feat(web): events dispatcher posts to /api/events on player transitions

useEventsDispatcher subscribes to player.current/state via \$effect:
on first transition to playing for a new track, POSTs play_started
and caches the id; on track-id change while a play is open, closes
the prior row as play_skipped; on natural completion (state
playing→paused with position >= duration > 0), POSTs play_ended;
on pagehide, navigator.sendBeacon fires a final play_skipped.
Stable per-tab client_id from sessionStorage.
This commit is contained in:
2026-04-26 09:42:11 -04:00
parent 599a19f780
commit b6f8a0c390
5 changed files with 289 additions and 0 deletions
+8
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@@ -56,3 +56,11 @@ export type SearchResponse = {
export type RadioResponse = {
tracks: TrackRef[];
};
export type EventRequest =
| { type: 'play_started'; track_id: string; client_id?: string }
| { type: 'play_ended'; play_event_id: string; duration_played_ms: number }
| { type: 'play_skipped'; play_event_id: string; position_ms: number };
export type PlayStartedResponse = { play_event_id: string; session_id: string };
export type EventOkResponse = { ok: true };
+19
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@@ -0,0 +1,19 @@
import { afterEach, beforeEach, describe, expect, test } from 'vitest';
import { getOrCreateClientId } from './clientId';
beforeEach(() => sessionStorage.clear());
afterEach(() => sessionStorage.clear());
describe('getOrCreateClientId', () => {
test('generates a UUID on first call and persists it in sessionStorage', () => {
const id = getOrCreateClientId();
expect(id).toMatch(/^[0-9a-f-]{36}$/);
expect(sessionStorage.getItem('minstrel.client_id')).toBe(id);
});
test('returns the same id on subsequent calls', () => {
const a = getOrCreateClientId();
const b = getOrCreateClientId();
expect(a).toBe(b);
});
});
+13
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@@ -0,0 +1,13 @@
const KEY = 'minstrel.client_id';
export function getOrCreateClientId(): string {
try {
const existing = sessionStorage.getItem(KEY);
if (existing) return existing;
} catch {
// sessionStorage unavailable (non-browser env). Generate ephemerally.
}
const id = crypto.randomUUID();
try { sessionStorage.setItem(KEY, id); } catch { /* ignore */ }
return id;
}
+142
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@@ -0,0 +1,142 @@
import { afterEach, beforeEach, describe, expect, test, vi } from 'vitest';
import { flushSync } from 'svelte';
vi.mock('$lib/api/client', () => ({
api: {
post: vi.fn().mockResolvedValue({ play_event_id: 'pe-1', session_id: 's-1' })
}
}));
vi.mock('./clientId', () => ({
getOrCreateClientId: () => 'test-client'
}));
import { useEventsDispatcher } from './events.svelte';
import {
playQueue,
reportStateFromAudio,
reportTimeUpdate,
reportDuration,
skipNext,
} from './store.svelte';
import { api } from '$lib/api/client';
import type { TrackRef } from '$lib/api/types';
function track(id: string, dur = 200): TrackRef {
return {
id, title: `T ${id}`,
album_id: 'a', album_title: 'A',
artist_id: 'ar', artist_name: 'Ar',
track_number: Number(id), disc_number: 1,
duration_sec: dur,
stream_url: `/api/tracks/${id}/stream`
};
}
beforeEach(() => {
vi.clearAllMocks();
// Reset the player store to idle.
playQueue([]);
});
afterEach(() => {
// sendBeacon spies are restored automatically per test.
});
describe('useEventsDispatcher', () => {
test('first transition into playing for a new track POSTs play_started', async () => {
const cleanup = $effect.root(() => useEventsDispatcher());
playQueue([track('1')]);
flushSync();
reportStateFromAudio('playing');
flushSync();
// Microtask drain so the api.post promise settles.
await Promise.resolve();
await Promise.resolve();
const calls = (api.post as ReturnType<typeof vi.fn>).mock.calls;
const startedCalls = calls.filter((c) => (c[1] as { type: string }).type === 'play_started');
expect(startedCalls.length).toBe(1);
expect(startedCalls[0][0]).toBe('/api/events');
expect(startedCalls[0][1]).toMatchObject({
type: 'play_started',
track_id: '1',
client_id: 'test-client'
});
cleanup();
});
test('track end (duration reached, paused) POSTs play_ended', async () => {
const cleanup = $effect.root(() => useEventsDispatcher());
playQueue([track('1', 200)]);
flushSync();
reportDuration(200);
reportStateFromAudio('playing');
flushSync();
await Promise.resolve();
await Promise.resolve();
// Reach end of track, then natural pause.
