# Copyright 2017 gRPC authors.
#
# 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.

import grpc


class _RequestIterator(object):

    def __init__(self, rpc, handler):
        self._rpc = rpc
        self._handler = handler

    def _next(self):
        read = self._handler.take_request()
        if read.requests_closed:
            raise StopIteration()
        elif read.terminated:
            rpc_error = grpc.RpcError()
            self._rpc.add_rpc_error(rpc_error)
            raise rpc_error
        else:
            return read.request

    def __iter__(self):
        return self

    def __next__(self):
        return self._next()

    def next(self):
        return self._next()


def _unary_response(argument, implementation, rpc, servicer_context):
    try:
        response = implementation(argument, servicer_context)
    except Exception as exception:  # pylint: disable=broad-except
        rpc.application_exception_abort(exception)
    else:
        rpc.unary_response_complete(response)


def _stream_response(argument, implementation, rpc, servicer_context):
    try:
        response_iterator = implementation(argument, servicer_context)
    except Exception as exception:  # pylint: disable=broad-except
        rpc.application_exception_abort(exception)
    else:
        while True:
            try:
                response = next(response_iterator)
            except StopIteration:
                rpc.stream_response_complete()
                break
            except Exception as exception:  # pylint: disable=broad-except
                rpc.application_exception_abort(exception)
                break
            else:
                rpc.stream_response(response)


def unary_unary(implementation, rpc, request, servicer_context):
    _unary_response(request, implementation, rpc, servicer_context)


def unary_stream(implementation, rpc, request, servicer_context):
    _stream_response(request, implementation, rpc, servicer_context)


def stream_unary(implementation, rpc, handler, servicer_context):
    _unary_response(
        _RequestIterator(rpc, handler), implementation, rpc, servicer_context)


def stream_stream(implementation, rpc, handler, servicer_context):
    _stream_response(
        _RequestIterator(rpc, handler), implementation, rpc, servicer_context)