refactored full rescan to use hook/lifecycle pattern and added rescan package

backend/app.go

@@ -148,13 +148,13 @@ func (yj *YellowJacketApp) OnStartup(ctx context.Context) {
 	yj.queue.SetPlayer(yj.player)
 	yj.queue.RestoreState()
 
-	// Give the library a reference to the queue so FullRescan can
-	// clear the queue and stop playback before wiping data.
-	yj.library.SetQueue(yj.queue)
-
-	// Give the library a reference to the playlist service so
-	// FullRescan can restore playlists from M3U8 files.
-	yj.library.SetPlaylistRestorer(yj.playlist)
+	// Wire cross-cutting rescan hooks so the library can
+	// orchestrate queue clearing and playlist restoration
+	// without depending on those packages directly.
+	yj.library.SetRescanHooks(library.RescanHooks{
+		PreClear: yj.queue.Clear,
+		PostScan: yj.playlist.RestoreAllPlaylists,
+	})
 
 	// Register playback finished handler to drive queue auto-advance.
 	yj.player.SetPlaybackFinishedHandler(yj.queue.OnPlaybackFinished)

backend/library/library.go

@@ -60,39 +60,33 @@ func newEntityCache() *entityCache {
 	}
 }
 
-// queueClearer is a narrow interface for clearing the playback queue.
-type queueClearer interface {
-	Clear()
-}
-
-// playlistRestorer is a narrow interface for restoring playlists
-// from M3U8 files after a library rescan.
-type playlistRestorer interface {
-	RestoreAllPlaylists()
+// RescanHooks holds optional callbacks that run before and after
+// the library-clear-and-scan phase of a full rescan.  The app
+// layer sets these to coordinate cross-cutting concerns (e.g.
+// clearing the queue, restoring playlists) without the library
+// needing to know about those packages.
+type RescanHooks struct {
+	// PreClear runs before library data is wiped
+	// (e.g. clear queue and stop playback).
+	PreClear func()
+	// PostScan runs after the scan completes
+	// (e.g. restore playlists from M3U8 files).
+	PostScan func()
 }
 
 // Library manages scanning and querying the music collection.
 type Library struct {
-	ctx              context.Context
-	logger           *slog.Logger
-	conf             *Config
-	db               *database.DB
-	queue            queueClearer
-	playlistRestorer playlistRestorer
+	ctx         context.Context
+	logger      *slog.Logger
+	conf        *Config
+	db          *database.DB
+	rescanHooks RescanHooks
 }
 
-// SetQueue provides the library with a reference to the queue so
-// that destructive operations like FullRescan can clear the queue
-// and stop playback before wiping data.
-func (l *Library) SetQueue(q queueClearer) {
-	l.queue = q
-}
-
-// SetPlaylistRestorer provides the library with a reference to
-// the playlist service so that FullRescan can restore playlists
-// from M3U8 files after wiping data.
-func (l *Library) SetPlaylistRestorer(p playlistRestorer) {
-	l.playlistRestorer = p
+// SetRescanHooks provides optional hooks for cross-cutting
+// orchestration during FullRescan.
+func (l *Library) SetRescanHooks(h RescanHooks) {
+	l.rescanHooks = h
 }
 
 // NewLibrary creates a new library with the given configuration.

backend/library/rescan.go

@@ -6,9 +6,6 @@ import (
 	"path/filepath"
 	"time"
 
-	"github.com/wailsapp/wails/v2/pkg/runtime"
-
-	"yellowjacket/backend/events"
 	"yellowjacket/backend/system"
 )
 
@@ -19,14 +16,13 @@ import (
 func (l *Library) FullRescan() (*ScanMetrics, error) {
 	l.logger.Info("beginning full library rescan")
 
-	runtime.EventsEmit(l.ctx, events.LibraryScanStarted)
-
-	// Stop playback and clear the queue before wiping data so
-	// the player is not referencing now-deleted tracks.
+	// Run the pre-clear hook (e.g. clear queue / stop playback)
+	// before wiping data so the player is not referencing
+	// now-deleted tracks.
 	clearQueueStart := time.Now()
 
-	if l.queue != nil {
-		l.queue.Clear()
+	if l.rescanHooks.PreClear != nil {
+		l.rescanHooks.PreClear()
 	}
 
 	clearQueueDur := time.Since(clearQueueStart)
@@ -68,10 +64,10 @@ func (l *Library) FullRescan() (*ScanMetrics, error) {
 			clearDBDur + clearFilesDur
 	}
 
-	// Restore playlists from M3U8 files now that the library
-	// has been rescanned and audio_files are populated again.
-	if l.playlistRestorer != nil {
-		l.playlistRestorer.RestoreAllPlaylists()
+	// Run the post-scan hook (e.g. restore playlists from M3U8
+	// files) now that audio_files are populated again.
+	if l.rescanHooks.PostScan != nil {
+		l.rescanHooks.PostScan()
 	}
 
 	return metrics, err