modify id to index map imperatively

src/lib/player/store.svelte.ts

@@ -29,14 +29,17 @@ class PlayerStore {
 	// Debounce timer for save()
 	private _saveTimer: ReturnType<typeof setTimeout> | null = null;
 
-	// O(1) index: track.id → index in queue
-	private idToIndex = $derived.by(() => {
+	// O(1) index: track.id → index in queue (maintained imperatively)
+	private idToIndex = $state(new Map<number, number>());
+
+	/** Rebuild the full index from the queue array. */
+	private rebuildIndex() {
 		const map = new Map<number, number>();
 		for (let i = 0; i < this.queue.length; i++) {
 			map.set(this.queue[i].id, i);
 		}
-		return map;
-	});
+		this.idToIndex = map;
+	}
 
 	// Derived
 	currentTrack = $derived.by(() => {
@@ -52,9 +55,7 @@ class PlayerStore {
 
 	displayQueue = $derived(
 		this.isShuffled
-			? this.shuffledIndices
-					.map((i) => this.queue[i])
-					.filter((t) => t !== undefined)
+			? this.shuffledIndices.map((i) => this.queue[i])
 			: this.queue,
 	);
 
@@ -80,6 +81,7 @@ class PlayerStore {
 		if (state.volume !== undefined) this.volume = state.volume;
 		if (state.isMuted !== undefined) this.isMuted = state.isMuted;
 		if (state.minimized !== undefined) this.uiOpen = !state.minimized;
+		this.rebuildIndex();
 	}
 
 	load() {
@@ -95,6 +97,7 @@ class PlayerStore {
 				this.repeatMode = data.repeatMode || "off";
 				this.volume = data.volume ?? 1;
 				this.isMuted = data.isMuted || false;
+				this.rebuildIndex();
 			}
 		} catch (e) {
 			console.error("Failed to load player state", e);
@@ -139,6 +142,7 @@ class PlayerStore {
 		} else {
 			// Add to end
 			this.queue.push(track);
+			this.idToIndex.set(track.id, this.queue.length - 1);
 
 			if (this.isShuffled) {
 				this.shuffledIndices.push(this.queue.length - 1);
@@ -166,6 +170,8 @@ class PlayerStore {
 		const insertIdx = currentIdx === -1 ? 0 : currentIdx + 1;
 
 		this.queue.splice(insertIdx, 0, targetTrack);
+		// Rebuild index — splice shifts everything after insertIdx
+		this.rebuildIndex();
 
 		if (this.isShuffled) {
 			// Shift indices that are >= insertIdx because we inserted a new item
@@ -199,6 +205,10 @@ class PlayerStore {
 
 		const startIdx = this.queue.length;
 		this.queue.push(...newTracks);
+		// Only index the newly added tracks
+		for (let i = 0; i < newTracks.length; i++) {
+			this.idToIndex.set(newTracks[i].id, startIdx + i);
+		}
 
 		if (this.isShuffled) {
 			const newIndices = newTracks.map((_, i) => startIdx + i);
@@ -224,6 +234,8 @@ class PlayerStore {
 		const wasCurrent = this.currentId === id;
 
 		this.queue.splice(idx, 1);
+		// Rebuild index — splice shifts everything after idx
+		this.rebuildIndex();
 
 		if (wasCurrent) {
 			this.currentId = null; // Or auto-advance?
@@ -240,6 +252,7 @@ class PlayerStore {
 
 	clearQueue() {
 		this.queue = [];
+		this.idToIndex = new Map();
 		this.currentId = null;
 		this.shuffledIndices = [];
 		this.history = [];
@@ -271,6 +284,7 @@ class PlayerStore {
 			const [item] = q.splice(fromIdx, 1);
 			q.splice(toIdx, 0, item);
 			this.queue = q;
+			this.rebuildIndex();
 		}
 	}