--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/sites/irclogs.qmsk.net/urltree.py Sat Feb 07 21:02:33 2009 +0200
@@ -0,0 +1,497 @@
+"""
+ Tree-based URL mapping
+"""
+
+import re
+import os.path
+
+# for Mapper
+from lib import map
+
+class URLError (Exception) :
+ """
+ Error with an URL definition
+ """
+
+ pass
+
+class LabelValue (object) :
+ """
+ Represents the value of a ValueLabel... love these names
+ """
+
+ def __init__ (self, label, value) :
+ """
+ Just store
+ """
+
+ self.label = label
+ self.value = value
+
+ def __str__ (self) :
+ return "%s=%r" % (self.label.key, self.value)
+
+ def __repr__ (self) :
+ return "<%s>" % self
+
+class Label (object) :
+ """
+ Base class for URL labels (i.e. the segments of the URL between /s)
+ """
+
+ @staticmethod
+ def parse (mask, defaults) :
+ """
+ Parse the given label-segment, and return a *Label instance
+ """
+
+ # empty?
+ if not mask :
+ return EmptyLabel()
+
+ # simple value?
+ match = SimpleValueLabel.EXPR.match(mask)
+
+ if match :
+ # key
+ key = match.group('key')
+
+ # type
+ type = match.group("type")
+
+ if type :
+ # XXX: resolve using eval() for now, should be a module or something
+ type = eval(type)
+
+ else :
+ type = str
+
+ # defaults?
+ default = defaults.get(key)
+
+ if not default :
+ default = match.group('default')
+
+ if default :
+ # apply type to default
+ default = type(default)
+
+ # build
+ return SimpleValueLabel(key, type, default)
+
+ # static?
+ match = StaticLabel.EXPR.match(mask)
+
+ if match :
+ return StaticLabel(match.group('name'))
+
+ # invalid
+ raise URLError("Invalid label: %r" % (mask, ))
+
+ def match (self, value=None) :
+ """
+ Match this label against the given value, returning either True to match without a value, a LabelValue
+ object, or boolean false to not match.
+
+ If value is None, this means that only a default value should be returned.
+ """
+
+ abstract
+
+class EmptyLabel (Label) :
+ """
+ An empty label, i.e. just a slash in the URL
+ """
+
+ def __eq__ (self, other) :
+ """
+ Just compares type
+ """
+
+ return isinstance(other, EmptyLabel)
+
+ def match (self, value=None) :
+ """
+ Match empty string -> True
+ """
+
+ # no default
+ if value is None :
+ return False
+
+ # only empty segments
+ if value == '' :
+ return True
+
+ def __str__ (self) :
+ return ''
+
+class StaticLabel (Label) :
+ """
+ A simple literal Label, used for fixed terms in the URL
+ """
+
+ EXPR = re.compile(r'^(?P<name>[a-zA-Z_.-]+)$')
+
+ def __init__ (self, name) :
+ """
+ The given name is the literal name of this label
+ """
+
+ self.name = name
+
+ def __eq__ (self, other) :
+ """
+ Compares names
+ """
+
+ return isinstance(other, StaticLabel) and self.name == other.name
+
+ def match (self, value=None) :
+ """
+ Match exactly -> True
+ """
+
+ # no defaults
+ if value is None :
+ return False
+
+ # match name
+ if value == self.name :
+ return True
+
+ def __str__ (self) :
+ return self.name
+
+class ValueLabel (Label) :
+ """
+ A label with a key and a value
+
+ XXX: do we even need this?
+ """
+
+ def __init__ (self, key, default) :
+ """
+ Set the key and default value. Default value may be None if there is no default value defined
+ """
+
+ self.key = key
+ self.default = default
+
+ def __eq__ (self, other) :
+ """
+ Compares keys
+ """
+
+ return isinstance(other, ValueLabel) and self.key == other.key
+
+class SimpleValueLabel (ValueLabel) :
+ """
+ A label that has a name and a simple string value
+ """
+
+ EXPR = re.compile(r'^\{(?P<key>[a-zA-Z_][a-zA-Z0-9_]*)(:(?P<type>[a-zA-Z_][a-zA-Z0-9_]*))?(=(?P<default>[^}]+))?\}$')
+
+ def __init__ (self, key, type=str, default=None) :
+ """
+ The given key is the name of this label's value
+ """
+
+ # type
+ self.type = type
+
+ # store
+ self.key = key
+ self.default = default
+
+ def match (self, value=None) :
+ """
+ Match -> LabelValue
+ """
+
+ # default?
+ if value is None and self.default :
+ return LabelValue(self, self.default)
+
+ # only non-empty values!
