Adding a 'coarse' user agent parser for KPI Backend

lib/coarse_user_agent_parser.js

+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Unlike most user agent string parsers, we don't want to be as accurate as possible.
+ * This is for several reasons:
+ *  * protect user privacy (no fingerprinting)
+ *  * Surface only 80% case uses in our visualization UI
+ *  * KISS
+
+ * Test data via http://www.useragentstring.com/pages/All/
+ * Converted with https://gist.github.com/2590522
+ *
+ */
+exports.parse = function (ua_string) {
+  var user_agent = {
+        os: 'Unknown',
+        browser: 'Unknown',
+        version: 'Unknown'
+      },
+      os_matchers = [
+        'iPod', 'iPad', 'iPhone',
+        'Android', 'BlackBerry', 'Linux', 'Macintosh',
+        // Windows 7       Windows Vista     Windows XP
+        'Windows NT 6.1', 'Windows NT 6.0', 'Windows NT 5.1'
+      ],
+      basic = function (ua_string) {
+        // Looks for SomeString/5.1 at the end of a UA and parses 5.1 as an integer returning 5
+        // Expected outputs... Firefox 14, Safari 533, Opera 12
+        try {
+          //console.log(parseInt(ua_string.split(' ').splice(-1)[0].split('/')[1]));
+          var v = parseInt(ua_string.split(' ').splice(-1)[0].split('/')[1], 10);
+          if (! isNaN(v)) {
+            return v;
+          }
+        } catch (e) {
+          console.error(e.toString());
+        }
+        return 'Unknown';
+      },
+      keyword = function (kw) {
+        //console.log('Keyword is ', kw);
+        return function (ua_string) {
+          //console.log(ua_string);
+          // Looks for MSIE 9.0 in the middle of the ua_string
+          var start = ua_string.indexOf(kw) + kw.length;
+          //console.log('start', start);
+          if (start !== -1) {
+            var end = ua_string.indexOf(' ', start + 1);
+            //console.log('end is ', end);
+            try {
+              //console.log('ua_string.substring(start, end)=' + ua_string.substring(start, end));
+              var v = parseInt(ua_string.substring(start, end), 10);
+              if (! isNaN(v)) {
+                return v;
+              }
+            } catch (e) {
+              console.error('ERROR: ' + e.toString());
+            }
+          }
+          return 'Unknown';
+        };
+      },
+      msie = keyword('MSIE '),
+      chrome = keyword('Chrome/'),
+      browser_matchers = [
+        ['Chrome', chrome], ['Opera Mini', basic], ['Opera Mobile', basic], ['Opera', basic],
+        ['MSIE', msie], ['Safari', basic], ['Firefox', basic]
+      ];
+  if (! ua_string) {
+    console.error('Empty UA String');
+    return;
+  }
+  // Safari uses basic version reader to get 533 instead of 5. This is probably more useful and matches Android, Mobile Safari, etc.
+
+  // In os_matchers and browser_matchers order matters, many browsers pretend to be other
+  // browsers http://webaim.org/blog/user-agent-string-history/
+  var os_known = false;
+  os_matchers.forEach(function (el, i) {
+    if (os_known) return;
+    if (ua_string.indexOf(el) !== -1) {
+      os_known = true;
+      user_agent.os = el;
+    }
+    return;
+  });
+
+  var browser_known = false;
+  browser_matchers.forEach(function (el, i) {
+    if (browser_known) return;
+    if (ua_string.indexOf(el[0]) !== -1) {
+      browser_known = true;
+      user_agent.browser = el[0];
+      user_agent.version = el[1](ua_string);
+    }
+    return;
+  });
+
+  return user_agent;
+}
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tests/coarse-user-agent-parser-test.js

+#!/usr/bin/env node
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const fs = require('fs'),
+      // TODO: convert to vows based test (or introduce nodeunit dependency)
+      vows = require('vows'),
+      coarse = require('../lib/coarse_user_agent_parser'),
+      path = require('path');
+
+var suite = vows.describe('coarse-user-agent-parser');
+
+// disable vows (often flakey?) async error behavior
+suite.options.error = false;
+
+/* Update test data with https://gist.github.com/2590547 */
+
+fs.readFile(path.join(__dirname, 'data/user_agents.json'), 'utf-8', function (err, data) {
+  if (err) {
+    console.error(err);
+  } else {
+    var test_data = JSON.parse(data);
+    for (var i=0; i < test_data.tests.length; i++) {
+      var t = test_data.tests[i];
+      if (t.ua) {
+        var actual = coarse.parse(t.ua);
+        if (actual.os != t.os) {
+          console.error('Error parsing ' + t.ua + ' expected [' + t.os + '] got [' + actual.os + ']');
+        }
+        if (actual.browser != t.browser) {
+          console.error('Error parsing ' + t.ua + ' expected [' + t.browser + '] got [' + actual.browser + ']');
+        }
+        if (actual.version != t.version) {
+          console.error('Error parsing ' + t.ua + ' expected [' + t.version + '] got [' + actual.version + ']');
+        }
+      }
+    }
+    console.log('Finished ' + test_data.tests.length);
+  }
+});
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