Introduce LanguageMode wrapper for Ace modes as a foundation of our own modes

LanguageMode is the central point for all language-specific behavior associated with an EditSession. There is one LanguageMode instance per EditSession. LanguageMode has access to the EditSession and its TokenizedBuffer, and in reverse the EditSession, DisplayBuffer, and TokenizedBuffer also make use of LanguageMode. This is a bit incestuous, but I think it's okay because you can think of LanguageMode as a swappable strategy object that governs language-specific aspects of that constellation of objects.

src/app/ace-adaptor.coffee

@@ -4,8 +4,8 @@ module.exports =
 class AceAdaptor
   foldWidgets: {}
 
-  constructor: (@tokenizedBuffer) ->
-    @buffer = @tokenizedBuffer.buffer
+  constructor: (@editSession) ->
+    @buffer = @editSession.buffer
 
   getLine: (bufferRow) ->
     @buffer.lineForRow(bufferRow)
@@ -14,7 +14,7 @@ class AceAdaptor
     @buffer.getLineCount()
 
   $findClosingBracket: (bracketType, bufferPosition) ->
-    @tokenizedBuffer.findClosingBracket([bufferPosition.row, bufferPosition.column - 1])
+    @editSession.tokenizedBuffer.findClosingBracket([bufferPosition.row, bufferPosition.column - 1])
 
   indentRows: (startRow, endRow, indentString) ->
     for row in [startRow..endRow]
@@ -25,4 +25,4 @@ class AceAdaptor
     @buffer.change(range, text)
 
   findMatchingBracket: ({row, column}) ->
-    @tokenizedBuffer.findOpeningBracket([row, column])
+    @editSession.tokenizedBuffer.findOpeningBracket([row, column])

src/app/display-buffer.coffee

@@ -12,6 +12,7 @@ module.exports =
 class DisplayBuffer
   @idCounter: 1
   lineMap: null
+  languageMode: null
   tokenizedBuffer: null
   activeFolds: null
   foldsById: null
@@ -19,7 +20,9 @@ class DisplayBuffer
 
   constructor: (@buffer, options={}) ->
     @id = @constructor.idCounter++
-    @tokenizedBuffer = new TokenizedBuffer(@buffer, options.tabText ? '  ')
+    options.tabText ?= '  '
+    @languageMode = options.languageMode
+    @tokenizedBuffer = new TokenizedBuffer(@buffer, options)
     @softWrapColumn = options.softWrapColumn ? Infinity
     @activeFolds = {}
     @foldsById = {}
@@ -51,14 +54,14 @@ class DisplayBuffer
 
   foldAll: ->
     for currentRow in [0..@buffer.getLastRow()]
-      [startRow, endRow] = @tokenizedBuffer.rowRangeForFoldAtBufferRow(currentRow) ? []
+      [startRow, endRow] = @languageMode.rowRangeForFoldAtBufferRow(currentRow) ? []
       continue unless startRow?
 
       @createFold(startRow, endRow)
 
   toggleFoldAtBufferRow: (bufferRow) ->
     for currentRow in [bufferRow..0]
-      [startRow, endRow] = @tokenizedBuffer.rowRangeForFoldAtBufferRow(currentRow) ? []
+      [startRow, endRow] = @languageMode.rowRangeForFoldAtBufferRow(currentRow) ? []
       continue unless startRow? and startRow <= bufferRow <= endRow
 
       if fold = @largestFoldStartingAtBufferRow(startRow)
@@ -209,7 +212,7 @@ class DisplayBuffer
     startBufferColumn = 0
     while currentBufferRow <= endBufferRow
       screenLine = @tokenizedBuffer.lineForScreenRow(currentBufferRow)
-      screenLine.foldable = @tokenizedBuffer.isBufferRowFoldable(currentBufferRow)
+      screenLine.foldable = @languageMode.isBufferRowFoldable(currentBufferRow)
 
       if fold = @largestFoldStartingAtBufferRow(currentBufferRow)
         screenLine = screenLine.copy()

src/app/edit-session.coffee

@@ -1,6 +1,7 @@
 Point = require 'point'
 Buffer = require 'buffer'
 Anchor = require 'anchor'
+LanguageMode = require 'language-mode'
 DisplayBuffer = require 'display-buffer'
 Cursor = require 'cursor'
 Selection = require 'selection'
@@ -22,6 +23,7 @@ class EditSession
 
