JI-1059 Add support for storing and resubmitting offline results

(cherry picked from commit cd869f8400)

h5p.classes.php

@@ -2007,7 +2007,8 @@ class H5PCore {
     'js/h5p-x-api.js',
     'js/h5p-content-type.js',
     'js/h5p-confirmation-dialog.js',
-    'js/h5p-action-bar.js'
+    'js/h5p-action-bar.js',
+    'js/request-queue.js',
   );
   public static $adminScripts = array(
     'js/jquery.js',
@@ -3479,6 +3480,9 @@ class H5PCore {
       'licenseExtras' => $this->h5pF->t('License Extras'),
       'changes' => $this->h5pF->t('Changelog'),
       'contentCopied' => $this->h5pF->t('Content is copied to the clipboard'),
+      'connectionLost' => $this->h5pF->t('Connection lost. Results will be stored and sent when you regain connection.'),
+      'connectionReestablished' => $this->h5pF->t('Connection reestablished.'),
+      'resubmitScores' => $this->h5pF->t('Attempting to submit stored results.'),
     );
   }
 }

js/h5p.js

@@ -214,6 +214,9 @@ H5P.init = function (target) {
       }
     });
 
+    // Handle requests that failed while the user was offline
+    H5P.offlineRequestQueue.resumeQueue();
+
     // Listen for xAPI events.
     H5P.on(instance, 'xAPI', H5P.xAPICompletedListener);
 
@@ -2065,13 +2068,17 @@ H5P.setFinished = function (contentId, score, maxScore, time) {
     };
 
     // Post the results
-    H5P.jQuery.post(H5PIntegration.ajax.setFinished, {
+    const data = {
       contentId: contentId,
       score: score,
       maxScore: maxScore,
       opened: toUnix(H5P.opened[contentId]),
       finished: toUnix(new Date()),
       time: time
+    };
+    H5P.jQuery.post(H5PIntegration.ajax.setFinished, data)
+      .fail(function () {
+        H5P.offlineRequestQueue.add(H5PIntegration.ajax.setFinished, data);
       });
   }
 };

