across at publish. Nothing has launched, so the column goes into 001_init.sql rather than a migration - The lock does not cover lyrics: it freezes what the song claims to be, and nobody reviewed the lyrics. So the submitter can still fix them afterwards, or paste them for an old song a year later - The review strip gained a second pane: lyrics on the left, review on the right, so following the words costs no scrolling. No lyrics means no pane, not an empty one. Below 1024px the panes stack - LRC timestamps are stored but stripped for reading — they belong to the player, not the reader - The lyrics box is capped and scrolls inside itself, so a long song cannot stretch the strip past the screen Fixes a real bug found on the way: saveMetadata cleared any field the request did not carry, so publishing wiped the lyrics the worker had just fetched. Fields absent from a request now keep their stored value. The client identifies itself to LRCLIB as "levyraati" and nothing more. Tests cover cleanLyrics keeping line breaks, and fetchLyrics against a local server: synced beats plain, instrumentals and wrong-length takes are skipped, and a miss is empty with no error.
This commit is contained in:
Esa Kataja
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package main
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import (
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"context"
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"encoding/json"
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"fmt"
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"io"
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"log/slog"
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"net/http"
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"net/url"
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"regexp"
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"strings"
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"time"
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)
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// LRCLIB is a community lyrics database with no API key. It is treated exactly like ffmpeg and
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// yt-dlp: an outside thing with a timeout, allowed to fail, never blocking anything.
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// A var rather than a const so tests can point it at a local server instead of the real service.
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var lrclibBase = "https://lrclib.net/api"
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const (
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// Identifies the client and nothing else. No URL, no host, no version: this app is private,
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// and a third party's logs are not the place to learn where it lives.
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lrclibAgent = "levyraati"
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lyricsTimout = 10 * time.Second
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)
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type lrclibResult struct {
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TrackName string `json:"trackName"`
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ArtistName string `json:"artistName"`
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Duration float64 `json:"duration"`
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Instrumental bool `json:"instrumental"`
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PlainLyrics string `json:"plainLyrics"`
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SyncedLyrics string `json:"syncedLyrics"`
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}
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// best returns the synced version when there is one — timestamps are what make the scroll possible
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// later, and plain text is the fallback rather than the goal.
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func (r lrclibResult) best() string {
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if r.SyncedLyrics != "" {
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return r.SyncedLyrics
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}
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return r.PlainLyrics
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}
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var lyricsClient = &http.Client{Timeout: lyricsTimout}
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// LRC timestamps are stored, because the highlight needs them, and stripped for reading, because
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// nobody wants to read [00:11.74] at the start of every line.
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var lrcStamp = regexp.MustCompile(`^(\[\d{1,2}:\d{2}(?:[.:]\d{1,3})?\]\s*)+`)
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func stripLRC(s string) string {
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if !strings.HasPrefix(strings.TrimSpace(s), "[") {
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return s
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}
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lines := strings.Split(s, "\n")
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for i, line := range lines {
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lines[i] = strings.TrimRight(lrcStamp.ReplaceAllString(line, ""), " ")
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}
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return strings.Join(lines, "\n")
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}
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func lrclibGet(ctx context.Context, path string, q url.Values) ([]byte, error) {
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ctx, cancel := context.WithTimeout(ctx, lyricsTimout)
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defer cancel()
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req, err := http.NewRequestWithContext(ctx, "GET", lrclibBase+path+"?"+q.Encode(), nil)
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if err != nil {
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return nil, err
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}
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req.Header.Set("User-Agent", lrclibAgent)
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resp, err := lyricsClient.Do(req)
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return nil, fmt.Errorf("lrclib %s: %s", path, resp.Status)
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}
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return io.ReadAll(io.LimitReader(resp.Body, 1<<20))
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}
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// fetchLyrics tries the exact match first — artist, track and duration within LRCLIB's ±2 s — and
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// falls back to a search, which is what saves songs whose tags are close but not exact. Returns an
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// empty string when nothing matches, which is a normal outcome rather than an error.
