feat(web/m7-364): localStorage persistence layer for queue

web/src/lib/player/persisted.test.ts

@@ -0,0 +1,69 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { readPersistedQueue, writePersistedQueue, clearPersistedQueue } from './persisted';
+import type { TrackRef } from '$lib/api/types';
+
+const sampleTrack: TrackRef = {
+  id: 't1',
+  title: 'Foo',
+  artist_name: 'Bar',
+  album_name: 'Baz',
+  duration_ms: 200000,
+  stream_url: '/stream/t1'
+} as TrackRef;
+
+describe('persisted queue', () => {
+  beforeEach(() => {
+    localStorage.clear();
+  });
+
+  afterEach(() => {
+    localStorage.clear();
+    vi.restoreAllMocks();
+  });
+
+  it('write-then-read round-trips queue / index / position', () => {
+    writePersistedQueue('user-1', { queue: [sampleTrack], index: 0, position: 42.5 });
+    const out = readPersistedQueue('user-1');
+    expect(out).not.toBeNull();
+    expect(out!.v).toBe(1);
+    expect(out!.queue).toEqual([sampleTrack]);
+    expect(out!.index).toBe(0);
+    expect(out!.position).toBe(42.5);
+    expect(typeof out!.savedAt).toBe('number');
+  });
+
+  it('read returns null when no entry is set', () => {
+    expect(readPersistedQueue('user-1')).toBeNull();
+  });
+
+  it('read returns null on malformed JSON', () => {
+    localStorage.setItem('minstrel.queue.user-1', '{not-json');
+    expect(readPersistedQueue('user-1')).toBeNull();
+  });
+
+  it('read returns null when version is not 1', () => {
+    localStorage.setItem(
+      'minstrel.queue.user-1',
+      JSON.stringify({ v: 2, queue: [], index: 0, position: 0, savedAt: 0 })
+    );
+    expect(readPersistedQueue('user-1')).toBeNull();
+  });
+
+  it('clearPersistedQueue removes only the named user key', () => {
+    writePersistedQueue('user-a', { queue: [sampleTrack], index: 0, position: 0 });
+    writePersistedQueue('user-b', { queue: [sampleTrack], index: 0, position: 0 });
+    clearPersistedQueue('user-a');
+    expect(readPersistedQueue('user-a')).toBeNull();
+    expect(readPersistedQueue('user-b')).not.toBeNull();
+  });
+
+  it('write swallows QuotaExceededError without throwing', () => {
+    const setItem = vi.spyOn(Storage.prototype, 'setItem').mockImplementation(() => {
+      throw new Error('QuotaExceededError');
+    });
+    expect(() =>
+      writePersistedQueue('user-1', { queue: [sampleTrack], index: 0, position: 0 })
+    ).not.toThrow();
+    setItem.mockRestore();
+  });
+});