added db query optimizations to playlists view, added caching

frontend/src/store/controllers/playlist-controller.ts

@@ -0,0 +1,75 @@
+import type { ReactiveController, ReactiveControllerHost } from 'lit';
+import type { playlist } from '@go/models';
+import { playlistStore } from '../playlist-store';
+
+/**
+ * PlaylistController connects a Lit component to the PlaylistStore.
+ *
+ * Usage in a component:
+ *
+ *   private playlistCtrl = new PlaylistController(this);
+ *
+ *   async connectedCallback() {
+ *     super.connectedCallback();
+ *     const playlists = await this.playlistCtrl.getPlaylists();
+ *   }
+ */
+export class PlaylistController implements ReactiveController {
+    private host: ReactiveControllerHost;
+    private unsubscribe?: () => void;
+
+    constructor(host: ReactiveControllerHost) {
+        this.host = host;
+        host.addController(this);
+    }
+
+    // ===================================================================
+    // LIFECYCLE HOOKS
+    // ===================================================================
+
+    hostConnected(): void {
+        this.unsubscribe = playlistStore.subscribe(() => {
+            this.host.requestUpdate();
+        });
+    }
+
+    hostDisconnected(): void {
+        this.unsubscribe?.();
+    }
+
+    // ===================================================================
+    // DATA ACCESS
+    // ===================================================================
+
+    async getPlaylists(): Promise<playlist.WithTracks[]> {
+        return playlistStore.getPlaylists();
+    }
+
+    get cachedPlaylists(): playlist.WithTracks[] | null {
+        return playlistStore.getCachedPlaylists();
+    }
+
+    get isLoading(): boolean {
+        return playlistStore.isLoading();
+    }
+
+    // ===================================================================
+    // SCROLL POSITION
+    // ===================================================================
+
+    getScrollPosition(): number {
+        return playlistStore.getScrollPosition();
+    }
+
+    setScrollPosition(offset: number): void {
+        playlistStore.setScrollPosition(offset);
+    }
+
+    // ===================================================================
+    // INVALIDATION
+    // ===================================================================
+
+    invalidate(): void {
+        playlistStore.invalidate();
+    }
+}