import {Router} from 'express';
import {DefaultConfig, Logger, urlJoin} from '.';
import {v4} from 'uuid';
import Timeout = NodeJS.Timeout;

export type ReloaderConfig = {
	// frontend directories to watch
	frontendDirs: string|string[],
	// auto reloader sub path (defaults to '/auto-reload')
	subPath?: string,
	// auto reloader js name (defaults to 'client.js')
	jsName?: string,
}

type IntReloaderConfig = {
	// frontend directories to watch
	frontendDirs: string[],
	// auto reloader sub path (defaults to '/auto-reload')
	subPath: string,
	// auto reloader js name (defaults to 'client.js')
	jsName: string,
}

function getRouter(opts: ReloaderConfig): Router {
	const config: IntReloaderConfig = {
		frontendDirs: Array.isArray(opts.frontendDirs) ? opts.frontendDirs : [opts.frontendDirs],
		subPath: opts.subPath || '/auto-reload',
		jsName: opts.jsName || 'client.js',
	};

	const router = Router();
	if (!DefaultConfig.isProduction) {
		let uuid = v4();
		let updateTimeout: Timeout|undefined = undefined;
		import('node-watch').then((watch) => {
			for (const frontendDir of config.frontendDirs) {
				watch.default(frontendDir, {recursive: true}, () => {
					if (updateTimeout !== undefined) clearTimeout(updateTimeout);
					updateTimeout = setTimeout(() => {
						uuid = v4();
					}, 200);
				});
			}
		}).catch((err) => { Logger.error(err); });

		// /auto-reload/client.js
		router.get(urlJoin(config.subPath, config.jsName), (req, res) => {
			Logger.debug(req.url, req.originalUrl, req.baseUrl);
			res.setHeader('Content-Type', 'application/javascript');
			// language=JavaScript
			res.send(`
		const loc = window.location;
		const url = loc.protocol+'//'+loc.host+'${urlJoin(req.baseUrl, config.subPath)}';
		// const parse = async res => (await res.json()).uuid;
		const parse = function(res) {
		    return res.json()
		    .then(function(json) {return json.uuid;}) }
		let hash = undefined;
		let hadError = false;
		setInterval(function() {
	    try {
        fetch(url)
        .then(function(res) { return parse(res) })
        .then(function(data) {
		      if (data) {
		          hash = hash === undefined ? data : hash;
		          if (hash !== data) {
		              window.location.reload();
		          }
		      }
        });
	    } catch (e) {
	        if (hadError === false) {
	            console.log(e);
	            hadError = true;
	        }
	    }
    }, 3000);
	`.replace(/\t/g, ''));
		});

		// /auto-reload
		router.get(urlJoin(config.subPath), (req, res) => {
			req.noHttpLogging = true;
			res.json({uuid});
		});
	}

	return router;
}



export const AutoReloader = {
	getRouter,
};