minstrel/internal/playlists/genre_mixes_db_test.go

package playlists_test

import (
	"context"
	"fmt"
	"strings"
	"testing"
	"time"

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

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/playlists"
)

// seedGenre creates artists × perArtist tracks tagged genre, each artist on
// its own album, and returns the tracks. seedTrack mints a new artist on
// every call (an artist without an mbid has no conflict key), so each
// artist's first track creates it and the rest join that track's album.
func seedGenre(t *testing.T, pool *pgxpool.Pool, genre string, artists, perArtist int) []dbq.Track {
	t.Helper()
	var out []dbq.Track
	for a := 0; a < artists; a++ {
		first := seedTrack(t, pool, fmt.Sprintf("%s %d-0", genre, a), fmt.Sprintf("%s Artist %d", genre, a))
		setGenre(t, pool, first.ID, genre)
		out = append(out, first)
		for k := 1; k < perArtist; k++ {
			tr := seedTrackForArtist(t, pool, fmt.Sprintf("%s %d-%d", genre, a, k), first.AlbumID, first.ArtistID)
			setGenre(t, pool, tr.ID, genre)
			out = append(out, tr)
		}
	}
	return out
}

// TestListGenreMixCandidates_TiersAndSizeFloor: a taste-profile genre is
// tier 1 (matched case-insensitively), a genre the user has only played is
// tier 2, an untouched one is tier 3, and a genre too small for a mix is not
// offered at all.
func TestListGenreMixCandidates_TiersAndSizeFloor(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "gmixcand")
	now := time.Now().UTC()

	seedGenre(t, pool, "Shoegaze", 6, 5)
	kraut := seedGenre(t, pool, "Krautrock", 6, 5)
	seedGenre(t, pool, "Dub", 6, 5)
	seedGenre(t, pool, "Zydeco", 2, 5) // 10 tracks, 2 artists: below the floor

	seedTasteTag(t, pool, u.ID, "shoegaze", 4)
	seedPlayEvent(t, pool, u.ID, kraut[0].ID, now.Add(-time.Hour), false)

	rows, err := dbq.New(pool).ListGenreMixCandidates(ctx, u.ID)
	if err != nil {
		t.Fatalf("list candidates: %v", err)
	}
	want := map[string]int32{"Shoegaze": 1, "Krautrock": 2, "Dub": 3}
	tier := map[string]int32{}
	order := []string{}
	for _, r := range rows {
		tier[r.Label] = r.Tier
		if _, mine := want[r.Label]; mine {
			order = append(order, r.Label)
		}
		if r.Label == "Shoegaze" && len(r.TrackIds) != 30 {
			t.Errorf("Shoegaze track_ids = %d, want 30", len(r.TrackIds))
		}
	}
	for label, w := range want {
		if got, ok := tier[label]; !ok || got != w {
			t.Errorf("%s tier = %d (present %v), want %d", label, got, ok, w)
		}
	}
	if _, ok := tier["Zydeco"]; ok {
		t.Error("Zydeco (10 tracks, 2 artists) offered as a genre mix")
	}
	if strings.Join(order, ",") != "Shoegaze,Krautrock,Dub" {
		t.Errorf("order = %v, want tier order Shoegaze, Krautrock, Dub", order)
	}
}

// TestListGenreMixTracks_LeavesOutSongsOfGenresAlreadyPicked: a track that
// also carries an excluded genre (matched case-insensitively) belongs to that
// genre's mix and is left out of this one.
func TestListGenreMixTracks_LeavesOutSongsOfGenresAlreadyPicked(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "gmixexcl")

	punk := seedGenre(t, pool, "Ska Punk", 4, 5)
	shared := punk[:5]
	for _, tr := range shared {
		setGenre(t, pool, tr.ID, "Ska Punk; Pop Punk")
	}

	rows, err := dbq.New(pool).ListGenreMixTracks(ctx, dbq.ListGenreMixTracksParams{
		UserID: u.ID, DateSeed: "2026-11-07", GenreKey: "ska punk", ExcludeGenres: []string{"pop punk"},
	})
	if err != nil {
		t.Fatalf("list tracks: %v", err)
	}
	if len(rows) != len(punk)-len(shared) {
		t.Fatalf("rows = %d, want %d (the Ska Punk tracks not also Pop Punk)", len(rows), len(punk)-len(shared))
	}
	got := map[pgtype.UUID]bool{}
	for _, r := range rows {
		got[r.ID] = true
	}
	for _, tr := range shared {
		if got[tr.ID] {
			t.Fatal("a track also tagged Pop Punk was offered after Pop Punk was excluded")
		}
	}
}

