feat: add mbid column to artist_settings

Additive migration 008 adds an mbid column to artist_settings, extend the
ArtistSettings struct and persistence functions (SaveArtistSettings,
GetArtistSettings, GetAllArtistSettings, UpdateArtistSettings) to carry the
MusicBrainz ID, and add round-trip tests covering empty and set MBID values.

internal/database/artist_settings_test.go

@@ -305,3 +305,158 @@ func TestUpdateArtistSettings_EmptyUpdates(t *testing.T) {
 		t.Error("expected error for empty updates, got nil")
 	}
 }
+
+// TestMigration008_MbidColumnExists verifies the 008 migration adds the mbid
+// column and that rows created before resolution have a NULL/empty MBID.
+func TestMigration008_MbidColumnExists(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	// Insert a row without supplying mbid (simulates a pre-resolution row).
+	if _, err := db.Conn().Exec(
+		"INSERT INTO artist_settings (id, name) VALUES (?, ?)",
+		"artist-1", "No MBID Yet",
+	); err != nil {
+		t.Fatalf("insert without mbid: %v", err)
+	}
+
+	var mbid sql.NullString
+	if err := db.Conn().QueryRow(
+		"SELECT mbid FROM artist_settings WHERE id = ?", "artist-1",
+	).Scan(&mbid); err != nil {
+		t.Fatalf("query mbid: %v", err)
+	}
+	if mbid.Valid && mbid.String != "" {
+		t.Errorf("expected empty mbid for pre-resolution row, got %q", mbid.String)
+	}
+}
+
+// TestArtistSettings_MbidRoundTrip verifies Save/Get round-trips an MBID,
+// and that an empty MBID is preserved (not overwritten with garbage).
+func TestArtistSettings_MbidRoundTrip(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	s := &ArtistSettings{
+		ID:    "artist-1",
+		Name:  "Test Artist",
+		MBID:  "f27e6623-8771-4a2e-8dcb-6c8b1a4f8b9a",
+		Monitored: true,
+	}
+	if err := SaveArtistSettings(db, s); err != nil {
+		t.Fatalf("SaveArtistSettings() error: %v", err)
+	}
+
+	got, err := GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.MBID != s.MBID {
+		t.Errorf("expected MBID %q, got %q", s.MBID, got.MBID)
+	}
+}
+
+// TestArtistSettings_MbidEmptyAllowed verifies an artist can be saved and
+// retrieved with no MBID set (lazy resolution not yet performed).
+func TestArtistSettings_MbidEmptyAllowed(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	s := &ArtistSettings{ID: "artist-1", Name: "No MBID", Monitored: true}
+	if err := SaveArtistSettings(db, s); err != nil {
+		t.Fatalf("SaveArtistSettings() error: %v", err)
+	}
+
+	got, err := GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.MBID != "" {
+		t.Errorf("expected empty MBID, got %q", got.MBID)
+	}
+}
+
+// TestArtistSettings_MbidUpdatePersists verifies UpdateArtistSettings can set
+// and clear the MBID column.
+func TestArtistSettings_MbidUpdatePersists(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	if err := SaveArtistSettings(db, &ArtistSettings{ID: "artist-1", Name: "Test", Monitored: true}); err != nil {
+		t.Fatalf("SaveArtistSettings() error: %v", err)
+	}
+
+	mbid := "f27e6623-8771-4a2e-8dcb-6c8b1a4f8b9a"
+	if err := UpdateArtistSettings(db, "artist-1", map[string]interface{}{"mbid": mbid}); err != nil {
+		t.Fatalf("UpdateArtistSettings(set mbid) error: %v", err)
+	}
+	got, err := GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.MBID != mbid {
+		t.Errorf("expected MBID %q after set, got %q", mbid, got.MBID)
+	}
+
+	// Clear it again.
+	if err := UpdateArtistSettings(db, "artist-1", map[string]interface{}{"mbid": ""}); err != nil {
+		t.Fatalf("UpdateArtistSettings(clear mbid) error: %v", err)
+	}
+	got, err = GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.MBID != "" {
+		t.Errorf("expected empty MBID after clear, got %q", got.MBID)
+	}
+}
+
+// TestArtistSettings_MbidInGetAll verifies GetAllArtistSettings returns the
+// MBID field for all rows.
+func TestArtistSettings_MbidInGetAll(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	artists := []ArtistSettings{
+		{ID: "a1", Name: "Artist One", MBID: "mbid-1", Monitored: true},
+		{ID: "a2", Name: "Artist Two", Monitored: true},
+	}
+	for _, a := range artists {
+		if err := SaveArtistSettings(db, &a); err != nil {
+			t.Fatalf("SaveArtistSettings(%s) error: %v", a.ID, err)
+		}
+	}
+
+	results, err := GetAllArtistSettings(db)
+	if err != nil {
+		t.Fatalf("GetAllArtistSettings() error: %v", err)
+	}
+	if len(results) != 2 {
+		t.Fatalf("expected 2 results, got %d", len(results))
+	}
+	byID := make(map[string]ArtistSettings)
+	for _, r := range results {
+		byID[r.ID] = r
+	}
+	if byID["a1"].MBID != "mbid-1" {
+		t.Errorf("artist a1: expected MBID 'mbid-1', got %q", byID["a1"].MBID)
+	}
+	if byID["a2"].MBID != "" {
+		t.Errorf("artist a2: expected empty MBID, got %q", byID["a2"].MBID)
+	}
+}