# Source code for rpyc.core.service

    """
    Services are the heart of RPyC: each side of the connection exposes a *service*,
    which define the capabilities available to the other side.

    Note that the services by both parties need not be symmetric, e.g., one side may
    exposed *service A*, while the other may expose *service B*. As long as the two
    can interoperate, you're good to go.
    """
    import importlib.util
    from functools import partial

    from rpyc.lib import hybridmethod
    from rpyc.lib.compat import execute
    from rpyc.core.protocol import Connection

    class Service(object):
        """The service base-class. Derive from this class to implement custom RPyC
        services:

        * The name of the class implementing the ``Foo`` service should match the
          pattern ``FooService`` (suffixed by the word 'Service') ::

              class FooService(Service):
                  pass

              FooService.get_service_name() # 'FOO'
              FooService.get_service_aliases() # ['FOO']

        * To supply a different name or aliases, use the ``ALIASES`` class attribute ::

              class Foobar(Service):
                  ALIASES = ["foo", "bar", "lalaland"]

              Foobar.get_service_name() # 'FOO'
              Foobar.get_service_aliases() # ['FOO', 'BAR', 'LALALAND']

        * Override :func:`on_connect` to perform custom initialization

        * Override :func:`on_disconnect` to perform custom finalization

        * To add exposed methods or attributes, simply define them normally,
          but prefix their name by ``exposed_``, e.g. ::

              class FooService(Service):
                  def exposed_add(self, x, y):
                      return x + y

        * All other names (not prefixed by ``exposed_``) are local (not accessible
          to the other party)

        .. note::
           You can override ``_rpyc_getattr``, ``_rpyc_setattr`` and ``_rpyc_delattr``
           to change attribute lookup -- but beware of possible **security implications!**
        """
        __slots__ = ()
        ALIASES = ()
        _protocol = Connection

        def on_connect(self, conn):
            """called when the connection is established"""
            pass

        def on_disconnect(self, conn):
            """called when the connection had already terminated for cleanup
            (must not perform any IO on the connection)"""
            pass

        # Using default defined in 'protocol.Connection._access_attr' for:
        # def _rpyc_getattr(self, name):

        def _rpyc_delattr(self, name):
            raise AttributeError("access denied")

        def _rpyc_setattr(self, name, value):
            raise AttributeError("access denied")

        @classmethod
        def get_service_aliases(cls):
            """returns a list of the aliases of this service"""
            if cls.ALIASES:
                return tuple(str(n).upper() for n in cls.ALIASES)
            name = cls.__name__.upper()
            if name.endswith("SERVICE"):
                name = name[:-7]
            return (name,)

        @classmethod
        def get_service_name(cls):
            """returns the canonical name of the service (which is its first
            alias)"""
            return cls.get_service_aliases()[0]

        exposed_get_service_aliases = get_service_aliases
        exposed_get_service_name = get_service_name

        @hybridmethod
        def _connect(self, channel, config={}):
            """Setup a connection via the given channel."""
            if isinstance(self, type):  # autovivify if accessed as class method
                self = self()
            # Note that we are here passing in `self` as root object for backward
            # compatibility and convenience. You could pass in a different root if
            # you wanted:
            conn = self._protocol(self, channel, config)
            self.on_connect(conn)
            return conn

    class VoidService(Service):
        """void service - an do-nothing service"""
        __slots__ = ()

    class ModuleNamespace(object):
        """used by the :class:`SlaveService` to implement the magical
        'module namespace'"""

        __slots__ = ["__getmodule", "__cache", "__weakref__"]

        def __init__(self, getmodule):
            self.__getmodule = getmodule
            self.__cache = {m: self.__getmodule(m) for m in ('builtins', 'importlib.util')}

        def __contains__(self, name):
            """Returns True if a module CAN be imported (the loader may still fail to execute module)"""
            return self.__cache['importlib.util']._find_spec_from_path(name) is not None

        def __getitem__(self, name):
            """Acts as a 'read-through-cache' for results of getmodule"""
            if name not in self.__cache:
                self.__cache[name] = self.__getmodule(name)
            return self.__cache[name]

        def __getattr__(self, name):
            """Provides dot notation access to modules"""
            try:
                return self[name]
            except ImportError:
                raise AttributeError(name)

    class Slave(object):
        __slots__ = ["_conn", "namespace"]

        def __init__(self):
            self._conn = None
            self.namespace = {}

        def execute(self, text):
            """execute arbitrary code (using ``exec``)"""
            execute(text, self.namespace)

        def eval(self, text):
            """evaluate arbitrary code (using ``eval``)"""
            return eval(text, self.namespace)

        def getmodule(self, name):
            """imports an arbitrary module"""
            if type(name) is tuple:
                name = ".".join(name)
            return importlib.import_module(name)

        def getconn(self):
            """returns the local connection instance to the other side"""
            return self._conn

    class SlaveService(Slave, Service):
        """The SlaveService allows the other side to perform arbitrary imports and
        execution arbitrary code on the server. This is provided for compatibility
        with the classic RPyC (2.6) modus operandi.

        This service is very useful in local, secure networks, but it exposes
        a **major security risk** otherwise."""
        __slots__ = ()

        def on_connect(self, conn):
            self._conn = conn
            self._conn._config.update(dict(
                allow_all_attrs=True,
                allow_pickle=True,
                allow_getattr=True,
                allow_setattr=True,
                allow_delattr=True,
                allow_exposed_attrs=False,
                import_custom_exceptions=True,
                instantiate_custom_exceptions=True,
                instantiate_oldstyle_exceptions=True,
            ))
            super().on_connect(conn)

    class FakeSlaveService(VoidService):
        """VoidService that can be used for connecting to peers that operate a
        :class:`MasterService`, :class:`ClassicService`, or the old
        ``SlaveService`` (pre v3.5) without exposing any functionality to them."""
        __slots__ = ()
        exposed_namespace = None
        exposed_execute = None
        exposed_eval = None
        exposed_getmodule = None
        exposed_getconn = None

    class MasterService(Service):

        """Peer for a new-style (>=v3.5) :class:`SlaveService`. Use this service
        if you want to connect to a ``SlaveService`` without exposing any
        functionality to them."""
        __slots__ = ()

        def on_connect(self, conn):
            super().on_connect(conn)
            self._install(conn, conn.root)

        @staticmethod
        def _install(conn, slave):
            modules = ModuleNamespace(slave.getmodule)
            conn.modules = modules
            conn.eval = slave.eval
            conn.execute = slave.execute
            conn.namespace = slave.namespace
            conn.builtins = modules.builtins
            conn.builtin = modules.builtins  # TODO: cruft from py2 that requires cleanup elsewhere and CHANGELOG note
            from rpyc.utils.classic import teleport_function
            conn.teleport = partial(teleport_function, conn)

    class ClassicService(MasterService, SlaveService):
        """Full duplex master/slave service, i.e. both parties have full control
        over the other. Must be used by both parties."""
        __slots__ = ()

    class ClassicClient(MasterService, FakeSlaveService):
        """MasterService that can be used for connecting to peers that operate a
        :class:`MasterService`, :class:`ClassicService` without exposing any
        functionality to them."""
        __slots__ = ()