server.js

import { createServer } from 'node:http';
import { createSecureServer } from 'node:http2';
import { existsSync } from 'node:fs';
import { HTTPRequest } from './HTTPRequest.js';
import { RequestCookieMap } from './RequestCookieMap.js';
import { HTTPError } from './HTTPError.js';
import { getFileURL, resolveStaticPath, respondWithFile, resolveModulePath } from './utils.js';

const _noop = () => undefined;

const _hasKeys = ({ key, cert }) => key instanceof Blob && cert instanceof Blob && key.type === 'application/pkcs8' && cert.type === 'application/x-pem-file';

const _isImmutableResponse = resp => resp.status > 299 && resp.status < 309 && resp.headers.has('Location');

async function _importMiddleware(src, index, list) {
	if (typeof src !== 'function') {
		const handler = await import(resolveModulePath(src));

		if (handler.default instanceof Function) {
			list[index] = handler.default;
		} else {
			throw new TypeError(`No default export for ${src}.`);
		}
	}
}

const _createServer = async (callback, {
	key,
	cert,
	allowHTTP1 = true,
	ALPNProtocols = ['h2', 'http/1.1'],
} = {}) => _hasKeys({ key, cert })
	? createSecureServer({
		key: await key.bytes(),
		cert: await cert.bytes(),
		allowHTTP1,
		ALPNProtocols,
	}, callback)
	: createServer(callback);

const _isTransformStream = (result) =>
	result instanceof TransformStream
	|| result instanceof CompressionStream
	|| (typeof result === 'object' && result.readable instanceof ReadableStream && result.writable instanceof WritableStream);

async function _open(url) {
	if (typeof url === 'string') {
		return await _open(URL.parse(url));
	} else if (! (url instanceof URL)) {
		throw new TypeError('URL must be a string or URL.');
	} else if (url.protocol === 'http:' || url.protocol === 'https:') {
		const { exec } = await import('node:child_process');
		const { promise, resolve, reject } = Promise.withResolvers();

		switch(process.platform) {
			case 'darwin':
				exec(`open "${url}"`, reject, resolve);
				break;

			case 'win32':
				exec(`start "${url}"`, reject, resolve);
				break;

			default:
				exec(`xdg-open "${url}"`, reject, resolve);
		}

		return await promise;
	} else {
		throw new TypeError(`Invalid URL: ${url.href}`);
	}
}

/**
 *
 * @param {Response} resp
 * @param {import('node:http').ServerResponse} respMessage
 * @param {object} details
 * @param {Function[]} [details.responsePostprocessors]
 * @param {object} [details.context]
 * @param {Request} [details.request]
 */
async function _send(resp, respMessage, { responsePostprocessors = [], context = {}, request } = {}) {
	if (context.signal.aborted) {
		if (! respMessage.headersSent) {
			respMessage.setHeader('Content-Type', 'application/json');
			respMessage.writeHead(408);
		}

		if (respMessage.writable) {
			const cause = context.signal.reason instanceof Error ? context.signal.reason : new Error(context.signal.reason);
			respMessage.write(JSON.stringify(new HTTPError(cause.message, { status: 408, cause })));
		}

		respMessage.end();
	} else if (resp instanceof Response) {
		const signal = context.signal;

		// Skip handling responses from `Response.redirect()`, which are immutable
		const body = _isImmutableResponse(resp)
			? resp.body
			: await Promise.allSettled(responsePostprocessors
				.map(postProcessor => Promise.try(() => postProcessor(resp, { request, context })))
			).then(results => resp.body instanceof ReadableStream
				? results
					.filter(result => _isTransformStream(result.value))
					.map(result => result.value)
					.reduce((stream, pipe) => stream.pipeThrough(pipe, { signal }), resp.body)
				: null
			);

		if (! respMessage.headersSent) {
			resp.headers.forEach((value, key) => {
				if (key !== 'set-cookie') {
					respMessage.setHeader(key, value);
				}
			});

			resp.headers.getSetCookie().forEach(cookie => respMessage.appendHeader('Set-Cookie', cookie));

			if (resp.headers.get('Connection') === 'Upgrade') {
				respMessage.writeHead(101);
			} else {
				respMessage.writeHead(resp.status === 0 ? 500 : resp.status);
			}
		}

		if (context.signal.aborted) {
			if (! respMessage.headersSent) {
				respMessage.setHeader('Content-Type', 'application/json');
				respMessage.writeHead(408);
			}

			if (respMessage.writable) {
				const cause = context.signal.reason instanceof Error ? context.signal.reason : new Error(context.signal.reason);
				respMessage.write(JSON.stringify(new HTTPError(cause.message, { status: 408, cause })));
			}

			respMessage.end();
		} else if (respMessage.writable && body instanceof ReadableStream && ! body.locked) {
			const reader = body.getReader();
			const cancel = reason => {
				if (body.locked) {
					reader.closed.then(() => {
						body.cancel(reason).catch(_noop);
					}).catch(_noop);

