philo/contrib/shipherd/models.py

   1 #encoding: utf-8
   2 from django.core.exceptions import ValidationError
   3 from django.core.urlresolvers import NoReverseMatch
   4 from django.core.validators import RegexValidator, MinValueValidator
   5 from django.db import models
   6 from django.forms.models import model_to_dict
   7 from philo.models import TreeEntity, Node, TreeManager, Entity, TargetURLModel
   8 from philo.validators import RedirectValidator
   9 from UserDict import DictMixin
  10
  11
  12 DEFAULT_NAVIGATION_DEPTH = 3
  13
  14
  15 class NavigationQuerySetMapper(object, DictMixin):
  16         """This class exists to prevent setting of items in the navigation cache through node.navigation."""
  17         def __init__(self, node):
  18                 self.node = node
  19
  20         def __getitem__(self, key):
  21                 return Navigation.objects.get_cache_for(self.node)[key]['root_items']
  22
  23         def keys(self):
  24                 return Navigation.objects.get_cache_for(self.node).keys()
  25
  26
  27 def navigation(self):
  28         if not hasattr(self, '_navigation'):
  29                 self._navigation = NavigationQuerySetMapper(self)
  30         return self._navigation
  31
  32
  33 Node.navigation = property(navigation)
  34
  35
  36 class NavigationCacheQuerySet(models.query.QuerySet):
  37         """
  38         This subclass will trigger general cache clearing for Navigation.objects when a mass
  39         update or deletion is performed. As there is no convenient way to iterate over the
  40         changed or deleted instances, there's no way to be more precise about what gets cleared.
  41         """
  42         def update(self, *args, **kwargs):
  43                 super(NavigationCacheQuerySet, self).update(*args, **kwargs)
  44                 Navigation.objects.clear_cache()
  45
  46         def delete(self, *args, **kwargs):
  47                 super(NavigationCacheQuerySet, self).delete(*args, **kwargs)
  48                 Navigation.objects.clear_cache()
  49
  50
  51 class NavigationManager(models.Manager):
  52         # Since navigation is going to be hit frequently and changed
  53         # relatively infrequently, cache it. Analogous to contenttypes.
  54         use_for_related = True
  55         _cache = {}
  56
  57         def get_queryset(self):
  58                 return NavigationCacheQuerySet(self.model, using=self._db)
  59
  60         def get_cache_for(self, node, update_targets=True):
  61                 created = False
  62                 if not self.has_cache_for(node):
  63                         self.create_cache_for(node)
  64                         created = True
  65
  66                 if update_targets and not created:
  67                         self.update_targets_for(node)
  68
  69                 return self.__class__._cache[self.db][node]
  70
  71         def has_cache_for(self, node):
  72                 return self.db in self.__class__._cache and node in self.__class__._cache[self.db]
  73
  74         def create_cache_for(self, node):
  75                 "This method loops through the nodes ancestors and caches all unique navigation keys."
  76                 ancestors = node.get_ancestors(ascending=True, include_self=True)
  77
  78                 nodes_to_cache = []
  79
  80                 for node in ancestors:
  81                         if self.has_cache_for(node):
  82                                 cache = self.get_cache_for(node).copy()
  83                                 break
  84                         else:
  85                                 nodes_to_cache.insert(0, node)
  86                 else:
  87                         cache = {}
  88
  89                 for node in nodes_to_cache:
  90                         cache = cache.copy()
  91                         cache.update(self._build_cache_for(node))
  92                         self.__class__._cache.setdefault(self.db, {})[node] = cache
  93
  94         def _build_cache_for(self, node):
  95                 cache = {}
  96                 tree_id_attr = NavigationItem._mptt_meta.tree_id_attr
  97                 level_attr = NavigationItem._mptt_meta.level_attr
  98
  99                 for navigation in node.navigation_set.all():
 100                         tree_ids = navigation.roots.values_list(tree_id_attr)
 101                         items = list(NavigationItem.objects.filter(**{'%s__in' % tree_id_attr: tree_ids, '%s__lt' % level_attr: navigation.depth}).order_by('order', 'lft'))
 102
 103                         root_items = []
 104
 105                         for item in items:
 106                                 item._is_cached = True
 107
 108                                 if not hasattr(item, '_cached_children'):
 109                                         item._cached_children = []
 110
 111                                 if item.parent:
 112                                         # alternatively, if I don't want to force it to a list, I could keep track of
 113                                         # instances where the parent hasn't yet been met and do this step later for them.
 114                                         # delayed action.
 115                                         item.parent = items[items.index(item.parent)]
 116                                         if not hasattr(item.parent, '_cached_children'):
 117                                                 item.parent._cached_children = []
 118                                         item.parent._cached_children.append(item)
 119                                 else:
 120                                         root_items.append(item)
 121
 122                         cache[navigation.key] = {
 123                                 'navigation': navigation,
 124                                 'root_items': root_items,
 125                                 'items': items
 126                         }
 127
 128                 return cache
 129
 130         def clear_cache_for(self, node):
 131                 # Clear the cache for this node and all its descendants. The
 132                 # navigation for this node has probably changed, and for now,
 133                 # it isn't worth it to only clear the descendants actually
 134                 # affected by this.
 135                 if not self.has_cache_for(node):
 136                         # Already cleared.
 137                         return
 138
 139                 descendants = node.get_descendants(include_self=True)
 140                 cache = self.__class__._cache[self.db]
 141                 for node in descendants:
 142                         cache.pop(node, None)
 143
 144         def update_targets_for(self, node):
 145                 # Manually update a cache's target nodes in case something's changed there.
