const HASH_EXTRACTOR = /^\#\/topic\/(?<topic_id>[A-Za-z\-]+)\/?(?<view>\w+)?/gm;
const UPDATE_TOPICS_FREQUENCY = 60_000;

const APP = {
	user: undefined,
	user_servers: [],
	user_watches: [],

	_event_callbacks: {},

	on: function( event_name, callback ) {
		this._event_callbacks[ event_name ] = this._event_callbacks[ event_name ] ?? new Set();
		this._event_callbacks[event_name ].add( callback );
		return true;
	},

	off: function( event_name, callback ) {
		return this._event_callbacks[ event_name ]?.delete( callback );
	},

	_emit: function( event_name, event_data ) {
		const event_callbacks = this._event_callbacks[ event_name ];
		event_callbacks?.forEach( ( callback ) => {
			callback( event_data );
		});
	},

	check_if_logged_in: async function () {
		try {
			const session_response = await api.fetch("/api/users/me");

			if (!session_response.ok) {
				const error_body = await session_response.json();
				const error = error_body?.error;

				console.dir({
					error_body,
					error,
				});
				return;
			}

			const user = await session_response.json();
			this.login( user );
		} catch (error) {
			console.dir({
				error,
			});
		}
	},

	extract_url_hash_info: async function () {
		HASH_EXTRACTOR.lastIndex = 0; // ugh, need this to have this work on multiple exec calls
		const {
			groups: { topic_id, view },
		} = HASH_EXTRACTOR.exec(window.location.hash ?? "") ?? {
			groups: {},
		};

		/*
		console.dir({
			url: window.location.href,
			hash: window.location.hash,
			topic_id,
			view,
		});
		*/

		if (!document.body.dataset.topic || document.body.dataset.topic !== topic_id) {
			const previous = document.body.dataset.topic;

			/*
			console.dir({
				topic_changed: {
					detail: {
						previous,
						topic_id,
					},
				},
			});
			*/

			document.body.dataset.topic = topic_id;

			this._emit( 'topic_changed', {
				previous,
				topic_id
			});

			if (!topic_id) {
				const first_topic_id = this.TOPICS.TOPIC_LIST[0]?.id;
				if (first_topic_id) {
					window.location.hash = `/topic/${first_topic_id}/chat`; // TODO: allow a different default than chat
				}
			}
		}

		if (!document.body.dataset.view || document.body.dataset.view !== view) {
			const previous = document.body.dataset.view;
			document.body.dataset.view = view;

			/*
			console.dir({
				view_changed: {
					detail: {
						previous,
						view,
					},
				},
			});
			*/

			this._emit( 'view_changed', {
				previous,
				view
			});
		}
	},

	load: async function() {
		this.server = {
			name: document.title,
			url: window.location.origin ?? window.location.href,
			icon: '/icons/favicon-128x128.png',
			icon_background: undefined
		};

		this.suggested_servers = [];
		try {
			const server_info_response = await api.fetch( '/files/settings/settings.json' );
			if ( server_info_response.ok ) {
				const this_server_info = await server_info_response.json();

				this.server = {
					name: this_server_info.name ?? this.server.name,
					url: this_server_info.url ?? this.server.url,
					icon: this_server_info.icon ?? this.server.icon,
					icon_background: this_server_info.icon_background ?? this.server.icon_background
				};
			}

			const suggested_servers_response = await api.fetch( '/files/settings/suggested_servers.json' );
			if ( suggested_servers_response.ok ) {
				this.suggested_servers = await suggested_servers_response.json();
			}
		}
		catch( error ) {
			console.error( error );
		}

		window.addEventListener("locationchange", this.extract_url_hash_info.bind( this ));
		window.addEventListener("locationchange", this.TOPICS.update );

		this.check_if_logged_in();
		this.extract_url_hash_info();
		this._emit( 'load', this );
	},

	update_user: async function( user ) {
		this.user = user;

		document.body.dataset.user = JSON.stringify(user);
		document.body.dataset.perms = user.permissions.join(":");

		this.TOPICS.update();

		this.user_servers = [];
		try {
			const user_server_response = await api.fetch( `/files/users/${ user.id }/settings/servers.json` );
			this.user_servers = user_server_response.ok ? await user_server_response.json() : [];
		}
		catch( error ) {
			console.error( error );
		}

		this.user_watches = [];
		try {
			const user_watches_response = await api.fetch( `/api/users/${ user.id }/watches` );
			this.user_watches = user_watches_response.ok ? await user_watches_response.json() : [];
		}
		catch( error ) {
			console.error( error );
		}

		// TODO: show unread indicators based on watches
	},

	login: async function( user ) {
		await this.update_user( user );
		this._emit( 'user_logged_in', { user } );
	},

	logout: function() {
		delete document.body.dataset.user;
		delete document.body.dataset.perms;
		window.location = "/";

		this._emit( "user_logged_out", {});
	},

	USERS: {
		_evict_timeouts: {},
		_update_timeouts: {},
		get: async (id, force) => {
			if (force || !APP.USERS[id]) {
				APP.USERS[id] = await (await api.fetch(`/api/users/${id}`)).json();
			}

			if (!APP.USERS._update_timeouts[id]) {
				APP.USERS._update_timeouts[id] = setInterval(() => {
					APP.USERS.get(id, true);
				}, 1 * 60_000);
			}

			if (!force) {
				if (APP.USERS._evict_timeouts[id]) {
					clearTimeout(APP.USERS._evict_timeouts[id]);
				}

				APP.USERS._evict_timeouts[id] = setTimeout(() => {
					if (APP.USERS._update_timeouts[id]) {
						clearTimeout(APP.USERS._update_timeouts[id]);
						delete APP.USERS._update_timeouts[id];
					}

					delete APP.USERS[id];
				}, 10 * 60_000);
			}

			return APP.USERS[id];
		},
	},

	TOPICS: {
		_last_topic_update: undefined,
		_update_topics_timeout: undefined,
		TOPIC_LIST: [],

		update: async () => {
			const now = new Date();
			const time_since_last_update = now - (APP.TOPICS._last_topic_update ?? 0);
			if (time_since_last_update < UPDATE_TOPICS_FREQUENCY / 2) {
				return;
			}

			if (APP.TOPICS._update_topics_timeout) {
				clearTimeout(APP.TOPICS._update_topics_timeout);
				APP.TOPICS._update_topics_timeout = undefined;
			}

			try {
				const topics_response = await api.fetch("/api/topics");
				if (topics_response.ok) {
					const new_topics = await topics_response.json();
					const has_differences =
						APP.TOPICS.TOPIC_LIST.length !== new_topics.length ||
						new_topics.some((topic, index) => {
							return (
								APP.TOPICS.TOPIC_LIST[index]?.id !== topic.id ||
								APP.TOPICS.TOPIC_LIST[index]?.name !== topic.name
							);
						});

					if (has_differences) {
						APP.TOPICS.TOPIC_LIST = [...new_topics];

						APP._emit( 'topics_updated', {
							topics: APP.TOPICS.TOPIC_LIST
						});
					}

					APP.TOPICS._last_topic_update = now;
				}
			} catch (error) {
				console.error(error);
			}

			APP.TOPICS._update_topics_timeout = setTimeout(
				APP.TOPICS.update,
				UPDATE_TOPICS_FREQUENCY,
			);

			// now that we have topics, make sure our url is all good
			APP.extract_url_hash_info();
		},
	},
};

document.addEventListener("DOMContentLoaded", APP.load.bind( APP ));