					reader.releaseLock();
				} else {
					body.cancel(reason).catch(_noop);
				}
			};

			try {
				signal.addEventListener('abort', ({ target }) => cancel(target.reason), { once: true });

				if (body.locked) {
					while (! signal.aborted) {
						const { done, value } = await reader.read();

						if (done) {
							reader.releaseLock();
							respMessage.end();
							body.cancel('Done').catch(_noop);
							break;
						} else {
							respMessage.write(value);
						}
					}
				} else {
					respMessage.destroySoon();
				}
			} catch(err) {
				respMessage.destroy(err);
				cancel(err);
			}
		} else if (resp.headers.get('Connection') !== 'Upgrade') {
			respMessage.end();
		} else {
			// IDK why this works...
			respMessage.end();
		}
	} else if (typeof resp === 'object') {
		const { headers: respHeaders = {}, body = null, status = 200, statusText } = resp;

		await _send(new Response(body, {
			status,
			statusText,
			headers: Array.isArray(respHeaders) ? Object.fromEntries(respHeaders) : respHeaders,
		}), respMessage, { responsePostprocessors, context, request });
	} else {
		await _send(new HTTPError('Invalid response.'), respMessage, { responsePostprocessors, context, request });
	}
}

/**
 * Starts a development server.
 *
 * @param {object} config Configuration options for the server.
 * @param {string} [config.hostname="localhost"] The hostname to listen on.
 * @param {string} [config.staticRoot="/"] The path to the directory containing static files.
 * @param {number} [config.port=8080] The port to listen on.
 * @param {Blob & { type: "application/pkcs8" }} [config.key] The private key in PEM format (PKCS#8 encoded).
 * @param {Blob & { type: "application/x-pem-file" }} [config.cert] The certificate in PEM format (X.509 encoded).
 * @param {string} [config.pathname="/"] The URL path to serve the application on.
 * @param {object} [config.routes={}] A map of URL patterns to route handlers.
 * @param {Function} [config.logger=console.error] A function to log messages.
 * @param {boolean} [config.open=false] Whether to open the application in the browser.
 * @param {Function[]} [config.requestPreprocessors] Functions run before request handling, capable of modifying context, logging, validating, or aborting requests.
 * @param {Function[]} [config.responsePostprocessors] Functions to modify a response after being created but before being sent.
 * @param {AbortSignal} [config.signal] A signal to abort the server.
 * @param {number} [config.timeout=1000] Max length to keep the incoming connection alive before aborting.
 * @param {boolean} [config.allowHTTP1] Whether or not to revert to HTTP 1.1 if HTTP 2 is not supported by the client.
 * @returns {Promise<{server: Server<typeof IncomingMessage, typeof ServerResponse>, url: string, whenServerClosed: Promise<void>}>} An object containing the server instance, the URL it is listening on, and a promise that resolves when the server is closed.
 */
export async function serve({
	hostname = 'localhost',
	staticRoot = '/',
	port = 8080,
	key,
	cert,
	pathname = '/',
	routes = {},
	logger = console.error,
	open = false,
	requestPreprocessors = [],
	responsePostprocessors = [],
	signal: passedSignal,
	timeout = 1000,
	allowHTTP1 = true,
} = {}) {
	const { promise: whenServerClosed, resolve: resolveClosed } = Promise.withResolvers();
	const schema = _hasKeys({ key, cert }) ? 'https:' : 'http:';
	const url = new URL(pathname, `${schema}//${hostname}:${port}`).href;
	const ROUTES = new Map(Object.entries(routes).map(([pattern, module]) => {
		// Only interested in the `pathname` & `search`, so parse those out. Origin should not matter.
		const { pathname, search } = new URLPattern(pattern, url);
		return [new URLPattern({ pathname, search }), module];
	}));

	await Promise.all([
		Promise.all(requestPreprocessors.map(_importMiddleware)),
		Promise.all(responsePostprocessors.map(_importMiddleware)),
	]);

	const server = await _createServer(
		/**
		* Handles incoming HTTP requests.
		*
		* @param {import('node:http').IncomingMessage} incomingMessage - The HTTP request.
		* @param {import('node:http').ServerResponse} serverResponse - The HTTP response.
		*/
		async function(incomingMessage, serverResponse) {
			const stack = new DisposableStack();
			const controller = stack.adopt(
				new AbortController(),
				controller => controller.abort(new DOMException('Stack disposed', 'AbortError'))
			);
			const signal = passedSignal instanceof AbortSignal
				? AbortSignal.any([passedSignal, controller.signal])
				: controller.signal;

			const request = HTTPRequest.createFromIncomingMessage(incomingMessage, { signal });
			const url = new URL(request.url);
			const fileURL = getFileURL(url, staticRoot);
			const pattern = ROUTES.keys().find(pattern => pattern.test(request.url));
			const cookies = new RequestCookieMap(request);
			const { resolve: resolveRequest, reject: rejectRequest, promise } = Promise.withResolvers();
			let settled = false;

