Move structural folding logic to LanguageMode

DisplayBuffer should just focus on providing basic support for folding.
Scanning the structure of the code, looking at scopes, etc is more the
domain of the LanguageMode object.

spec/app/display-buffer-spec.coffee

@@ -534,7 +534,7 @@ describe "DisplayBuffer", ->
 
   describe "markers", ->
     beforeEach ->
-      displayBuffer.foldBufferRow(4)
+      editSession.foldBufferRow(4)
 
     describe "marker creation and manipulation", ->
       it "allows markers to be created in terms of both screen and buffer coordinates", ->
@@ -607,7 +607,7 @@ describe "DisplayBuffer", ->
         }
         observeHandler.reset()
 
-        displayBuffer.unfoldBufferRow(4)
+        editSession.unfoldBufferRow(4)
         expect(observeHandler).toHaveBeenCalled()
         expect(observeHandler.argsForCall[0][0]).toEqual {
           oldHeadScreenPosition: [8, 23]
@@ -623,7 +623,7 @@ describe "DisplayBuffer", ->
         }
         observeHandler.reset()
 
-        displayBuffer.foldBufferRow(4)
+        editSession.foldBufferRow(4)
         expect(observeHandler).toHaveBeenCalled()
         expect(observeHandler.argsForCall[0][0]).toEqual {
           oldHeadScreenPosition: [11, 23]
@@ -710,7 +710,7 @@ describe "DisplayBuffer", ->
       it "allows observation subscriptions to be cancelled", ->
         subscription.cancel()
         displayBuffer.setMarkerHeadScreenPosition(marker, [8, 20])
-        displayBuffer.unfoldBufferRow(4)
+        editSession.unfoldBufferRow(4)
         expect(observeHandler).not.toHaveBeenCalled()
 
       it "updates the position of markers before emitting buffer change events, but does not notify their observers until the change event", ->
@@ -739,7 +739,7 @@ describe "DisplayBuffer", ->
           expect(displayBuffer.getMarkerTailScreenPosition(marker)).toEqual [8, 4]
         displayBuffer.on 'changed', changeHandler
 
-        displayBuffer.unfoldBufferRow(4)
+        editSession.unfoldBufferRow(4)
 
         expect(changeHandler).toHaveBeenCalled()
         expect(observeHandler).toHaveBeenCalled()

src/app/display-buffer.coffee

@@ -13,7 +13,6 @@ module.exports =
 class DisplayBuffer
   @idCounter: 1
   lineMap: null
-  languageMode: null
   tokenizedBuffer: null
   activeFolds: null
   foldsById: null
@@ -25,7 +24,6 @@ class DisplayBuffer
 
   constructor: (@buffer, options={}) ->
     @id = @constructor.idCounter++
-    @languageMode = options.languageMode
     @tokenizedBuffer = new TokenizedBuffer(@buffer, options)
     @softWrapColumn = options.softWrapColumn ? Infinity
     @activeFolds = {}
@@ -97,56 +95,6 @@ class DisplayBuffer
   bufferRowsForScreenRows: (startRow, endRow) ->
     @lineMap.bufferRowsForScreenRows(startRow, endRow)
 
-  # Public: Folds all the foldable lines in the buffer.
-  foldAll: ->
-    for currentRow in [0..@buffer.getLastRow()]
-      [startRow, endRow] = @languageMode.rowRangeForFoldAtBufferRow(currentRow) ? []
-      continue unless startRow?
-
-      @createFold(startRow, endRow)
-
-  # Public: Unfolds all the foldable lines in the buffer.
-  unfoldAll: ->
-    for row in [@buffer.getLastRow()..0]
-      @activeFolds[row]?.forEach (fold) => @destroyFold(fold)
-
-  rowRangeForCommentAtBufferRow: (row) ->
-    return unless @tokenizedBuffer.lineForScreenRow(row).isComment()
-
-    startRow = row
-    for currentRow in [row-1..0]
-      break if @buffer.isRowBlank(currentRow)
-      break unless @tokenizedBuffer.lineForScreenRow(currentRow).isComment()
-      startRow = currentRow
-    endRow = row
-    for currentRow in [row+1..@buffer.getLastRow()]
-      break if @buffer.isRowBlank(currentRow)
-      break unless @tokenizedBuffer.lineForScreenRow(currentRow).isComment()
-      endRow = currentRow
-    return [startRow, endRow] if startRow isnt endRow
-
-  # Public: Given a buffer row, this folds it.
-  #
-  # bufferRow - A {Number} indicating the buffer row
-  foldBufferRow: (bufferRow) ->
-    for currentRow in [bufferRow..0]
-      rowRange = @rowRangeForCommentAtBufferRow(currentRow)
-      rowRange ?= @languageMode.rowRangeForFoldAtBufferRow(currentRow)
-      [startRow, endRow] = rowRange ? []
-      continue unless startRow? and startRow <= bufferRow <= endRow
-      fold = @largestFoldStartingAtBufferRow(startRow)
-      continue if fold
-
-      @createFold(startRow, endRow)
-
-      return
-
-  # Public: Given a buffer row, this unfolds it.
-  #
-  # bufferRow - A {Number} indicating the buffer row
-  unfoldBufferRow: (bufferRow) ->
-    @largestFoldContainingBufferRow(bufferRow)?.destroy()
-
   # Public: Creates a new fold between two row numbers.
   #
   # startRow - The row {Number} to start folding at
@@ -202,6 +150,9 @@ class DisplayBuffer
       for fold in new Array(folds...)
         fold.destroy() if fold.getBufferRange().containsRow(bufferRow)
 
