ace Editor uses Document held by Buffer.

spec/atom/app-spec.coffee

@@ -23,4 +23,4 @@ describe "App", ->
       expect(newWindow.editor).toBeDefined()
       expect(newWindow.editor.buffer).toBeDefined()
       expect(newWindow.editor.buffer.url).toEqual filePath
-      expect(newWindow.editor.buffer.text).toEqual fs.read(filePath)
+      expect(newWindow.editor.buffer.getText()).toEqual fs.read(filePath)

spec/atom/buffer-spec.coffee

@@ -6,4 +6,4 @@ describe 'Buffer', ->
     it "loads the contents of the given url", ->
       filePath = require.resolve 'fixtures/sample.txt'
       buffer = new Buffer filePath
-      expect(buffer.text).toBe fs.read(filePath)
+      expect(buffer.getText()).toBe fs.read(filePath)

spec/atom/editor-spec.coffee

@@ -17,10 +17,10 @@ describe "Editor", ->
   describe "constructor", ->
     it "attaches itself to the #main element and opens a buffer with the given url", ->
       expect(editor.buffer.url).toEqual filePath
-      expect(mainDiv.children('#editor').html()).not.toBe ''
+      expect(mainDiv.children('.editor').html()).not.toBe ''
 
     it "populates the editor with the contents of the buffer", ->
-      expect(editor.aceEditor.getSession().getValue()).toBe editor.buffer.text
+      expect(editor.aceEditor.getSession().getValue()).toBe editor.buffer.getText()
 
   describe 'destroy', ->
     it 'destroys the ace editor and removes #editor from the dom.', ->
@@ -28,7 +28,10 @@ describe "Editor", ->
 
       editor.destroy()
       expect(editor.aceEditor.destroy).toHaveBeenCalled()
-      expect(mainDiv.children('#editor').length).toBe 0
+      expect(mainDiv.children('.editor').length).toBe 0
 
   describe "when the text is changed via the ace editor", ->
     it "updates the buffer text", ->
+      expect(editor.buffer.getText()).not.toMatch /^.ooo/
+      editor.aceEditor.getSession().insert {row: 0, column: 1}, 'ooo'
+      expect(editor.buffer.getText()).toMatch /^.ooo/

src/atom/buffer.coffee

@@ -1,9 +1,14 @@
 fs = require 'fs'
+{Document} = require 'ace/document'
 
 module.exports =
 class Buffer
-  text: null
+  aceDocument: null
   url: null
 
   constructor: (@url) ->
-    @text = fs.read @url
+    @aceDocument = new Document fs.read(@url)
+
+  getText: ->
+    @aceDocument.getValue()
+

src/atom/editor.coffee

@@ -1,4 +1,5 @@
 Buffer = require 'buffer'
+{EditSession} = require 'ace/edit_session'
 ace = require 'ace/ace'
 $ = require 'jquery'
 
@@ -10,14 +11,17 @@ class Editor
   constructor: (url) ->
     @buffer = new Buffer(url)
     @buildAceEditor()
-    @setText @buffer.text
-
-  setText: (text) ->
-    @aceEditor.getSession().setValue @buffer.text
 
   buildAceEditor: ->
-    $('#main').append("<div id='editor'>")
-    @aceEditor = ace.edit 'editor'
+    editorElement = $("<div class='editor'>")
+    $('#main').append(editorElement)
+    @aceEditor = ace.edit editorElement[0]
+    @aceEditor.setSession(new EditSession(@buffer.aceDocument))
+    @aceEditor.setTheme(require "ace/theme/twilight")
+    window.x = this
+
+  getAceSession: ->
+    @aceEditor.getSession()
 
   destroy: ->
     @aceEditor.destroy()