WebServer: Enable deflate and gzip compression (#3677)

* get-index: Enable deflate and gzip compression

* Spaces -> Tabs

* listen: Add optional `gzip=yes` parameter (defaults to "no")

* get-index: Add comment explaining the usage of `zlib.*Sync` instead of async.

core/language/en-GB/Help/listen.tid

@@ -28,6 +28,7 @@ All parameters are optional with safe defaults, and can be specified in any orde
 * ''tls-cert'' - pathname of TLS certificate file (relative to wiki folder)
 * ''tls-key'' - pathname of TLS key file (relative to wiki folder)
 * ''debug-level'' - optional debug level; set to "debug" to view request details (defaults to "none")
+* ''gzip'' - set to "yes" to enable gzip compression for some http endpoints (defaults to "no")
 
 For information on opening up your instance to the entire local network, and possible security concerns, see the WebServer tiddler at TiddlyWiki.com.
 

core/modules/server/routes/get-index.js

@@ -12,14 +12,40 @@ GET /
 /*global $tw: false */
 "use strict";
 
+var zlib = require('zlib');
+
 exports.method = "GET";
 
 exports.path = /^\/$/;
 
 exports.handler = function(request,response,state) {
-	response.writeHead(200, {"Content-Type": state.server.get("root-serve-type")});
+	var acceptEncoding = request.headers['accept-encoding'];
+	if (!acceptEncoding) { acceptEncoding = ''; }
+
 	var text = state.wiki.renderTiddler(state.server.get("root-render-type"),state.server.get("root-tiddler"));
-	response.end(text,"utf8");
+
+	var responseHeaders = {
+		"Content-Type": state.server.get("root-serve-type")
+	};
+
+	/*
+	If the gzip=yes flag for `listen` is set, check if the user agent permits
+	compression. If so, compress our response. Note that we use the synchronous
+	functions from zlib to stay in the imperative style. The current `Server`
+	doesn't depend on this, and we may just as well use the async versions.
+	*/
+	if(state.server.enableGzip) {
+		if (/\bdeflate\b/.test(acceptEncoding)) {
+			responseHeaders['Content-Encoding'] = 'deflate';
+			text = zlib.deflateSync(text);
+		} else if (/\bgzip\b/.test(acceptEncoding)) {
+			responseHeaders['Content-Encoding'] = 'gzip';
+			text = zlib.gzipSync(text);
+		}
+	}
+
+	response.writeHead(200, responseHeaders);
+	response.end(text);
 };
 
 }());

core/modules/server/server.js

@@ -43,6 +43,8 @@ function Server(options) {
 	$tw.utils.extend({},this.defaultVariables,options.variables);
 	// Initialise CSRF
 	this.csrfDisable = this.get("csrf-disable") === "yes";
+	// Initialize Gzip compression
+	this.enableGzip = this.get("gzip") === "yes";
 	// Initialise authorization
 	var authorizedUserName = (this.get("username") && this.get("password")) ? this.get("username") : "(anon)";
 	this.authorizationPrincipals = {
@@ -84,7 +86,8 @@ Server.prototype.defaultVariables = {
 	"tiddler-render-template": "$:/core/templates/server/static.tiddler.html",
 	"system-tiddler-render-type": "text/plain",
 	"system-tiddler-render-template": "$:/core/templates/wikified-tiddler",
-	"debug-level": "none"
+	"debug-level": "none",
+	"gzip": "no"
 };
 
 Server.prototype.get = function(name) {