ui: Expands create-listeners API to allow recursive and functions

1. Adds a Listeners class, which lets us...
2. Add Listeners recursively. So you can
createListeners().add(createListeners())
3. Also add the ability to `.add` as a plain function

This moves the entire idea more towards a generic teardown utility

ui-v2/app/utils/dom/create-listeners.js

@@ -1,32 +1,40 @@
-export default function(listeners = []) {
-  const add = function(target, event, handler) {
-    let addEventListener = 'addEventListener';
-    let removeEventListener = 'removeEventListener';
-    if (typeof target[addEventListener] === 'undefined') {
-      addEventListener = 'on';
-      removeEventListener = 'off';
+class Listeners {
+  constructor(listeners = []) {
+    this.listeners = listeners;
+  }
+  add(target, event, handler) {
+    let remove;
+    if (typeof target === 'function') {
+      remove = target;
+    } else if (target instanceof Listeners) {
+      remove = target.remove.bind(target);
+    } else {
+      let addEventListener = 'addEventListener';
+      let removeEventListener = 'removeEventListener';
+      if (typeof target[addEventListener] === 'undefined') {
+        addEventListener = 'on';
+        removeEventListener = 'off';
+      }
+      target[addEventListener](event, handler);
+      remove = function() {
+        target[removeEventListener](event, handler);
+        return handler;
+      };
     }
-    target[addEventListener](event, handler);
-    const remove = function() {
-      target[removeEventListener](event, handler);
-      return handler;
+    this.listeners.push(remove);
+    return () => {
+      const pos = this.listeners.findIndex(function(item) {
+        return item === remove;
+      });
+      return this.listeners.splice(pos, 1)[0]();
     };
-    listeners.push(remove);
-    return remove;
-  };
-  // TODO: Allow passing of a 'listener remove' in here
-  // call it, find in the array and remove
-  // Post-thoughts, pretty sure this is covered now by returning the remove
-  // function above, use-case for wanting to use this method to remove individual
-  // listeners is probably pretty limited, this method itself could be easily implemented
-  // from the outside also, but I suppose its handy to keep here
-  const remove = function() {
-    const handlers = listeners.map(item => item());
-    listeners.splice(0, listeners.length);
+  }
+  remove() {
+    const handlers = this.listeners.map(item => item());
+    this.listeners.splice(0, this.listeners.length);
     return handlers;
-  };
-  return {
-    add: add,
-    remove: remove,
-  };
+  }
+}
+export default function(listeners = []) {
+  return new Listeners(listeners);
 }

ui-v2/tests/unit/utils/dom/create-listeners-test.js

@@ -9,7 +9,7 @@ test('it has add and remove methods', function(assert) {
   assert.ok(typeof listeners.add === 'function');
   assert.ok(typeof listeners.remove === 'function');
 });
-test('add returns an remove function', function(assert) {
+test('add returns a remove function', function(assert) {
   const listeners = createListeners();
   const remove = listeners.add({
     addEventListener: function() {},
@@ -64,6 +64,30 @@ test('listeners are removed on remove', function(assert) {
   assert.ok(stub.calledOnce);
   assert.ok(stub.calledWith(name, handler));
 });
+test('listeners as functions are removed on remove', function(assert) {
+  const listeners = createListeners();
+  const stub = this.stub();
+  const remove = listeners.add(stub);
+  remove();
+  assert.ok(stub.calledOnce);
+});
+test('listeners as other listeners are removed on remove', function(assert) {
+  const listeners = createListeners();
+  const listeners2 = createListeners();
+  const stub = this.stub();
+  listeners2.add(stub);
+  const remove = listeners.add(listeners2);
+  remove();
+  assert.ok(stub.calledOnce);
+});
+test('listeners as functions of other listeners are removed on remove', function(assert) {
+  const listeners = createListeners();
+  const listeners2 = createListeners();
+  const stub = this.stub();
+  const remove = listeners.add(listeners2.add(stub));
+  remove();
+  assert.ok(stub.calledOnce);
+});
 test('remove returns the original handler', function(assert) {
   const listeners = createListeners();
   const target = {