// TestListGenreMixTracks_SplitsFamiliarAndDropsRejectedTracks: played and
// liked tracks come back familiar, the rest unheard; a track skipped more
// often than played through is left out, while a favourite with stray skips
// stays; tracks of other genres never appear.
func TestListGenreMixTracks_SplitsFamiliarAndDropsRejectedTracks(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "gmixtracks")
	now := time.Now().UTC()

	shoegaze := seedGenre(t, pool, "Shoegaze", 6, 5)
	other := seedGenre(t, pool, "Dub", 3, 2)
	played, liked, rejected, favourite := shoegaze[0], shoegaze[1], shoegaze[2], shoegaze[3]

	seedPlayEvent(t, pool, u.ID, played.ID, now.Add(-time.Hour), false)
	if _, err := pool.Exec(ctx, `INSERT INTO general_likes (user_id, track_id) VALUES ($1, $2)`, u.ID, liked.ID); err != nil {
		t.Fatalf("like: %v", err)
	}
	for i := 0; i < 2; i++ {
		seedPlayEvent(t, pool, u.ID, rejected.ID, now.Add(-time.Duration(i+2)*time.Hour), true)
	}
	for i := 0; i < 5; i++ {
		seedPlayEvent(t, pool, u.ID, favourite.ID, now.Add(-time.Duration(i+10)*time.Hour), false)
	}
	for i := 0; i < 2; i++ {
		seedPlayEvent(t, pool, u.ID, favourite.ID, now.Add(-time.Duration(i+20)*time.Hour), true)
	}

	rows, err := dbq.New(pool).ListGenreMixTracks(ctx, dbq.ListGenreMixTracksParams{
		UserID: u.ID, DateSeed: "2026-11-05", GenreKey: "shoegaze",
	})
	if err != nil {
		t.Fatalf("list tracks: %v", err)
	}
	familiar := map[pgtype.UUID]bool{}
	for _, r := range rows {
		familiar[r.ID] = r.Familiar
	}
	if len(rows) != len(shoegaze)-1 {
		t.Errorf("rows = %d, want %d (every Shoegaze track but the rejected one)", len(rows), len(shoegaze)-1)
	}
	for _, tr := range other {
		if _, in := familiar[tr.ID]; in {
			t.Fatalf("a Dub track appeared in the Shoegaze pool")
		}
	}
	if _, in := familiar[rejected.ID]; in {
		t.Error("a track skipped twice and never played through was offered")
	}
	for name, tr := range map[string]dbq.Track{"played": played, "liked": liked, "favourite": favourite} {
		if f, in := familiar[tr.ID]; !in || !f {
			t.Errorf("%s track: present %v familiar %v, want present and familiar", name, in, f)
		}
	}
	if f := familiar[shoegaze[4].ID]; f {
		t.Error("an untouched track came back familiar")
	}
}

// TestBuildSystemPlaylists_GenreMixes: a full build gives the user a mix for
// the genre they listen to, holding only that genre's tracks, with both
// halves of the blend stamped.
func TestBuildSystemPlaylists_GenreMixes(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "gmixbuild")
	now := time.Now().UTC()

	shoegaze := seedGenre(t, pool, "Shoegaze", 8, 5)
	seedGenre(t, pool, "Dub", 6, 5)
	seedTasteTag(t, pool, u.ID, "Shoegaze", 5)
	for i, tr := range shoegaze[:12] {
		seedPlayEvent(t, pool, u.ID, tr.ID, now.Add(-time.Duration(i+1)*time.Hour), false)
	}

	if err := playlists.BuildSystemPlaylists(ctx, pool, discardLogger(), u.ID, now, t.TempDir()); err != nil {
		t.Fatalf("build: %v", err)
	}

	var plID pgtype.UUID
	if err := pool.QueryRow(ctx, `
		SELECT id FROM playlists
		 WHERE user_id = $1 AND system_variant = 'genre_mix' AND name = 'Shoegaze mix'`,
		u.ID).Scan(&plID); err != nil {
		t.Fatalf("no Shoegaze mix built: %v", err)
	}

	inGenre := map[pgtype.UUID]bool{}
	for _, tr := range shoegaze {
		inGenre[tr.ID] = true
	}
	rows, err := pool.Query(ctx, `SELECT track_id, pick_kind FROM playlist_tracks WHERE playlist_id = $1`, plID)
	if err != nil {
		t.Fatalf("list mix tracks: %v", err)
	}
	defer rows.Close()
	kinds := map[string]int{}
	n := 0
	for rows.Next() {
		var id pgtype.UUID
		var kind *string
		if err := rows.Scan(&id, &kind); err != nil {
			t.Fatalf("scan: %v", err)
		}
		n++
		if !inGenre[id] {
			t.Errorf("track %s in the Shoegaze mix is not a Shoegaze track", uuidString(id))
		}
		if kind != nil {
			kinds[*kind]++
		}
	}
	if n < 15 {
		t.Fatalf("Shoegaze mix holds %d tracks, want at least 15", n)
	}
	if kinds["taste"] == 0 || kinds["taste_unheard"] == 0 {
		t.Errorf("pick kinds = %v, want both taste and taste_unheard", kinds)
	}
}

