Add template tag to hangle acl in navigation

apps/acls/templatetags/acl_tags.py

@@ -0,0 +1,54 @@
+from django.core.exceptions import PermissionDenied
+from django.template import (TemplateSyntaxError, Library,
+    Node, Variable, VariableDoesNotExist)
+
+from acls.models import AccessEntry
+
+register = Library()
+
+
+class CheckAccessNode(Node):
+    def __init__(self, permission_list=None, requester=None, obj=None, *args, **kwargs):
+        self.requester = requester
+        self.permission_list = permission_list
+        self.obj = obj
+
+    def render(self, context):
+        permission_list = Variable(self.permission_list).resolve(context)
+        try:
+            # Check access_object, useful for document_page views
+            obj = Variable('access_object').resolve(context)
+        except VariableDoesNotExist:
+            try:
+                obj = Variable(self.obj).resolve(context)
+            except VariableDoesNotExist:
+                context[u'access'] = True
+                return u''
+        
+        requester = Variable(self.requester).resolve(context)
+
+        if not permission_list or not obj:
+            # There is no permissions list to check against which means
+            # this link is available for all
+            context[u'access'] = True
+            return u''
+
+        try:
+            AccessEntry.objects.check_accesses(permission_list, requester, obj)
+        except PermissionDenied:
+            context[u'access'] = False
+            return u''
+        else:
+            context[u'access'] = True
+            return u''
+
+
+@register.tag
+def check_access(parser, token):
+    try:
+        # Splitting by None == splitting by spaces.
+        tag_name, args = token.contents.split(None, 1)
+    except ValueError:
+        raise TemplateSyntaxError(u'%r tag requires arguments' % token.contents.split()[0])
+
+    return CheckAccessNode(*args.split())