# Copyright 2016 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.
"""Translates gRPC's server-side API into gRPC's server-side Beta API."""

import collections
import threading

import grpc
from grpc import _common
from grpc.beta import _metadata
from grpc.beta import interfaces
from grpc.framework.common import cardinality
from grpc.framework.common import style
from grpc.framework.foundation import abandonment
from grpc.framework.foundation import logging_pool
from grpc.framework.foundation import stream
from grpc.framework.interfaces.face import face

# pylint: disable=too-many-return-statements

_DEFAULT_POOL_SIZE = 8


class _ServerProtocolContext(interfaces.GRPCServicerContext):

    def __init__(self, servicer_context):
        self._servicer_context = servicer_context

    def peer(self):
        return self._servicer_context.peer()

    def disable_next_response_compression(self):
        pass  # TODO(https://github.com/grpc/grpc/issues/4078): design, implement.


class _FaceServicerContext(face.ServicerContext):

    def __init__(self, servicer_context):
        self._servicer_context = servicer_context

    def is_active(self):
        return self._servicer_context.is_active()

    def time_remaining(self):
        return self._servicer_context.time_remaining()

    def add_abortion_callback(self, abortion_callback):
        raise NotImplementedError(
            'add_abortion_callback no longer supported server-side!')

    def cancel(self):
        self._servicer_context.cancel()

    def protocol_context(self):
        return _ServerProtocolContext(self._servicer_context)

    def invocation_metadata(self):
        return _metadata.beta(self._servicer_context.invocation_metadata())

    def initial_metadata(self, initial_metadata):
        self._servicer_context.send_initial_metadata(
            _metadata.unbeta(initial_metadata))

    def terminal_metadata(self, terminal_metadata):
        self._servicer_context.set_terminal_metadata(
            _metadata.unbeta(terminal_metadata))

    def code(self, code):
        self._servicer_context.set_code(code)

    def details(self, details):
        self._servicer_context.set_details(details)


def _adapt_unary_request_inline(unary_request_inline):

    def adaptation(request, servicer_context):
        return unary_request_inline(request,
                                    _FaceServicerContext(servicer_context))

    return adaptation


def _adapt_stream_request_inline(stream_request_inline):

    def adaptation(request_iterator, servicer_context):
        return stream_request_inline(request_iterator,
                                     _FaceServicerContext(servicer_context))

    return adaptation


class _Callback(stream.Consumer):

    def __init__(self):
        self._condition = threading.Condition()
        self._values = []
        self._terminated = False
        self._cancelled = False

    def consume(self, value):
        with self._condition:
            self._values.append(value)
            self._condition.notify_all()

    def terminate(self):
        with self._condition:
            self._terminated = True
            self._condition.notify_all()

    def consume_and_terminate(self, value):
        with self._condition:
            self._values.append(value)
            self._terminated = True
            self._condition.notify_all()

    def cancel(self):
        with self._condition:
            self._cancelled = True
            self._condition.notify_all()

    def draw_one_value(self):
        with self._condition:
            while True:
                if self._cancelled:
                    raise abandonment.Abandoned()
                elif self._values:
                    return self._values.pop(0)
                elif self._terminated:
                    return None
                else:
                    self._condition.wait()

    def draw_all_values(self):
        with self._condition:
            while True:
                if self._cancelled:
                    raise abandonment.Abandoned()
                elif self._terminated:
                    all_values = tuple(self._values)
                    self._values = None
                    return all_values
                else:
                    self._condition.wait()


def _run_request_pipe_thread(request_iterator, request_consumer,
                             servicer_context):
    thread_joined = threading.Event()

    def pipe_requests():
        for request in request_iterator:
            if not servicer_context.is_active() or thread_joined.is_set():
                return
            request_consumer.consume(request)
            if not servicer_context.is_active() or thread_joined.is_set():
                return
        request_consumer.terminate()

    request_pipe_thread = threading.Thread(target=pipe_requests)
    request_pipe_thread.daemon = True
    request_pipe_thread.start()


def _adapt_unary_unary_event(unary_unary_event):

    def adaptation(request, servicer_context):
        callback = _Callback()
        if not servicer_context.add_callback(callback.cancel):
            raise abandonment.Abandoned()
        unary_unary_event(request, callback.consume_and_terminate,
                          _FaceServicerContext(servicer_context))
        return callback.draw_all_values()[0]

    return adaptation


def _adapt_unary_stream_event(unary_stream_event):

    def adaptation(request, servicer_context):
        callback = _Callback()
        if not servicer_context.add_callback(callback.cancel):
            raise abandonment.Abandoned()
        unary_stream_event(request, callback,
                           _FaceServicerContext(servicer_context))
        while True:
            response = callback.draw_one_value()
            if response is None:
                return
            else:
                yield response

    return adaptation


def _adapt_stream_unary_event(stream_unary_event):

    def adaptation(request_iterator, servicer_context):
        callback = _Callback()
        if not servicer_context.add_callback(callback.cancel):
            raise abandonment.Abandoned()
        request_consumer = stream_unary_event(
            callback.consume_and_terminate,
            _FaceServicerContext(servicer_context))
        _run_request_pipe_thread(request_iterator, request_consumer,
                                 servicer_context)
        return callback.draw_all_values()[0]

    return adaptation


def _adapt_stream_stream_event(stream_stream_event):