+  foldsStartingAtBufferRow: (bufferRow) ->
+    new Array((@activeFolds[bufferRow] ? [])...)
+
   # Public: Given a buffer row, this returns the largest fold that starts there.
   #
   # Largest is defined as the fold whose difference between its start and end points

src/app/edit-session.coffee

@@ -617,11 +617,11 @@ class EditSession
 
   # Public: Folds all the rows.
   foldAll: ->
-    @displayBuffer.foldAll()
+    @languageMode.foldAll()
 
   # Public: Unfolds all the rows.
   unfoldAll: ->
-    @displayBuffer.unfoldAll()
+    @languageMode.unfoldAll()
 
   # Public: Folds the current row.
   foldCurrentRow: ->
@@ -632,7 +632,7 @@ class EditSession
   #
   # bufferRow - A {Number} indicating the buffer row
   foldBufferRow: (bufferRow) ->
-    @displayBuffer.foldBufferRow(bufferRow)
+    @languageMode.foldBufferRow(bufferRow)
 
   # Public: Unfolds the current row.
   unfoldCurrentRow: ->
@@ -643,7 +643,7 @@ class EditSession
   #
   # bufferRow - A {Number} indicating the buffer row
   unfoldBufferRow: (bufferRow) ->
-    @displayBuffer.unfoldBufferRow(bufferRow)
+    @languageMode.unfoldBufferRow(bufferRow)
 
   # Public: Folds all selections.
   foldSelection: ->

src/app/language-mode.coffee

@@ -91,6 +91,34 @@ class LanguageMode
         for row in [start..end]
           buffer.insert([row, 0], commentStartString)
 
+  # Public: Folds all the foldable lines in the buffer.
+  foldAll: ->
+    for currentRow in [0..@buffer.getLastRow()]
+      [startRow, endRow] = @rowRangeForFoldAtBufferRow(currentRow) ? []
+      continue unless startRow?
+
+      @editSession.createFold(startRow, endRow)
+
+  # Public: Unfolds all the foldable lines in the buffer.
+  unfoldAll: ->
+    for row in [@buffer.getLastRow()..0]
+      fold.destroy() for fold in @editSession.displayBuffer.foldsStartingAtBufferRow(row)
+
+  foldBufferRow: (bufferRow) ->
+    for currentRow in [bufferRow..0]
+      rowRange = @rowRangeForCommentAtBufferRow(currentRow)
+      rowRange ?= @rowRangeForFoldAtBufferRow(currentRow)
+      [startRow, endRow] = rowRange ? []
+      continue unless startRow? and startRow <= bufferRow <= endRow
+      fold = @editSession.displayBuffer.largestFoldStartingAtBufferRow(startRow)
+      return @editSession.createFold(startRow, endRow) unless fold
+
+  # Public: Given a buffer row, this unfolds it.
+  #
+  # bufferRow - A {Number} indicating the buffer row
+  unfoldBufferRow: (bufferRow) ->
+    @editSession.displayBuffer.largestFoldContainingBufferRow(bufferRow)?.destroy()
+
   doesBufferRowStartFold: (bufferRow) ->
     return false if @editSession.isBufferRowBlank(bufferRow)
     nextNonEmptyRow = @editSession.nextNonBlankBufferRow(bufferRow)
@@ -114,6 +142,21 @@ class LanguageMode
 
     [bufferRow, foldEndRow]
 
+  rowRangeForCommentAtBufferRow: (row) ->
+    return unless @editSession.displayBuffer.tokenizedBuffer.lineForScreenRow(row).isComment()
+
+    startRow = row
+    for currentRow in [row-1..0]
+      break if @buffer.isRowBlank(currentRow)
+      break unless @editSession.displayBuffer.tokenizedBuffer.lineForScreenRow(currentRow).isComment()
+      startRow = currentRow
+    endRow = row
+    for currentRow in [row+1..@buffer.getLastRow()]
+      break if @buffer.isRowBlank(currentRow)
+      break unless @editSession.displayBuffer.tokenizedBuffer.lineForScreenRow(currentRow).isComment()
+      endRow = currentRow
+    return [startRow, endRow] if startRow isnt endRow
+
   # Public: Given a buffer row, this returns a suggested indentation level.
   #
   # The indentation level provided is based on the current {LanguageMode}.