1# -*- coding: utf-8 -*-
2# Copyright 2009-2013, Peter A. Bigot
3#
4# Licensed under the Apache License, Version 2.0 (the "License"); you may
5# not use this file except in compliance with the License. You may obtain a
6# copy of the License at:
7#
8#            http://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13# License for the specific language governing permissions and limitations
14# under the License.
15
16"""Utility functions related to U{XML Namespaces<http://www.w3.org/TR/2006/REC-xml-names-20060816/index.html>}."""
17
18import logging
19import pyxb
20import pyxb.namespace
21from pyxb.utils import six
22
23_log = logging.getLogger(__name__)
24
25def NamespaceInstance (namespace):
26    """Get a namespace instance for the given namespace.
27
28    This is used when it is unclear whether the namespace is specified by URI
29    or by instance or by any other mechanism we might dream up in the
30    future."""
31    if isinstance(namespace, pyxb.namespace.Namespace):
32        return namespace
33    if isinstance(namespace, six.string_types):
34        return NamespaceForURI(namespace, True)
35    raise pyxb.LogicError('Cannot identify namespace from value of type %s' % (type(namespace),))
36
37def NamespaceForURI (uri, create_if_missing=False):
38    """Given a URI, provide the L{Namespace} instance corresponding to it.
39
40    This can only be used to lookup or create real namespaces.  To create
41    absent namespaces, use L{CreateAbsentNamespace}.
42
43    @param uri: The URI that identifies the namespace
44    @type uri: A non-empty C{str} or C{unicode} string
45    @keyword create_if_missing: If C{True}, a namespace for the given URI is
46    created if one has not already been registered.  Default is C{False}.
47    @type create_if_missing: C{bool}
48    @return: The Namespace corresponding to C{uri}, if available
49    @rtype: L{Namespace} or C{None}
50    @raise pyxb.LogicError: The uri is not a non-empty string
51    """
52    if not isinstance(uri, six.string_types):
53        raise pyxb.LogicError('Cannot lookup absent namespaces')
54    if 0 == len(uri):
55        raise pyxb.LogicError('Namespace URIs must not be empty strings')
56    rv = pyxb.namespace.Namespace._NamespaceForURI(uri)
57    if (rv is None) and create_if_missing:
58        rv = pyxb.namespace.Namespace(uri)
59    return rv
60
61def CreateAbsentNamespace ():
62    """Create an absent namespace.
63
64    Use this when you need a namespace for declarations in a schema with no
65    target namespace.  Absent namespaces are not stored in the infrastructure;
66    it is your responsibility to hold on to the reference you get from this,
67    because you won't be able to look it up."""
68    return pyxb.namespace.Namespace.CreateAbsentNamespace()
69
70def AvailableNamespaces ():
71    """Return the complete set of Namespace instances known to the system."""
72    return pyxb.namespace.Namespace.AvailableNamespaces()
73