import * as fs from 'fs';
import * as path from 'path';
import { resolve, URL } from 'url';
import { ClientRequest, ServerResponse } from 'http';
import cookie from 'cookie';
import mkdirp from 'mkdirp';
import rimraf from 'rimraf';
import devalue from 'devalue';
import fetch from 'node-fetch';
import { lookup } from './middleware/mime';
import { create_routes, create_compilers } from './core';
import { locations, dev } from './config';
import { Route, Template } from './interfaces';
import sourceMapSupport from 'source-map-support';

sourceMapSupport.install();

type RouteObject = {
	id: string;
	type: 'page' | 'route';
	pattern: RegExp;
	params: (match: RegExpMatchArray) => Record<string, string>;
	module: Component;
	error?: string;
}

type Handler = (req: Req, res: ServerResponse, next: () => void) => void;

type Store = {
	get: () => any
};

interface Req extends ClientRequest {
	url: string;
	baseUrl: string;
	originalUrl: string;
	method: string;
	path: string;
	params: Record<string, string>;
	headers: Record<string, string>;
}

interface Component {
	render: (data: any, opts: { store: Store }) => {
		head: string;
		css: { code: string, map: any };
		html: string
	},
	preload: (data: any) => any | Promise<any>
}

export default function middleware({ App, routes, store }: {
	App: Component,
	routes: RouteObject[],
	store: (req: Req) => Store
}) {
	if (!App) {
		throw new Error(`As of 0.12, you must supply an App component to Sapper — see https://sapper.svelte.technology/guide#0-11-to-0-12 for more information`);
	}

	const output = locations.dest();

	const client_info = JSON.parse(fs.readFileSync(path.join(output, 'client_info.json'), 'utf-8'));

	const middleware = compose_handlers([
		(req: Req, res: ServerResponse, next: () => void) => {
			if (req.baseUrl === undefined) {
				req.baseUrl = req.originalUrl
					? req.originalUrl.slice(0, -req.url.length)
					: '';
			}

			if (req.path === undefined) {
				req.path = req.url.replace(/\?.*/, '');
			}

			next();
		},

		fs.existsSync(path.join(output, 'index.html')) && serve({
			pathname: '/index.html',
			cache_control: 'max-age=600'
		}),

		fs.existsSync(path.join(output, 'service-worker.js')) && serve({
			pathname: '/service-worker.js',
			cache_control: 'max-age=600'
		}),

		fs.existsSync(path.join(output, 'service-worker.js.map')) && serve({
			pathname: '/service-worker.js.map',
			cache_control: 'max-age=600'
		}),

		serve({
			prefix: '/client/',
			cache_control: 'max-age=31536000'
		}),

		get_route_handler(client_info.assets, App, routes, store)
	].filter(Boolean));

	return middleware;
}

function serve({ prefix, pathname, cache_control }: {
	prefix?: string,
	pathname?: string,
	cache_control: string
}) {
	const filter = pathname
		? (req: Req) => req.path === pathname
		: (req: Req) => req.path.startsWith(prefix);

	const output = locations.dest();

	const cache: Map<string, Buffer> = new Map();

	const read = dev()
		? (file: string) => fs.readFileSync(path.resolve(output, file))
		: (file: string) => (cache.has(file) ? cache : cache.set(file, fs.readFileSync(path.resolve(output, file)))).get(file)

	return (req: Req, res: ServerResponse, next: () => void) => {
		if (filter(req)) {
			const type = lookup(req.path);

			try {
				const data = read(req.path.slice(1));

				res.setHeader('Content-Type', type);
				res.setHeader('Cache-Control', cache_control);
				res.end(data);
			} catch (err) {
				res.statusCode = 404;
				res.end('not found');
			}
		} else {
			next();
		}
	};
}

const resolved = Promise.resolve();

function get_route_handler(chunks: Record<string, string>, App: Component, routes: RouteObject[], store_getter: (req: Req) => Store) {
	const template = dev()
		? () => fs.readFileSync(`${locations.app()}/template.html`, 'utf-8')
		: (str => () => str)(fs.readFileSync(`${locations.dest()}/template.html`, 'utf-8'));

	function handle_route(route: RouteObject, req: Req, res: ServerResponse) {
		req.params = route.params(route.pattern.exec(req.path));

		const handlers = route.handlers[Symbol.iterator]();

		function next() {
			try {
				const { value: handler, done } = handlers.next();

				if (done) {
					handle_error(req, res, 404, 'Not found');
					return;
				}

				const mod = handler.module;

				if (handler.type === 'page') {
					res.setHeader('Content-Type', 'text/html');

