"""Python version compatibility support for minidom.

This module contains internal implementation details and
should not be imported; use xml.dom.minidom instead.
"""

# This module should only be imported using "import *".
#
# The following names are defined:
#
# NodeList -- lightest possible NodeList implementation
#
# EmptyNodeList -- lightest possible NodeList that is guaranteed to
# remain empty (immutable)
#
# StringTypes -- tuple of defined string types
#
# defproperty -- function used in conjunction with GetattrMagic;
# using these together is needed to make them work
# as efficiently as possible in both Python 2.2+
# and older versions. For example:
#
# class MyClass(GetattrMagic):
# def _get_myattr(self):
# return something
#
# defproperty(MyClass, "myattr",
# "return some value")
#
# For Python 2.2 and newer, this will construct a
# property object on the class, which avoids
# needing to override __getattr__(). It will only
# work for read-only attributes.
#
# For older versions of Python, inheriting from
# GetattrMagic will use the traditional
# __getattr__() hackery to achieve the same effect,
# but less efficiently.
#
# defproperty() should be used for each version of
# the relevant _get_<property>() function.

__all__ = ["NodeList", "EmptyNodeList", "StringTypes", "defproperty"]

import xml.dom

StringTypes = (str,)


class NodeList(list):
 __slots__ = ()

 def item(self, index):
 if 0 <= index < len(self):
 return self[index]

 def _get_length(self):
 return len(self)

 def _set_length(self, value):
 raise xml.dom.NoModificationAllowedErr(
 "attempt to modify read-only attribute 'length'")

 length = property(_get_length, _set_length,
 doc="The number of nodes in the NodeList.")

 # For backward compatibility
 def __setstate__(self, state):
 if state is None:
 state = []
 self[:] = state


class EmptyNodeList(tuple):
 __slots__ = ()

 def __add__(self, other):
 NL = NodeList()
 NL.extend(other)
 return NL

 def __radd__(self, other):
 NL = NodeList()
 NL.extend(other)
 return NL

 def item(self, index):
 return None

 def _get_length(self):
 return 0

 def _set_length(self, value):
 raise xml.dom.NoModificationAllowedErr(
 "attempt to modify read-only attribute 'length'")

 length = property(_get_length, _set_length,
 doc="The number of nodes in the NodeList.")


def defproperty(klass, name, doc):
 get = getattr(klass, ("_get_" + name))
 def set(self, value, name=name):
 raise xml.dom.NoModificationAllowedErr(
 "attempt to modify read-only attribute " + repr(name))
 assert not hasattr(klass, "_set_" + name), \
 "expected not to find _set_" + name
 prop = property(get, set, doc=doc)
 setattr(klass, name, prop)