philo/utils/__init__.py

   1 from django.db import models
   2 from django.contrib.contenttypes.models import ContentType
   3 from django.core.paginator import Paginator, EmptyPage
   4 from django.template import Context
   5 from django.template.loader_tags import ExtendsNode, ConstantIncludeNode
   6
   7
   8 def fattr(*args, **kwargs):
   9         """
  10         Returns a wrapper which takes a function as its only argument and sets the key/value pairs passed in with kwargs as attributes on that function. This can be used as a decorator.
  11
  12         Example::
  13
  14                 >>> from philo.utils import fattr
  15                 >>> @fattr(short_description="Hello World!")
  16                 ... def x():
  17                 ...     pass
  18                 ...
  19                 >>> x.short_description
  20                 'Hello World!'
  21
  22         """
  23         def wrapper(function):
  24                 for key in kwargs:
  25                         setattr(function, key, kwargs[key])
  26                 return function
  27         return wrapper
  28
  29
  30 ### ContentTypeLimiters
  31
  32
  33 class ContentTypeLimiter(object):
  34         def q_object(self):
  35                 return models.Q(pk__in=[])
  36
  37         def add_to_query(self, query, *args, **kwargs):
  38                 query.add_q(self.q_object(), *args, **kwargs)
  39
  40
  41 class ContentTypeRegistryLimiter(ContentTypeLimiter):
  42         """Can be used to limit the choices for a :class:`ForeignKey` or :class:`ManyToManyField` to the :class:`ContentType`\ s which have been registered with this limiter."""
  43         def __init__(self):
  44                 self.classes = []
  45
  46         def register_class(self, cls):
  47                 """Registers a model class with this limiter."""
  48                 self.classes.append(cls)
  49
  50         def unregister_class(self, cls):
  51                 """Unregisters a model class from this limiter."""
  52                 self.classes.remove(cls)
  53
  54         def q_object(self):
  55                 contenttype_pks = []
  56                 for cls in self.classes:
  57                         try:
  58                                 if issubclass(cls, models.Model):
  59                                         if not cls._meta.abstract:
  60                                                 contenttype = ContentType.objects.get_for_model(cls)
  61                                                 contenttype_pks.append(contenttype.pk)
  62                         except:
  63                                 pass
  64                 return models.Q(pk__in=contenttype_pks)
  65
  66
  67 class ContentTypeSubclassLimiter(ContentTypeLimiter):
  68         """
  69         Can be used to limit the choices for a :class:`ForeignKey` or :class:`ManyToManyField` to the :class:`ContentType`\ s for all non-abstract models which subclass the class passed in on instantiation.
  70
  71         :param cls: The class whose non-abstract subclasses will be valid choices.
  72         :param inclusive: Whether ``cls`` should also be considered a valid choice (if it is a non-abstract subclass of :class:`models.Model`)
  73
  74         """
  75         def __init__(self, cls, inclusive=False):
  76                 self.cls = cls
  77                 self.inclusive = inclusive
  78
  79         def q_object(self):
  80                 contenttype_pks = []
  81                 def handle_subclasses(cls):
  82                         for subclass in cls.__subclasses__():
  83                                 try:
  84                                         if issubclass(subclass, models.Model):
  85                                                 if not subclass._meta.abstract:
  86                                                         if not self.inclusive and subclass is self.cls:
  87                                                                 continue
  88                                                         contenttype = ContentType.objects.get_for_model(subclass)
  89                                                         contenttype_pks.append(contenttype.pk)
  90                                         handle_subclasses(subclass)
  91                                 except:
  92                                         pass
  93                 handle_subclasses(self.cls)
  94                 return models.Q(pk__in=contenttype_pks)
  95
  96
  97 ### Pagination
  98
  99
 100 def paginate(objects, per_page=None, page_number=1):
 101         """
 102         Given a list of objects, return a (``paginator``, ``page``, ``objects``) tuple.
 103
 104         :param objects: The list of objects to be paginated.
 105         :param per_page: The number of objects per page.
 106         :param page_number: The number of the current page.
 107         :returns tuple: (``paginator``, ``page``, ``objects``) where ``paginator`` is a :class:`django.core.paginator.Paginator` instance, ``page`` is the result of calling :meth:`Paginator.page` with ``page_number``, and objects is ``page.objects``. Any of the return values which can't be calculated will be returned as ``None``.
 108
 109         """
 110         try:
 111                 per_page = int(per_page)
 112         except (TypeError, ValueError):
 113                 # Then either it wasn't set or it was set to an invalid value
 114                 paginator = page = None
 115         else:
 116                 # There also shouldn't be pagination if the list is too short. Try count()
 117                 # first - good chance it's a queryset, where count is more efficient.
 118                 try:
 119                         if objects.count() <= per_page:
 120                                 paginator = page = None
 121                 except AttributeError:
 122                         if len(objects) <= per_page:
 123                                 paginator = page = None
 124
 125         try:
 126                 return paginator, page, objects
 127         except NameError:
 128                 pass
 129
 130         paginator = Paginator(objects, per_page)
 131         try:
 132                 page_number = int(page_number)
 133         except:
 134                 page_number = 1
 135
 136         try:
 137                 page = paginator.page(page_number)
 138         except EmptyPage:
 139                 page = None
 140         else:
 141                 objects = page.object_list
 142
 143         return paginator, page, objects
 144
 145
 146 ### Facilitating template analysis.
 147
 148
 149 LOADED_TEMPLATE_ATTR = '_philo_loaded_template'
 150 BLANK_CONTEXT = Context()
 151
 152
 153 def get_extended(self):
 154         return self.get_parent(BLANK_CONTEXT)
 155
 156
 157 def get_included(self):
 158         return self.template
 159
 160
 161 # We ignore the IncludeNode because it will never work in a blank context.
 162 setattr(ExtendsNode, LOADED_TEMPLATE_ATTR, property(get_extended))
 163 setattr(ConstantIncludeNode, LOADED_TEMPLATE_ATTR, property(get_included))