'use strict';
const http2 = require('http2');
const {Writable} = require('stream');
const {Agent, globalAgent} = require('./agent');
const IncomingMessage = require('./incoming-message');
const urlToOptions = require('./utils/url-to-options');
const proxyEvents = require('./utils/proxy-events');
const isRequestPseudoHeader = require('./utils/is-request-pseudo-header');
const {
	ERR_INVALID_ARG_TYPE,
	ERR_INVALID_PROTOCOL,
	ERR_HTTP_HEADERS_SENT,
	ERR_INVALID_HTTP_TOKEN,
	ERR_HTTP_INVALID_HEADER_VALUE,
	ERR_INVALID_CHAR
} = require('./utils/errors');

const {
	HTTP2_HEADER_STATUS,
	HTTP2_HEADER_METHOD,
	HTTP2_HEADER_PATH,
	HTTP2_METHOD_CONNECT
} = http2.constants;

const kHeaders = Symbol('headers');
const kOrigin = Symbol('origin');
const kSession = Symbol('session');
const kOptions = Symbol('options');
const kFlushedHeaders = Symbol('flushedHeaders');
const kJobs = Symbol('jobs');

const isValidHttpToken = /^[\^`\-\w!#$%&*+.|~]+$/;
const isInvalidHeaderValue = /[^\t\u0020-\u007E\u0080-\u00FF]/;

class ClientRequest extends Writable {
	constructor(input, options, callback) {
		super({
			autoDestroy: false
		});

		const hasInput = typeof input === 'string' || input instanceof URL;
		if (hasInput) {
			input = urlToOptions(input instanceof URL ? input : new URL(input));
		}

		if (typeof options === 'function' || options === undefined) {
			// (options, callback)
			callback = options;
			options = hasInput ? input : {...input};
		} else {
			// (input, options, callback)
			options = {...input, ...options};
		}

		if (options.h2session) {
			this[kSession] = options.h2session;
		} else if (options.agent === false) {
			this.agent = new Agent({maxFreeSessions: 0});
		} else if (typeof options.agent === 'undefined' || options.agent === null) {
			if (typeof options.createConnection === 'function') {
				// This is a workaround - we don't have to create the session on our own.
				this.agent = new Agent({maxFreeSessions: 0});
				this.agent.createConnection = options.createConnection;
			} else {
				this.agent = globalAgent;
			}
		} else if (typeof options.agent.request === 'function') {
			this.agent = options.agent;
		} else {
			throw new ERR_INVALID_ARG_TYPE('options.agent', ['Agent-like Object', 'undefined', 'false'], options.agent);
		}

		if (options.protocol && options.protocol !== 'https:') {
			throw new ERR_INVALID_PROTOCOL(options.protocol, 'https:');
		}

		const port = options.port || options.defaultPort || (this.agent && this.agent.defaultPort) || 443;
		const host = options.hostname || options.host || 'localhost';

		// Don't enforce the origin via options. It may be changed in an Agent.
		delete options.hostname;
		delete options.host;
		delete options.port;

		const {timeout} = options;
		options.timeout = undefined;

		this[kHeaders] = Object.create(null);
		this[kJobs] = [];

		this.socket = null;
		this.connection = null;

		this.method = options.method || 'GET';
		this.path = options.path;

		this.res = null;
		this.aborted = false;
		this.reusedSocket = false;

		if (options.headers) {
			for (const [header, value] of Object.entries(options.headers)) {
				this.setHeader(header, value);
			}
		}

		if (options.auth && !('authorization' in this[kHeaders])) {
			this[kHeaders].authorization = 'Basic ' + Buffer.from(options.auth).toString('base64');
		}

		options.session = options.tlsSession;
		options.path = options.socketPath;

		this[kOptions] = options;

