import {
	CacheType,
	Client,
	GatewayIntentBits,
	Interaction,
	Message,
	OAuth2Scopes,
	PermissionFlagsBits,
	VoiceState
} from 'discord.js';
import { Logger } from './utils/log';
import { config } from './utils/config';
import { CommandManager } from './commands';

type BotEventListeners = {
	messageCreate: (message: Message) => void;
	interactionCreate: (interaction: Interaction) => void;
	voiceStateUpdate: (oldState: VoiceState, newState: VoiceState) => void;
};
type BotEventListener<K extends keyof BotEventListeners> = BotEventListeners[K];

export class Bot {
	private client: Client | undefined;
	private cmdMgr: CommandManager;

	private readonly log: Logger;

	private eventListeners: {
		[K in keyof BotEventListeners]?: BotEventListener<K>[];
	} = {};

	/*
        class methods
    */
	private constructor() {
		this.log = new Logger('Bot');
		this.cmdMgr = new CommandManager('./commands');
	}

	public async init(): Promise<void> {
		this.log.info('Bot init');

		if (this.client)
			throw new Error('Client already exists, was init called twice?');

		this.log.info('Loading commands');
		await this.cmdMgr.init();

		this.log.info('Instantiating client');
		this.client = new Client({
			intents: [
				GatewayIntentBits.Guilds,
				GatewayIntentBits.GuildMessages,
				GatewayIntentBits.GuildVoiceStates,
				GatewayIntentBits.MessageContent
			]
		});

		this.log.info('Registering callbacks');
		this.client.on('clientReady', () => this.onReady());
		this.client.on('error', (err) => this.onError(err, false));
		this.client.on('shardError', (err) => this.onError(err, true));
		this.client.on('messageCreate', (message: Message<boolean>) =>
			this.onMessage(message)
		);
		this.client.on('interactionCreate', (interaction: Interaction<CacheType>) =>
			this.onInteraction(interaction)
		);
		this.client.on(
			'voiceStateUpdate',
			(oldState: VoiceState, newState: VoiceState) =>
				this.onVoiceStateUpdate(oldState, newState)
		);

		this.log.info('Logging in...');
		await this.client.login(config.token);
	}

	/*
        event listeners
    */
	private onReady(): void {
		this.log.info('Logged in');

		const inviteLink = this.client?.generateInvite({
			scopes: [OAuth2Scopes.ApplicationsCommands, OAuth2Scopes.Bot],
			permissions: [
				PermissionFlagsBits.AddReactions,
				PermissionFlagsBits.AttachFiles,
				PermissionFlagsBits.ChangeNickname,
				PermissionFlagsBits.Connect,
				PermissionFlagsBits.Speak,
				PermissionFlagsBits.ViewChannel,
				PermissionFlagsBits.ReadMessageHistory,
				PermissionFlagsBits.SendMessages,
				PermissionFlagsBits.SendMessagesInThreads,
				PermissionFlagsBits.SendVoiceMessages,
				PermissionFlagsBits.EmbedLinks
			]
		});

		this.log.info('Invite link: %s', inviteLink);
	}

	private onError(error: Error, isShardError: boolean): void {
		if (isShardError)
			this.log.error(
				'A shard error ocurred: %s - %s - %s',
				error.name,
				error.message,
				error.stack
			);
		else
			this.log.error(
				'An error ocurred: %s - %s - %s',
				error.name,
				error.message,
				error.stack
			);
	}

	/*
        public event listeners
    */
	private async onInteraction(interaction: Interaction): Promise<void> {
		this.emit('interactionCreate', interaction);
	}

	private async onMessage(message: Message): Promise<void> {
		this.emit('messageCreate', message);
	}

	private async onVoiceStateUpdate(
		oldState: VoiceState,
		newState: VoiceState
	): Promise<void> {
		this.emit('voiceStateUpdate', oldState, newState);
	}

	/*
        registerable event system
    */
	public on<K extends keyof BotEventListeners>(
		event: K,
		listener: BotEventListener<K>
	): void {
		if (!this.eventListeners[event]) {
			this.eventListeners[event] = [];
		}
		(this.eventListeners[event] as BotEventListener<K>[]).push(listener);
	}

	public off<K extends keyof BotEventListeners>(
		event: K,
		listener: BotEventListener<K>
	): boolean {
		const listeners = this.eventListeners[event];
		if (!listeners) return false;

		const index = (listeners as BotEventListener<K>[]).indexOf(listener);
		if (index > -1) {
			(listeners as BotEventListener<K>[]).splice(index, 1);
			return true;
		}
		return false;
	}

	public once<K extends keyof BotEventListeners>(
		event: K,
		listener: BotEventListener<K>
	): void {
		const onceWrapper = ((...args: Parameters<BotEventListener<K>>) => {
			this.off(event, onceWrapper as BotEventListener<K>);
			(listener as (...args: unknown[]) => void)(...args);
		}) as BotEventListener<K>;

		this.on(event, onceWrapper);
	}

	private emit<K extends keyof BotEventListeners>(
		event: K,
		...args: Parameters<BotEventListener<K>>
	): void {
		const listeners = this.eventListeners[event];
		if (listeners) {
			for (const listener of listeners as BotEventListener<K>[]) {
				try {
					(listener as (...args: unknown[]) => void)(...args);
				} catch (error) {
					this.log.error(
						`Error in event listener for ${String(event)}:`,
						error
					);
				}
			}
		}
	}

	/*
        singleton logic
    */
	static #instance: Bot | null = null;

	public static get get(): Bot {
		if (!Bot.#instance) Bot.#instance = new Bot();
		return Bot.#instance;
	}
}