js/request-queue.js

@@ -0,0 +1,216 @@
+/**
+ * Queue requests and handle them at your convenience
+ *
+ * @type {RequestQueue}
+ */
+H5P.RequestQueue = (function ($) {
+  /**
+   * A queue for requests, will be automatically processed when regaining connection
+   *
+   * @param {string} itemName Name that requests will be stored as in local storage
+   * @param {string} eventName Name of event that will be triggered when a new item is added to the queue
+   * @constructor
+   */
+  const RequestQueue = function (itemName, eventName) {
+    this.processingQueue = false;
+
+    this.itemName = itemName;
+    this.eventName = eventName;
+
+    // Initialize listener for when requests are added to queue
+    window.addEventListener('offline', this.updateOnlineStatus.bind(this));
+    window.addEventListener('online', this.updateOnlineStatus.bind(this));
+  };
+
+  /**
+   * Add request to queue
+   *
+   * @param {string} url
+   * @param {Object} data
+   * @returns {boolean}
+   */
+  RequestQueue.prototype.add = function (url, data) {
+    if (!window.localStorage) {
+      return false;
+    }
+
+    let storedStatements = this.getStoredRequests();
+    if (!storedStatements) {
+      storedStatements = [];
+    }
+
+    storedStatements.push({
+      url: url,
+      data: data,
+    });
+
+    window.localStorage.setItem(this.itemName, JSON.stringify(storedStatements));
+
+    H5P.externalDispatcher.trigger(this.eventName);
+    return true;
+  };
+
+  /**
+   * Get stored requests
+   *
+   * @returns {boolean|Array} Stored requests
+   */
+  RequestQueue.prototype.getStoredRequests = function () {
+    if (!window.localStorage) {
+      return false;
+    }
+
+    const item = window.localStorage.getItem(this.itemName);
+    if (!item) {
+      return [];
+    }
+
+    return JSON.parse(item);
+  };
+
+  /**
+   * Clear stored requests
+   *
+   * @returns {boolean} True if the storage was successfully cleared
+   */
+  RequestQueue.prototype.clear = function () {
+    if (!window.localStorage) {
+      return false;
+    }
+
+    window.localStorage.removeItem(this.itemName);
+    return true;
+  };
+
+  /**
+   * Start processing of requests queue
+   */
+  RequestQueue.prototype.resumeQueue = function () {
+    // Not supported
+    if (!H5PIntegration || !window.navigator || !window.localStorage) {
+      return;
+    }
+
+    // Already processing
+    if (this.processingQueue) {
+      return;
+    }
+
+    // Application is offline, re-send when we detect a connection
+    if (!window.navigator.onLine) {
+      return;
+    }
+
+    // We're online, attempt to send queued requests
+    const queue = this.getStoredRequests();
+    const queueLength = queue.length;
+
+    // Clear storage, failed requests will be re-added
+    this.clear();
+
+    // No items left in queue
+    if (!queueLength) {
+      return;
+    }
+
+    // Make sure requests are not changed while they're being handled
+    this.processingQueue = true;
+
+    // Process queue in original order
+    this.processQueue(queue);
+  };
+
+  /**
+   * Process first item in the request queue
+   *
+   * @param {Array} queue Request queue
+   */
+  RequestQueue.prototype.processQueue = function (queue) {
+    if (!queue.length) {
+      return;
+    }
+
+    // Make sure the requests are processed in a FIFO order
+    const request = queue.shift();
+
+    const self = this;
+    $.post(request.url, request.data)
+      .fail(self.onQueuedRequestFail.bind(self, request))
+      .always(self.onQueuedRequestProcessed.bind(self, queue))
+  };
+
+  /**
+   * Request fail handler
+   *
+   * @param {Object} request
+   */
+  RequestQueue.prototype.onQueuedRequestFail = function (request) {
+    // Queue the failed request again if we're offline
+    if (!window.navigator.onLine) {
+      this.add(request.url, request.data);
+    }
+  };
+
+  RequestQueue.prototype.onQueuedRequestProcessed = function (queue) {
+    if (queue.length) {
+      this.processQueue(queue);
+      return;
+    }
+
+    // Finished processing this queue
+    this.processingQueue = false;
+    if (!window.navigator.onLine) {
+      return;
+    }
+
+    // Process next queue if items were added while processing current queue
+    const requestQueue = this.getStoredRequests();
+    if (requestQueue.length) {
+      this.resumeQueue();
+    }
+  };
+
+  /**
+   * Display toast message on the first content of current page
+   *
+   * @param {string} msg Message to display
+   */
+  RequestQueue.prototype.displayToastMessage = function (msg) {
+    H5P.attachToastTo(
+      H5P.jQuery('.h5p-content:first')[0],
+      msg,
+      {
+        position: {
+          horizontal: 'centered',
+          vertical: 'centered',
+          noOverflowX: true
+        }
+      }
+    );
+  };
+
+  /**
+   * Update online status
+   */
+  RequestQueue.prototype.updateOnlineStatus = function () {
+    // Lost connection
+    if (!window.navigator.onLine) {
+      this.displayToastMessage(H5P.t('connectionLost'));
+      return;
+    }
+
+    // Re-connected, resume processing of queue
+    let message = H5P.t('connectionReestablished');
+    const requestQueue = this.getStoredRequests();
+    if (requestQueue.length) {
+      message += ' ' + H5P.t('resubmitScores');
+      this.resumeQueue();
+    }
+
+    this.displayToastMessage(message);
+  };
+
+  return RequestQueue;
+})(H5P.jQuery);
+
+H5P.offlineRequestQueue = new H5P.RequestQueue('requestQueue', 'requestQueued');