Make problem previews work by saving problem state in the current request session

cms/djangoapps/contentstore/views.py

 from util.json_request import expect_json
 import json
+import logging
+from collections import defaultdict
 
 from django.http import HttpResponse, Http404
 from django.contrib.auth.decorators import login_required
@@ -15,6 +17,10 @@ from static_replace import replace_urls
 from mitxmako.shortcuts import render_to_response, render_to_string
 from xmodule.modulestore.django import modulestore
 from xmodule_modifiers import replace_static_urls, wrap_xmodule
+from xmodule.exceptions import NotFoundError
+from functools import partial
+
+log = logging.getLogger(__name__)
 
 
 # ==== Public views ==================================================
@@ -103,7 +109,7 @@ def edit_item(request):
         'js_module': item.js_module_name,
         'category': item.category,
         'name': item.name,
-        'previews': get_module_previews(item),
+        'previews': get_module_previews(request, item),
     })
 
 
@@ -124,16 +130,64 @@ def user_author_string(user):
 
 
 @login_required
-def preview_dispatch(request, module_id, dispatch):
+def preview_dispatch(request, preview_id, location, dispatch=None):
     """
     Dispatch an AJAX action to a preview XModule
 
     Expects a POST request, and passes the arguments to the module
 
-    module_id: The Location of the module to dispatch to
+    preview_id (str): An identifier specifying which preview this module is used for
+    location: The Location of the module to dispatch to
     dispatch: The action to execute
     """
-    pass
+
+    instance_state, shared_state = load_preview_state(request, preview_id, location)
+    descriptor = modulestore().get_item(location)
+    instance = load_preview_module(request, preview_id, descriptor, instance_state, shared_state)
+    # Let the module handle the AJAX
+    try:
+        ajax_return = instance.handle_ajax(dispatch, request.POST)
+    except NotFoundError:
+        log.exception("Module indicating to user that request doesn't exist")
+        raise Http404
+    except:
+        log.exception("error processing ajax call")
+        raise
+
+    save_preview_state(request, preview_id, location, instance.get_instance_state(), instance.get_shared_state())
+    return HttpResponse(ajax_return)
+
+
+def load_preview_state(request, preview_id, location):
+    """
+    Load the state of a preview module from the request
+
+    preview_id (str): An identifier specifying which preview this module is used for
+    location: The Location of the module to dispatch to
+    """
+    if 'preview_states' not in request.session:
+        request.session['preview_states'] = defaultdict(dict)
+
+    instance_state = request.session['preview_states'][preview_id, location].get('instance')
+    shared_state = request.session['preview_states'][preview_id, location].get('shared')
+
+    return instance_state, shared_state
+
+
+def save_preview_state(request, preview_id, location, instance_state, shared_state):
+    """
+    Load the state of a preview module to the request
+
+    preview_id (str): An identifier specifying which preview this module is used for
+    location: The Location of the module to dispatch to
+    instance_state: The instance state to save
+    shared_state: The shared state to save
+    """
+    if 'preview_states' not in request.session:
+        request.session['preview_states'] = defaultdict(dict)
+
+    request.session['preview_states'][preview_id, location]['instance'] = instance_state
+    request.session['preview_states'][preview_id, location]['shared'] = shared_state
 
 
 def render_from_lms(template_name, dictionary, context=None, namespace='main'):
@@ -143,54 +197,64 @@ def render_from_lms(template_name, dictionary, context=None, namespace='main'):
     return render_to_string(template_name, dictionary, context, namespace="lms." + namespace)
 
 
-def sample_module_system(descriptor):
+def preview_module_system(request, preview_id, descriptor):
     """
     Returns a ModuleSystem for the specified descriptor that is specialized for
     rendering module previews.
+
+    request: The active django request
+    preview_id (str): An identifier specifying which preview this module is used for
+    descriptor: An XModuleDescriptor
     """
     return ModuleSystem(
-        ajax_url=reverse('preview_dispatch', args=[descriptor.location.url(), '']),
+        ajax_url=reverse('preview_dispatch', args=[preview_id, descriptor.location.url(), '']),
         # TODO (cpennington): Do we want to track how instructors are using the preview problems?
-        track_function=lambda x: None,
+        track_function=lambda type, event: None,
         filestore=descriptor.system.resources_fs,
-        get_module=get_sample_module,
+        get_module=partial(get_preview_module, request, preview_id),
         render_template=render_from_lms,
         debug=True,
         replace_urls=replace_urls
     )
 
