import {RequestHandler} from 'express';
import * as polyfillLibrary from 'polyfill-library';
import {DefaultConfig, Logger, WaitForSync} from '.';
import {spawn, Thread, Worker} from 'threads';
import {WorkerFunction} from 'threads/dist/types/worker';

export type PolyfillFeatureList = {
	[featureName: string]: {
		flags?: string[]
	}
};

export type PolyfillOptions = {
	minify: boolean,
	unknown: 'polyfill'|'ignore',
	features: PolyfillFeatureList,
	excludes: string[],
	uaString: string,
	rum: boolean,
}

function getRouter(fileToWatch: string, opts?: Partial<PolyfillOptions>): RequestHandler {
	const features = new WaitForSync<PolyfillFeatureList>();
	(async () => {
		const worker = await spawn<WorkerFunction>(new Worker('./polyfill-worker'));
		const feats = await worker(fileToWatch) as PolyfillFeatureList;
		await Thread.terminate(worker);
		return feats;
	})()
		.then(feats => {
			feats['fetch'] = {};
			Logger.debug('Polyfill analysed:', Object.keys(feats));
			features.setData(feats);
		})
		.catch(err => features.setError(err));

	const options: Partial<PolyfillOptions> = {
		minify: DefaultConfig.isProduction,
		unknown: 'polyfill',
		...opts,
	};
	return async (req, res) => {
		const polyfillBundle = await polyfillLibrary.getPolyfillString({
			...options,
			uaString: req.header('user-agent'),
			features: await features.resolve(),
			stream: false,
		});
		res.setHeader('Content-Type', 'text/javascript');
		res.send(polyfillBundle);
	};
}
export const Polyfill = {
	getRouter: getRouter,
};