class JSONRPCController(WSGIController):

    """

     A WSGI-speaking JSON-RPC controller class

     See the specification:

     <http://json-rpc.org/wiki/specification>`.

     Valid controller return values should be json-serializable objects.

     Sub-classes should catch their exceptions and raise JSONRPCError

     if they want to pass meaningful errors to the client.

     """

    def _get_ip_addr(self, environ):

        return _get_ip(environ)

    def _get_method_args(self):

        """

        Return `self._rpc_args` to dispatched controller method

        chosen by __call__

        """

        return self._rpc_args

    def __call__(self, environ, start_response):

        """

        Parse the request body as JSON, look up the method on the

        controller and if it exists, dispatch to it.

        """

        try:

            return self._handle_request(environ, start_response)

        finally:

            meta.Session.remove()

    def _handle_request(self, environ, start_response):

        start = time.time()

        ip_addr = self.ip_addr = self._get_ip_addr(environ)

        self._req_id = None

        if 'CONTENT_LENGTH' not in environ:

            log.debug("No Content-Length")

            return jsonrpc_error(retid=self._req_id,

                                 message="No Content-Length in request")

        else:

            length = environ['CONTENT_LENGTH'] or 0

            length = int(environ['CONTENT_LENGTH'])

            log.debug('Content-Length: %s', length)

        if length == 0:

            return jsonrpc_error(retid=self._req_id,

                                 message="Content-Length is 0")

        raw_body = environ['wsgi.input'].read(length)

        try:

            json_body = json.loads(raw_body)

        except ValueError as e:

            # catch JSON errors Here

            return jsonrpc_error(retid=self._req_id,

                                 message="JSON parse error ERR:%s RAW:%r"

                                 % (e, raw_body))

        # check AUTH based on API key

        try:

            self._req_api_key = json_body['api_key']

            self._req_id = json_body['id']

            self._req_method = json_body['method']

            self._request_params = json_body['args']

            if not isinstance(self._request_params, dict):

                self._request_params = {}

            log.debug(

                'method: %s, params: %s', self._req_method,

                                            self._request_params

            )

        except KeyError as e:

            return jsonrpc_error(retid=self._req_id,

                                 message='Incorrect JSON query missing %s' % e)

        # check if we can find this session using api_key

        try:

            u = User.get_by_api_key(self._req_api_key)

            if u is None:

                return jsonrpc_error(retid=self._req_id,

                                     message='Invalid API key')

            auth_u = AuthUser(dbuser=u)

            if not AuthUser.check_ip_allowed(auth_u, ip_addr):

                return jsonrpc_error(retid=self._req_id,

                        message='request from IP:%s not allowed' % (ip_addr,))

            else:

                log.info('Access for IP:%s allowed', ip_addr)

        except Exception as e:

            return jsonrpc_error(retid=self._req_id,

                                 message='Invalid API key')

        # This attribute will need to be first param of a method that uses

        # api_key, which is translated to instance of user at that name

        USER_SESSION_ATTR = 'apiuser'

        if USER_SESSION_ATTR not in arglist:

            return jsonrpc_error(

                retid=self._req_id,

                message='This method [%s] does not support '

                         'authentication (missing %s param)' % (

                                    self._func.__name__, USER_SESSION_ATTR)

            )

        # get our arglist and check if we provided them as args

        for arg, default in func_kwargs.iteritems():

            if arg == USER_SESSION_ATTR:

                # USER_SESSION_ATTR is something translated from API key and

                # this is checked before so we don't need validate it

                continue

            # skip the required param check if it's default value is

            # NotImplementedType (default_empty)

            if default == default_empty and arg not in self._request_params:

                return jsonrpc_error(

                    retid=self._req_id,

                    message=(

                        'Missing non optional `%s` arg in JSON DATA' % arg

                    )

                )

        self._rpc_args = {USER_SESSION_ATTR: u}

        self._rpc_args.update(self._request_params)

        self._rpc_args['action'] = self._req_method

        self._rpc_args['environ'] = environ

        self._rpc_args['start_response'] = start_response

        status = []

        headers = []

        exc_info = []

        def change_content(new_status, new_headers, new_exc_info=None):

            status.append(new_status)

            headers.extend(new_headers)

            exc_info.append(new_exc_info)

        output = WSGIController.__call__(self, environ, change_content)

        replace_header(headers, 'Content-Type', 'application/json')

        start_response(status[0], headers, exc_info[0])

        log.info('IP: %s Request to %s time: %.3fs' % (

            self._get_ip_addr(environ),

            safe_unicode(_get_access_path(environ)), time.time() - start)

        )

        return output

    def _dispatch_call(self):

        """

        Implement dispatch interface specified by WSGIController

        """

        raw_response = ''

        try:

            raw_response = self._inspect_call(self._func)

            if isinstance(raw_response, HTTPError):

                self._error = str(raw_response)

        except JSONRPCError as e:

            self._error = safe_str(e)

        except Exception as e:

            log.error('Encountered unhandled exception: %s',

                      traceback.format_exc(),)

            json_exc = JSONRPCError('Internal server error')

            self._error = safe_str(json_exc)

        if self._error is not None:

            raw_response = None

        response = dict(id=self._req_id, result=raw_response, error=self._error)

        try:

            return json.dumps(response)

        except TypeError as e:

            log.error('API FAILED. Error encoding response: %s', e)

            return json.dumps(

                dict(

                    id=self._req_id,

                    result=None,

                    error="Error encoding response"

                )

            )

    def _find_method(self):

        """

        Return method named by `self._req_method` in controller if able

        """

        log.debug('Trying to find JSON-RPC method: %s', self._req_method)

        if self._req_method.startswith('_'):

            raise AttributeError("Method not allowed")