minstrel/internal/similarity/worker_integration_test.go

package similarity

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"os"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/jackc/pgx/v5/pgtype"
	"github.com/jackc/pgx/v5/pgxpool"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db"
	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/dbtest"
	"git.fabledsword.com/bvandeusen/minstrel/internal/scrobble/listenbrainz"
)

func testPool(t *testing.T) (*pgxpool.Pool, *dbq.Queries) {
	t.Helper()
	if testing.Short() {
		t.Skip("skipping in -short mode")
	}
	dsn := os.Getenv("MINSTREL_TEST_DATABASE_URL")
	if dsn == "" {
		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
	}
	if err := db.Migrate(dsn, slog.New(slog.NewTextHandler(io.Discard, nil))); err != nil {
		t.Fatalf("migrate: %v", err)
	}
	pool, err := pgxpool.New(context.Background(), dsn)
	if err != nil {
		t.Fatalf("pool: %v", err)
	}
	t.Cleanup(pool.Close)
	dbtest.ResetDB(t, pool)
	return pool, dbq.New(pool)
}

type fixture struct {
	pool   *pgxpool.Pool
	q      *dbq.Queries
	user   pgtype.UUID
	artist dbq.Artist
	album  dbq.Album
}

func newFixture(t *testing.T) fixture {
	t.Helper()
	pool, q := testPool(t)
	ctx := context.Background()
	u, err := q.CreateUser(ctx, dbq.CreateUserParams{
		Username: dbtest.TestUserPrefix + "tester", PasswordHash: "x", ApiTokenHash: "x", IsAdmin: false,
	})
	if err != nil {
		t.Fatalf("user: %v", err)
	}
	artistMbid := "aaaaaaaa-1111-1111-1111-111111111111"
	a, err := q.UpsertArtist(ctx, dbq.UpsertArtistParams{
		Name: "X", SortName: "X", Mbid: &artistMbid,
	})
	if err != nil {
		t.Fatalf("artist: %v", err)
	}
	al, err := q.UpsertAlbum(ctx, dbq.UpsertAlbumParams{
		Title: "X", SortTitle: "X", ArtistID: a.ID,
	})
	if err != nil {
		t.Fatalf("album: %v", err)
	}
	return fixture{pool: pool, q: q, user: u.ID, artist: a, album: al}
}

func seedTrack(t *testing.T, f fixture, title string, mbid *string) dbq.Track {
	t.Helper()
	tr, err := f.q.UpsertTrack(context.Background(), dbq.UpsertTrackParams{
		Title:      title,
		AlbumID:    f.album.ID,
		ArtistID:   f.artist.ID,
		FilePath:   "/tmp/" + title + ".flac",
		DurationMs: 200_000,
		Mbid:       mbid,
	})
	if err != nil {
		t.Fatalf("track: %v", err)
	}
	return tr
}

func markPlayed(t *testing.T, f fixture, trackID pgtype.UUID) {
	t.Helper()
	var sessionID pgtype.UUID
	if err := f.pool.QueryRow(context.Background(),
		`INSERT INTO play_sessions (user_id, started_at, last_event_at, client_id)
		 VALUES ($1, now() - interval '5 minutes', now(), 'test') RETURNING id`,
		f.user).Scan(&sessionID); err != nil {
		t.Fatalf("session: %v", err)
	}
	if _, err := f.pool.Exec(context.Background(),
		`INSERT INTO play_events (user_id, track_id, session_id, started_at, ended_at, duration_played_ms, completion_ratio, was_skipped)
		 VALUES ($1, $2, $3, now() - interval '1 minute', now(), 250000, 0.83, false)`,
		f.user, trackID, sessionID); err != nil {
		t.Fatalf("play_event: %v", err)
	}
}

func newTestWorker(f fixture, lbBaseURL string) *Worker {
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	return &Worker{
		pool: f.pool,
		// LabsBaseURL must point at the stub too: similarity calls hit
		// the Labs API (commit 4fca0e6), so an unset LabsBaseURL would
		// fall through to the real labs.api and the stub never runs.
		client: &listenbrainz.Client{BaseURL: lbBaseURL, LabsBaseURL: lbBaseURL, HTTP: http.DefaultClient},
		logger: logger,
		tick:   1 * time.Hour,
		batch:  5,
		topK:   20,
	}
}

