GoogleAnalytics: Unique cid per user

Instead of generating a new cid everytime `build` launches,
make it dependant on the computer (the MAC address), so it is
the same for each user (in reality each computer). The MAC is
hashed before sent so it can not be used for tracing.

lib/GoogleAnalytics.js

@@ -2,11 +2,25 @@
 
 var _ = require('lodash');
 var querystring = require('querystring');
-var cid = require('node-uuid').v4();
+var cid;
 
 module.exports = (function () {
   function GoogleAnalytics () {}
 
+  GoogleAnalytics.getCid = function (cb) {
+    if (cid) {
+      return cb(cid);
+    }
+
+    require('getmac').getMac(function(error, macAddress) {
+      if (error) {
+        return cb(cid = require('node-uuid').v4());
+      }
+
+      return cb(require('crypto').createHash('sha1').update(macAddress, 'utf8').digest('hex'));
+    });
+  };
+
   GoogleAnalytics.sendEvent = function(category, action, label, value) {
     var params = {
       t: 'event',
@@ -29,8 +43,10 @@ module.exports = (function () {
       return;
     }
 
-    _.extend(params, GoogleAnalytics.defaultParams());
-    GoogleAnalytics.request('https://www.google-analytics.com/collect?' + querystring.stringify(params));
+    GoogleAnalytics.getCid(function (cid) {
+      _.extend(params, { cid: cid }, GoogleAnalytics.defaultParams());
+      GoogleAnalytics.request('https://www.google-analytics.com/collect?' + querystring.stringify(params));
+    });
   };
 
   GoogleAnalytics.request = function (url) {
@@ -51,7 +67,6 @@ module.exports = (function () {
     return {
       v: 1,
       tid: 'UA-47615700-5',
-      cid: cid
     };
   };
 

package.json

@@ -15,7 +15,8 @@
     "fs-plus": "^2.4.0",
     "atom-space-pen-views": "^2.0.3",
     "xregexp": "^2.0.0",
-    "node-uuid": "^1.4.3"
+    "node-uuid": "^1.4.3",
+    "getmac": "^1.0.7"
   },
   "devDependencies": {
     "jshint": "^2.5.11",