# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2013 Red Hat, Inc.
# 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.

"""
RPC Controller
"""
import datetime
import traceback

from oslo.config import cfg
from webob import exc

from glance.common import client
from glance.common import exception
from glance.common import wsgi
import glance.openstack.common.importutils as imp
import glance.openstack.common.log as logging
from glance.openstack.common import timeutils

LOG = logging.getLogger(__name__)


rpc_opts = [
    # NOTE(flaper87): Shamelessly copied
    # from oslo rpc.
    cfg.ListOpt('allowed_rpc_exception_modules',
                default=['openstack.common.exception',
                         'glance.common.exception',
                         'exceptions',
                         ],
                help='Modules of exceptions that are permitted to be recreated'
                     'upon receiving exception data from an rpc call.'),
]

CONF = cfg.CONF
CONF.register_opts(rpc_opts)


class RPCJSONSerializer(wsgi.JSONResponseSerializer):

    def _sanitizer(self, obj):
        def to_primitive(_type, _value):
            return {"_type": _type, "_value": _value}

        if isinstance(obj, datetime.datetime):
            return to_primitive("datetime", timeutils.strtime(obj))

        return super(RPCJSONSerializer, self)._sanitizer(obj)


class RPCJSONDeserializer(wsgi.JSONRequestDeserializer):

    def _to_datetime(self, obj):
        return timeutils.parse_strtime(obj)

    def _sanitizer(self, obj):
        try:
            _type, _value = obj["_type"], obj["_value"]
            return getattr(self, "_to_" + _type)(_value)
        except (KeyError, AttributeError):
            return obj


class Controller(object):
    """
    Base RPCController.

    This is the base controller for RPC based APIs. Commands
    handled by this controller respect the following form:

        [{
            'command': 'method_name',
            'kwargs': {...}
        }]

    The controller is capable of processing more than one command
    per request and will always return a list of results.

    :params raise_exc: Boolean that specifies whether to raise
    exceptions instead of "serializing" them.
    """

    def __init__(self, raise_exc=False):
        self._registered = {}
        self.raise_exc = raise_exc

    def register(self, resource, filtered=None, excluded=None, refiner=None):
        """
        Exports methods through the RPC Api.

        :params resource: Resource's instance to register.
        :params filtered: List of methods that *can* me registered. Read
        as "Method must be in this list".
        :params excluded: List of methods to exclude.
        :params refiner: Callable to use as filter for methods.

        :raises AssertionError: If refiner is not callable.
        """

        funcs = filter(lambda x: not x.startswith("_"), dir(resource))

        if filtered:
            funcs = [f for f in funcs if f in filtered]

        if excluded:
            funcs = [f for f in funcs if f not in excluded]

        if refiner:
            assert callable(refiner), "Refiner must be callable"
            funcs = filter(refiner, funcs)

        for name in funcs:
            meth = getattr(resource, name)

            if not callable(meth):
                continue

            self._registered[name] = meth

    def __call__(self, req, body):
        """
        Executes the command
        """

        if not isinstance(body, list):
            msg = _("Request must be a list of commands")
            raise exc.HTTPBadRequest(explanation=msg)

        def validate(cmd):
            if not isinstance(cmd, dict):
                msg = _("Bad Command: %s") % str(cmd)
                raise exc.HTTPBadRequest(explanation=msg)

            command, kwargs = cmd.get("command"), cmd.get("kwargs")

            if (not command or not isinstance(command, basestring) or
                    (kwargs and not isinstance(kwargs, dict))):
                msg = _("Wrong command structure: %s") % (str(cmd))
                raise exc.HTTPBadRequest(explanation=msg)

            method = self._registered.get(command)
            if not method:
                # Just raise 404 if the user tries to
                # access a private method. No need for
                # 403 here since logically the command
                # is not registered to the rpc dispatcher
                raise exc.HTTPNotFound(explanation=_("Command not found"))

            return True

        # If more than one command were sent then they might
        # be intended to be executed sequentially, that for,
        # lets first verify they're all valid before executing
        # them.
        commands = filter(validate, body)

        results = []
        for cmd in commands:
            # kwargs is not required
            command, kwargs = cmd["command"], cmd.get("kwargs", {})
            method = self._registered[command]
            try:
                result = method(req.context, **kwargs)
            except Exception as e:
                if self.raise_exc:
                    raise

                cls, val = e.__class__, str(e)
                msg = (_("RPC Call Error: %(val)s\n%(tb)s") %
                       dict(val=val, tb=traceback.format_exc()))
                LOG.error(msg)

                # NOTE(flaper87): Don't propagate all exceptions
                # but the ones allowed by the user.
                module = cls.__module__
                if module not in CONF.allowed_rpc_exception_modules:
                    cls = exception.RPCError
                    val = str(exception.RPCError(cls=cls, val=val))

                cls_path = "%s.%s" % (cls.__module__, cls.__name__)
                result = {"_error": {"cls": cls_path, "val": val}}
            results.append(result)
        return results


class RPCClient(client.BaseClient):

    def __init__(self, *args, **kwargs):
        self._serializer = RPCJSONSerializer()
        self._deserializer = RPCJSONDeserializer()

        self.raise_exc = kwargs.pop("raise_exc", True)
        self.base_path = kwargs.pop("base_path", '/rpc')
        super(RPCClient, self).__init__(*args, **kwargs)

    @client.handle_unauthenticated
    def bulk_request(self, commands):
        """
        Execute multiple commands in a single request.

        :params commands: List of commands to send. Commands
        must respect the following form:

            {
                'command': 'method_name',
                'kwargs': method_kwargs
            }
        """
        body = self._serializer.to_json(commands)
        response = super(RPCClient, self).do_request('POST',
                                                     self.base_path,
                                                     body)
        return self._deserializer.from_json(response.read())

    def do_request(self, method, **kwargs):
        """
        Simple do_request override. This method serializes
        the outgoing body and builds the command that will
        be sent.

        :params method: The remote python method to call
        :params kwargs: Dynamic parameters that will be
            passed to the remote method.
        """
        content = self.bulk_request([{'command': method,
                                      'kwargs': kwargs}])

        # NOTE(flaper87): Return the first result if
        # a single command was executed.
        content = content[0]

        # NOTE(flaper87): Check if content is an error
        # and re-raise it if raise_exc is True. Before
        # checking if content contains the '_error' key,
        # verify if it is an instance of dict - since the
        # RPC call may have returned something different.
        if self.raise_exc and (isinstance(content, dict)
                               and '_error' in content):
            error = content['_error']
            try:
                exc_cls = imp.import_class(error['cls'])
                raise exc_cls(error['val'])
            except ImportError:
                # NOTE(flaper87): The exception
                # class couldn't be imported, using
                # a generic exception.
                raise exception.RPCError(**error)
        return content

    def __getattr__(self, item):
        """
        This method returns a method_proxy that
        will execute the rpc call in the registry
        service.
        """
        if item.startswith('_'):
            raise AttributeError(item)

        def method_proxy(**kw):
            return self.do_request(item, **kw)

        return method_proxy