					// preload main.js and current route
					// TODO detect other stuff we can preload? images, CSS, fonts?
					const link = []
						.concat(chunks.main, chunks[route.id])
						.filter(file => !file.match(/\.map$/))
						.map(file => `<${req.baseUrl}/client/${file}>;rel="preload";as="script"`)
						.join(', ');

					res.setHeader('Link', link);

					const store = store_getter ? store_getter(req) : null;
					const props = { params: req.params, query: req.query, path: req.path };

					let redirect: { statusCode: number, location: string };
					let error: { statusCode: number, message: Error | string };

					Promise.resolve(
						mod.preload ? mod.preload.call({
							redirect: (statusCode: number, location: string) => {
								redirect = { statusCode, location };
							},
							error: (statusCode: number, message: Error | string) => {
								error = { statusCode, message };
							},
							fetch: (url: string, opts?: any) => {
								const parsed = new URL(url, `http://127.0.0.1:${process.env.PORT}${req.baseUrl ? req.baseUrl + '/'  :''}`);

								if (opts) {
									opts = Object.assign({}, opts);

									const include_cookies = (
										opts.credentials === 'include' ||
										opts.credentials === 'same-origin' && parsed.origin === `http://127.0.0.1:${process.env.PORT}`
									);

									if (include_cookies) {
										const cookies: Record<string, string> = {};
										if (!opts.headers) opts.headers = {};

										const str = []
											.concat(
												cookie.parse(req.headers.cookie || ''),
												cookie.parse(opts.headers.cookie || ''),
												cookie.parse(res.getHeader('Set-Cookie') || '')
											)
											.map(cookie => {
												return Object.keys(cookie)
													.map(name => `${name}=${encodeURIComponent(cookie[name])}`)
													.join('; ');
											})
											.filter(Boolean)
											.join(', ');

										opts.headers.cookie = str;
									}
								}

								return fetch(parsed.href, opts);
							},
						store
						}, req) : {}
					).catch(err => {
						error = { statusCode: 500, message: err };
					}).then(preloaded => {
						if (redirect) {
							res.statusCode = redirect.statusCode;
							res.setHeader('Location', `${req.baseUrl}/${redirect.location}`);
							res.end();

							return;
						}

						if (error) {
							handle_error(req, res, error.statusCode, error.message);
							return;
						}

						const serialized = {
							preloaded: mod.preload && try_serialize(preloaded),
							store: store && try_serialize(store.get())
						};
						Object.assign(props, preloaded);

						const { html, head, css } = App.render({ Page: mod, props }, {
							store
						});

						let scripts = []
							.concat(chunks.main) // chunks main might be an array. it might not! thanks, webpack
							.filter(file => !file.match(/\.map$/))
							.map(file => `<script src='${req.baseUrl}/client/${file}'></script>`)
							.join('');

						let inline_script = `__SAPPER__={${[
							`baseUrl: "${req.baseUrl}"`,
							serialized.preloaded && `preloaded: ${serialized.preloaded}`,
							serialized.store && `store: ${serialized.store}`
						].filter(Boolean).join(',')}};`;

						const has_service_worker = fs.existsSync(path.join(locations.dest(), 'service-worker.js'));
						if (has_service_worker) {
							inline_script += `if ('serviceWorker' in navigator) navigator.serviceWorker.register('${req.baseUrl}/service-worker.js');`;
						}

						const page = template()
							.replace('%sapper.base%', `<base href="${req.baseUrl}/">`)
							.replace('%sapper.scripts%', `<script>${inline_script}</script>${scripts}`)
							.replace('%sapper.html%', html)
							.replace('%sapper.head%', `<noscript id='sapper-head-start'></noscript>${head}<noscript id='sapper-head-end'></noscript>`)
							.replace('%sapper.styles%', (css && css.code ? `<style>${css.code}</style>` : ''));

						res.end(page);

						if (process.send) {
							process.send({
								__sapper__: true,
								url: req.url,
								method: req.method,
								status: 200,
								type: 'text/html',
								body: page
							});
						}
					});
				}

				else {
					const method = req.method.toLowerCase();
					// 'delete' cannot be exported from a module because it is a keyword,
					// so check for 'del' instead
					const method_export = method === 'delete' ? 'del' : method;
					const handle_method = mod[method_export];
					if (handle_method) {
						if (process.env.SAPPER_EXPORT) {
							const { write, end, setHeader } = res;
							const chunks: any[] = [];
							const headers: Record<string, string> = {};

