Replace dynamite code with tested version

lms/static/coffee/fixtures/problem_content.html

@@ -6,6 +6,10 @@
   <section class="action">
     <input type="hidden" name="problem_id" value="1">
 
+    <input type="text" name="input_example_1" id="input_example_1" value="" class="math" />
+    <span id="display_example_1"></span>
+    <span id="input_example_1_dynamath"></span>
+
     <input class="check" type="button" value="Check">
     <input class="reset" type="button" value="Reset">
     <input class="save" type="button" value="Save">

lms/static/coffee/spec/modules/problem_spec.coffee

@@ -1,7 +1,11 @@
 describe 'Problem', ->
   beforeEach ->
     # Stub MathJax
-    window.MathJax = { Hub: { Queue: -> } }
+    window.MathJax =
+      Hub: jasmine.createSpyObj('MathJax.Hub', ['getAllJax', 'Queue'])
+      Callback: jasmine.createSpyObj('MathJax.Callback', ['After'])
+    @stubbedJax = root: jasmine.createSpyObj('jax.root', ['toMathML'])
+    MathJax.Hub.getAllJax.andReturn [@stubbedJax]
     window.update_schematics = ->
 
     loadFixtures 'problem.html'
@@ -25,8 +29,8 @@ describe 'Problem', ->
 
   describe 'bind', ->
     beforeEach ->
-      spyOn MathJax.Hub, 'Queue'
       spyOn window, 'update_schematics'
+      MathJax.Hub.getAllJax.andReturn [@stubbedJax]
       @problem = new Problem 1, '/problem/url/'
 
     it 'set mathjax typeset', ->
@@ -50,6 +54,12 @@ describe 'Problem', ->
     it 'bind the save button', ->
       expect($('section.action input.save')).toHandleWith 'click', @problem.save
 
+    it 'bind the math input', ->
+      expect($('input.math')).toHandleWith 'keyup', @problem.refreshMath
+
+    it 'display the math input', ->
+      expect(@stubbedJax.root.toMathML).toHaveBeenCalled()
+
   describe 'render', ->
     beforeEach ->
       @problem = new Problem 1, '/problem/url/'
@@ -223,6 +233,30 @@ describe 'Problem', ->
       @problem.save()
       expect(window.alert).toHaveBeenCalledWith 'Saved'
 
+  describe 'refreshMath', ->
+    beforeEach ->
+      @problem = new Problem 1, '/problem/url/'
+      @stubbedJax.root.toMathML.andReturn '<MathML>'
+      $('#input_example_1').val 'E=mc^2'
+
+    describe 'when there is no exception', ->
+      beforeEach ->
+        @problem.refreshMath target: $('#input_example_1').get(0)
+
+      it 'should convert and display the MathML object', ->
+        expect(MathJax.Hub.Queue).toHaveBeenCalledWith ['Text', @stubbedJax, 'E=mc^2']
+
+      it 'should display debug output in hidden div', ->
+        expect($('#input_example_1_dynamath')).toHaveValue '<MathML>'
+
+    describe 'when there is an exception', ->
+      beforeEach ->
+        @stubbedJax.root.toMathML.andThrow {restart: true}
+        @problem.refreshMath target: $('#input_example_1').get(0)
+
+      it 'should queue up the exception', ->
+        expect(MathJax.Callback.After).toHaveBeenCalledWith [@problem.refreshMath, @stubbedJax], true
+
   describe 'refreshAnswers', ->
     beforeEach ->
       @problem = new Problem 1, '/problem/url/'

lms/static/coffee/src/modules/problem.coffee

@@ -15,6 +15,7 @@ class @Problem
     @$('section.action input.reset').click @reset
     @$('section.action input.show').click @show
     @$('section.action input.save').click @save
+    @$('input.math').keyup(@refreshMath).each(@refreshMath)
 
   render: (content) ->
     if content
@@ -62,6 +63,20 @@ class @Problem
       if response.success
         alert 'Saved'
 
+  refreshMath: (event, element) =>
+    element = event.target unless element
+    target = "display_#{element.id.replace(/^input_/, '')}"
+
+    if jax = MathJax.Hub.getAllJax(target)[0]
+      MathJax.Hub.Queue ['Text', jax, $(element).val()]
+
+      try
+        output = jax.root.toMathML ''
+        $("##{element.id}_dynamath").val(output)
+      catch exception
+        throw exception unless exception.restart
+        MathJax.Callback.After [@refreshMath, jax], exception.restart
+
   refreshAnswers: =>
     @$('input.schematic').each (index, element) ->
       element.schematic.update_value()