// stubLB returns an httptest server that responds to similar-recordings and
// similar-artists with the given JSON payloads.
func stubLB(recordingsBody, artistsBody string, status int) *httptest.Server {
	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if status != 0 && status != http.StatusOK {
			w.WriteHeader(status)
			return
		}
		if strings.Contains(r.URL.Path, "/similar-recordings/") {
			_, _ = w.Write([]byte(recordingsBody))
			return
		}
		if strings.Contains(r.URL.Path, "/similar-artists/") {
			_, _ = w.Write([]byte(artistsBody))
			return
		}
		w.WriteHeader(http.StatusNotFound)
	}))
}

func countTrackSim(t *testing.T, f fixture, a pgtype.UUID) int {
	t.Helper()
	var n int
	if err := f.pool.QueryRow(context.Background(),
		`SELECT count(*) FROM track_similarity WHERE track_a_id = $1`, a).Scan(&n); err != nil {
		t.Fatalf("count: %v", err)
	}
	return n
}

func countArtistSim(t *testing.T, f fixture, a pgtype.UUID) int {
	t.Helper()
	var n int
	if err := f.pool.QueryRow(context.Background(),
		`SELECT count(*) FROM artist_similarity WHERE artist_a_id = $1`, a).Scan(&n); err != nil {
		t.Fatalf("count: %v", err)
	}
	return n
}

func TestTickOnce_NoPlayedTracks_NoOp(t *testing.T) {
	f := newFixture(t)
	srv := stubLB(`[]`, `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	var n int
	_ = f.pool.QueryRow(context.Background(), `SELECT count(*) FROM track_similarity`).Scan(&n)
	if n != 0 {
		t.Errorf("track_similarity rows = %d, want 0", n)
	}
	_ = f.pool.QueryRow(context.Background(), `SELECT count(*) FROM artist_similarity`).Scan(&n)
	if n != 0 {
		t.Errorf("artist_similarity rows = %d, want 0", n)
	}
}

func TestTickOnce_MapsLBResponseToLocalLibrary(t *testing.T) {
	f := newFixture(t)
	mbidA := "11111111-1111-1111-1111-111111111111"
	mbidB := "22222222-2222-2222-2222-222222222222"
	mbidC := "99999999-9999-9999-9999-999999999999" // NOT in library
	trackA := seedTrack(t, f, "A", &mbidA)
	_ = seedTrack(t, f, "B", &mbidB)
	markPlayed(t, f, trackA.ID)
	body := `[
		{"recording_mbid": "` + mbidB + `", "score": 0.9},
		{"recording_mbid": "` + mbidC + `", "score": 0.7}
	]`
	srv := stubLB(body, `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	if got := countTrackSim(t, f, trackA.ID); got != 1 {
		t.Errorf("track_similarity rows = %d, want 1 (only mbidB is in-library)", got)
	}
}

// LB's scores are counts, not 0 to 1 (16 to 1445 on the operator's library).
// An edge is stored over the seed's best score in the whole answer, in the
// library or not, so the scorer reads it as 0 to 1 (#6177).
func TestTickOnce_EdgeIsRelativeToTheSeedsBest(t *testing.T) {
	f := newFixture(t)
	mbidA := "11111111-1111-1111-1111-111111111111"
	mbidB := "22222222-2222-2222-2222-222222222222"
	mbidC := "99999999-9999-9999-9999-999999999999" // NOT in library
	trackA := seedTrack(t, f, "A", &mbidA)
	trackB := seedTrack(t, f, "B", &mbidB)
	markPlayed(t, f, trackA.ID)
	body := `[
		{"recording_mbid": "` + mbidC + `", "score": 1445},
		{"recording_mbid": "` + mbidB + `", "score": 289}
	]`
	srv := stubLB(body, `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	var score float64
	if err := f.pool.QueryRow(context.Background(),
		`SELECT score FROM track_similarity WHERE track_a_id = $1 AND track_b_id = $2 AND source = 'listenbrainz'`,
		trackA.ID, trackB.ID).Scan(&score); err != nil {
		t.Fatalf("edge: %v", err)
	}
	if score != 0.2 {
		t.Errorf("score = %v, want 0.2 (289 over the seed's best, 1445)", score)
	}
}

