python-tackerclient/tackerclient/common/serializer.py

# Copyright 2013 OpenStack Foundation.
# All Rights Reserved
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import logging
from xml.etree import ElementTree as etree
from xml.parsers import expat

from oslo_serialization import jsonutils
import six

from tackerclient.common import constants
from tackerclient.common import exceptions as exception
from tackerclient.i18n import _

LOG = logging.getLogger(__name__)

if six.PY3:
    long = int


class ActionDispatcher(object):
    """Maps method name to local methods through action name."""

    def dispatch(self, *args, **kwargs):
        """Find and call local method."""
        action = kwargs.pop('action', 'default')
        action_method = getattr(self, str(action), self.default)
        return action_method(*args, **kwargs)

    def default(self, data):
        raise NotImplementedError()


class DictSerializer(ActionDispatcher):
    """Default request body serialization."""

    def serialize(self, data, action='default'):
        return self.dispatch(data, action=action)

    def default(self, data):
        return ""


class JSONDictSerializer(DictSerializer):
    """Default JSON request body serialization."""

    def default(self, data):
        def sanitizer(obj):
            return six.text_type(obj)
        return jsonutils.dumps(data, default=sanitizer)


class XMLDictSerializer(DictSerializer):

    def __init__(self, metadata=None, xmlns=None):
        """XMLDictSerializer constructor.

        :param metadata: information needed to deserialize XML into
                         a dictionary.
        :param xmlns: XML namespace to include with serialized XML
        """
        super(XMLDictSerializer, self).__init__()
        self.metadata = metadata or {}
        if not xmlns:
            xmlns = self.metadata.get('xmlns')
        if not xmlns:
            xmlns = constants.XML_NS_V10
        self.xmlns = xmlns

    def default(self, data):
        """Default serializer of XMLDictSerializer.

        :param data: expect data to contain a single key as XML root, or
                     contain another '*_links' key as atom links. Other
                     case will use 'VIRTUAL_ROOT_KEY' as XML root.
        """
        try:
            links = None
            has_atom = False
            if data is None:
                root_key = constants.VIRTUAL_ROOT_KEY
                root_value = None
            else:
                link_keys = [k for k in six.iterkeys(data) or []
                             if k.endswith('_links')]
                if link_keys:
                    links = data.pop(link_keys[0], None)
                    has_atom = True
                root_key = (len(data) == 1 and
                            list(data.keys())[0] or constants.VIRTUAL_ROOT_KEY)
                root_value = data.get(root_key, data)
            doc = etree.Element("_temp_root")
            used_prefixes = []
            self._to_xml_node(doc, self.metadata, root_key,
                              root_value, used_prefixes)
            if links:
                self._create_link_nodes(list(doc)[0], links)
            return self.to_xml_string(list(doc)[0], used_prefixes, has_atom)
        except AttributeError as e:
            LOG.exception(str(e))
            return ''

    def __call__(self, data):
        # Provides a migration path to a cleaner WSGI layer, this
        # "default" stuff and extreme extensibility isn't being used
        # like originally intended
        return self.default(data)

    def to_xml_string(self, node, used_prefixes, has_atom=False):
        self._add_xmlns(node, used_prefixes, has_atom)
        return etree.tostring(node, encoding='UTF-8')

    # NOTE(ameade): the has_atom should be removed after all of the
    # XML serializers and view builders have been updated to the current
    # spec that required all responses include the xmlns:atom, the has_atom
    # flag is to prevent current tests from breaking
    def _add_xmlns(self, node, used_prefixes, has_atom=False):
        node.set('xmlns', self.xmlns)
        node.set(constants.TYPE_XMLNS, self.xmlns)
        if has_atom:
            node.set(constants.ATOM_XMLNS, constants.ATOM_NAMESPACE)
        node.set(constants.XSI_NIL_ATTR, constants.XSI_NAMESPACE)
        ext_ns = self.metadata.get(constants.EXT_NS, {})
        for prefix in used_prefixes:
            if prefix in ext_ns:
                node.set('xmlns:' + prefix, ext_ns[prefix])