							// intercept data so that it can be exported
							res.write = function(chunk: any) {
								chunks.push(new Buffer(chunk));
								write.apply(res, arguments);
							};

							res.setHeader = function(name: string, value: string) {
								headers[name.toLowerCase()] = value;
								setHeader.apply(res, arguments);
							};

							res.end = function(chunk?: any) {
								if (chunk) chunks.push(new Buffer(chunk));
								end.apply(res, arguments);

								process.send({
									__sapper__: true,
									url: req.url,
									method: req.method,
									status: res.statusCode,
									type: headers['content-type'],
									body: Buffer.concat(chunks).toString()
								});
							};
						}

						const handle_bad_result = (err?: Error) => {
							if (err) {
								console.error(err.stack);
								res.statusCode = 500;
								res.end(err.message);
							} else {
								process.nextTick(next);
							}
						};

						try {
							handle_method(req, res, handle_bad_result);
						} catch (err) {
							handle_bad_result(err);
						}
					} else {
						// no matching handler for method
						process.nextTick(next);
					}
				}
			} catch (error) {
				handle_error(req, res, 500, error);
			}
		}

		next();
	}

	const not_found_route = routes.find((route: RouteObject) => route.error === '4xx');
	const error_route = routes.find((route: RouteObject) => route.error === '5xx');

	function handle_error(req: Req, res: ServerResponse, statusCode: number, message: Error | string) {
		res.statusCode = statusCode;
		res.setHeader('Content-Type', 'text/html');

		const error = message instanceof Error ? message : new Error(message);

		const not_found = statusCode >= 400 && statusCode < 500;

		const route = not_found
			? not_found_route
			: error_route;

		function render_page({ head, css, html }) {
			const page = template()
				.replace('%sapper.base%', `<base href="${req.baseUrl}/">`)
				.replace('%sapper.scripts%', `<script>__SAPPER__={baseUrl: "${req.baseUrl}"}</script><script src='${req.baseUrl}/client/${chunks.main}'></script>`)
				.replace('%sapper.html%', html)
				.replace('%sapper.head%', `<noscript id='sapper-head-start'></noscript>${head}<noscript id='sapper-head-end'></noscript>`)
				.replace('%sapper.styles%', (css && css.code ? `<style>${css.code}</style>` : ''));

			res.end(page);
		}

		function handle_notfound() {
			const title: string = not_found
				? 'Not found'
				: `Internal server error: ${error.message}`;

			render_page({ head: '', css: null, html: title });
		}

		if (route) {
			const handlers = route.handlers[Symbol.iterator]();

			function next() {
				const { value: handler, done } = handlers.next();

				if (done) {
					handle_notfound();
				} else if (handler.type === 'page') {
					render_page(handler.module.render({
						status: statusCode,
						error
					}, {
						store: store_getter && store_getter(req)
					}));
				} else {
					const handle_method = mod[method_export];
					if (handle_method) {
						handle_method(req, res, next);
					} else {
						next();
					}
				}
			}

			next();
		} else {
			handle_notfound();
		}
	}

	return function find_route(req: Req, res: ServerResponse) {
		for (const route of routes) {
			if (!route.error && route.pattern.test(req.path)) return handle_route(route, req, res);
		}

		handle_error(req, res, 404, 'Not found');
	};
}

function compose_handlers(handlers: Handler[]) {
	return (req: Req, res: ServerResponse, next: () => void) => {
		let i = 0;
		function go() {
			const handler = handlers[i];

			if (handler) {
				handler(req, res, () => {
					i += 1;
					go();
				});
			} else {
				next();
			}
		}

		go();
	};
}

function read_json(file: string) {
	return JSON.parse(fs.readFileSync(file, 'utf-8'));
}

function try_serialize(data: any) {
	try {
		return devalue(data);
	} catch (err) {
		return null;
	}
}