 146                 # This should be a less complex operation than reloading the models each
 147                 # time. Not as good as selective updates... but not much to be done
 148                 # about that. TODO: Benchmark it.
 149                 caches = self.__class__._cache[self.db][node].values()
 150
 151                 target_pks = set()
 152
 153                 for cache in caches:
 154                         target_pks |= set([item.target_node_id for item in cache['items']])
 155
 156                 # A distinct query is not strictly necessary. TODO: benchmark the efficiency
 157                 # with/without distinct.
 158                 targets = list(Node.objects.filter(pk__in=target_pks).distinct())
 159
 160                 for cache in caches:
 161                         for item in cache['items']:
 162                                 if item.target_node_id:
 163                                         item.target_node = targets[targets.index(item.target_node)]
 164
 165         def clear_cache(self):
 166                 self.__class__._cache.pop(self.db, None)
 167
 168
 169 class Navigation(Entity):
 170         objects = NavigationManager()
 171
 172         node = models.ForeignKey(Node, related_name='navigation_set', help_text="Be available as navigation for this node.")
 173         key = models.CharField(max_length=255, validators=[RegexValidator("\w+")], help_text="Must contain one or more alphanumeric characters or underscores.", db_index=True)
 174         depth = models.PositiveSmallIntegerField(default=DEFAULT_NAVIGATION_DEPTH, validators=[MinValueValidator(1)], help_text="Defines the maximum display depth of this navigation.")
 175
 176         def __init__(self, *args, **kwargs):
 177                 super(Navigation, self).__init__(*args, **kwargs)
 178                 self._initial_data = model_to_dict(self)
 179
 180         def __unicode__(self):
 181                 return "%s[%s]" % (self.node, self.key)
 182
 183         def _has_changed(self):
 184                 return self._initial_data != model_to_dict(self)
 185
 186         def save(self, *args, **kwargs):
 187                 super(Navigation, self).save(*args, **kwargs)
 188
 189                 if self._has_changed():
 190                         Navigation.objects.clear_cache_for(self.node)
 191                         self._initial_data = model_to_dict(self)
 192
 193         def delete(self, *args, **kwargs):
 194                 super(Navigation, self).delete(*args, **kwargs)
 195                 Navigation.objects.clear_cache_for(self.node)
 196
 197         class Meta:
 198                 unique_together = ('node', 'key')
 199
 200
 201 class NavigationItemManager(TreeManager):
 202         use_for_related = True
 203
 204         def get_queryset(self):
 205                 return NavigationCacheQuerySet(self.model, using=self._db)
 206
 207
 208 class NavigationItem(TreeEntity, TargetURLModel):
 209         objects = NavigationItemManager()
 210
 211         navigation = models.ForeignKey(Navigation, blank=True, null=True, related_name='roots', help_text="Be a root in this navigation tree.")
 212         text = models.CharField(max_length=50)
 213
 214         order = models.PositiveSmallIntegerField(default=0)
 215
 216         def __init__(self, *args, **kwargs):
 217                 super(NavigationItem, self).__init__(*args, **kwargs)
 218                 self._initial_data = model_to_dict(self)
 219                 self._is_cached = False
 220
 221         def __unicode__(self):
 222                 return self.get_path(field='text', pathsep=u' › ')
 223
 224         def clean(self):
 225                 super(NavigationItem, self).clean()
 226                 if bool(self.parent) == bool(self.navigation):
 227                         raise ValidationError("Exactly one of `parent` and `navigation` must be defined.")
 228
 229         def is_active(self, request):
 230                 if self.target_url == request.path:
 231                         # Handle the `default` case where the target_url and requested path
 232                         # are identical.
 233                         return True
 234
 235                 if self.target_node is None and self.url_or_subpath == "http%s://%s%s" % (request.is_secure() and 's' or '', request.get_host(), request.path):
 236                         # If there's no target_node, double-check whether it's a full-url
 237                         # match.
 238                         return True
 239
 240                 if self.target_node and not self.url_or_subpath:
 241                         # If there is a target node and it's targeted simply, but the target URL is not
 242                         # the same as the request path, check whether the target node is an ancestor
 243                         # of the requested node. If so, this is active unless the target node
 244                         # is the same as the ``host node`` for this navigation structure.
 245                         try:
 246                                 host_node = self.get_root().navigation.node
 247                         except AttributeError:
 248                                 pass
 249                         else:
 250                                 if self.target_node != host_node and self.target_node.is_ancestor_of(request.node):
 251                                         return True
 252
 253                 return False
 254
 255         def has_active_descendants(self, request):
 256                 for child in self.get_children():
 257                         if child.is_active(request) or child.has_active_descendants(request):
 258                                 return True
 259                 return False
 260
 261         def _has_changed(self):
 262                 if model_to_dict(self) == self._initial_data:
 263                         return False
 264                 return True
 265
 266         def _clear_cache(self):
 267                 try:
 268                         root = self.get_root()
 269                         if self.get_level() < root.navigation.depth:
 270                                 Navigation.objects.clear_cache_for(self.get_root().navigation.node)
 271                 except AttributeError:
 272                         pass
 273
 274         def save(self, *args, **kwargs):
 275                 super(NavigationItem, self).save(*args, **kwargs)
 276
 277                 if self._has_changed():
 278                         self._clear_cache()
 279
 280         def delete(self, *args, **kwargs):
 281                 super(NavigationItem, self).delete(*args, **kwargs)
 282                 self._clear_cache()