// The 20-per-seed cap is gone with the cache (#5296): LB's answer is at most
// 50, and every recording of it that is in the library becomes an edge.
func TestTickOnce_KeepsEveryInLibraryMatch(t *testing.T) {
	f := newFixture(t)
	mbidSeed := "11111111-1111-1111-1111-111111111111"
	seed := seedTrack(t, f, "Seed", &mbidSeed)
	markPlayed(t, f, seed.ID)
	type lbRow struct {
		MBID  string  `json:"recording_mbid"`
		Score float64 `json:"score"`
	}
	rows := make([]lbRow, 0, 25)
	for i := 0; i < 25; i++ {
		mbid := fmt.Sprintf("20000000-0000-0000-0000-%012d", i+1)
		_ = seedTrack(t, f, fmt.Sprintf("T%02d", i+1), &mbid)
		rows = append(rows, lbRow{MBID: mbid, Score: 1.0 - 0.01*float64(i)})
	}
	body, _ := json.Marshal(rows)
	srv := stubLB(string(body), `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	if got := countTrackSim(t, f, seed.ID); got != 25 {
		t.Errorf("got %d rows, want all 25 in-library matches", got)
	}
}

func TestTickOnce_RecentFetchIsNotRepeated(t *testing.T) {
	f := newFixture(t)
	mbid := "11111111-1111-1111-1111-111111111111"
	trackA := seedTrack(t, f, "A", &mbid)
	markPlayed(t, f, trackA.ID)
	recordFetch(t, f, trackA.ID, "now() - interval '29 days'")
	srv, asked := recordingLB(func(string) string { return `[]` })
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	if n := len(asked()); n != 0 {
		t.Errorf("a seed fetched 29 days ago was asked again (%d requests)", n)
	}
}

func TestTickOnce_RefreshesStaleRow(t *testing.T) {
	f := newFixture(t)
	mbid := "11111111-1111-1111-1111-111111111111"
	trackA := seedTrack(t, f, "A", &mbid)
	markPlayed(t, f, trackA.ID)
	otherMbid := "55555555-5555-5555-5555-555555555555"
	other := seedTrack(t, f, "Other", &otherMbid)
	if _, err := f.pool.Exec(context.Background(),
		`INSERT INTO track_similarity (track_a_id, track_b_id, score, source, fetched_at)
		 VALUES ($1, $2, 0.5, 'listenbrainz', now() - interval '31 days')`, trackA.ID, other.ID); err != nil {
		t.Fatalf("seed sim: %v", err)
	}
	recordFetch(t, f, trackA.ID, "now() - interval '31 days'")
	srv := stubLB(`[{"recording_mbid":"`+otherMbid+`","score":0.95}]`, `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	var score float64
	var fetchedAt time.Time
	_ = f.pool.QueryRow(context.Background(),
		`SELECT score, fetched_at FROM track_similarity WHERE track_a_id = $1 AND track_b_id = $2 AND source = 'listenbrainz'`,
		trackA.ID, other.ID).Scan(&score, &fetchedAt)
	// The seed's only answer is its best, so the refreshed edge is 1.0 (#6177).
	if score != 1.0 {
		t.Errorf("score = %v, want 1.0 (refreshed, relative to the seed's best)", score)
	}
	if time.Since(fetchedAt) > time.Minute {
		t.Errorf("fetched_at not bumped: %v ago", time.Since(fetchedAt))
	}
}

func TestTickOnce_429AbortsTick(t *testing.T) {
	f := newFixture(t)
	mbid := "11111111-1111-1111-1111-111111111111"
	trackA := seedTrack(t, f, "A", &mbid)
	markPlayed(t, f, trackA.ID)
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Retry-After", "60")
		w.WriteHeader(http.StatusTooManyRequests)
	}))
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	_ = w.tickOnce(context.Background())
	if got := countTrackSim(t, f, trackA.ID); got != 0 {
		t.Errorf("rows on 429 = %d, want 0 (tick aborted before any inserts)", got)
	}
}

