try: from django.conf import settings from auth.models import UserProfile except: settings = None from lxml import etree import json import hashlib import logging ''' This file will eventually form an abstraction layer between the course XML file and the rest of the system. TODO: Shift everything from xml.dom.minidom to XPath (or XQuery) ''' log = logging.getLogger("mitx.courseware") def fasthash(string): m = hashlib.new("md4") m.update(string) return "id"+m.hexdigest() def xpath(xml, query_string, **args): ''' Safe xpath query into an xml tree: * xml is the tree. * query_string is the query * args are the parameters. Substitute for {params}. We should remove this with the move to lxml. We should also use lxml argument passing. ''' doc = etree.fromstring(xml) print type(doc) def escape(x): # TODO: This should escape the string. For now, we just assume it's made of valid characters. # Couldn't figure out how to escape for lxml in a few quick Googles valid_chars="".join(map(chr, range(ord('a'),ord('z')+1)+range(ord('A'),ord('Z')+1)+range(ord('0'), ord('9')+1)))+"_ " for e in x: if e not in valid_chars: raise Exception("Invalid char in xpath expression. TODO: Escape") return x args=dict( ((k, escape(args[k])) for k in args) ) print args results = doc.xpath(query_string.format(**args)) return results def xpath_remove(tree, path): ''' Remove all items matching path from lxml tree. Works in place.''' items = tree.xpath(path) for item in items: item.getparent().remove(item) return tree if __name__=='__main__': print xpath('', '/{search}/problem[@name="{name}"]', search='html', name="Bob") def item(l, default="", process=lambda x:x): if len(l)==0: return default elif len(l)==1: return process(l[0]) else: raise Exception('Malformed XML') def id_tag(course): ''' Tag all course elements with unique IDs ''' default_ids = {'video':'youtube', 'problem':'filename', 'sequential':'id', 'html':'filename', 'vertical':'id', 'tab':'id', 'schematic':'id'} # Tag elements with unique IDs elements = course.xpath("|".join(['//'+c for c in default_ids])) for elem in elements: if elem.get('id'): pass elif elem.get(default_ids[elem.tag]): new_id = elem.get(default_ids[elem.tag]) # Convert to alphanumeric new_id = "".join([a for a in new_id if a.isalnum()]) elem.set('id', new_id) else: elem.set('id', fasthash(etree.tostring(elem))) def due_tag(element, parent_due_date=None): ''' This call is to pass down due dates. If an element has a due date, all of the elements children will inherit this due date (unless the element has a due date of its own). This is called recursively''' if (parent_due_date == None): #This is the entry call. Select all due elements all_due_elements = element.xpath("//*[@due]") for due_element in all_due_elements: due_date = due_element.get('due') for child_element in due_element: due_tag(child_element, due_date) else: #The hack below is because we would get _ContentOnlyELements from the #iterator that can't have due dates set. We can't find API for it if not element.get('due') and type(element) == etree._Element: element.set('due', parent_due_date) due_date = parent_due_date else: due_date = element.get('due') for child_element in element: due_tag(child_element, due_date) def course_file(user): # TODO: Cache. tree = etree.parse(settings.DATA_DIR+UserProfile.objects.get(user=user).courseware) id_tag(tree) due_tag(tree) return tree def module_xml(coursefile, module, id_tag, module_id): ''' Get XML for a module based on module and module_id. Assumes module occurs once in courseware XML file.. ''' doc = coursefile # Sanitize input if not module.isalnum(): raise Exception("Module is not alphanumeric") if not module_id.isalnum(): raise Exception("Module ID is not alphanumeric") xpath_search='//*/{module}[(@{id_tag} = "{id}") or (@id = "{id}")]'.format(module=module, id_tag=id_tag, id=module_id) #result_set=doc.xpathEval(xpath_search) result_set=doc.xpath(xpath_search) if len(result_set)>1: print "WARNING: Potentially malformed course file", module, module_id if len(result_set)==0: return None return etree.tostring(result_set[0]) #return result_set[0].serialize() def toc_from_xml(dom, active_chapter, active_section): name = dom.xpath('//course/@name')[0] chapters = dom.xpath('//course[@name=$name]/chapter', name=name) ch=list() for c in chapters: if c.get('name') == 'hidden': continue sections=list() for s in dom.xpath('//course[@name=$name]/chapter[@name=$chname]/section', name=name, chname=c.get('name')): sections.append({'name':s.get("name") or "", 'time':s.get("time") or "", 'format':s.get("format") or "", 'due':s.get("due") or "", 'active':(c.get("name")==active_chapter and \ s.get("name")==active_section)}) ch.append({'name':c.get("name"), 'sections':sections, 'active':(c.get("name")==active_chapter)}) return ch