From 70acf7c24f8578c177702d47f8c31b4618ad4173 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ale=C5=A1=20Smodi=C5=A1?= <aless@guru.si>
Date: Wed, 23 Sep 2015 18:27:51 +0200
Subject: Add support for loading static web resources through standard AJAX,
 implementing loading of a programming language data.

---
 js/codeq/comms.js | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

(limited to 'js/codeq/comms.js')

diff --git a/js/codeq/comms.js b/js/codeq/comms.js
index b04a2fc..140e48e 100644
--- a/js/codeq/comms.js
+++ b/js/codeq/comms.js
@@ -1,4 +1,8 @@
 (function () {
+    // ================================================================================
+    // Errors generated in this module
+    // ================================================================================
+
     var BinaryMessageError = function (message) {
         var e = new Error(message);
         this.message = message;
@@ -22,6 +26,10 @@
     MessageParseError.prototype = new Error();
     MessageParseError.prototype.name = 'MessageParseError';
 
+    // ================================================================================
+    // engine.io communication support functions (long polling / websocket communication)
+    // ================================================================================
+
     var currentTID = 0, // transaction ID of the next message
         sid = null, // session ID, changes after each successful initial login
         socket = null,
@@ -152,6 +160,57 @@
             }
         };
 
+    // ================================================================================
+    // AJAX communication support functions (loading of static web resources)
+    // ================================================================================
+
+    var languageCache = {},// language defs, keyed by language identifier
+        problemCache = {},// problem cache, 3-level, keyed by: language, problem group, and problem identifier
+        ajaxGet = function (url) {
+            return Q.Promise(function (resolve, reject, notify) {
+                $.ajax({
+                    dataType: 'application/json',
+                    type: 'GET',
+                    url: url,
+                    error: function (jqXHR, textStatus, errorThrown) {
+                        codeq.log.error('AJAX to ' + url + ' failed with status ' + textStatus, errorThrown);
+                        reject(errorThrown || new Error(textStatus));
+                    },
+                    success: function (data, textStatus, jqXHR) {
+                        var s;
+                        if ((typeof data === 'object') && (data !== null)) {
+                            // got a JSON
+                            resolve(data);
+                        }
+                        else {
+                            s = 'AJAX to ' + url + ' did not result in a JSON object';
+                            if (typeof data === 'string') {
+                                s += ', the response was:\n' + data;
+                            }
+                            else if (typeof textStatus === 'string') {
+                                s += ', status was: ' + textStatus;
+                            }
+                            codeq.log.error(s);
+                            reject(new Error(s));
+                        }
+                    }
+                });
+            });
+        },
+        ajaxPrefix;
+
+    ajaxPrefix = location.pathname;
+    if (!ajaxPrefix) ajaxPrefix = '/';
+    else if (ajaxPrefix[ajaxPrefix.length - 1] !== '/') {
+        ajaxPrefix = ajaxPrefix.split('/');
+        ajaxPrefix[ajaxPrefix.length - 1] = '';
+        ajaxPrefix = ajaxPrefix.join('/');
+    }
+
+    // ================================================================================
+    // This module's API methods
+    // ================================================================================
+
     codeq.comms = {
         'connect': function () {
             var deferred = Q.defer();
@@ -320,6 +379,33 @@
                     }
                 }
             }
+        },
+
+        'getLanguageDef': function (identifier) {
+            var x = languageCache[identifier];
+            if ((typeof x === 'object') && (x !== null)) {
+                // already defined
+                if (typeof x.then === 'function') {
+                    // it's a promise, it means it's not resolved yet
+                    return x;
+                }
+                else {
+                    // return a resolved promise with the cached value
+                    return Q(x);
+                }
+            }
+            x = ajaxGet(ajaxPrefix + identifier + '/language.json').then(
+                function getLanguageDefSuccess(data) {
+                    languageCache[identifier] = data;
+                    return data; // proxy further
+                },
+                function getLanguageDefFail(exception) {
+                    delete languageCache[identifier];
+                    throw exception || new Error('Could not load language ' + identifer); // proxy further
+                }
+            );
+            languageCache[identifier] = x;
+            return x;
         }
     };
 })();
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