func TestTickOnce_TransientErrorSkipsTrack(t *testing.T) {
	f := newFixture(t)
	mbidA := "11111111-1111-1111-1111-111111111111"
	mbidB := "22222222-2222-2222-2222-222222222222"
	otherMbid := "55555555-5555-5555-5555-555555555555"
	trackA := seedTrack(t, f, "A", &mbidA)
	trackB := seedTrack(t, f, "B", &mbidB)
	_ = seedTrack(t, f, "Other", &otherMbid)
	markPlayed(t, f, trackA.ID)
	markPlayed(t, f, trackB.ID)
	var seen atomic.Int32
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !strings.Contains(r.URL.Path, "/similar-recordings/") {
			_, _ = w.Write([]byte(`[]`))
			return
		}
		n := seen.Add(1)
		if n == 1 {
			w.WriteHeader(http.StatusServiceUnavailable)
			return
		}
		_, _ = w.Write([]byte(`[{"recording_mbid":"` + otherMbid + `","score":0.7}]`))
	}))
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	_ = w.tickOnce(context.Background())
	a := countTrackSim(t, f, trackA.ID)
	b := countTrackSim(t, f, trackB.ID)
	if a+b != 1 {
		t.Errorf("expected exactly one track to succeed: a=%d b=%d", a, b)
	}
}

func TestTickOnce_FiltersInLibrary(t *testing.T) {
	f := newFixture(t)
	mbid := "11111111-1111-1111-1111-111111111111"
	trackA := seedTrack(t, f, "A", &mbid)
	markPlayed(t, f, trackA.ID)
	body := `[
		{"recording_mbid":"99999999-9999-9999-9999-999999999991","score":0.9},
		{"recording_mbid":"99999999-9999-9999-9999-999999999992","score":0.8},
		{"recording_mbid":"99999999-9999-9999-9999-999999999993","score":0.7}
	]`
	srv := stubLB(body, `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	if got := countTrackSim(t, f, trackA.ID); got != 0 {
		t.Errorf("filtered out-of-library: got %d, want 0", got)
	}
}

func TestTickOnce_ArtistPassMirrors(t *testing.T) {
	f := newFixture(t)
	mbid := "11111111-1111-1111-1111-111111111111"
	trackA := seedTrack(t, f, "A", &mbid)
	markPlayed(t, f, trackA.ID)
	bMbid := "bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb"
	_, err := f.q.UpsertArtist(context.Background(), dbq.UpsertArtistParams{
		Name: "Other", SortName: "Other", Mbid: &bMbid,
	})
	if err != nil {
		t.Fatalf("artist: %v", err)
	}
	body := `[{"artist_mbid":"` + bMbid + `","score":0.85}]`
	srv := stubLB(`[]`, body, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	if got := countArtistSim(t, f, f.artist.ID); got != 1 {
		t.Errorf("artist_similarity rows = %d, want 1", got)
	}
}

func TestTickOnce_NoMBIDOnTrack_Skipped(t *testing.T) {
	f := newFixture(t)
	trackNoMbid := seedTrack(t, f, "NoMbid", nil)
	markPlayed(t, f, trackNoMbid.ID)
	srv := stubLB(`[{"recording_mbid":"11111111-1111-1111-1111-111111111111","score":0.9}]`, `[]`, http.StatusOK)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	if got := countTrackSim(t, f, trackNoMbid.ID); got != 0 {
		t.Errorf("no-MBID track produced rows: %d", got)
	}
}

// TestUpsertArtistSimilar_PersistsUnmatchedToTable: M5c. Calls
// upsertArtistSimilar directly with a mix of in-library and out-of-library
// similar-artist payloads; verifies the matched path lands in
// artist_similarity (1 row), the unmatched path lands in
// artist_similarity_unmatched (3 rows), and rows with empty Name are
// skipped (we can't render a suggestion without a name).
func TestUpsertArtistSimilar_PersistsUnmatchedToTable(t *testing.T) {
	f := newFixture(t)
	ctx := context.Background()

	// Seed one additional in-library artist that will be the in-library match.
	inLibMBID := "in-lib-mbid-123"
	inLibArtist, err := f.q.UpsertArtist(ctx, dbq.UpsertArtistParams{
		Name: "InLib Artist", SortName: "InLib Artist", Mbid: &inLibMBID,
	})
	if err != nil {
		t.Fatalf("seed in-lib artist: %v", err)
	}

	w := newTestWorker(f, "")

	similars := []listenbrainz.SimilarArtist{
		// LB's scores are counts; rows are stored over the seed's best (#6177).
		{MBID: inLibMBID, Name: "InLib Artist", Score: 1000},
		{MBID: "out-mbid-1", Name: "Outsider One", Score: 850},
		{MBID: "out-mbid-2", Name: "Outsider Two", Score: 800},
		{MBID: "out-mbid-3", Name: "Outsider Three", Score: 700},
		{MBID: "out-mbid-4", Name: "", Score: 600}, // empty name — skipped
	}
	w.upsertArtistSimilar(ctx, f.q, f.artist.ID, similars)

