add debounce service, with mock tests

src/kibana/services/debounce.js

@@ -0,0 +1,49 @@
+// Debounce service, angularized version of lodash debounce
+// borrowed heavily from https://github.com/shahata/angular-debounce
+
+define(function (require) {
+  var _ = require('lodash');
+  var module = require('modules').get('kibana');
+
+  module.service('debounce', ['$timeout', function ($timeout) {
+    return function (func, wait, options) {
+      var timeout, args, context, result;
+      options = _.defaults(options, {
+        leading: false,
+        trailing: true
+      });
+
+      function debounce() {
+        context = this;
+        args = arguments;
+
+        var later = function () {
+          timeout = null;
+          if (!options.leading || options.trailing) {
+            result = func.apply(context, args);
+          }
+        };
+
+        var callNow = options.leading && !timeout;
+
+        if (timeout) {
+          $timeout.cancel(timeout);
+        }
+        timeout = $timeout(later, wait);
+
+        if (callNow) {
+          result = func.apply(context, args);
+        }
+
+        return result;
+      }
+
+      debounce.cancel = function () {
+        $timeout.cancel(timeout);
+        timeout = null;
+      };
+
+      return debounce;
+    };
+  }]);
+});

test/unit/index.html

@@ -98,6 +98,7 @@
           'specs/filters/rison',
           'specs/filters/short_dots',
           'specs/filters/start_from',
+          'specs/services/debounce',
           'specs/services/storage',
           'specs/services/persisted_log',
           'specs/services/url',

test/unit/specs/services/debounce.js

@@ -0,0 +1,7 @@
+define(function (require) {
+  describe('debounce service', function () {
+    it('should delay execution');
+    it('should fire on leading edge');
+    it('should only fire on leading edge');
+  });
+});