		// Clients that generate HTTP/2 requests directly SHOULD use the :authority pseudo-header field instead of the Host header field.
		if (port === 443) {
			this[kOrigin] = `https://${host}`;

			if (!(':authority' in this[kHeaders])) {
				this[kHeaders][':authority'] = host;
			}
		} else {
			this[kOrigin] = `https://${host}:${port}`;

			if (!(':authority' in this[kHeaders])) {
				this[kHeaders][':authority'] = `${host}:${port}`;
			}
		}

		if (timeout) {
			this.setTimeout(timeout);
		}

		if (callback) {
			this.once('response', callback);
		}

		this[kFlushedHeaders] = false;
	}

	get method() {
		return this[kHeaders][HTTP2_HEADER_METHOD];
	}

	set method(value) {
		if (value) {
			this[kHeaders][HTTP2_HEADER_METHOD] = value.toUpperCase();
		}
	}

	get path() {
		return this[kHeaders][HTTP2_HEADER_PATH];
	}

	set path(value) {
		if (value) {
			this[kHeaders][HTTP2_HEADER_PATH] = value;
		}
	}

	get _mustNotHaveABody() {
		return this.method === 'GET' || this.method === 'HEAD' || this.method === 'DELETE';
	}

	_write(chunk, encoding, callback) {
		// https://github.com/nodejs/node/blob/654df09ae0c5e17d1b52a900a545f0664d8c7627/lib/internal/http2/util.js#L148-L156
		if (this._mustNotHaveABody) {
			callback(new Error('The GET, HEAD and DELETE methods must NOT have a body'));
			/* istanbul ignore next: Node.js 12 throws directly */
			return;
		}

		this.flushHeaders();

		const callWrite = () => this._request.write(chunk, encoding, callback);
		if (this._request) {
			callWrite();
		} else {
			this[kJobs].push(callWrite);
		}
	}

	_final(callback) {
		if (this.destroyed) {
			return;
		}

		this.flushHeaders();

		const callEnd = () => {
			// For GET, HEAD and DELETE
			if (this._mustNotHaveABody) {
				callback();
				return;
			}

			this._request.end(callback);
		};

		if (this._request) {
			callEnd();
		} else {
			this[kJobs].push(callEnd);
		}
	}

	abort() {
		if (this.res && this.res.complete) {
			return;
		}

		if (!this.aborted) {
			process.nextTick(() => this.emit('abort'));
		}

		this.aborted = true;

		this.destroy();
	}

	_destroy(error, callback) {
		if (this.res) {
			this.res._dump();
		}

		if (this._request) {
			this._request.destroy();
		}

		callback(error);
	}

	async flushHeaders() {
		if (this[kFlushedHeaders] || this.destroyed) {
			return;
		}

		this[kFlushedHeaders] = true;

		const isConnectMethod = this.method === HTTP2_METHOD_CONNECT;

		// The real magic is here
		const onStream = stream => {
			this._request = stream;

			if (this.destroyed) {
				stream.destroy();
				return;
			}

			// Forwards `timeout`, `continue`, `close` and `error` events to this instance.
			if (!isConnectMethod) {
				proxyEvents(stream, this, ['timeout', 'continue', 'close', 'error']);
			}

			// Wait for the `finish` event. We don't want to emit the `response` event
			// before `request.end()` is called.
			const waitForEnd = fn => {
				return (...args) => {
					if (!this.writable && !this.destroyed) {
						fn(...args);
					} else {
						this.once('finish', () => {
							fn(...args);
						});
					}
				};
			};

			// This event tells we are ready to listen for the data.
			stream.once('response', waitForEnd((headers, flags, rawHeaders) => {
				// If we were to emit raw request stream, it would be as fast as the native approach.
				// Note that wrapping the raw stream in a Proxy instance won't improve the performance (already tested it).
				const response = new IncomingMessage(this.socket, stream.readableHighWaterMark);
				this.res = response;

				response.req = this;
				response.statusCode = headers[HTTP2_HEADER_STATUS];
				response.headers = headers;
				response.rawHeaders = rawHeaders;

				response.once('end', () => {
					if (this.aborted) {
						response.aborted = true;
						response.emit('aborted');
					} else {
						response.complete = true;

