Initial commit

lib/assets/javascripts/dashboard/data/background-polling/poller.js

@@ -0,0 +1,83 @@
+const _ = require('underscore');
+/*
+ * Periodically fetches a model/collection. It waits for ongoing
+ * fetch requests before trying to fetch again. A stop condition
+ * can be specified.
+ *
+ * Usage example:
+ *
+ * var poller = new Poller(model, {
+ *   interval: 1000,
+ *   stopWhen: function (model) {
+ *     return model.get('state') === 'completed';
+ *   }
+ * });
+ *
+ * poller.start();
+ *
+ * // ...
+ *
+ * poller.stop();
+ *
+ */
+const Poller = function (model, options) {
+  this.model = model;
+  this.numberOfRequests = 0;
+  this.polling = false;
+  this.interval = options['interval'];
+
+  if (typeof this.interval !== 'function') {
+    this.interval = function () { return options['interval']; };
+  }
+
+  this.stopWhen = options['stopWhen'];
+  this.error = options['error'];
+  this.autoStart = options['autoStart'];
+
+  if (this.autoStart) {
+    this.start();
+  }
+};
+
+Poller.prototype.start = function () {
+  if (this.timeout) {
+    return;
+  }
+
+  this._scheduleFetch();
+};
+
+Poller.prototype._scheduleFetch = function () {
+  this.timeout = setTimeout(this._fetch.bind(this), this.interval(this.numberOfRequests));
+};
+
+Poller.prototype._fetch = function () {
+  if (!this.polling) {
+    this.polling = true;
+    this.model.fetch({
+      success: () => {
+        this.polling = false;
+        this.numberOfRequests++;
+        if (this._continuePolling()) {
+          this._scheduleFetch();
+        }
+      },
+      error: (e) => {
+        _.isFunction(this.error) && this.error(this.model);
+      }
+    });
+  }
+};
+
+Poller.prototype._continuePolling = function () {
+  return !this.stopWhen ||
+    (_.isFunction(this.stopWhen) && !this.stopWhen(this.model));
+};
+
+Poller.prototype.stop = function () {
+  this.polling = false;
+  clearTimeout(this.timeout);
+  delete this.timeout;
+};
+
+module.exports = Poller;