"""
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, types) :
"""
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")
# lookup type, None for default
type = types[type]
# 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: %s" % (value, self.type.__name__, type(e).__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 URLConfig (object) :
"""
Global configuration relevant to all URLs
"""
# built-in type codes
BUILTIN_TYPES = {
# default
None : str,
# integer
'int' : int,
}
def __init__ (self, type_dict=None) :
"""
Create an URLConfig for use with URL
If type_dict is given, it should be a mapping of type names -> callables, and they will be available for
type specifications in addition to the defaults.
"""
# build our type_dict
self.type_dict = self.BUILTIN_TYPES.copy()
# apply the given type_dict
if type_dict :
self.type_dict.update(type_dict)
class URL (object) :
"""
Represents a specific URL
"""
def __init__ (self, config, url_mask, handler, type_dict=None, **defaults) :
"""
Create an URL using the given URLConfig, with the given url mask, handler, and default values.
"""
# store
self.config = config
self.url_mask = url_mask
self.handler = handler
self.defaults = defaults
# build our labels
self.label_path = [Label.parse(mask, defaults, config.type_dict) 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.copy()
# 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: %s + %s + %s" % (self.get_url(), label, '/'.join(str(l) for l in label_path)))
# 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 get_url (self) :
"""
Returns the URL for this node, by iterating over our parents
"""
# URL segments in reverse order
segments = ['']
# start with ourself
node = self
# iterate up to root
while node :
segments.append(str(node.label))
node = node.parent
# reverse
segments.reverse()
# return
return '/'.join(segments)
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.
"""
# split it into labels
path = url.split('/')
# empty URL is empty
if url :
# ensure that it doesn't start with a /
assert not self.root.label.match(path[0]), "URL must not 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 requested URL
request_url = request.get_page_name()
# find the URL+values to use
url, label_values = self.match(request_url)
# let the URL handle it
return url.execute(request, label_values)