// genreDrawPositions runs ListGenreMixTracks for ten different days and
// returns, per track, the sum of its positions within its own half
// (familiar or unheard). The draw is random per day, so a lean shows up as
// an earlier average position across days, not in any single one.
func genreDrawPositions(t *testing.T, pool *pgxpool.Pool, userID pgtype.UUID, genreKey string) map[pgtype.UUID]int {
	t.Helper()
	sum := map[pgtype.UUID]int{}
	for day := 1; day <= 10; day++ {
		rows, err := dbq.New(pool).ListGenreMixTracks(context.Background(), dbq.ListGenreMixTracksParams{
			UserID: userID, DateSeed: fmt.Sprintf("2026-11-%02d", day), GenreKey: genreKey,
		})
		if err != nil {
			t.Fatalf("list tracks: %v", err)
		}
		pos := map[bool]int{}
		for _, r := range rows {
			sum[r.ID] += pos[r.Familiar]
			pos[r.Familiar]++
		}
	}
	return sum
}

func meanPosition(sum map[pgtype.UUID]int, tracks []dbq.Track) float64 {
	total := 0
	for _, tr := range tracks {
		total += sum[tr.ID]
	}
	return float64(total) / float64(len(tracks))
}

// TestListGenreMixTracks_FamiliarLeansTowardFavourites: among the tracks the
// user knows, ones played often and liked come up earlier than ones played
// once.
func TestListGenreMixTracks_FamiliarLeansTowardFavourites(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "gmixfav")
	now := time.Now().UTC()

	tracks := seedGenre(t, pool, "Krautrock", 4, 5)
	favourites, onceOnly := tracks[:10], tracks[10:]
	for i, tr := range favourites {
		for k := 0; k < 5; k++ {
			seedPlayEvent(t, pool, u.ID, tr.ID, now.Add(-time.Duration(i*10+k+1)*time.Hour), false)
		}
		if _, err := pool.Exec(ctx, `INSERT INTO general_likes (user_id, track_id) VALUES ($1, $2)`, u.ID, tr.ID); err != nil {
			t.Fatalf("like: %v", err)
		}
	}
	for i, tr := range onceOnly {
		seedPlayEvent(t, pool, u.ID, tr.ID, now.Add(-time.Duration(200+i)*time.Hour), false)
	}

	sum := genreDrawPositions(t, pool, u.ID, "krautrock")
	fav, once := meanPosition(sum, favourites), meanPosition(sum, onceOnly)
	if fav >= once {
		t.Errorf("favourites' summed position %.1f, played-once %.1f: want favourites earlier", fav, once)
	}
}

// TestListGenreMixTracks_UnheardLeansTowardTheUsersArtists: among unheard
// tracks, an artist the user plays and likes comes up earlier than one they
// have never met, and so does an artist similar to theirs. The stranger
// still appears: the lean tilts the draw, it does not exclude.
func TestListGenreMixTracks_UnheardLeansTowardTheUsersArtists(t *testing.T) {
	pool := newPool(t)
	ctx := context.Background()
	u := seedUser(t, pool, "gmixartist")
	now := time.Now().UTC()

	tracks := seedGenre(t, pool, "Shoegaze", 3, 12)
	loved, similar, stranger := tracks[:12], tracks[12:24], tracks[24:]
	for k := 0; k < 15; k++ {
		seedPlayEvent(t, pool, u.ID, loved[0].ID, now.Add(-time.Duration(k+1)*time.Hour), false)
	}
	for _, tr := range loved[1:3] {
		if _, err := pool.Exec(ctx, `INSERT INTO general_likes (user_id, track_id) VALUES ($1, $2)`, u.ID, tr.ID); err != nil {
			t.Fatalf("like: %v", err)
		}
	}
	if _, err := pool.Exec(ctx, `
		INSERT INTO artist_similarity (artist_a_id, artist_b_id, score, source)
		VALUES ($1, $2, 0.9, 'listenbrainz')`, loved[0].ArtistID, similar[0].ArtistID); err != nil {
		t.Fatalf("seed similarity: %v", err)
	}

	sum := genreDrawPositions(t, pool, u.ID, "shoegaze")
	l, s, x := meanPosition(sum, loved[3:]), meanPosition(sum, similar), meanPosition(sum, stranger)
	if l >= x {
		t.Errorf("loved artist's unheard tracks at %.1f, stranger's at %.1f: want the loved artist earlier", l, x)
	}
	if s >= x {
		t.Errorf("similar artist's tracks at %.1f, stranger's at %.1f: want the similar artist earlier", s, x)
	}
	for _, tr := range stranger {
		if _, in := sum[tr.ID]; !in {
			t.Fatalf("a stranger's track was left out of the pool; the lean must not exclude")
		}
	}
}