feat: complete filter centralization pattern and document in CLAUDE.md

internal/database/artist_settings.go

@@ -70,7 +70,7 @@ func SaveArtistSettings(db *DB, settings *ArtistSettings) error {
 			monitored = excluded.monitored,
 			last_synced = COALESCE(excluded.last_synced, artist_settings.last_synced)
 	`,
-		settings.ID, settings.Name, nullIfEmpty(settings.MBID), settings.IgnoreSingles, settings.IgnoreCompilations, settings.Monitored, settings.ID,
+		settings.ID, settings.Name, nullIfEmpty(settings.MBID), settings.IgnoreSingles, settings.IgnoreCompilations, settings.Monitored, nullIfEmptyTime(settings.LastSynced),
 	)
 	if err != nil {
 		return fmt.Errorf("save artist settings: %w", err)

internal/database/artist_settings_test.go

@@ -3,6 +3,7 @@ package database
 import (
 	"database/sql"
 	"testing"
+	"time"
 )
 
 // TestGetArtistSettings_Found verifies retrieving an existing artist.
@@ -460,3 +461,134 @@ func TestArtistSettings_MbidInGetAll(t *testing.T) {
 		t.Errorf("artist a2: expected empty MBID, got %q", byID["a2"].MBID)
 	}
 }
+
+// TestSaveArtistSettings_LastSyncedPreserved verifies that last_synced is preserved
+// on update when not explicitly provided in the update.
+func TestSaveArtistSettings_LastSyncedPreserved(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	// Set a fixed time for testing
+	fixedTime := time.Date(2023, 1, 1, 12, 0, 0, 0, time.UTC)
+
+	// Insert initial row with a specific last_synced time
+	s1 := &ArtistSettings{
+		ID:                 "artist-1",
+		Name:               "Original Name",
+		IgnoreSingles:      false,
+		IgnoreCompilations: false,
+		Monitored:          true,
+		LastSynced:         fixedTime,
+	}
+	if err := SaveArtistSettings(db, s1); err != nil {
+		t.Fatalf("first SaveArtistSettings() error: %v", err)
+	}
+
+	// Verify it was inserted with correct last_synced
+	got, err := GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.LastSynced != fixedTime {
+		t.Fatalf("expected last_synced %v, got %v", fixedTime, got.LastSynced)
+	}
+
+	// Update the row with new values but without specifying last_synced
+	// This should preserve the original last_synced value
+	s2 := &ArtistSettings{
+		ID:                 "artist-1",
+		Name:               "Updated Name",
+		IgnoreSingles:      true,
+		IgnoreCompilations: true,
+		Monitored:          false,
+		// Note: LastSynced is intentionally left as zero value
+	}
+	if err := SaveArtistSettings(db, s2); err != nil {
+		t.Fatalf("second SaveArtistSettings() error: %v", err)
+	}
+
+	got, err = GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.Name != "Updated Name" {
+		t.Errorf("expected Name 'Updated Name', got %q", got.Name)
+	}
+	if !got.IgnoreSingles {
+		t.Error("expected IgnoreSingles true")
+	}
+	if !got.IgnoreCompilations {
+		t.Error("expected IgnoreCompilations true")
+	}
+	if got.Monitored {
+		t.Error("expected Monitored false")
+	}
+	// Most importantly: last_synced should be preserved
+	if got.LastSynced != fixedTime {
+		t.Errorf("expected last_synced to be preserved as %v, got %v", fixedTime, got.LastSynced)
+	}
+}
+
+// TestSaveArtistSettings_LastSyncedUpdated verifies that last_synced can be updated
+// when explicitly provided.
+func TestSaveArtistSettings_LastSyncedUpdated(t *testing.T) {
+	db, err := New(":memory:")
+	if err != nil {
+		t.Fatalf("New() error: %v", err)
+	}
+	defer db.Close()
+
+	// Set fixed times for testing
+	oldTime := time.Date(2023, 1, 1, 12, 0, 0, 0, time.UTC)
+	newTime := time.Date(2023, 12, 31, 23, 59, 59, 0, time.UTC)
+
+	// Insert initial row
+	s1 := &ArtistSettings{
+		ID:                 "artist-1",
+		Name:               "Original Name",
+		IgnoreSingles:      false,
+		IgnoreCompilations: false,
+		Monitored:          true,
+		LastSynced:         oldTime,
+	}
+	if err := SaveArtistSettings(db, s1); err != nil {
+		t.Fatalf("first SaveArtistSettings() error: %v", err)
+	}
+
+	// Update the row with a new last_synced time
+	s2 := &ArtistSettings{
+		ID:                 "artist-1",
+		Name:               "Updated Name",
+		IgnoreSingles:      true,
+		IgnoreCompilations: true,
+		Monitored:          false,
+		LastSynced:         newTime,
+	}
+	if err := SaveArtistSettings(db, s2); err != nil {
+		t.Fatalf("second SaveArtistSettings() error: %v", err)
+	}
+
+	got, err := GetArtistSettings(db, "artist-1")
+	if err != nil {
+		t.Fatalf("GetArtistSettings() error: %v", err)
+	}
+	if got.Name != "Updated Name" {
+		t.Errorf("expected Name 'Updated Name', got %q", got.Name)
+	}
+	if !got.IgnoreSingles {
+		t.Error("expected IgnoreSingles true")
+	}
+	if !got.IgnoreCompilations {
+		t.Error("expected IgnoreCompilations true")
+	}
+	if got.Monitored {
+		t.Error("expected Monitored false")
+	}
+	// last_synced should be updated to the new value
+	if got.LastSynced != newTime {
+		t.Errorf("expected last_synced to be updated to %v, got %v", newTime, got.LastSynced)
+	}
+}