From f4147f7922e1f19b1f442546f2225b7bc3193b48 Mon Sep 17 00:00:00 2001
From: Peter Jaszkowiak <p.jaszkow@gmail.com>
Date: Mon, 23 Jan 2017 21:06:34 -0700
Subject: [PATCH] Generate cache buster on build

---
 build.js                | 23 ++++++++++++++-------
 src/meta/cacheBuster.js | 46 +++++++++++++++++++++++++++++++++++++++++
 src/meta/configs.js     | 14 +++++++++----
 3 files changed, 72 insertions(+), 11 deletions(-)
 create mode 100644 src/meta/cacheBuster.js

diff --git a/build.js b/build.js
index 73013231d5..89c55177ad 100644
--- a/build.js
+++ b/build.js
@@ -44,6 +44,8 @@ exports.build = function build(targets, callback) {
 
 exports.buildTargets = function (targets, callback) {
 	var meta = require('./src/meta');
+	var cacheBuster = require('./src/meta/cacheBuster');
+
 	buildStart = buildStart || Date.now();
 
 	var step = function (startTime, target, next, err) {
@@ -114,14 +116,21 @@ exports.buildTargets = function (targets, callback) {
 			return process.exit(1);
 		}
 
-		var time = (Date.now() - buildStart) / 1000;
+		cacheBuster.write(function (err) {
+			if (err) {
+				winston.error('[build] Failed to write `cache-buster.conf`: ' + err.message);
+				return process.exit(1);
+			}
 
-		winston.info('[build] Asset compilation successful. Completed in ' + time + 's.');
+			var time = (Date.now() - buildStart) / 1000;
 
-		if (typeof callback === 'function') {
-			callback();
-		} else {
-			process.exit(0);
-		}
+			winston.info('[build] Asset compilation successful. Completed in ' + time + 's.');
+
+			if (typeof callback === 'function') {
+				callback();
+			} else {
+				process.exit(0);
+			}
+		});
 	});
 };
\ No newline at end of file
diff --git a/src/meta/cacheBuster.js b/src/meta/cacheBuster.js
new file mode 100644
index 0000000000..ca00fba057
--- /dev/null
+++ b/src/meta/cacheBuster.js
@@ -0,0 +1,46 @@
+'use strict';
+
+var fs = require('fs');
+var path = require('path');
+var mkdirp = require('mkdirp');
+var winston = require('winston');
+
+var filePath = path.join(__dirname, '../../build/cache-buster');
+
+var cached;
+
+// cache buster is an 11-character, lowercase, alphanumeric string
+function generate() {
+	return (Math.random() * 1e18).toString(32).slice(0, 11);
+}
+
+exports.write = function write(callback) {
+	mkdirp(path.dirname(filePath), function (err) {
+		if (err) {
+			return callback(err);
+		}
+
+		fs.writeFile(filePath, generate(), callback);
+	});
+};
+
+exports.read = function read(callback) {
+	if (cached) {
+		return callback(null, cached);
+	}
+
+	fs.readFile(filePath, function (err, buffer) {
+		if (err) {
+			winston.warn('[cache-buster] could not read cache buster: ' + err.message);
+			return callback();
+		}
+
+		buffer = buffer.toString();
+		if (buffer) {
+			cached = buffer;
+			return callback(null, cached);
+		}
+
+		callback();
+	});
+};
diff --git a/src/meta/configs.js b/src/meta/configs.js
index 75da0595d2..907e0ef477 100644
--- a/src/meta/configs.js
+++ b/src/meta/configs.js
@@ -6,7 +6,7 @@ var nconf = require('nconf');
 
 var db = require('../database');
 var pubsub = require('../pubsub');
-var utils = require('../../public/src/utils');
+var cacheBuster = require('./cacheBuster');
 
 module.exports = function (Meta) {
 
@@ -21,10 +21,16 @@ module.exports = function (Meta) {
 				Meta.configs.list(next);
 			},
 			function (config, next) {
-				config['cache-buster'] = 'v=' + utils.generateUUID();
+				cacheBuster.read(function (err, buster) {
+					if (err) {
+						return next(err);
+					}
+					
+					config['cache-buster'] = 'v=' + (buster || Date.now());
 
-				Meta.config = config;
-				setImmediate(next);
+					Meta.config = config;
+					next();
+				});
 			}
 		], callback);
 	};