# 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.
    """
    from rpyc.lib.compat import execute, is_py3k

    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__ = ["_conn"]
        ALIASES = ()

        def __init__(self, conn):
            self._conn = conn
        def on_connect(self):
            """called when the connection is established"""
            pass
        def on_disconnect(self):
            """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

    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 = {}
        def __contains__(self, name):
            try:
                self[name]
            except ImportError:
                return False
            else:
                return True
        def __getitem__(self, name):
            if type(name) is tuple:
                name = ".".join(name)
            if name not in self.__cache:
                self.__cache[name] = self.__getmodule(name)
            return self.__cache[name]
        def __getattr__(self, name):
            return self[name]

    class SlaveService(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__ = ["exposed_namespace"]

        def on_connect(self):
            self.exposed_namespace = {}
            self._conn._config.update(dict(
                allow_all_attrs = True,
                allow_pickle = True,
                allow_getattr = True,
                allow_setattr = True,
                allow_delattr = True,
                import_custom_exceptions = True,
                instantiate_custom_exceptions = True,
                instantiate_oldstyle_exceptions = True,
            ))
            # shortcuts
            self._conn.modules = ModuleNamespace(self._conn.root.getmodule)
            self._conn.eval = self._conn.root.eval
            self._conn.execute = self._conn.root.execute
            self._conn.namespace = self._conn.root.namespace
            if is_py3k:
                self._conn.builtin = self._conn.modules.builtins
            else:
                self._conn.builtin = self._conn.modules.__builtin__
            self._conn.builtins = self._conn.builtin

        def exposed_execute(self, text):
            """execute arbitrary code (using ``exec``)"""
            execute(text, self.exposed_namespace)
        def exposed_eval(self, text):
            """evaluate arbitrary code (using ``eval``)"""
            return eval(text, self.exposed_namespace)
        def exposed_getmodule(self, name):
            """imports an arbitrary module"""
            return __import__(name, None, None, "*")
        def exposed_getconn(self):
            """returns the local connection instance to the other side"""
            return self._conn