# Source code for rdflib.query

    import os
    import shutil
    import tempfile
    import warnings
    import types

    from urllib.parse import urlparse
    try:
        from io import BytesIO
        assert BytesIO
    except:
        from io import StringIO as BytesIO

    from . import py3compat

    __all__ = ['Processor', 'Result', 'ResultParser', 'ResultSerializer',
               'ResultException']

    class Processor(object):
        """
        Query plugin interface.

        This module is useful for those wanting to write a query processor
        that can plugin to rdf. If you are wanting to execute a query you
        likely want to do so through the Graph class query method.

        """

        def __init__(self, graph):
            pass

        def query(self, strOrQuery, initBindings={}, initNs={}, DEBUG=False):
            pass

    class UpdateProcessor(object):
        """
        Update plugin interface.

        This module is useful for those wanting to write an update
        processor that can plugin to rdflib. If you are wanting to execute
        an update statement you likely want to do so through the Graph
        class update method.

        .. versionadded:: 4.0

        """

        def __init__(self, graph):
            pass
        def update(self, strOrQuery, initBindings={}, initNs={}):
            pass

    class ResultException(Exception):
        pass

    class EncodeOnlyUnicode(object):
        """
        This is a crappy work-around for
        http://bugs.python.org/issue11649

        """

        def __init__(self, stream):
            self.__stream = stream

        def write(self, arg):
            if isinstance(arg, str):
                self.__stream.write(arg.encode("utf-8"))
            else:
                self.__stream.write(arg)

        def __getattr__(self, name):
            return getattr(self.__stream, name)

    class ResultRow(tuple):
        """
        a single result row
        allows accessing bindings as attributes or with []

        >>> from rdflib import URIRef, Variable
        >>> rr=ResultRow({ Variable('a'): URIRef('urn:cake') }, [Variable('a')])

        >>> rr[0]
        rdflib.term.URIRef(%(u)s'urn:cake')
        >>> rr[1]
        Traceback (most recent call last):
            ...
        IndexError: tuple index out of range

        >>> rr.a
        rdflib.term.URIRef(%(u)s'urn:cake')
        >>> rr.b
        Traceback (most recent call last):
            ...
        AttributeError: b

        >>> rr['a']
        rdflib.term.URIRef(%(u)s'urn:cake')
        >>> rr['b']
        Traceback (most recent call last):
            ...
        KeyError: 'b'

        >>> rr[Variable('a')]
        rdflib.term.URIRef(%(u)s'urn:cake')

        .. versionadded:: 4.0

        """
        __doc__ = py3compat.format_doctest_out(__doc__)

        def __new__(cls, values, labels):

            instance = super(ResultRow, cls).__new__(
                cls, (values.get(v) for v in labels))
            instance.labels = dict((str(x[1]), x[0])
                                   for x in enumerate(labels))
            return instance

        def __getattr__(self, name):
            if name not in self.labels:
                raise AttributeError(name)
            return tuple.__getitem__(self, self.labels[name])

        def __getitem__(self, name):
            try:
                return tuple.__getitem__(self, name)
            except TypeError:
                if name in self.labels:
                    return tuple.__getitem__(self, self.labels[name])
                if str(name) in self.labels:  # passing in variable object
                    return tuple.__getitem__(self, self.labels[str(name)])
                raise KeyError(name)

        def asdict(self):
            return dict((v, self[v]) for v in self.labels if self[v] != None)

    class Result(object):
        """
        A common class for representing query result.

        There is a bit of magic here that makes this appear like different
        Python objects, depending on the type of result.

        If the type is "SELECT", iterating will yield lists of QueryRow objects

        If the type is "ASK", iterating will yield a single bool (or
        bool(result) will return the same bool)

        If the type is "CONSTRUCT" or "DESCRIBE" iterating will yield the
        triples.

        len(result) also works.