   scrollTop: 0
   scrollLeft: 0
+  languageMode: null
   displayBuffer: null
   anchors: null
   anchorRanges: null
@@ -34,7 +36,8 @@ class EditSession
   constructor: ({@project, @buffer, @tabText, @autoIndent, @softTabs, @softWrap}) ->
     @id = @constructor.idCounter++
     @softTabs ?= true
-    @displayBuffer = new DisplayBuffer(@buffer, { @tabText })
+    @languageMode = new LanguageMode(this, @buffer.getExtension())
+    @displayBuffer = new DisplayBuffer(@buffer, { @languageMode, @tabText })
     @tokenizedBuffer = @displayBuffer.tokenizedBuffer
     @anchors = []
     @anchorRanges = []
@@ -242,17 +245,17 @@ class EditSession
     @displayBuffer.largestFoldStartingAtScreenRow(screenRow)
 
   indentationForRow: (row) ->
-    @tokenizedBuffer.indentationForRow(row)
+    @languageMode.indentationForRow(row)
 
   autoIndentTextAfterBufferPosition: (text, bufferPosition) ->
     return { text } unless @autoIndent
-    @tokenizedBuffer.autoIndentTextAfterBufferPosition(text, bufferPosition)
+    @languageMode.autoIndentTextAfterBufferPosition(text, bufferPosition)
 
   autoOutdentBufferRow: (bufferRow) ->
-    @tokenizedBuffer.autoOutdentBufferRow(bufferRow)
+    @languageMode.autoOutdentBufferRow(bufferRow)
 
   toggleLineCommentsInRange: (range) ->
-    @tokenizedBuffer.toggleLineCommentsInRange(range)
+    @languageMode.toggleLineCommentsInRange(range)
 
   mutateSelectedText: (fn) ->
     @transact => fn(selection) for selection in @getSelections()

src/app/language-mode.coffee

@@ -0,0 +1,60 @@
+AceAdaptor = require 'ace-adaptor'
+Range = require 'range'
+
+module.exports =
+class LanguageMode
+  constructor: (@editSession) ->
+    @buffer = @editSession.buffer
+    @aceMode = @requireAceMode()
+    @aceAdaptor = new AceAdaptor(@editSession)
+
+  requireAceMode: (fileExtension) ->
+    modeName = switch @editSession.buffer.getExtension()
+      when 'js' then 'javascript'
+      when 'coffee' then 'coffee'
+      when 'rb', 'ru' then 'ruby'
+      when 'c', 'h', 'cpp' then 'c_cpp'
+      when 'html', 'htm' then 'html'
+      when 'css' then 'css'
+      when 'java' then 'java'
+      when 'xml' then 'xml'
+      else 'text'
+    new (require("ace/mode/#{modeName}").Mode)
+
+  toggleLineCommentsInRange: (range) ->
+    range = Range.fromObject(range)
+    @aceMode.toggleCommentLines(@tokenizedBuffer.stateForRow(range.start.row), @aceAdaptor, range.start.row, range.end.row)
+
+  isBufferRowFoldable: (bufferRow) ->
+    @aceMode.foldingRules?.getFoldWidget(@aceAdaptor, null, bufferRow) == "start"
+
+  rowRangeForFoldAtBufferRow: (bufferRow) ->
+    if aceRange = @aceMode.foldingRules?.getFoldWidgetRange(@aceAdaptor, null, bufferRow)
+      [aceRange.start.row, aceRange.end.row]
+    else
+      null
+
+  indentationForRow: (row) ->
+    state = @tokenizedBuffer.stateForRow(row)
+    previousRowText = @buffer.lineForRow(row - 1)
+    @aceMode.getNextLineIndent(state, previousRowText, @editSession.tabText)
+
+  autoIndentTextAfterBufferPosition: (text, bufferPosition) ->
+    { row, column} = bufferPosition
+    state = @tokenizedBuffer.stateForRow(row)
+    lineBeforeCursor = @buffer.lineForRow(row)[0...column]
+    if text[0] == "\n"
+      indent = @aceMode.getNextLineIndent(state, lineBeforeCursor, @editSession.tabText)
+      text = text[0] + indent + text[1..]
+    else if @aceMode.checkOutdent(state, lineBeforeCursor, text)
+      shouldOutdent = true
+
+    {text, shouldOutdent}
+
+  autoOutdentBufferRow: (bufferRow) ->
+    state = @tokenizedBuffer.stateForRow(bufferRow)
+    @aceMode.autoOutdent(state, @aceAdaptor, bufferRow)
+
+  getLineTokens: (line, state) ->
+    {tokens, state} = @aceMode.getTokenizer().getLineTokens(line, state)
+

