Sockets: Go rewrite

Work in progress. I haven't written documentation for the Go code or
confirmed whether this works as intended on Windows yet.

This turned into a pretty substantial refactor of the Node version of
sockets-related code to not only to make using Go child processes
possible, but to optimize it and make unit testing of it and any code
dependent on it possible to write entirely synchronously. sockets.js
and sockets-workers.js are now written in Typescript, though they won't
be able to be transpiled until after Config, Users, Dnsbl, and Monitor
work with it as well.

Fixes smogon#2943

config/config-example.js

@@ -10,6 +10,13 @@ exports.port = 8000;
 //   know what you are doing.
 exports.proxyip = false;
 
+// Go language - whether or not to use Go instead of Node.js to host the static
+//	 and SockJS servers. Go is more likely to be more performant than Node.js for
+//	 this purpose, but this should be kept set to false unless you're capable of
+//	 debugging any issues that may arise due to the additional complexity of
+//	 the code needed for this to run.
+exports.golang = false;
+
 // Pokemon of the Day - put a pokemon's name here to make it Pokemon of the Day
 //   The PotD will always be in the #2 slot (not #1 so it won't be a lead)
 //   in every Random Battle team.

dev-tools/sockets.js

@@ -0,0 +1,35 @@
+'use strict';
+
+const {Session, SockJSConnection} = require('sockjs/lib/transport');
+
+const chars = 'abcdefghijklmnopqrstuvwxyz1234567890-';
+let sessionidCount = 0;
+
+/**
+ * @return string
+ */
+function generateSessionid() {
+	let ret = '';
+	let idx = sessionidCount;
+	for (let i = 0; i < 8; i++) {
+		ret = chars[idx % chars.length] + ret;
+		idx = idx / chars.length | 0;
+	}
+	sessionidCount++;
+	return ret;
+}
+
+/**
+ * @param {string} sessionid
+ * @param {{options: {{}}} config
+ * @return SockJSConnection
+ */
+exports.createSocket = function (sessionid = generateSessionid(), config = {options: {}}) {
+	let session = new Session(sessionid, config);
+	let socket = new SockJSConnection(session);
+	socket.remoteAddress = '127.0.0.1';
+	socket.protocol = 'websocket';
+	return socket;
+};
+
+// TODO: move worker mocks here, use require('../sockets-workers').Multiplexer to stub IPC

pokemon-showdown

@@ -2,6 +2,8 @@
 'use strict';
 
 const child_process = require('child_process');
+const fs = require('fs');
+const path = require('path');
 
 // Make sure we're Node 6+
 
@@ -22,6 +24,78 @@ try {
 	child_process.execSync('npm install --production', {stdio: 'inherit'});
 }
 
+// Check if the server is configured to use Go, and ensure the required
+// environment variables and dependencies are available if that is the case
+
+let config;
+try {
+	config = require('./config/config');
+} catch (e) {}
+
+if (config && config.golang) {
+	if (!process.env.GOPATH) {
+		console.log('The GOPATH environment variable is not set! It is required in order to run the server using Go.');
+		process.exit(0);
+	}
+	if (!process.env.GOROOT) {
+		console.log('The GOROOT environment variable is not set! It is required in order to run the server using Go.');
+		process.exit(0);
+	}
+
+	const dependencies = ['github.com/gorilla/mux', 'github.com/igm/sockjs-go/sockjs'];
+	let packages = child_process.execSync('go list all', {stdio: null, encoding: 'utf8'});
+	for (let dep of dependencies) {
+		if (!packages.includes(dep)) {
+			console.log(`Dependency ${dep} is not installed. Fetching...`);
+			child_process.execSync(`go get ${dep}`, {stdio: 'inherit'});
+		}
+	}
+
+	const {GOPATH} = process.env;
+	let stat;
+	let needsSrcDir = false;
+	try {
+		stat = fs.lstatSync(path.resolve(GOPATH, 'src/github.com/Zarel'));
+	} catch (e) {
+		needsSrcDir = true;
+	} finally {
+		if (stat && !stat.isDirectory()) {
+			needsSrcDir = true;
+		}
+	}
+
+	if (needsSrcDir) {
+		try {
+			fs.mkdirSync(path.resolve(GOPATH, 'src/github.com/Zarel'));
+		} catch (e) {
+			console.error(`Cannot make go source directory for the sockets library files! Symlink them manually from ${__dirname} to ${path.resolve(GOPATH, 'src/github.com/Zarel/Pokemon-Showdown/')}`);
+			process.exit(0);
+		}
+	}
+
+	try {
+		stat = fs.lstatSync(path.resolve(GOPATH, 'src/github.com/Zarel/Pokemon-Showdown'));
+	} catch (e) {}
+
+	if (!stat || !stat.isSymbolicLink()) {
+		try {
+			// FIXME: does this even work on Windows? Check to see if `mklink /J`
+			// might be needed instead
+			fs.symlink(__dirname, path.resolve(GOPATH, 'src/github.com/Zarel/Pokemon-Showdown'));
+		} catch (e) {
+			console.error(`Cannot make go source directory for the sockets library files! Symlink them manually from ${__dirname} to ${path.resolve(GOPATH, './src/github.com/Zarel/Pokemon-Showdown/')}`);
+			process.exit(0);
+		}
+	}
+
+	console.log('Building Go source libs...');
+	try {
+		child_process.execSync('go install github.com/Zarel/Pokemon-Showdown/sockets', {stdio: 'inherit'});
+	} catch (e) {
+		process.exit(0);
+	}
+}
+
 // Start the server. We manually load app.js so it can be configured to run as
 // the main module, rather than this file being considered the main module.
 // This ensures any dependencies that were just installed can be found when