import * as fs from "fs-extra"
import * as net from "net"
import * as path from "path"
import * as tls from "tls"
import { Emitter } from "../common/emitter"
import { generateUuid } from "../common/util"
import { tmpdir } from "./util"

/**
 * Provides a way to proxy a TLS socket. Can be used when you need to pass a
 * socket to a child process since you can't pass the TLS socket.
 */
export class SocketProxyProvider {
 private readonly onProxyConnect = new Emitter<net.Socket>()
 private proxyPipe = path.join(tmpdir, "tls-proxy")
 private _proxyServer?: Promise<net.Server>
 private readonly proxyTimeout = 5000

 /**
 * Stop the proxy server.
 */
 public stop(): void {
 if (this._proxyServer) {
 this._proxyServer.then((server) => server.close())
 this._proxyServer = undefined
 }
 }

 /**
 * Create a socket proxy for TLS sockets. If it's not a TLS socket the
 * original socket is returned. This will spawn a proxy server on demand.
 */
 public async createProxy(socket: net.Socket): Promise<net.Socket> {
 if (!(socket instanceof tls.TLSSocket)) {
 return socket
 }

 await this.startProxyServer()

 return new Promise((resolve, reject) => {
 const id = generateUuid()
 const proxy = net.connect(this.proxyPipe)
 proxy.once("connect", () => proxy.write(id))

 const timeout = setTimeout(() => {
 listener.dispose() // eslint-disable-line @typescript-eslint/no-use-before-define
 socket.destroy()
 proxy.destroy()
 reject(new Error("TLS socket proxy timed out"))
 }, this.proxyTimeout)

 const listener = this.onProxyConnect.event((connection) => {
 connection.once("data", (data) => {
 if (!socket.destroyed && !proxy.destroyed && data.toString() === id) {
 clearTimeout(timeout)
 listener.dispose()
 ;[
 [proxy, socket],
 [socket, proxy],
 ].forEach(([a, b]) => {
 a.pipe(b)
 a.on("error", () => b.destroy())
 a.on("close", () => b.destroy())
 a.on("end", () => b.end())
 })
 resolve(connection)
 }
 })
 })
 })
 }

 private async startProxyServer(): Promise<net.Server> {
 if (!this._proxyServer) {
 this._proxyServer = this.findFreeSocketPath(this.proxyPipe)
 .then((pipe) => {
 this.proxyPipe = pipe
 return Promise.all([fs.mkdirp(tmpdir), fs.remove(this.proxyPipe)])
 })
 .then(() => {
 return new Promise((resolve) => {
 const proxyServer = net.createServer((p) => this.onProxyConnect.emit(p))
 proxyServer.once("listening", () => resolve(proxyServer))
 proxyServer.listen(this.proxyPipe)
 })
 })
 }
 return this._proxyServer
 }

 public async findFreeSocketPath(basePath: string, maxTries = 100): Promise<string> {
 const canConnect = (path: string): Promise<boolean> => {
 return new Promise((resolve) => {
 const socket = net.connect(path)
 socket.once("error", () => resolve(false))
 socket.once("connect", () => {
 socket.destroy()
 resolve(true)
 })
 })
 }

 let i = 0
 let path = basePath
 while ((await canConnect(path)) && i < maxTries) {
 path = `${basePath}-${++i}`
 }
 return path
 }
}