+import itertools
+
+from django.template import TextNode, VariableNode, Context
+from django.template.loader_tags import BlockNode, ExtendsNode, BlockContext, ConstantIncludeNode
+from django.utils.datastructures import SortedDict
+
+from philo.templatetags.containers import ContainerNode
+
+
+LOADED_TEMPLATE_ATTR = '_philo_loaded_template'
+BLANK_CONTEXT = Context()
+
+
+def get_extended(self):
+ return self.get_parent(BLANK_CONTEXT)
+
+
+def get_included(self):
+ return self.template
+
+
+# We ignore the IncludeNode because it will never work in a blank context.
+setattr(ExtendsNode, LOADED_TEMPLATE_ATTR, property(get_extended))
+setattr(ConstantIncludeNode, LOADED_TEMPLATE_ATTR, property(get_included))
+
+
+def get_containers(template):
+ # Build a tree of the templates we're using, placing the root template first.
+ levels = build_extension_tree(template.nodelist)
+
+ contentlet_specs = []
+ contentreference_specs = SortedDict()
+ blocks = {}
+
+ for level in reversed(levels):
+ level.initialize()
+ contentlet_specs.extend(itertools.ifilter(lambda x: x not in contentlet_specs, level.contentlet_specs))
+ contentreference_specs.update(level.contentreference_specs)
+ for name, block in level.blocks.items():
+ if block.block_super:
+ blocks.setdefault(name, []).append(block)
+ else:
+ blocks[name] = [block]
+
+ for block_list in blocks.values():
+ for block in block_list:
+ block.initialize()
+ contentlet_specs.extend(itertools.ifilter(lambda x: x not in contentlet_specs, block.contentlet_specs))
+ contentreference_specs.update(block.contentreference_specs)
+
+ return contentlet_specs, contentreference_specs
+
+
+class LazyContainerFinder(object):
+ def __init__(self, nodes, extends=False):
+ self.nodes = nodes
+ self.initialized = False
+ self.contentlet_specs = []
+ self.contentreference_specs = SortedDict()
+ self.blocks = {}
+ self.block_super = False
+ self.extends = extends
+
+ def process(self, nodelist):
+ for node in nodelist:
+ if self.extends:
+ if isinstance(node, BlockNode):
+ self.blocks[node.name] = block = LazyContainerFinder(node.nodelist)
+ block.initialize()
+ self.blocks.update(block.blocks)
+ continue
+
+ if isinstance(node, ContainerNode):
+ if not node.references:
+ self.contentlet_specs.append(node.name)
+ else:
+ if node.name not in self.contentreference_specs.keys():
+ self.contentreference_specs[node.name] = node.references
+ continue
+
+ if isinstance(node, VariableNode):
+ if node.filter_expression.var.lookups == (u'block', u'super'):
+ self.block_super = True
+
+ if hasattr(node, 'child_nodelists'):
+ for nodelist_name in node.child_nodelists:
+ if hasattr(node, nodelist_name):
+ nodelist = getattr(node, nodelist_name)
+ self.process(nodelist)
+
+ # LOADED_TEMPLATE_ATTR contains the name of an attribute philo uses to declare a
+ # node as rendering an additional template. Philo monkeypatches the attribute onto
+ # the relevant default nodes and declares it on any native nodes.
+ if hasattr(node, LOADED_TEMPLATE_ATTR):
+ loaded_template = getattr(node, LOADED_TEMPLATE_ATTR)
+ if loaded_template:
+ nodelist = loaded_template.nodelist
+ self.process(nodelist)
+
+ def initialize(self):
+ if not self.initialized:
+ self.process(self.nodes)
+ self.initialized = True
+
+
+def build_extension_tree(nodelist):
+ nodelists = []
+ extends = None
+ for node in nodelist:
+ if not isinstance(node, TextNode):
+ if isinstance(node, ExtendsNode):
+ extends = node
+ break
+
+ if extends:
+ if extends.nodelist:
+ nodelists.append(LazyContainerFinder(extends.nodelist, extends=True))
+ loaded_template = getattr(extends, LOADED_TEMPLATE_ATTR)
+ nodelists.extend(build_extension_tree(loaded_template.nodelist))
+ else:
+ # Base case: root.
+ nodelists.append(LazyContainerFinder(nodelist))
+ return nodelists
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