import { createEngineSound } from '$sound';
import type { EngineSound, SoundDom, SoundTimers } from '$sound';
import type { AppServiceFactory } from '../services.ts';

/**
 * `defineEngineSound()` produces the service factory for the `sound` slot — the
 * shared Web Audio runtime extracted from sema's `SoundChannel` (2026-07-30).
 *
 * It is a SINGLE engine on purpose: the browser caps concurrent
 * `AudioContext`s and the autoplay unlock gesture is per-context, so a second
 * one would leave either the UI earcons or the app's own content mute. Every
 * consumer — sema's sound channel, a media player, a waveform, a visualiser —
 * meets here and hangs its graph off `sound.context`.
 *
 * Needs the DOM service (the global unlock listener) via
 * `serviceDependencies: ['dom']`, and the core `timers` for the earcon's
 * completion. Both degrade: without `dom` a suspended context is resumed on the
 * next `prime()` instead of on the next gesture; without `timers` the engine
 * falls back to `setTimeout`.
 */
export function defineEngineSound(): AppServiceFactory<
	'sound',
	readonly ['timers'],
	readonly ['dom'],
	EngineSound
> {
	return {
		name: 'sound',
		coreDependencies: ['timers'],
		serviceDependencies: ['dom'],
		initMode: 'lazy',
		create({ core, services }): EngineSound {
			return createEngineSound({
				dom: services.dom as SoundDom | undefined,
				timers: core.timers as SoundTimers | undefined
			});
		},
		dispose(instance) {
			instance.dispose();
		}
	};
}