						// Has no effect, just be consistent with the Node.js behavior
						response.socket = null;
						response.connection = null;
					}
				});

				if (isConnectMethod) {
					response.upgrade = true;

					// The HTTP1 API says the socket is detached here,
					// but we can't do that so we pass the original HTTP2 request.
					if (this.emit('connect', response, stream, Buffer.alloc(0))) {
						this.emit('close');
					} else {
						// No listeners attached, destroy the original request.
						stream.destroy();
					}
				} else {
					// Forwards data
					stream.on('data', chunk => {
						if (!response._dumped && !response.push(chunk)) {
							stream.pause();
						}
					});

					stream.once('end', () => {
						response.push(null);
					});

					if (!this.emit('response', response)) {
						// No listeners attached, dump the response.
						response._dump();
					}
				}
			}));

			// Emits `information` event
			stream.once('headers', waitForEnd(
				headers => this.emit('information', {statusCode: headers[HTTP2_HEADER_STATUS]})
			));

			stream.once('trailers', waitForEnd((trailers, flags, rawTrailers) => {
				const {res} = this;

				// Assigns trailers to the response object.
				res.trailers = trailers;
				res.rawTrailers = rawTrailers;
			}));

			const {socket} = stream.session;
			this.socket = socket;
			this.connection = socket;

			for (const job of this[kJobs]) {
				job();
			}

			this.emit('socket', this.socket);
		};

		// Makes a HTTP2 request
		if (this[kSession]) {
			try {
				onStream(this[kSession].request(this[kHeaders]));
			} catch (error) {
				this.emit('error', error);
			}
		} else {
			this.reusedSocket = true;

			try {
				onStream(await this.agent.request(this[kOrigin], this[kOptions], this[kHeaders]));
			} catch (error) {
				this.emit('error', error);
			}
		}
	}

	getHeader(name) {
		if (typeof name !== 'string') {
			throw new ERR_INVALID_ARG_TYPE('name', 'string', name);
		}

		return this[kHeaders][name.toLowerCase()];
	}

	get headersSent() {
		return this[kFlushedHeaders];
	}

	removeHeader(name) {
		if (typeof name !== 'string') {
			throw new ERR_INVALID_ARG_TYPE('name', 'string', name);
		}

		if (this.headersSent) {
			throw new ERR_HTTP_HEADERS_SENT('remove');
		}

		delete this[kHeaders][name.toLowerCase()];
	}

	setHeader(name, value) {
		if (this.headersSent) {
			throw new ERR_HTTP_HEADERS_SENT('set');
		}

		if (typeof name !== 'string' || (!isValidHttpToken.test(name) && !isRequestPseudoHeader(name))) {
			throw new ERR_INVALID_HTTP_TOKEN('Header name', name);
		}

		if (typeof value === 'undefined') {
			throw new ERR_HTTP_INVALID_HEADER_VALUE(value, name);
		}

		if (isInvalidHeaderValue.test(value)) {
			throw new ERR_INVALID_CHAR('header content', name);
		}

		this[kHeaders][name.toLowerCase()] = value;
	}

	setNoDelay() {
		// HTTP2 sockets cannot be malformed, do nothing.
	}

	setSocketKeepAlive() {
		// HTTP2 sockets cannot be malformed, do nothing.
	}

	setTimeout(ms, callback) {
		const applyTimeout = () => this._request.setTimeout(ms, callback);

		if (this._request) {
			applyTimeout();
		} else {
			this[kJobs].push(applyTimeout);
		}

		return this;
	}

	get maxHeadersCount() {
		if (!this.destroyed && this._request) {
			return this._request.session.localSettings.maxHeaderListSize;
		}

		return undefined;
	}

	set maxHeadersCount(_value) {
		// Updating HTTP2 settings would affect all requests, do nothing.
	}
}

module.exports = ClientRequest;