From d14fd0f70ed984c4c97e07215e5c9bdc344de4f1 Mon Sep 17 00:00:00 2001
From: Robert Lord <robert@lord.io>
Date: Sat, 20 Jun 2015 01:49:25 -0400
Subject: [PATCH] Update language tabs to not disturb existing query strings,
 fixes #57

---
 source/javascripts/app/_lang.js | 88 +++++++++++++++++++++++++++++++--
 1 file changed, 83 insertions(+), 5 deletions(-)

diff --git a/source/javascripts/app/_lang.js b/source/javascripts/app/_lang.js
index c3b48ed..79d3903 100644
--- a/source/javascripts/app/_lang.js
+++ b/source/javascripts/app/_lang.js
@@ -40,6 +40,83 @@ under the License.
     }
   }
 
+  // parseURL and stringifyURL are from https://github.com/sindresorhus/query-string
+  // MIT licensed
+  // https://github.com/sindresorhus/query-string/blob/7bee64c16f2da1a326579e96977b9227bf6da9e6/license
+  function parseURL(str) {
+    if (typeof str !== 'string') {
+      return {};
+    }
+
+    str = str.trim().replace(/^(\?|#|&)/, '');
+
+    if (!str) {
+      return {};
+    }
+
+    return str.split('&').reduce(function (ret, param) {
+      var parts = param.replace(/\+/g, ' ').split('=');
+      var key = parts[0];
+      var val = parts[1];
+
+      key = decodeURIComponent(key);
+      // missing `=` should be `null`:
+      // http://w3.org/TR/2012/WD-url-20120524/#collect-url-parameters
+      val = val === undefined ? null : decodeURIComponent(val);
+
+      if (!ret.hasOwnProperty(key)) {
+        ret[key] = val;
+      } else if (Array.isArray(ret[key])) {
+        ret[key].push(val);
+      } else {
+        ret[key] = [ret[key], val];
+      }
+
+      return ret;
+    }, {});
+  };
+
+  function stringifyURL(obj) {
+    return obj ? Object.keys(obj).sort().map(function (key) {
+      var val = obj[key];
+
+      if (Array.isArray(val)) {
+        return val.sort().map(function (val2) {
+          return encodeURIComponent(key) + '=' + encodeURIComponent(val2);
+        }).join('&');
+      }
+
+      return encodeURIComponent(key) + '=' + encodeURIComponent(val);
+    }).join('&') : '';
+  };
+
+  // gets the language set in the query string
+  function getLanguageFromQueryString() {
+    if (location.search.length >= 1) {
+      var language = parseURL(location.search).language
+      if (language) {
+        return language;
+      } else if (jQuery.inArray(location.search.substr(1), languages) != -1) {
+        return location.search.substr(1);
+      }
+    }
+
+    return false;
+  }
+
+  // returns a new query string with the new language in it
+  function generateNewQueryString(language) {
+    if (location.search.length >= 1) {
+      var url = parseURL(location.search);
+      if (url.language) {
+        url.language = language;
+        return stringifyURL(url);
+      } else {
+        return language
+      }
+    }
+  }
+
   // if a button is clicked, add the state to the history
   function pushURL(language) {
     if (!history) { return; }
@@ -47,7 +124,7 @@ under the License.
     if (hash) {
       hash = hash.replace(/^#+/, '');
     }
-    history.pushState({}, '', '?' + language + '#' + hash);
+    history.pushState({}, '', '?' + generateNewQueryString(language) + '#' + hash);
 
     // save language as next default
     localStorage.setItem("language", language);
@@ -58,11 +135,12 @@ under the License.
 
     languages = l;
 
-    if ((location.search.substr(1) !== "") && (jQuery.inArray(location.search.substr(1), languages)) != -1) {
+    var presetLanguage = getLanguageFromQueryString();
+    if (presetLanguage) {
       // the language is in the URL, so use that language!
-      activateLanguage(location.search.substr(1));
+      activateLanguage(presetLanguage);
 
-      localStorage.setItem("language", location.search.substr(1));
+      localStorage.setItem("language", presetLanguage);
     } else if ((defaultLanguage !== null) && (jQuery.inArray(defaultLanguage, languages) != -1)) {
       // the language was the last selected one saved in localstorage, so use that language!
       activateLanguage(defaultLanguage);
@@ -81,7 +159,7 @@ under the License.
       return false;
     });
     window.onpopstate = function() {
-      activateLanguage(window.location.search.substr(1));
+      activateLanguage(getLanguageFromQueryString());
     };
   });
 })(window);