	// Matched path: 1 row in artist_similarity for the in-library candidate.
	var matchedCount int
	if err := f.pool.QueryRow(ctx,
		"SELECT count(*) FROM artist_similarity WHERE artist_a_id = $1",
		f.artist.ID,
	).Scan(&matchedCount); err != nil {
		t.Fatalf("count matched: %v", err)
	}
	if matchedCount != 1 {
		t.Errorf("artist_similarity rows = %d, want 1 (only the in-library match)", matchedCount)
	}
	var matchedScore float64
	if err := f.pool.QueryRow(ctx,
		"SELECT score FROM artist_similarity WHERE artist_a_id = $1 AND artist_b_id = $2",
		f.artist.ID, inLibArtist.ID,
	).Scan(&matchedScore); err != nil {
		t.Fatalf("fetch matched score: %v", err)
	}
	if matchedScore != 1.0 {
		t.Errorf("matched score = %v, want 1.0 (the seed's best)", matchedScore)
	}

	// Unmatched path: 3 rows (out-mbid-1/2/3); the empty-name row is skipped.
	var unmatchedCount int
	if err := f.pool.QueryRow(ctx,
		"SELECT count(*) FROM artist_similarity_unmatched WHERE seed_artist_id = $1",
		f.artist.ID,
	).Scan(&unmatchedCount); err != nil {
		t.Fatalf("count unmatched: %v", err)
	}
	if unmatchedCount != 3 {
		t.Errorf("artist_similarity_unmatched rows = %d, want 3", unmatchedCount)
	}

	// Verify a specific row's name + score round-tripped correctly.
	var name string
	var score float64
	if err := f.pool.QueryRow(ctx,
		"SELECT candidate_name, score FROM artist_similarity_unmatched WHERE seed_artist_id = $1 AND candidate_mbid = $2",
		f.artist.ID, "out-mbid-1",
	).Scan(&name, &score); err != nil {
		t.Fatalf("fetch out-mbid-1: %v", err)
	}
	if name != "Outsider One" || score != 0.85 {
		t.Errorf("row = (%q, %v), want (Outsider One, 0.85)", name, score)
	}

}

// recordFetch stamps a seed as answered by ListenBrainz at the given SQL time.
func recordFetch(t *testing.T, f fixture, trackID pgtype.UUID, at string) {
	t.Helper()
	if _, err := f.pool.Exec(context.Background(),
		`INSERT INTO track_similarity_fetches (track_id, fetched_at, returned) VALUES ($1, `+at+`, 0)`,
		trackID); err != nil {
		t.Fatalf("record fetch: %v", err)
	}
}

// recordingLB answers similar-recordings with answer(mbid) and similar-artists
// with an empty list, and reports which recording MBIDs it was asked about.
func recordingLB(answer func(mbid string) string) (*httptest.Server, func() []string) {
	var mu sync.Mutex
	var asked []string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !strings.Contains(r.URL.Path, "/similar-recordings/") {
			_, _ = w.Write([]byte(`[]`))
			return
		}
		mbid := r.URL.Query().Get("recording_mbids")
		mu.Lock()
		asked = append(asked, mbid)
		mu.Unlock()
		_, _ = w.Write([]byte(answer(mbid)))
	}))
	return srv, func() []string {
		mu.Lock()
		defer mu.Unlock()
		return append([]string(nil), asked...)
	}
}

// The starvation #3879 measured: a seed whose answer matched nothing in the
// library wrote nothing, stayed due, and was asked again every tick ahead of
// everything behind it. Recording the fetch moves the queue on.
func TestTickOnce_UnmatchedAnswerDoesNotHoldTheQueue(t *testing.T) {
	f := newFixture(t)
	mbids := []string{
		"11111111-1111-1111-1111-111111111111",
		"22222222-2222-2222-2222-222222222222",
		"33333333-3333-3333-3333-333333333333",
	}
	for i := range mbids {
		tr := seedTrack(t, f, fmt.Sprintf("S%d", i), &mbids[i])
		markPlayed(t, f, tr.ID)
	}
	srv, asked := recordingLB(func(string) string {
		return `[{"recording_mbid":"99999999-9999-9999-9999-999999999999","score":0.9}]`
	})
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	w.batch = 1
	for i := 0; i < len(mbids); i++ {
		if err := w.tickOnce(context.Background()); err != nil {
			t.Fatalf("tick %d: %v", i, err)
		}
	}
	seen := map[string]bool{}
	for _, m := range asked() {
		seen[m] = true
	}
	if len(seen) != len(mbids) {
		t.Errorf("three ticks of one asked about %d distinct seeds (%v), want all %d",
			len(seen), asked(), len(mbids))
	}
	var fetched int
	_ = f.pool.QueryRow(context.Background(), `SELECT count(*) FROM track_similarity_fetches`).Scan(&fetched)
	if fetched != len(mbids) {
		t.Errorf("track_similarity_fetches = %d, want %d", fetched, len(mbids))
	}
}