 
-def get_sample_module(location):
+def get_preview_module(request, preview_id, location):
     """
-    Returns a sample XModule at the specified location. The sample_data is chosen arbitrarily
-    from the set of sample data for the descriptor specified by Location
+    Returns a preview XModule at the specified location. The preview_data is chosen arbitrarily
+    from the set of preview data for the descriptor specified by Location
 
+    request: The active django request
+    preview_id (str): An identifier specifying which preview this module is used for
     location: A Location
     """
     descriptor = modulestore().get_item(location)
     instance_state, shared_state = descriptor.get_sample_state()[0]
-    return load_sample_module(descriptor, instance_state, shared_state)
+    return load_preview_module(request, preview_id, descriptor, instance_state, shared_state)
 
 
-def load_sample_module(descriptor, instance_state, shared_state):
+def load_preview_module(request, preview_id, descriptor, instance_state, shared_state):
     """
-    Return a sample XModule instantiated from the supplied descriptor, instance_state, and shared_state
+    Return a preview XModule instantiated from the supplied descriptor, instance_state, and shared_state
 
+    request: The active django request
+    preview_id (str): An identifier specifying which preview this module is used for
     descriptor: An XModuleDescriptor
     instance_state: An instance state string
     shared_state: A shared state string
     """
-    system = sample_module_system(descriptor)
+    system = preview_module_system(request, preview_id, descriptor)
     module = descriptor.xmodule_constructor(system)(instance_state, shared_state)
     module.get_html = replace_static_urls(
         wrap_xmodule(module.get_html, module, "xmodule_display.html"),
         module.metadata['data_dir']
     )
+    save_preview_state(request, preview_id, descriptor.location.url(),
+        module.get_instance_state(), module.get_shared_state())
 
     return module
 
 
-def get_module_previews(descriptor):
+def get_module_previews(request, descriptor):
     """
     Returns a list of preview XModule html contents. One preview is returned for each
     pair of states returned by get_sample_state() for the supplied descriptor.
@@ -198,8 +262,8 @@ def get_module_previews(descriptor):
     descriptor: An XModuleDescriptor
     """
     preview_html = []
-    for instance_state, shared_state in descriptor.get_sample_state():
-        module = load_sample_module(descriptor, instance_state, shared_state)
+    for idx, (instance_state, shared_state) in enumerate(descriptor.get_sample_state()):
+        module = load_preview_module(request, str(idx), descriptor, instance_state, shared_state)
         preview_html.append(module.get_html())
     return preview_html
 
@@ -225,6 +289,6 @@ def save_item(request):
         export_to_github(course, "CMS Edit", author_string)
 
     descriptor = modulestore().get_item(item_location)
-    preview_html = get_module_previews(descriptor)
+    preview_html = get_module_previews(request, descriptor)
 
     return HttpResponse(json.dumps(preview_html))

cms/urls.py

@@ -14,7 +14,8 @@ urlpatterns = ('',
     url(r'^(?P<org>[^/]+)/(?P<course>[^/]+)/course/(?P<name>[^/]+)$',
         'contentstore.views.course_index', name='course_index'),
     url(r'^github_service_hook$', 'github_sync.views.github_post_receive'),
-    url(r'^preview/modx/(?P<location>.*?)/(?P<dispatch>[^/]*)$', 'contentstore.views.preview_dispatch', name='preview_dispatch')
+    url(r'^preview/modx/(?P<preview_id>[^/]*)/(?P<location>.*?)/(?P<dispatch>[^/]*)$',
+        'contentstore.views.preview_dispatch', name='preview_dispatch')
 )
 
 # User creation and updating views

lms/templates/accordion.html

@@ -21,9 +21,3 @@
 % for chapter in toc:
     ${make_chapter(chapter)}
 % endfor
-
-## add a link to allow course.xml to be reloaded from the git content repo
-##% if settings.QUICKEDIT:
-##    <h3><a href="#">quickedit</a></h3>
-##    <ul><li><a href="${MITX_ROOT_URL}/quickedit/course.xml">gitreload</a></li></ul>
-##% endif

lms/templates/problem.html

@@ -4,12 +4,6 @@
   % if problem['weight'] != 1:
     : ${ problem['weight'] } points
   % endif
-
-  % if settings.QUICKEDIT:
-  <section class="staff">
-    <a href=${MITX_ROOT_URL}/quickedit/${id}>Quick Edit Problem</a>
-  </section>
-  % endif
 </h2>
 
 <section class="problem">