    def _to_xml_node(self, parent, metadata, nodename, data, used_prefixes):
        """Recursive method to convert data members to XML nodes."""
        result = etree.SubElement(parent, nodename)
        if ":" in nodename:
            used_prefixes.append(nodename.split(":", 1)[0])
        # TODO(bcwaldon): accomplish this without a type-check
        if isinstance(data, list):
            if not data:
                result.set(
                    constants.TYPE_ATTR,
                    constants.TYPE_LIST)
                return result
            singular = metadata.get('plurals', {}).get(nodename, None)
            if singular is None:
                if nodename.endswith('s'):
                    singular = nodename[:-1]
                else:
                    singular = 'item'
            for item in data:
                self._to_xml_node(result, metadata, singular, item,
                                  used_prefixes)
        # TODO(bcwaldon): accomplish this without a type-check
        elif isinstance(data, dict):
            if not data:
                result.set(
                    constants.TYPE_ATTR,
                    constants.TYPE_DICT)
                return result
            attrs = metadata.get('attributes', {}).get(nodename, {})
            for k, v in sorted(data.items()):
                if k in attrs:
                    result.set(k, str(v))
                else:
                    self._to_xml_node(result, metadata, k, v,
                                      used_prefixes)
        elif data is None:
            result.set(constants.XSI_ATTR, 'true')
        else:
            if isinstance(data, bool):
                result.set(
                    constants.TYPE_ATTR,
                    constants.TYPE_BOOL)
            elif isinstance(data, int):
                result.set(
                    constants.TYPE_ATTR,
                    constants.TYPE_INT)
            elif isinstance(data, long):
                result.set(
                    constants.TYPE_ATTR,
                    constants.TYPE_LONG)
            elif isinstance(data, float):
                result.set(
                    constants.TYPE_ATTR,
                    constants.TYPE_FLOAT)
            LOG.debug("Data %(data)s type is %(type)s",
                      {'data': data,
                       'type': type(data)})
            result.text = six.text_type(data)
        return result

    def _create_link_nodes(self, xml_doc, links):
        for link in links:
            link_node = etree.SubElement(xml_doc, 'atom:link')
            link_node.set('rel', link['rel'])
            link_node.set('href', link['href'])


class TextDeserializer(ActionDispatcher):
    """Default request body deserialization."""

    def deserialize(self, datastring, action='default'):
        return self.dispatch(datastring, action=action)

    def default(self, datastring):
        return {}


class JSONDeserializer(TextDeserializer):

    def _from_json(self, datastring):
        try:
            return jsonutils.loads(datastring)
        except ValueError:
            msg = _("Cannot understand JSON")
            raise exception.MalformedResponseBody(reason=msg)

    def default(self, datastring):
        return {'body': self._from_json(datastring)}


class XMLDeserializer(TextDeserializer):

    def __init__(self, metadata=None):
        """XMLDeserializer constructor.

        :param metadata: information needed to deserialize XML into
                         a dictionary.
        """
        super(XMLDeserializer, self).__init__()
        self.metadata = metadata or {}
        xmlns = self.metadata.get('xmlns')
        if not xmlns:
            xmlns = constants.XML_NS_V10
        self.xmlns = xmlns

    def _get_key(self, tag):
        tags = tag.split("}", 1)
        if len(tags) == 2:
            ns = tags[0][1:]
            bare_tag = tags[1]
            ext_ns = self.metadata.get(constants.EXT_NS, {})
            if ns == self.xmlns:
                return bare_tag
            for prefix, _ns in ext_ns.items():
                if ns == _ns:
                    return prefix + ":" + bare_tag
        else:
            return tag

    def _get_links(self, root_tag, node):
        link_nodes = node.findall(constants.ATOM_LINK_NOTATION)
        root_tag = self._get_key(node.tag)
        link_key = "%s_links" % root_tag
        link_list = []
        for link in link_nodes:
            link_list.append({'rel': link.get('rel'),
                              'href': link.get('href')})
            # Remove link node in order to avoid link node being
            # processed as an item in _from_xml_node
            node.remove(link)
        return link_list and {link_key: link_list} or {}

