discord.js/packages/voice/src/DataStore.ts

import { GatewayOpcodes } from 'discord-api-types/v10';
import type { VoiceConnection } from './VoiceConnection';
import type { AudioPlayer } from './audio/index';

export interface JoinConfig {
	channelId: string | null;
	group: string;
	guildId: string;
	selfDeaf: boolean;
	selfMute: boolean;
}

/**
 * Sends a voice state update to the main websocket shard of a guild, to indicate joining/leaving/moving across
 * voice channels.
 *
 * @param config - The configuration to use when joining the voice channel
 */
export function createJoinVoiceChannelPayload(config: JoinConfig) {
	return {
		op: GatewayOpcodes.VoiceStateUpdate,
		// eslint-disable-next-line id-length
		d: {
			guild_id: config.guildId,
			channel_id: config.channelId,
			self_deaf: config.selfDeaf,
			self_mute: config.selfMute,
		},
	};
}

// Voice Connections
const groups = new Map<string, Map<string, VoiceConnection>>();
groups.set('default', new Map());

function getOrCreateGroup(group: string) {
	const existing = groups.get(group);
	if (existing) return existing;
	const map = new Map<string, VoiceConnection>();
	groups.set(group, map);
	return map;
}

/**
 * Retrieves the map of group names to maps of voice connections. By default, all voice connections
 * are created under the 'default' group.
 *
 * @returns The group map
 */
export function getGroups() {
	return groups;
}

/**
 * Retrieves all the voice connections under the 'default' group.
 *
 * @param group - The group to look up
 * @returns The map of voice connections
 */
export function getVoiceConnections(group?: 'default'): Map<string, VoiceConnection>;

/**
 * Retrieves all the voice connections under the given group name.
 *
 * @param group - The group to look up
 * @returns The map of voice connections
 */
export function getVoiceConnections(group: string): Map<string, VoiceConnection> | undefined;

/**
 * Retrieves all the voice connections under the given group name. Defaults to the 'default' group.
 *
 * @param group - The group to look up
 * @returns The map of voice connections
 */
export function getVoiceConnections(group = 'default') {
	return groups.get(group);
}

/**
 * Finds a voice connection with the given guild id and group. Defaults to the 'default' group.
 *
 * @param guildId - The guild id of the voice connection
 * @param group - the group that the voice connection was registered with
 * @returns The voice connection, if it exists
 */
export function getVoiceConnection(guildId: string, group = 'default') {
	return getVoiceConnections(group)?.get(guildId);
}

export function untrackVoiceConnection(voiceConnection: VoiceConnection) {
	return getVoiceConnections(voiceConnection.joinConfig.group)?.delete(voiceConnection.joinConfig.guildId);
}

export function trackVoiceConnection(voiceConnection: VoiceConnection) {
	return getOrCreateGroup(voiceConnection.joinConfig.group).set(voiceConnection.joinConfig.guildId, voiceConnection);
}

// Audio Players

// Each audio packet is 20ms long
const FRAME_LENGTH = 20;

let audioCycleInterval: NodeJS.Timeout | undefined;
let nextTime = -1;

/**
 * A list of created audio players that are still active and haven't been destroyed.
 */
const audioPlayers: AudioPlayer[] = [];

/**
 * Called roughly every 20 milliseconds. Dispatches audio from all players, and then gets the players to prepare
 * the next audio frame.
 */
function audioCycleStep() {
	if (nextTime === -1) return;

	nextTime += FRAME_LENGTH;
	const available = audioPlayers.filter((player) => player.checkPlayable());

	for (const player of available) {
		// eslint-disable-next-line @typescript-eslint/dot-notation
		player['_stepDispatch']();
	}

	prepareNextAudioFrame(available);
}

/**
 * Recursively gets the players that have been passed as parameters to prepare audio frames that can be played
 * at the start of the next cycle.
 */
function prepareNextAudioFrame(players: AudioPlayer[]) {
	const nextPlayer = players.shift();

	if (!nextPlayer) {
		if (nextTime !== -1) {
			audioCycleInterval = setTimeout(() => audioCycleStep(), nextTime - Date.now());
		}

		return;
	}

	// eslint-disable-next-line @typescript-eslint/dot-notation
	nextPlayer['_stepPrepare']();

	// setImmediate to avoid long audio player chains blocking other scheduled tasks
	setImmediate(() => prepareNextAudioFrame(players));
}

/**
 * Checks whether or not the given audio player is being driven by the data store clock.
 *
 * @param target - The target to test for
 * @returns `true` if it is being tracked, `false` otherwise
 */
export function hasAudioPlayer(target: AudioPlayer) {
	return audioPlayers.includes(target);
}

/**
 * Adds an audio player to the data store tracking list, if it isn't already there.
 *
 * @param player - The player to track
 */
export function addAudioPlayer(player: AudioPlayer) {
	if (hasAudioPlayer(player)) return player;
	audioPlayers.push(player);
	if (audioPlayers.length === 1) {
		nextTime = Date.now();
		setImmediate(() => audioCycleStep());
	}

	return player;
}

/**
 * Removes an audio player from the data store tracking list, if it is present there.
 */
export function deleteAudioPlayer(player: AudioPlayer) {
	const index = audioPlayers.indexOf(player);
	if (index === -1) return;
	audioPlayers.splice(index, 1);
	if (audioPlayers.length === 0) {
		nextTime = -1;
		if (audioCycleInterval !== undefined) clearTimeout(audioCycleInterval);
	}
}