Add Ember.computed.limit and use it in LimitedArray

arrayComputed was added recently in order to make array computations
easier. Using arrayComputed we can improve LimitedArray which now uses
an isolated multipurpose Ember.computed.limit.

assets/scripts/lib/ext/ember/computed.js

@@ -0,0 +1,26 @@
+Ember.computed.limit = function(dependentKey, limitKey) {
+  var options = {
+    addedItem: function(array, item, changeMeta, instanceMeta) {
+      var limit = Ember.get(this, limitKey);
+      if (changeMeta.index < limit) {
+        array.insertAt(changeMeta.index, item);
+        if (Ember.get(array, "length") > limit) {
+          array.popObject();
+        }
+      }
+      return array;
+    },
+    removedItem: function(array, item, changeMeta, instanceMeta) {
+      var limit = Ember.get(this, limitKey);
+      if (changeMeta.index < limit && changeMeta.index < Ember.get(array, 'length')) {
+        array.removeAt(changeMeta.index, 1);
+        var toPush = changeMeta.arrayChanged.objectAt(limit);
+        if (toPush) {
+          array.pushObject(toPush);
+        }
+      }
+      return array;
+    }
+  };
+  return Ember.arrayComputed(dependentKey, limitKey, options);
+};

assets/scripts/lib/travis/limited_array.coffee

@@ -1,17 +1,7 @@
 Travis.LimitedArray = Em.ArrayProxy.extend
   limit: 10
   isLoadedBinding: 'content.isLoaded'
-
-  init: ->
-    @_super.apply this, arguments
-
-  arrangedContent: (->
-    content = @get('content')
-    if @get('disabled')
-      content
-    else if content
-      content.slice(0, @get('limit'))
-  ).property('content', 'limit', 'disabled')
+  arrangedContent: Ember.computed.limit('content', 'limit')
 
   totalLength: (->
     @get('content.length')
@@ -21,54 +11,13 @@ Travis.LimitedArray = Em.ArrayProxy.extend
     totalLength = @get('totalLength')
     limit       = @get('limit')
 
-    if @get('disabled') || totalLength <= limit
-      0
-    else
-      totalLength - limit
-  ).property('totalLength', 'limit', 'disabled')
+    left = totalLength - limit
+    if left < 0 then 0 else left
+  ).property('totalLength', 'limit')
 
   isMore: (->
-    !@get('disabled') && @get('leftLength') > 0
+    @get('leftLength') > 0
   ).property('leftLength')
 
   showAll: ->
-    @set 'disabled', true
-
-  contentArrayWillChange: (array, index, removedCount, addedCount) ->
-    @_super.apply this, arguments
-
-    return if @get('disabled')
-
-    if removedCount
-      arrangedContent = @get 'arrangedContent'
-      removedObjects = array.slice(index, index + removedCount);
-      arrangedContent.removeObjects(removedObjects)
-
-  contentArrayDidChange: (array, index, removedCount, addedCount) ->
-    @_super.apply this, arguments
-
-    return if @get('disabled')
-
-    limit = @get('limit')
-
-    if addedCount
-      if index < limit
-        addedObjects = array.slice(index, index + addedCount)
-        @get('arrangedContent').replace(index, 0, addedObjects)
-
-    @balanceArray()
-
-  balanceArray: ->
-    limit  = @get 'limit'
-    arrangedContent = @get 'arrangedContent'
-    length = arrangedContent.get 'length'
-    content = @get 'content'
-
-    if length > limit
-      arrangedContent.replace(limit, length - limit)
-    else if length < limit && content.get('length') > length
-      count = limit - length
-      while count > 0
-        if next = content.find( (object) -> !arrangedContent.contains(object) )
-          arrangedContent.pushObject(next)
-        count -= 1
+    @set 'limit', Infinity

assets/scripts/spec/unit/limited_array_spec.coffee

@@ -41,7 +41,8 @@ test 'allows to expand array to show all items', ->
   content = [1, 2, 3]
   array = Travis.LimitedArray.create content: content, limit: 2
 
-  array.showAll()
+  Ember.run ->
+    array.showAll()
 
   equal( array.get('length'), 3)
   deepEqual( array.toArray(), [1, 2, 3])

assets/scripts/travis.coffee

@@ -1,5 +1,6 @@
 require 'ext/jquery'
 require 'ext/ember/namespace'
+require 'ext/ember/computed'
 require 'app'
 
 window.ENV ||= {}