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func fetchLyrics(ctx context.Context, title, artist string, seconds int) (string, error) {
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title, artist = strings.TrimSpace(title), strings.TrimSpace(artist)
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if title == "" {
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return "", nil // nothing to match on; the submitter has not named it yet
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}
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if artist != "" && seconds > 0 {
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body, err := lrclibGet(ctx, "/get", url.Values{
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"track_name": {title},
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"artist_name": {artist},
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"duration": {fmt.Sprint(seconds)},
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})
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if err == nil {
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var res lrclibResult
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if json.Unmarshal(body, &res) == nil && !res.Instrumental {
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if l := res.best(); l != "" {
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return l, nil
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}
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}
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}
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}
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// Looser: let LRCLIB do the matching on a free-text query.
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q := title
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if artist != "" {
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q = artist + " " + title
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}
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body, err := lrclibGet(ctx, "/search", url.Values{"q": {q}})
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if err != nil {
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return "", err
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}
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var results []lrclibResult
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if err := json.Unmarshal(body, &results); err != nil {
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return "", err
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}
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for _, res := range results {
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if res.Instrumental {
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continue
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}
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// A duration within 5 s is the strongest signal we have that it is the same recording.
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if seconds > 0 && res.Duration > 0 && abs(int(res.Duration)-seconds) > 5 {
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continue
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}
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if l := res.best(); l != "" {
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return l, nil
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}
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}
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return "", nil
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}
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func abs(n int) int {
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if n < 0 {
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return -n
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}
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return n
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}
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// --- the button on the waiting page ---
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// Suggests lyrics for whatever title and artist are currently typed, and never overwrites what the
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// submitter has already put in the field — the response fills the textarea, and they can accept it,
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// edit it or clear it.
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func (a *app) suggestLyrics(w http.ResponseWriter, r *http.Request) {
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s := a.loadSubmission(w, r)
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if s == nil {
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return
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}
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title := clean(r.FormValue("title"), maxTitle)
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artist := clean(r.FormValue("artist"), maxArtist)
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if title == "" {
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title, artist = s.Title, s.Artist
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}
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seconds := 0
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if meta, err := probe(r.Context(), s.TmpPath); err == nil {
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seconds = int(meta.Duration.Seconds())
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}
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lyrics, err := fetchLyrics(r.Context(), title, artist, seconds)
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if err != nil {
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slog.Warn("lyrics lookup", "ctx", "submissions", "error", err, "submission", s.ID)
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}
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// Keep whatever the submitter already typed: a suggestion never overwrites their own words.
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if existing := cleanLyrics(r.FormValue("lyrics")); existing != "" {
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lyrics = existing
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}
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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data := map[string]any{
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"ID": s.ID, "Lyrics": lyrics, "Found": lyrics != "", "Searched": true,
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}
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if err := pages["submission.html"].ExecuteTemplate(w, "lyricsfield", data); err != nil {
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slog.Error("render lyrics field", "ctx", "submissions", "error", err)
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}
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}
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// Called from the conversion worker: one automatic attempt, best effort, and only when the
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// submitter has not already pasted something.
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func (a *app) autoFetchLyrics(ctx context.Context, subID int64, title, artist string, seconds int) {
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if title == "" {
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return
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}
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lyrics, err := fetchLyrics(ctx, title, artist, seconds)
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if err != nil {
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slog.Warn("lyrics lookup", "ctx", "submissions", "error", err, "submission", subID)
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return
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}
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if lyrics == "" {
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return
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}
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tag, err := a.pool.Exec(ctx,
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`update submissions set lyrics = $2 where id = $1 and lyrics is null`,
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subID, cleanLyrics(lyrics))
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if err != nil {
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slog.Error("save lyrics", "ctx", "submissions", "error", err, "submission", subID)
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return
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}
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if tag.RowsAffected() > 0 {
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slog.Info("lyrics found", "ctx", "submissions", "submission", subID)
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}
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}
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