reportTimeUpdate(200);
flushSync();
reportStateFromAudio('ended');
flushSync();
await Promise.resolve();
const calls = (api.post as ReturnType<typeof vi.fn>).mock.calls;
const types = calls.map((c) => (c[1] as { type: string }).type);
expect(types).toContain('play_started');
expect(types).toContain('play_ended');
cleanup();
});
test('user-initiated skip mid-track POSTs play_skipped', async () => {
const cleanup = $effect.root(() => useEventsDispatcher());
playQueue([track('1'), track('2')]);
flushSync();
reportStateFromAudio('playing');
flushSync();
await Promise.resolve();
await Promise.resolve();
skipNext();
flushSync();
await Promise.resolve();
const calls = (api.post as ReturnType<typeof vi.fn>).mock.calls;
const types = calls.map((c) => (c[1] as { type: string }).type);
expect(types).toContain('play_skipped');
cleanup();
});
test('pagehide fires sendBeacon when a play is open', async () => {
// jsdom doesn't ship navigator.sendBeacon — install a stub before spy.
if (typeof navigator.sendBeacon !== 'function') {
Object.defineProperty(navigator, 'sendBeacon', {
value: () => true,
configurable: true
});
}
const cleanup = $effect.root(() => useEventsDispatcher());
const beacon = vi.spyOn(navigator, 'sendBeacon').mockReturnValue(true);
playQueue([track('1')]);
flushSync();
reportStateFromAudio('playing');
flushSync();
await Promise.resolve();
await Promise.resolve();
window.dispatchEvent(new Event('pagehide'));
expect(beacon).toHaveBeenCalled();
expect(beacon.mock.calls[0][0]).toBe('/api/events');
cleanup();
beacon.mockRestore();
});
});
+107
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@@ -0,0 +1,107 @@
import { player } from './store.svelte';
import { api } from '$lib/api/client';
import { getOrCreateClientId } from './clientId';
import type { PlayStartedResponse, EventOkResponse } from '$lib/api/types';
// useEventsDispatcher installs $effect-based watchers that emit play events
// to /api/events. Call once from +layout.svelte's mount.
//
// The dispatcher is a small state machine over (current track id, state).
// Per spec data-flow:
// - First transition into 'playing' for a new track → POST play_started.
// - Track id changes while a play is open → POST play_skipped on the prior.
// - Natural completion (state moves from 'playing' to 'paused' AND
// position >= duration > 0) → POST play_ended on the open row.
// - pagehide with a live row → navigator.sendBeacon a play_skipped.
export function useEventsDispatcher(): void {
let openPlayEventId: string | null = null;
let openTrackId: string | null = null;
let lastPositionMs = 0;
let prevTrackId: string | null = null;
let prevState: string | null = null;
const clientId = getOrCreateClientId();
// Track the latest position for use by close events. Cheap; no API call.
$effect(() => {
lastPositionMs = Math.round(player.position * 1000);
});
// Main state machine. Reacts only to (current track id, state) transitions.
$effect(() => {
const t = player.current;
const s = player.state;
const tid = t?.id ?? null;
// Track changed: close any prior open play as a skip.
if (tid !== prevTrackId && openPlayEventId) {
const id = openPlayEventId;
const pos = lastPositionMs;
openPlayEventId = null;
openTrackId = null;
api.post<EventOkResponse>('/api/events', {
type: 'play_skipped',
play_event_id: id,
position_ms: pos
}).catch(() => {});
}
// Entered playing for a new track (no open row yet for this track).
if (tid && s === 'playing' && openTrackId !== tid) {
void startNew(tid);
}
// Natural end: state went playing -> paused while at/past duration.
if (
prevState === 'playing' &&
s === 'paused' &&
openPlayEventId &&
player.duration > 0 &&
player.position >= player.duration
) {
const id = openPlayEventId;
const dur = lastPositionMs;
openPlayEventId = null;
openTrackId = null;
api.post<EventOkResponse>('/api/events', {
type: 'play_ended',
play_event_id: id,
duration_played_ms: dur
}).catch(() => {});
}
prevTrackId = tid;
prevState = s;
});
// Page close: sendBeacon a play_skipped if an open play exists.
if (typeof window !== 'undefined') {
const onPageHide = () => {
if (!openPlayEventId) return;
const payload = JSON.stringify({
type: 'play_skipped',
play_event_id: openPlayEventId,
position_ms: lastPositionMs
});
navigator.sendBeacon('/api/events', new Blob([payload], { type: 'application/json' }));
};
window.addEventListener('pagehide', onPageHide);
}
async function startNew(trackId: string): Promise<void> {
try {
const res = await api.post<PlayStartedResponse>('/api/events', {
type: 'play_started',
track_id: trackId,
client_id: clientId
});
// The user may have moved on by the time the response arrives. Only
// adopt the id if we're still on the same track and still playing.
if (player.current?.id === trackId && player.state === 'playing') {
openPlayEventId = res.play_event_id;
openTrackId = trackId;
}
} catch {
// Best-effort; missed events are OK in v1.
}
}
}