    def _from_xml(self, datastring):
        if datastring is None:
            return None
        plurals = set(self.metadata.get('plurals', {}))
        try:
            node = etree.fromstring(datastring)
            root_tag = self._get_key(node.tag)
            links = self._get_links(root_tag, node)
            result = self._from_xml_node(node, plurals)
            # There is no case where root_tag = constants.VIRTUAL_ROOT_KEY
            # and links is not None because of the way data are serialized
            if root_tag == constants.VIRTUAL_ROOT_KEY:
                return result
            return dict({root_tag: result}, **links)
        except Exception as e:
            parseError = False
            # Python2.7
            if (hasattr(etree, 'ParseError') and
                    isinstance(e, getattr(etree, 'ParseError'))):
                parseError = True
            # Python2.6
            elif isinstance(e, expat.ExpatError):
                parseError = True
            if parseError:
                msg = _("Cannot understand XML")
                raise exception.MalformedResponseBody(reason=msg)
            else:
                raise

    def _from_xml_node(self, node, listnames):
        """Convert a minidom node to a simple Python type.

        :param node: minidom node name
        :param listnames: list of XML node names whose subnodes should
                          be considered list items.

        """
        attrNil = node.get(str(etree.QName(constants.XSI_NAMESPACE, "nil")))
        attrType = node.get(str(etree.QName(
            self.metadata.get('xmlns'), "type")))
        if (attrNil and attrNil.lower() == 'true'):
            return None
        elif not len(node) and not node.text:
            if (attrType and attrType == constants.TYPE_DICT):
                return {}
            elif (attrType and attrType == constants.TYPE_LIST):
                return []
            else:
                return ''
        elif (len(node) == 0 and node.text):
            converters = {constants.TYPE_BOOL:
                          lambda x: x.lower() == 'true',
                          constants.TYPE_INT:
                          lambda x: int(x),
                          constants.TYPE_LONG:
                          lambda x: long(x),
                          constants.TYPE_FLOAT:
                          lambda x: float(x)}
            if attrType and attrType in converters:
                return converters[attrType](node.text)
            else:
                return node.text
        elif self._get_key(node.tag) in listnames:
            return [self._from_xml_node(n, listnames) for n in node]
        else:
            result = dict()
            for attr in node.keys():
                if (attr == 'xmlns' or
                        attr.startswith('xmlns:') or
                        attr == constants.XSI_ATTR or
                        attr == constants.TYPE_ATTR):
                    continue
                result[self._get_key(attr)] = node.get(attr)
            children = list(node)
            for child in children:
                result[self._get_key(child.tag)] = self._from_xml_node(
                    child, listnames)
            return result

    def default(self, datastring):
        return {'body': self._from_xml(datastring)}

    def __call__(self, datastring):
        # Adding a migration path to allow us to remove unncessary classes
        return self.default(datastring)


# NOTE(maru): this class is duplicated from tacker.wsgi
class Serializer(object):
    """Serializes and deserializes dictionaries to certain MIME types."""

    def __init__(self, metadata=None, default_xmlns=None):
        """Create a serializer based on the given WSGI environment.

        'metadata' is an optional dict mapping MIME types to information
        needed to serialize a dictionary to that type.

        """
        self.metadata = metadata or {}
        self.default_xmlns = default_xmlns

    def _get_serialize_handler(self, content_type):
        handlers = {
            'application/json': JSONDictSerializer(),
            'application/xml': XMLDictSerializer(self.metadata),
        }

        try:
            return handlers[content_type]
        except Exception:
            raise exception.InvalidContentType(content_type=content_type)

    def serialize(self, data, content_type):
        """Serialize a dictionary into the specified content type."""
        return self._get_serialize_handler(content_type).serialize(data)

    def deserialize(self, datastring, content_type):
        """Deserialize a string to a dictionary.

        The string must be in the format of a supported MIME type.
        """
        return self.get_deserialize_handler(content_type).deserialize(
            datastring)

    def get_deserialize_handler(self, content_type):
        handlers = {
            'application/json': JSONDeserializer(),
            'application/xml': XMLDeserializer(self.metadata),
        }

        try:
            return handlers[content_type]
        except Exception:
            raise exception.InvalidContentType(content_type=content_type)