import clamp from 'just-clamp';
import { persisted } from 'svelte-local-storage-store';

export interface UserPreferences {
	playback_rate: number;
	volume: number;
	muted: boolean;
}

/**
 * The default user preferences
 */
const DEFAULT_USER_PREFERENCES: UserPreferences = {
	playback_rate: 1,
	volume: 1,
	muted: false,
};

/**
 * The user preferences store
 */
export const USER_PREFERENCES_STORE = persisted<UserPreferences>(
	'USER_PREFERENCE',
	DEFAULT_USER_PREFERENCES,
);

/**
 * Sets the playback rate for the user
 * @param  value - The playback rate value
 */
const set_playback_rate = (value: number) => {
	const playback_rate = clamp(value, 0.5, 5);
	return USER_PREFERENCES_STORE.update((prefs) => ({
		...prefs,
		playback_rate,
	}));
};

/**
 * Sets the volume for the user
 * @param  value - The volume value
 */
const set_volume = (value: number) => {
	const volume = clamp(value, 0, 1);
	return USER_PREFERENCES_STORE.update((prefs) => ({ ...prefs, volume }));
};

/**
 * Sets the muted state for the user. This is the single source of truth
 * for mute: the audio element is kept in sync with it.
 * @param  value - The muted value
 */
const set_muted = (value: boolean) => {
	return USER_PREFERENCES_STORE.update((prefs) => ({ ...prefs, muted: value }));
};

/**
 * Clears user preferences store
 */
const clear_store = () => USER_PREFERENCES_STORE.set(DEFAULT_USER_PREFERENCES);

/**
 * The user preferences object
 */
export const user_preferences = {
	subscribe: USER_PREFERENCES_STORE.subscribe,
	set_playback_rate,
	set_volume,
	set_muted,
	clear: clear_store,
};