// The point of the cache (#5296): a recording LB named while it was not in the
// library becomes an edge once it arrives, on the next tick's resolve, without
// asking LB again. One edge per recording when the library holds two copies,
// and none to a copy that is missing.
func TestTickOnce_CachedAnswerResolvesWhenTheRecordingArrives(t *testing.T) {
	f := newFixture(t)
	ctx := context.Background()
	seedMbid := "11111111-1111-1111-1111-111111111111"
	laterMbid := "77777777-7777-7777-7777-777777777777"
	goneMbid := "88888888-8888-8888-8888-888888888888"
	seed := seedTrack(t, f, "Seed", &seedMbid)
	markPlayed(t, f, seed.ID)
	srv, asked := recordingLB(func(string) string {
		return `[{"recording_mbid":"` + laterMbid + `","score":0.9},
		         {"recording_mbid":"` + goneMbid + `","score":0.8}]`
	})
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(ctx); err != nil {
		t.Fatalf("tick 1: %v", err)
	}
	if got := countTrackSim(t, f, seed.ID); got != 0 {
		t.Fatalf("edges before the recording is in the library = %d, want 0", got)
	}
	var cached int
	_ = f.pool.QueryRow(ctx, `SELECT count(*) FROM listenbrainz_similar_recordings WHERE seed_track_id = $1`,
		seed.ID).Scan(&cached)
	if cached != 2 {
		t.Fatalf("cached answer rows = %d, want 2 (both out of library)", cached)
	}

	// The recording arrives twice (an mp3 beside its flac); the other one
	// arrives only as a missing row.
	_ = seedTrack(t, f, "Later mp3", &laterMbid)
	_ = seedTrack(t, f, "Later flac", &laterMbid)
	gone := seedTrack(t, f, "Gone", &goneMbid)
	if _, err := f.pool.Exec(ctx, `UPDATE tracks SET missing_since = now() WHERE id = $1`, gone.ID); err != nil {
		t.Fatal(err)
	}
	if err := w.tickOnce(ctx); err != nil {
		t.Fatalf("tick 2: %v", err)
	}
	if got := countTrackSim(t, f, seed.ID); got != 1 {
		t.Errorf("edges after the recording arrived = %d, want 1 (one per recording, none to a missing copy)", got)
	}
	if n := len(asked()); n != 1 {
		t.Errorf("LB asked %d times, want 1: the resolve needs no new fetch", n)
	}
}

// A 4xx answer is permanent for that MBID; it is recorded like an empty one
// so the seed waits its turn instead of being re-asked every hour.
func TestTickOnce_PermanentErrorCountsAsFetched(t *testing.T) {
	f := newFixture(t)
	mbid := "11111111-1111-1111-1111-111111111111"
	trackA := seedTrack(t, f, "A", &mbid)
	markPlayed(t, f, trackA.ID)
	srv := stubLB(``, ``, http.StatusBadRequest)
	defer srv.Close()
	w := newTestWorker(f, srv.URL)
	if err := w.tickOnce(context.Background()); err != nil {
		t.Fatalf("tickOnce: %v", err)
	}
	var tracks, artists int
	_ = f.pool.QueryRow(context.Background(), `SELECT count(*) FROM track_similarity_fetches`).Scan(&tracks)
	_ = f.pool.QueryRow(context.Background(), `SELECT count(*) FROM artist_similarity_fetches`).Scan(&artists)
	if tracks != 1 || artists != 1 {
		t.Errorf("fetches recorded: tracks=%d artists=%d, want 1 and 1", tracks, artists)
	}
}