			if (typeof timeout === 'number' && ! Number.isNaN(timeout) && request.body instanceof ReadableStream) {
				const timeoutHandle = setTimeout(() => {
					const err = new HTTPError('Connection timed out.', { status: 408 });
					controller.abort(err);
				}, timeout);

				incomingMessage.once('end', () => clearTimeout(timeoutHandle));
			}

			const resolve = result => {
				if (! settled) {
					resolveRequest(result);
					settled = true;
				}
			};

			const reject = reason => {
				if (! settled) {
					rejectRequest(reason);
					settled = true;
				}
			};

			const matches = pattern instanceof URLPattern ? pattern.exec(request.url) : undefined;
			const params = typeof matches === 'object'
				? {
					...matches.protocol.groups, ...matches.username.groups, ...matches.password.groups, ...matches.hostname.groups,
					...matches.port.groups, ...matches.pathname.groups, ...matches.search.groups, ...matches.hash.groups,
				} : {};
			delete params['0'];

			const context = {
				url,
				searchParams: url.searchParams,
				matches: pattern instanceof URLPattern ? Object.freeze(matches) : null,
				params: Object.freeze(params),
				cookies,
				ip: incomingMessage.socket.remoteAddress,
				controller,
				signal: controller.signal,
				stack,
				socket: incomingMessage.socket,
				resolve,
				reject,
			};

			try {
				incomingMessage.socket.once('close', () => controller.abort('Socket closed'));
				signal.addEventListener('abort', () => incomingMessage.removeAllListeners(), { once: true });

				const hookErrs = await Promise.allSettled(requestPreprocessors.map(plugin => plugin(request, context)))
					.then(results => results.filter(result => result.status === 'rejected').map(result => result.reason));

				Object.freeze(context);

				if (signal.aborted) {
					reject(signal.reason);
				} else if (hookErrs.length === 1) {
					reject(hookErrs[0]);
				} else if (hookErrs.length !== 0) {
					reject(new AggregateError(hookErrs));
				} else if (controller.signal.aborted) {
					// Controller would be aborted if any of the pre-hooks aborted it.
					reject(controller.signal.reason);
				} else if (! settled && pattern instanceof URLPattern) {
					const moduleSpecifier = ROUTES.get(pattern);
					const module = moduleSpecifier instanceof Function
						? { default: moduleSpecifier }
						: await import(moduleSpecifier).catch(err => err);

					if (module instanceof Error) {
						reject(module);
					} else if (! (module.default instanceof Function)) {
						reject(HTTPError('There was an error handling the request.', {
							status: 500,
							cause: new Error(`${moduleSpecifier} is missing a default export.`),
						}));
					} else {
						const resp = await Promise.try(() => module.default(request, context)).catch(err => err);

						if (resp instanceof Response) {
							resolve(resp);
						} else if (resp instanceof URL) {
							resolve(Response.redirect(resp));
						} else if (resp instanceof Error) {
							reject(resp);
						} else {
							reject(new TypeError(`${moduleSpecifier} did not return a response.`));
						}
					}
				} else if (! settled && existsSync(fileURL)) {
					const resolved = await resolveStaticPath(fileURL.pathname);

					if (typeof resolved === 'string') {
						const resp = await respondWithFile(resolved);

						resolve(resp);
					} else {
						reject(new HTTPError(`<${request.url}> not found.`, { status: 404 }));
					}
				} else if (! settled) {
					reject(new HTTPError(`<${request.url}> not found.`, { status: 404 }));
				}
			} catch(err) {
				reject(err);
			}

			await promise
				.then(resp =>  _send(resp, serverResponse, { responsePostprocessors, request, context }))
				.catch(async err => {
					if (logger instanceof Function) {
						Promise.try(() => logger(err));
					}

					if (err instanceof HTTPError) {
						await _send(err.response, serverResponse, { responsePostprocessors, request, context });
					} else {
						await _send(new HTTPError('An unknown error occured', { cause: err, status: 500 }).response, serverResponse, { responsePostprocessors, context });
					}
				}).finally(() => stack.dispose());
		},
		{ key, cert, allowHTTP1 }
	);

	server.listen(port, hostname);

	if (passedSignal instanceof AbortSignal) {
		passedSignal.addEventListener('abort', () => server.close(), { once: true });
	}

	await new Promise(resolve =>  server.once('listening', resolve));
	server.once('close', resolveClosed);

	// Check if a given signal aborted during server start-up
	if (passedSignal instanceof AbortSignal && passedSignal.aborted) {
		server.close();

		throw passedSignal.reason;
	}

	if (open) {
		_open(url).catch(console.error);
	}

	return Object.freeze({ server, url, whenServerClosed });
}