"""Python version compatibility support for minidom."""

# This module should only be imported using "import *".

#

# The following names are defined:

#

#   NodeList      -- lightest possible NodeList implementation

#

#   EmptyNodeList -- lightest possible NodeList that is guarateed 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

try:

    unicode

except NameError:

    StringTypes = type(''),

else:

    StringTypes = type(''), type(unicode(''))

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.")

    def __getstate__(self):

        return list(self)

    def __setstate__(self, 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)).im_func

    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)