Initial commit

lib/assets/javascripts/builder/data/background-importer/poller.js

@@ -0,0 +1,83 @@
+var _ = 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();
+ *
+ */
+var Poller = function (model, opts) {
+  this.model = model;
+  this.numberOfRequests = 0;
+  this.polling = false;
+  this.interval = opts.interval;
+  if (typeof this.interval !== 'function') {
+    this.interval = function () { return opts.interval; };
+  }
+  this.stopWhen = opts.stopWhen;
+  this.error = opts.error;
+  this.autoStart = opts.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 () {
+  var self = this;
+  if (!self.polling) {
+    self.polling = true;
+    self.model.fetch({
+      success: function () {
+        self.polling = false;
+        self.numberOfRequests++;
+        if (self._continuePolling()) {
+          self._scheduleFetch();
+        }
+      },
+      error: function (e) {
+        _.isFunction(self.error) && self.error(self.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;