From 69321b4497bda00b03e84483706d0e7e4860ea46 Mon Sep 17 00:00:00 2001
From: Calen Pennington <calen.pennington@gmail.com>
Date: Wed, 16 May 2012 13:45:00 -0400
Subject: [PATCH] Display the appropriate type of error message depending on
 the type of the incoming request

---
 djangoapps/courseware/views.py  | 17 +++++++++++---
 envs/common.py                  |  1 +
 lib/util/middleware.py          | 27 ++++++++++++++++++++++
 settings.py                     |  1 +
 templates/courseware-error.html | 40 ++++-----------------------------
 5 files changed, 47 insertions(+), 39 deletions(-)

diff --git a/djangoapps/courseware/views.py b/djangoapps/courseware/views.py
index 9cfdc2fe9f..6f991e261c 100644
--- a/djangoapps/courseware/views.py
+++ b/djangoapps/courseware/views.py
@@ -227,7 +227,15 @@ def modx_dispatch(request, module=None, dispatch=None, id=None):
     ajax_url = settings.MITX_ROOT_URL + '/modx/'+module+'/'+id+'/'
 
     # Grab the XML corresponding to the request from course.xml
-    xml = content_parser.module_xml(request.user, module, 'id', id)
+    try:
+        xml = content_parser.module_xml(request.user, module, 'id', id)
+    except:
+        record_exception(log, "Unable to load module during ajax call")
+        if 'text/html' in request.accepted_types:
+            return render_to_response("module-error.html", {})
+        else:
+            response = HttpResponse(json.dumps({'success': "We're sorry, this module is temporarily unavailable. Our staff is working to fix it as soon as possible"}))
+        return response
 
     # Create the module
     system = I4xSystem(track_function = make_track_function(request), 
@@ -242,8 +250,11 @@ def modx_dispatch(request, module=None, dispatch=None, id=None):
                                                              id, 
                                                              state=oldstate)
     except:
-        record_exception(log, "Unable to load module during ajax call")
-        response = HttpResponse(json.dumps({'success': "We're sorry, this module is temporarily unavailable. Our staff is working to fix it as soon as possible"}))
+        record_exception(log, "Unable to load module instance during ajax call")
+        if 'text/html' in request.accepted_types:
+            return render_to_response("module-error.html", {})
+        else:
+            response = HttpResponse(json.dumps({'success': "We're sorry, this module is temporarily unavailable. Our staff is working to fix it as soon as possible"}))
         return response
 
     # Let the module handle the AJAX
diff --git a/envs/common.py b/envs/common.py
index 1ae4a90e8d..3576b31968 100644
--- a/envs/common.py
+++ b/envs/common.py
@@ -226,6 +226,7 @@ TEMPLATE_LOADERS = (
 
 MIDDLEWARE_CLASSES = (
     'util.middleware.ExceptionLoggingMiddleware',
+    'util.middleware.AcceptMiddleware',
     'django.middleware.cache.UpdateCacheMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
diff --git a/lib/util/middleware.py b/lib/util/middleware.py
index 342fff1790..84ea2b4656 100644
--- a/lib/util/middleware.py
+++ b/lib/util/middleware.py
@@ -13,3 +13,30 @@ class ExceptionLoggingMiddleware(object):
         def process_exception(self, request, exception):
             log.exception(exception)
             return HttpResponseServerError("Server Error - Please try again later.")
+
+# From http://djangosnippets.org/snippets/1042/
+def parse_accept_header(accept):
+    """Parse the Accept header *accept*, returning a list with pairs of
+    (media_type, q_value), ordered by q values.
+    """
+    result = []
+    for media_range in accept.split(","):
+        parts = media_range.split(";")
+        media_type = parts.pop(0)
+        media_params = []
+        q = 1.0
+        for part in parts:
+            (key, value) = part.lstrip().split("=", 1)
+            if key == "q":
+                q = float(value)
+            else:
+                media_params.append((key, value))
+        result.append((media_type, tuple(media_params), q))
+    result.sort(lambda x, y: -cmp(x[2], y[2]))
+    return result
+
+class AcceptMiddleware(object):
+    def process_request(self, request):
+        accept = parse_accept_header(request.META.get("HTTP_ACCEPT", ""))
+        request.accept = accept
+        request.accepted_types = map(lambda (t, p, q): t, accept)
diff --git a/settings.py b/settings.py
index 21458b5fef..e0119c6fb0 100644
--- a/settings.py
+++ b/settings.py
@@ -140,6 +140,7 @@ TEMPLATE_LOADERS = (
 
 MIDDLEWARE_CLASSES = (
     'util.middleware.ExceptionLoggingMiddleware',
+    'util.middleware.AcceptMiddleware',
     'django.middleware.cache.UpdateCacheMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
diff --git a/templates/courseware-error.html b/templates/courseware-error.html
index 547c43e221..0863ffe7e8 100644
--- a/templates/courseware-error.html
+++ b/templates/courseware-error.html
@@ -2,43 +2,11 @@
 <%block name="bodyclass">courseware</%block>
 <%block name="title"><title>Courseware – MITx 6.002x</title></%block>
 
-<%block name="headextra">
-<script type="text/javascript" src="/static/js/flot/jquery.flot.js"></script>
-</%block>
-
-<%block name="js_extra">
-##Is there a reason this isn't in header_extra? Is it important that the javascript is at the bottom of the generated document?
-<!-- TODO: http://docs.jquery.com/Plugins/Validation -->
-<script type="text/javascript">
-  $(function() {
-    ${init}
-
-    $(".sequence-nav li a").hover(function(){
-      $(this).siblings().toggleClass("shown");
-      });
-  });
-</script>
-</%block>
-
 <%include file="navigation.html" args="active_page='courseware'" />
 
 <section class="main-content">
-  <div class="course-wrapper">
-    <section class="course-index">
-      <header id="open_close_accordion">
-        <h2>Courseware Index</h2>
-        <a href="#">close</a>
-      </header>
-
-      <div id="accordion">
-        <nav>
-          ${accordion}
-        </nav>
-      </div>
-    </section>
-
-    <section class="course-content">
-      ${content}
-    </section>
-  </div>
+  <section class="outside-app">
+    <h1>There has been an error on the <em>MITx</em> servers</h1>
+    <p>We're sorry, this module is temporarily unavailable. Our staff is working to fix it as soon as possible. Please email us at <a href="mailto:technical@mitx.mit.edu">technical@mitx.mit.edu</a> to report any problems or downtime.</p>
+  </section>
 </section>