+ elif value :
+ # convert with type
+ try :
+ value = self.type(value)
+
+ except Exception, e :
+ raise URLError("Bad value %r for type %s: %s" % (value, self.type.__name__, e))
+
+ return LabelValue(self, value)
+
+ def __str__ (self) :
+ return '{%s%s%s}' % (
+ self.key,
+ ':%s' % (self.type.__name__ ) if self.type != str else '',
+ '=%s' % (self.default, ) if self.default else '',
+ )
+
+class URL (object) :
+ """
+ Represents a specific URL
+ """
+
+ def __init__ (self, url_mask, handler, **defaults) :
+ """
+ Create an URL with the given url mask, handler, and default values
+ """
+
+ # store
+ self.url_mask = url_mask
+ self.handler = handler
+ self.defaults = defaults
+
+ # build our labels
+ self.label_path = [Label.parse(mask, defaults) for mask in url_mask.split('/')]
+
+ def get_label_path (self) :
+ """
+ Returns a list containing the labels in this url
+ """
+
+ # copy self.label_path
+ return list(self.label_path)
+
+ def execute (self, request, label_values) :
+ """
+ Invoke the handler, using the given label values
+ """
+
+ # start with the defaults
+ kwargs = self.defaults()
+
+ # then add all the values
+ for label_value in label_values :
+ kwargs[label_value.label.key] = label_value.value
+
+ # execute the handler
+ return self.handler(request, **kwargs)
+
+ def __str__ (self) :
+ return '/'.join(str(label) for label in self.label_path)
+
+ def __repr__ (self) :
+ return "URL(%r, %r)" % (str(self), self.handler)
+
+class URLNode (object) :
+ """
+ Represents a node in the URLTree
+ """
+
+ def __init__ (self, parent, label) :
+ """
+ Initialize with the given parent and label, empty children dict
+ """
+
+ # the parent URLNode
+ self.parent = parent
+
+ # this node's Label
+ self.label = label
+
+ # list of child URLNodes
+ self.children = []
+
+ # this node's URL, set by add_url for an empty label_path
+ self.url = None
+
+ def _build_child (self, label) :
+ """
+ Build, insert and return a new child Node
+ """
+
+ # build new child
+ child = URLNode(self, label)
+
+ # add to children
+ self.children.append(child)
+
+ # return
+ return child
+
+ def add_url (self, url, label_path) :
+ """
+ Add a URL object to this node under the given path. Uses recursion to process the path.
+
+ The label_path argument is a (partial) label path as returned by URL.get_label_path.
+
+ If label_path is empty (len zero, or begins with EmptyLabel), then the given url is assigned to this node, if no
+ url was assigned before.
+ """
+
+ # matches this node?
+ if not label_path or isinstance(label_path[0], EmptyLabel) :
+ if self.url :
+ raise URLError(url, "node already defined")
+
+ else :
+ # set
+ self.url = url
+
+ else :
+ # pop child label from label_path
+ child_label = label_path.pop(0)
+
+ # look for the child to recurse into
+ child = None
+
+ # look for an existing child with that label
+ for child in self.children :
+ if child.label == child_label :
+ # found, use this
+ break
+
+ else :
+ # build a new child
+ child = self._build_child(child_label)
+
+ # recurse to handle the rest of the label_path
+ child.add_url(url, label_path)
+
+ def match (self, label_path) :
+ """
+ Locate the URL object corresponding to the given label_path value under this node.
+
+ Returns a (url, label_values) tuple
+ """
+
+ # determine value to use
+ value = None
+
+ # empty label_path?
+ if not label_path or label_path[0] == '' :
+ # the search ends at this node
+ if self.url :
+ # this URL is the best match
+ return (self.url, [])
+
+ elif not self.children :
+ # incomplete URL
+ raise URLError("no URL handler defined for this Node")
+
+ else :
+ # use default value, i.e. Label.match(None)
+ label = None
+
+ else :
+ # pop the next label from the label path
+ label = label_path.pop(0)
+
+ # return one match...
+ match = value = None
+
+ # recurse through our children, DFS
+ for child in self.children :
+ # match value
+ value = child.label.match(label)
+
+ # skip those that don't match at all
+ if not value :
+ continue;
+
+ # already found a match? :/
+ if match :
+ raise URLError("Ambiguous URL")
+
+ # ok, but continue looking to make sure there's no ambiguous URLs
+ match = child
+
+ # found something?
+ if not match :
+ raise URLError("No child found for label")
+
+ # ok, recurse into the match
+ url, label_value = match.match(label_path)
+
+ # add our value?
+ if isinstance(value, LabelValue) :
+ label_value.append(value)
+
+ # return the match
+ return url, label_value
+
+ def dump (self, indent=0) :
+ """
+ Returns a multi-line string representation of this Node
+ """
+
+ return '\n'.join([
+ "%-45s%s" % (
+ ' '*indent + str(self.label) + ('/' if self.children else ''),
+ (' -> %r' % self.url) if self.url else ''
+ )
+ ] + [
+ child.dump(indent + 4) for child in self.children
+ ])
+
+ def __str__ (self) :
+ return "%s/[%s]" % (self.label, ','.join(str(child) for child in self.children))
+
+class URLTree (map.Mapper) :
+ """
+ Map requests to handlers, using a defined tree of URLs
+ """
+
+ def __init__ (self, url_list) :
+ """
+ Initialize the tree using the given list of URLs
+ """
+
+ # root node
+ self.root = URLNode(None, EmptyLabel())
+
+ # just add each URL
+ for url in url_list :
+ self.add_url(url)
+
+ def add_url (self, url) :
+ """
+ Adds the given URL to the tree. The URL must begin with a root slash.
+ """
+ # get url's label path
+ path = url.get_label_path()
+
+ # should begin with root
+ root_label = path.pop(0)
+ assert root_label == self.root.label, "URL must begin with root"
+
+ # add to root
+ self.root.add_url(url, path)
+
+ def match (self, url) :
+ """
+ Find the URL object best corresponding to the given url, matching any ValueLabels.
+
+ Returns an (URL, [LabelValue]) tuple.
+ """
+
+ # normalize the URL
+ url = os.path.normpath(url)
+
+ # split it into labels
+ path = url.split('/')
+
+ # ensure that it starts with a /
+ root_label = path.pop(0)
+ assert self.root.label.match(root_label), "URL must begin with root"
+
+ # just match starting at root
+ return self.root.match(path)
+
+ def handle_request (self, request) :
+ """
+ Looks up the request's URL, and invokes its handler
+ """
+
+ # get the request's URL path
+ url, label_values = self.match(request.get_page_name())
+
+ # let the URL handle it
+ url.execute(request, label_values)
+
+