    def adaptation(request_iterator, servicer_context):
        callback = _Callback()
        if not servicer_context.add_callback(callback.cancel):
            raise abandonment.Abandoned()
        request_consumer = stream_stream_event(
            callback, _FaceServicerContext(servicer_context))
        _run_request_pipe_thread(request_iterator, request_consumer,
                                 servicer_context)
        while True:
            response = callback.draw_one_value()
            if response is None:
                return
            else:
                yield response

    return adaptation


class _SimpleMethodHandler(
        collections.namedtuple('_MethodHandler', (
            'request_streaming',
            'response_streaming',
            'request_deserializer',
            'response_serializer',
            'unary_unary',
            'unary_stream',
            'stream_unary',
            'stream_stream',
        )), grpc.RpcMethodHandler):
    pass


def _simple_method_handler(implementation, request_deserializer,
                           response_serializer):
    if implementation.style is style.Service.INLINE:
        if implementation.cardinality is cardinality.Cardinality.UNARY_UNARY:
            return _SimpleMethodHandler(False, False, request_deserializer,
                                        response_serializer,
                                        _adapt_unary_request_inline(
                                            implementation.unary_unary_inline),
                                        None, None, None)
        elif implementation.cardinality is cardinality.Cardinality.UNARY_STREAM:
            return _SimpleMethodHandler(False, True, request_deserializer,
                                        response_serializer, None,
                                        _adapt_unary_request_inline(
                                            implementation.unary_stream_inline),
                                        None, None)
        elif implementation.cardinality is cardinality.Cardinality.STREAM_UNARY:
            return _SimpleMethodHandler(True, False, request_deserializer,
                                        response_serializer, None, None,
                                        _adapt_stream_request_inline(
                                            implementation.stream_unary_inline),
                                        None)
        elif implementation.cardinality is cardinality.Cardinality.STREAM_STREAM:
            return _SimpleMethodHandler(
                True, True, request_deserializer, response_serializer, None,
                None, None,
                _adapt_stream_request_inline(
                    implementation.stream_stream_inline))
    elif implementation.style is style.Service.EVENT:
        if implementation.cardinality is cardinality.Cardinality.UNARY_UNARY:
            return _SimpleMethodHandler(False, False, request_deserializer,
                                        response_serializer,
                                        _adapt_unary_unary_event(
                                            implementation.unary_unary_event),
                                        None, None, None)
        elif implementation.cardinality is cardinality.Cardinality.UNARY_STREAM:
            return _SimpleMethodHandler(False, True, request_deserializer,
                                        response_serializer, None,
                                        _adapt_unary_stream_event(
                                            implementation.unary_stream_event),
                                        None, None)
        elif implementation.cardinality is cardinality.Cardinality.STREAM_UNARY:
            return _SimpleMethodHandler(True, False, request_deserializer,
                                        response_serializer, None, None,
                                        _adapt_stream_unary_event(
                                            implementation.stream_unary_event),
                                        None)
        elif implementation.cardinality is cardinality.Cardinality.STREAM_STREAM:
            return _SimpleMethodHandler(True, True, request_deserializer,
                                        response_serializer, None, None, None,
                                        _adapt_stream_stream_event(
                                            implementation.stream_stream_event))
    raise ValueError()


def _flatten_method_pair_map(method_pair_map):
    method_pair_map = method_pair_map or {}
    flat_map = {}
    for method_pair in method_pair_map:
        method = _common.fully_qualified_method(method_pair[0], method_pair[1])
        flat_map[method] = method_pair_map[method_pair]
    return flat_map


class _GenericRpcHandler(grpc.GenericRpcHandler):

    def __init__(self, method_implementations, multi_method_implementation,
                 request_deserializers, response_serializers):
        self._method_implementations = _flatten_method_pair_map(
            method_implementations)
        self._request_deserializers = _flatten_method_pair_map(
            request_deserializers)
        self._response_serializers = _flatten_method_pair_map(
            response_serializers)
        self._multi_method_implementation = multi_method_implementation

    def service(self, handler_call_details):
        method_implementation = self._method_implementations.get(
            handler_call_details.method)
        if method_implementation is not None:
            return _simple_method_handler(method_implementation,
                                          self._request_deserializers.get(
                                              handler_call_details.method),
                                          self._response_serializers.get(
                                              handler_call_details.method))
        elif self._multi_method_implementation is None:
            return None
        else:
            try:
                return None  #TODO(user): call the multimethod.
            except face.NoSuchMethodError:
                return None


class _Server(interfaces.Server):

    def __init__(self, grpc_server):
        self._grpc_server = grpc_server

    def add_insecure_port(self, address):
        return self._grpc_server.add_insecure_port(address)

    def add_secure_port(self, address, server_credentials):
        return self._grpc_server.add_secure_port(address, server_credentials)

    def start(self):
        self._grpc_server.start()

    def stop(self, grace):
        return self._grpc_server.stop(grace)

    def __enter__(self):
        self._grpc_server.start()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self._grpc_server.stop(None)
        return False


def server(service_implementations, multi_method_implementation,
           request_deserializers, response_serializers, thread_pool,
           thread_pool_size):
    generic_rpc_handler = _GenericRpcHandler(
        service_implementations, multi_method_implementation,
        request_deserializers, response_serializers)
    if thread_pool is None:
        effective_thread_pool = logging_pool.pool(_DEFAULT_POOL_SIZE
                                                  if thread_pool_size is None
                                                  else thread_pool_size)
    else:
        effective_thread_pool = thread_pool
    return _Server(
        grpc.server(effective_thread_pool, handlers=(generic_rpc_handler,)))