src/app/tokenized-buffer.coffee

@@ -4,70 +4,21 @@ EventEmitter = require 'event-emitter'
 Token = require 'token'
 Range = require 'range'
 Point = require 'point'
-AceAdaptor = require 'ace-adaptor'
 
 module.exports =
 class TokenizedBuffer
   @idCounter: 1
 
+  languageMode: null
   buffer: null
-  aceMode: null
   aceAdaptor: null
   screenLines: null
 
-  constructor: (@buffer, @tabText) ->
+  constructor: (@buffer, { @languageMode, @tabText }) ->
+    @languageMode.tokenizedBuffer = this
     @id = @constructor.idCounter++
-    @aceMode = @requireAceMode()
     @screenLines = @buildScreenLinesForRows('start', 0, @buffer.getLastRow())
     @buffer.on "change.tokenized-buffer#{@id}", (e) => @handleBufferChange(e)
-    @aceAdaptor = new AceAdaptor(this)
-
-  requireAceMode: ->
-    modeName = switch @buffer.getExtension()
-      when 'js' then 'javascript'
-      when 'coffee' then 'coffee'
-      when 'rb', 'ru' then 'ruby'
-      when 'c', 'h', 'cpp' then 'c_cpp'
-      when 'html', 'htm' then 'html'
-      when 'css' then 'css'
-      when 'java' then 'java'
-      when 'xml' then 'xml'
-      else 'text'
-    new (require("ace/mode/#{modeName}").Mode)
-
-  toggleLineCommentsInRange: (range) ->
-    range = Range.fromObject(range)
-    @aceMode.toggleCommentLines(@stateForRow(range.start.row), @aceAdaptor, range.start.row, range.end.row)
-
-  isBufferRowFoldable: (bufferRow) ->
-    @aceMode.foldingRules?.getFoldWidget(@aceAdaptor, null, bufferRow) == "start"
-
-  rowRangeForFoldAtBufferRow: (bufferRow) ->
-    if aceRange = @aceMode.foldingRules?.getFoldWidgetRange(@aceAdaptor, null, bufferRow)
-      [aceRange.start.row, aceRange.end.row]
-    else
-      null
-
-  indentationForRow: (row) ->
-    state = @stateForRow(row)
-    previousRowText = @buffer.lineForRow(row - 1)
-    @aceMode.getNextLineIndent(state, previousRowText, @tabText)
-
-  autoIndentTextAfterBufferPosition: (text, bufferPosition) ->
-    { row, column} = bufferPosition
-    state = @stateForRow(row)
-    lineBeforeCursor = @buffer.lineForRow(row)[0...column]
-    if text[0] == "\n"
-      indent = @aceMode.getNextLineIndent(state, lineBeforeCursor, @tabText)
-      text = text[0] + indent + text[1..]
-    else if @aceMode.checkOutdent(state, lineBeforeCursor, text)
-      shouldOutdent = true
-
-    {text, shouldOutdent}
-
-  autoOutdentBufferRow: (bufferRow) ->
-    state = @stateForRow(bufferRow)
-    @aceMode.autoOutdent(state, @aceAdaptor, bufferRow)
 
   handleBufferChange: (e) ->
     oldRange = e.oldRange.copy()
@@ -108,9 +59,8 @@ class TokenizedBuffer
       screenLine
 
   buildScreenLineForRow: (state, row) ->
-    tokenizer = @aceMode.getTokenizer()
     line = @buffer.lineForRow(row)
-    {tokens, state} = tokenizer.getLineTokens(line, state)
+    {tokens, state} = @languageMode.getLineTokens(line, state)
     tokenObjects = []
     for tokenProperties in tokens
       token = new Token(tokenProperties)