web-player: split player, navigation and accent state into focused modules

web-player/src/lib/utils/collections.ts

@@ -0,0 +1,24 @@
+export function shuffle<T>(items: T[]): T[] {
+	const copy = [...items];
+	for (let i = copy.length - 1; i > 0; i--) {
+		const j = Math.floor(Math.random() * (i + 1));
+		[copy[i], copy[j]] = [copy[j], copy[i]];
+	}
+	return copy;
+}
+
+export function appendUnique<T>(
+	current: T[],
+	incoming: T[],
+	keyOf: (item: T) => string | number
+): T[] {
+	const seen = new Set(current.map(keyOf));
+	const added: T[] = [];
+	for (const item of incoming) {
+		const key = keyOf(item);
+		if (seen.has(key)) continue;
+		seen.add(key);
+		added.push(item);
+	}
+	return added.length > 0 ? [...current, ...added] : current;
+}