Everything tested and ready for Tom to fix

cms/djangoapps/contentstore/course_info_model.py

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+from xmodule.modulestore.exceptions import ItemNotFoundError
+from xmodule.modulestore import Location
+from xmodule.modulestore.django import modulestore
+from lxml import etree
+import re
+from django.http import HttpResponseBadRequest
+
+## TODO store as array of { date, content } and override  course_info_module.definition_from_xml
+## This should be in a class which inherits from XmlDescriptor
+def get_course_updates(location):
+    """
+    Retrieve the relevant course_info updates and unpack into the model which the client expects:
+    [{id : location.url() + idx to make unique, date : string, content : html string}]
+    """
+    try:
+        course_updates = modulestore('direct').get_item(location)
+    except ItemNotFoundError:
+        template = Location(['i4x', 'edx', "templates", 'course_info', "Empty"])
+        course_updates = modulestore('direct').clone_item(template, Location(location))
+
+    # current db rep: {"_id" : locationjson, "definition" : { "data" : "<ol>[<li><h2>date</h2>content</li>]</ol>"} "metadata" : ignored}
+    location_base = course_updates.location.url()
+    
+    # purely to handle free formed updates not done via editor. Actually kills them, but at least doesn't break.
+    try:
+        course_html_parsed = etree.fromstring(course_updates.definition['data'], etree.XMLParser(remove_blank_text=True))
+    except etree.XMLSyntaxError:
+        course_html_parsed = etree.fromstring("<ol></ol>")
+        
+    # Confirm that root is <ol>, iterate over <li>, pull out <h2> subs and then rest of val
+    course_upd_collection = []
+    if course_html_parsed.tag == 'ol':
+        # 0 is the oldest so that new ones get unique idx
+        for idx, update in enumerate(course_html_parsed.iter("li")):
+            if (len(update) == 0):
+                continue
+            elif (len(update) == 1):
+                content = update.find("h2").tail
+            else:
+                content = etree.tostring(update[1])
+                
+            course_upd_collection.append({"id" : location_base + "/" + str(idx),
+                                          "date" : update.findtext("h2"),
+                                          "content" : content})
+    # return newest to oldest
+    course_upd_collection.reverse()
+    return course_upd_collection
+
+def update_course_updates(location, update, passed_id=None):
+    """
+    Either add or update the given course update. It will add it if the passed_id is absent or None. It will update it if
+    it has an passed_id which has a valid value. Until updates have distinct values, the passed_id is the location url + an index
+    into the html structure. 
+    """
+    try:
+        course_updates = modulestore('direct').get_item(location)
+    except ItemNotFoundError:
+        return HttpResponseBadRequest
+    
+    # purely to handle free formed updates not done via editor. Actually kills them, but at least doesn't break.
+    try:
+        course_html_parsed = etree.fromstring(course_updates.definition['data'], etree.XMLParser(remove_blank_text=True))
+    except etree.XMLSyntaxError:
+        course_html_parsed = etree.fromstring("<ol></ol>")
+
+    try:
+        new_html_parsed = etree.fromstring(update['content'], etree.XMLParser(remove_blank_text=True))
+    except etree.XMLSyntaxError:
+        new_html_parsed = None
+        
+    # Confirm that root is <ol>, iterate over <li>, pull out <h2> subs and then rest of val
+    if course_html_parsed.tag == 'ol':
+        # ??? Should this use the id in the json or in the url or does it matter?
+        if passed_id:
+            element = course_html_parsed.findall("li")[get_idx(passed_id)]
+            element[0].text = update['date']
+            if (len(element) == 1):
+                if new_html_parsed is not None:
+                    element[0].tail = None
+                    element.append(new_html_parsed)
+                else:
+                    element[0].tail = update['content']
+            else:
+                if new_html_parsed is not None:
+                    element[1] = new_html_parsed
+                else:
+                    element.pop(1)
+                    element[0].tail = update['content']
+        else:
+            idx = len(course_html_parsed.findall("li"))
+            passed_id = course_updates.location.url() + "/" + str(idx)
+            element =  etree.SubElement(course_html_parsed, "li")
+            date_element = etree.SubElement(element, "h2")
+            date_element.text = update['date']
+            if new_html_parsed is not None:
+                element[1] = new_html_parsed
+            else:
+                date_element.tail = update['content']
+        
+        # update db record
+        course_updates.definition['data'] = etree.tostring(course_html_parsed)
+        modulestore('direct').update_item(location, course_updates.definition['data'])
+        
+        return {"id" : passed_id,
+                "date" : update['date'],
+                "content" :update['content']}
+
+def delete_course_update(location, update, passed_id):
+    """
+    Delete the given course_info update from the db.
+    Returns the resulting course_updates b/c their ids change.
+    """
+    if not passed_id:
+        return HttpResponseBadRequest
+        
+    try:
+        course_updates = modulestore('direct').get_item(location)
+    except ItemNotFoundError:
+        return HttpResponseBadRequest
+    
+    # TODO use delete_blank_text parser throughout and cache as a static var in a class
+    # purely to handle free formed updates not done via editor. Actually kills them, but at least doesn't break.
+    try:
+        course_html_parsed = etree.fromstring(course_updates.definition['data'], etree.XMLParser(remove_blank_text=True))
+    except etree.XMLSyntaxError:
+        course_html_parsed = etree.fromstring("<ol></ol>")
+        
+    if course_html_parsed.tag == 'ol':
+        # ??? Should this use the id in the json or in the url or does it matter?
+        element_to_delete = course_html_parsed.xpath('/ol/li[position()=' + str(get_idx(passed_id) + 1) + "]")
+        if element_to_delete:
+            course_html_parsed.remove(element_to_delete[0])
+
+        # update db record
+        course_updates.definition['data'] = etree.tostring(course_html_parsed)
+        store = modulestore('direct')
+        store.update_item(location, course_updates.definition['data'])  
+          
+    return get_course_updates(location)
+    
+def get_idx(passed_id):
+    """
+    From the url w/ idx appended, get the idx.
+    """
+    # TODO compile this regex into a class static and reuse for each call
+    idx_matcher = re.search(r'.*/(\d)+$', passed_id)
+    if idx_matcher:
+        return int(idx_matcher.group(1))