Finish refactoring to OO style.

lib/rga.js

@@ -443,29 +443,15 @@ RGA.AceEditorRGA = function AceEditorRga(id, editor, history, queue) {
   editor.setValue(this._lastText, -1);
 
   // The flow of operations is (unavoidably) bidirectional. First, when Ace
-  // notifies us of an edit, use _takeUserEdits to fold those changes into the
-  // RGA.
+  // notifies us of an edit, fold those changes into the RGA.
   var self = this;
   this._changeCallback = function () { self._takeUserEdits() };
   editor.getSession().on("change", this._changeCallback);
 
-  // Now for the other direction. Here we replace the callback that
-  // receives changes from other RGAs.
-  this.downstream = function rgaToEditor(source, op) {
-    // Always check for new user edits *before* accepting ops from the internet.
-    // That way, _takeUserEdits() knows that all differences between
-    // `_lastText` and `editor.getValue()` are the result of new user input.
-    self._takeUserEdits();
-
-    // Since applyOpToEditor uses the RGA to look up the location of the
-    // inserted/deleted character in the document, and determine whether it has in fact
-    // already been inserted/deleted, we have to call that first,
-    // before modifying the RGA.
-    self._applyOpToEditor(op);  // first update the editor
-    self._downstream.call(self, source, op);  // then update the RGA
-    self._lastText = self.editor.getValue();
-
-    self._assertInSync({op: op});
+  // Now for the other direction. Replace the callback that receives changes
+  // from other RGAs with a new one that also updates the editor.
+  this.downstream = function (source, op) {
+    self._customDownstream(source, op);
   };
   this.downstream._id = id;
 };
@@ -551,6 +537,23 @@ Object.assign(RGA.AceEditorRGA.prototype, {
       });
       break;
     }
+  },
+
+  _customDownstream: function (source, op) {
+    // Always check for new user edits *before* accepting ops from the internet.
+    // That way, _takeUserEdits() knows that all differences between
+    // `_lastText` and `editor.getValue()` are the result of new user input.
+    this._takeUserEdits();
+
+    // Since applyOpToEditor uses the RGA to look up the location of the
+    // inserted/deleted character in the document, and determine whether it has in fact
+    // already been inserted/deleted, we have to call that first,
+    // before modifying the RGA.
+    this._applyOpToEditor(op);  // first update the editor
+    this._downstream(source, op);  // then update the RGA
+    this._lastText = this.editor.getValue();
+
+    this._assertInSync({op: op});
   }
 });