wehub-resource-sync
113 lines
3.9 KiB
TypeScript
113 lines
3.9 KiB
TypeScript
/**
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* MediaSessionService — OS-level "now playing" state, modeled after Android's
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* `MediaSession` / `MediaSessionManager` so widgets/lockscreen/notification
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* media controls don't have to know which music app is the source.
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*
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* Real Android flow
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* -----------------
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* 1. A media app (Spotify, Apple Music, ...) creates a `MediaSession` and
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* calls `setMetadata()` / `setPlaybackState()` as playback changes.
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* 2. System surfaces (lockscreen, notification controls, MAML music widget)
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* enumerate sessions via `MediaSessionManager.getActiveSessions()` and
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* pick the most recently active one.
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* 3. Surfaces read metadata via `MediaController` and never import code from
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* the source app.
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*
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* mobile-gym mirror
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* -----------------
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* - {@link MediaSessionService.setActiveSession} — publisher API; the source
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* app calls this on play-state / track changes.
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* - {@link MediaSessionService.getActiveSession} — consumer API; the music
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* ambient adapter in `os/providers/SystemWidgetProvider.ts` reads here.
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* - Multi-session support: simplified to a single "active" session pointer.
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* Last publisher wins. Add a session stack only if a future scenario needs
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* independent sessions from multiple apps simultaneously.
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*
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* State is volatile (no persistence). Sessions die with the page refresh.
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*/
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import BroadcastBus from './BroadcastBus';
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import { createVolatileOsStore } from './createOsStore';
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export const ACTION_MEDIA_SESSION_CHANGED = 'com.miui.os.MEDIA_SESSION_CHANGED';
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export interface ActiveMediaSession {
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/** Display title of the current track. */
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title: string;
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/** Artist/creator string. */
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artist: string;
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/** Track duration in ms (0 if unknown). */
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durationMs: number;
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/** Current playback position in ms (0 if unknown / not tracked). */
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positionMs: number;
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/** True iff playback is currently advancing. */
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isPlaying: boolean;
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/**
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* Source app's package name. The MAML music widget reads this to attribute
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* playback (`music_control.package`). Required because widgets must show
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* the icon of the controlling app.
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*/
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packageName: string;
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/** Source app's launcher activity / class name. */
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activityClass: string;
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}
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interface MediaSessionState {
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active: ActiveMediaSession | null;
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}
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const store = createVolatileOsStore<MediaSessionState>(
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'media_session',
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{ active: null },
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{ registerToServiceRegistry: true },
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);
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function emit(): void {
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BroadcastBus.sendBroadcast({ action: ACTION_MEDIA_SESSION_CHANGED });
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}
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export const MediaSessionService = {
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/**
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* Publish or update the active session. Pass `null` to clear (e.g. when
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* the user stops playback and exits the source app).
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*
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* Callers (publishers): typically the source music app's state module,
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* subscribed to its own store so any track/play-state change forwards
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* here. See `apps/Spotify/state.ts` for an example.
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*/
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setActiveSession(session: ActiveMediaSession | null): void {
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const prev = store.getState().active;
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if (prev === session) return;
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if (prev && session && areSessionsEqual(prev, session)) return;
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store.setState({ active: session });
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emit();
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},
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/**
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* Read the current active session, or `null` if no app is publishing.
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* Used by the WMR music ambient adapter and any other consumer that needs
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* "what's playing right now".
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*/
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getActiveSession(): ActiveMediaSession | null {
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return store.getState().active;
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},
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/** Convenience: clear the active session. */
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clearActiveSession(): void {
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MediaSessionService.setActiveSession(null);
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},
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};
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function areSessionsEqual(a: ActiveMediaSession, b: ActiveMediaSession): boolean {
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return (
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a.title === b.title &&
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a.artist === b.artist &&
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a.durationMs === b.durationMs &&
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a.positionMs === b.positionMs &&
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a.isPlaying === b.isPlaying &&
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a.packageName === b.packageName &&
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a.activityClass === b.activityClass
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);
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}
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export default MediaSessionService;
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