        """
        def __init__(self, type_):

            if type_ not in ('CONSTRUCT', 'DESCRIBE', 'SELECT', 'ASK'):
                raise ResultException('Unknown Result type: %s' % type_)

            self.type = type_
            self.vars = None
            self._bindings = None
            self._genbindings = None
            self.askAnswer = None
            self.graph = None

        def _get_bindings(self):
            if self._genbindings:
                self._bindings += list(self._genbindings)
                self._genbindings = None

            return self._bindings

        def _set_bindings(self, b):
            if isinstance(b, types.GeneratorType):
                self._genbindings = b
                self._bindings = []
            else:
                self._bindings = b

        bindings = property(
            _get_bindings, _set_bindings, doc="a list of variable bindings as dicts")

        @staticmethod
        def parse(source, format='xml', **kwargs):
            from rdflib import plugin
            parser = plugin.get(format, ResultParser)()
            return parser.parse(source, **kwargs)

        def serialize(
                self, destination=None, encoding="utf-8", format='xml', **args):

            if self.type in ('CONSTRUCT', 'DESCRIBE'):
                return self.graph.serialize(
                    destination, encoding=encoding, format=format, **args)

            """stolen wholesale from graph.serialize"""
            from rdflib import plugin
            serializer = plugin.get(format, ResultSerializer)(self)
            if destination is None:
                stream = BytesIO()
                stream2 = EncodeOnlyUnicode(stream)
                serializer.serialize(stream2, encoding=encoding, **args)
                return stream.getvalue()
            if hasattr(destination, "write"):
                stream = destination
                serializer.serialize(stream, encoding=encoding, **args)
            else:
                location = destination
                scheme, netloc, path, params, query, fragment = urlparse(location)
                if netloc != "":
                    print(("WARNING: not saving as location" +
                          "is not a local file reference"))
                    return
                fd, name = tempfile.mkstemp()
                stream = os.fdopen(fd, 'wb')
                serializer.serialize(stream, encoding=encoding, **args)
                stream.close()
                if hasattr(shutil, "move"):
                    shutil.move(name, path)
                else:
                    shutil.copy(name, path)
                    os.remove(name)

        def __len__(self):
            if self.type == 'ASK':
                return 1
            elif self.type == 'SELECT':
                return len(self.bindings)
            else:
                return len(self.graph)

        def __bool__(self):
            if self.type == 'ASK':
                return self.askAnswer
            else:
                return len(self)>0

        def __iter__(self):
            if self.type in ("CONSTRUCT", "DESCRIBE"):
                for t in self.graph:
                    yield t
            elif self.type == 'ASK':
                yield self.askAnswer
            elif self.type == 'SELECT':
                # this iterates over ResultRows of variable bindings

                if self._genbindings:
                    for b in self._genbindings:
                        if b:  # don't add a result row in case of empty binding {}
                            self._bindings.append(b)
                            yield ResultRow(b, self.vars)
                    self._genbindings = None
                else:
                    for b in self._bindings:
                        if b:  # don't add a result row in case of empty binding {}
                            yield ResultRow(b, self.vars)

        def __getattr__(self, name):
            if self.type in ("CONSTRUCT", "DESCRIBE") and self.graph is not None:
                return self.graph.__getattr__(self, name)
            elif self.type == 'SELECT' and name == 'result':
                warnings.warn(
                    "accessing the 'result' attribute is deprecated."
                    " Iterate over the object instead.",
                    DeprecationWarning, stacklevel=2)
                # copied from __iter__, above
                return [(tuple(b[v] for v in self.vars)) for b in self.bindings]
            else:
                raise AttributeError(
                    "'%s' object has no attribute '%s'" % (self, name))

        def __eq__(self, other):
            try:
                if self.type != other.type:
                    return False
                if self.type == 'ASK':
                    return self.askAnswer == other.askAnswer
                elif self.type == 'SELECT':
                    return self.vars == other.vars \
                        and self.bindings == other.bindings
                else:
                    return self.graph == other.graph

            except:
                return False

    class ResultParser(object):

        def __init__(self):
            pass

        def parse(self, source, **kwargs):
            """return a Result object"""
            pass  # abstract

    class ResultSerializer(object):

        def __init__(self, result):
            self.result = result

        def serialize(self, stream, encoding="utf-8", **kwargs):
            """return a string properly serialized"""
            pass  # abstract