# Copyright 2020 The 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.
"""Abstract base classes for Channel objects and Multicallable objects."""

import abc
from typing import Generic, Optional

import grpc

from . import _base_call
from ._typing import DeserializingFunction
from ._typing import MetadataType
from ._typing import RequestIterableType
from ._typing import RequestType
from ._typing import ResponseType
from ._typing import SerializingFunction


class UnaryUnaryMultiCallable(Generic[RequestType, ResponseType], abc.ABC):
    """Enables asynchronous invocation of a unary-call RPC."""

    @abc.abstractmethod
    def __call__(
        self,
        request: RequestType,
        *,
        timeout: Optional[float] = None,
        metadata: Optional[MetadataType] = None,
        credentials: Optional[grpc.CallCredentials] = None,
        wait_for_ready: Optional[bool] = None,
        compression: Optional[grpc.Compression] = None,
    ) -> _base_call.UnaryUnaryCall[RequestType, ResponseType]:
        """Asynchronously invokes the underlying RPC.

        Args:
          request: The request value for the RPC.
          timeout: An optional duration of time in seconds to allow
            for the RPC.
          metadata: Optional :term:`metadata` to be transmitted to the
            service-side of the RPC.
          credentials: An optional CallCredentials for the RPC. Only valid for
            secure Channel.
          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
          compression: An element of grpc.compression, e.g.
            grpc.compression.Gzip.

        Returns:
          A UnaryUnaryCall object.

        Raises:
          RpcError: Indicates that the RPC terminated with non-OK status. The
            raised RpcError will also be a Call for the RPC affording the RPC's
            metadata, status code, and details.
        """


class UnaryStreamMultiCallable(Generic[RequestType, ResponseType], abc.ABC):
    """Enables asynchronous invocation of a server-streaming RPC."""

    @abc.abstractmethod
    def __call__(
        self,
        request: RequestType,
        *,
        timeout: Optional[float] = None,
        metadata: Optional[MetadataType] = None,
        credentials: Optional[grpc.CallCredentials] = None,
        wait_for_ready: Optional[bool] = None,
        compression: Optional[grpc.Compression] = None,
    ) -> _base_call.UnaryStreamCall[RequestType, ResponseType]:
        """Asynchronously invokes the underlying RPC.

        Args:
          request: The request value for the RPC.
          timeout: An optional duration of time in seconds to allow
            for the RPC.
          metadata: Optional :term:`metadata` to be transmitted to the
            service-side of the RPC.
          credentials: An optional CallCredentials for the RPC. Only valid for
            secure Channel.
          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
          compression: An element of grpc.compression, e.g.
            grpc.compression.Gzip.

        Returns:
          A UnaryStreamCall object.

        Raises:
          RpcError: Indicates that the RPC terminated with non-OK status. The
            raised RpcError will also be a Call for the RPC affording the RPC's
            metadata, status code, and details.
        """


class StreamUnaryMultiCallable(abc.ABC):
    """Enables asynchronous invocation of a client-streaming RPC."""

    @abc.abstractmethod
    def __call__(
        self,
        request_iterator: Optional[RequestIterableType] = None,
        timeout: Optional[float] = None,
        metadata: Optional[MetadataType] = None,
        credentials: Optional[grpc.CallCredentials] = None,
        wait_for_ready: Optional[bool] = None,
        compression: Optional[grpc.Compression] = None,
    ) -> _base_call.StreamUnaryCall:
        """Asynchronously invokes the underlying RPC.

        Args:
          request_iterator: An optional async iterable or iterable of request
            messages for the RPC.
          timeout: An optional duration of time in seconds to allow
            for the RPC.
          metadata: Optional :term:`metadata` to be transmitted to the
            service-side of the RPC.
          credentials: An optional CallCredentials for the RPC. Only valid for
            secure Channel.
          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
          compression: An element of grpc.compression, e.g.
            grpc.compression.Gzip.

        Returns:
          A StreamUnaryCall object.

        Raises:
          RpcError: Indicates that the RPC terminated with non-OK status. The
            raised RpcError will also be a Call for the RPC affording the RPC's
            metadata, status code, and details.
        """


class StreamStreamMultiCallable(abc.ABC):
    """Enables asynchronous invocation of a bidirectional-streaming RPC."""

    @abc.abstractmethod
    def __call__(
        self,
        request_iterator: Optional[RequestIterableType] = None,
        timeout: Optional[float] = None,
        metadata: Optional[MetadataType] = None,
        credentials: Optional[grpc.CallCredentials] = None,
        wait_for_ready: Optional[bool] = None,
        compression: Optional[grpc.Compression] = None,
    ) -> _base_call.StreamStreamCall:
        """Asynchronously invokes the underlying RPC.

        Args:
          request_iterator: An optional async iterable or iterable of request
            messages for the RPC.
          timeout: An optional duration of time in seconds to allow
            for the RPC.
          metadata: Optional :term:`metadata` to be transmitted to the
            service-side of the RPC.
          credentials: An optional CallCredentials for the RPC. Only valid for
            secure Channel.
          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
          compression: An element of grpc.compression, e.g.
            grpc.compression.Gzip.

        Returns:
          A StreamStreamCall object.

        Raises:
          RpcError: Indicates that the RPC terminated with non-OK status. The
            raised RpcError will also be a Call for the RPC affording the RPC's
            metadata, status code, and details.
        """


class Channel(abc.ABC):
    """Enables asynchronous RPC invocation as a client.

    Channel objects implement the Asynchronous Context Manager (aka. async
    with) type, although they are not supportted to be entered and exited
    multiple times.
    """

    @abc.abstractmethod
    async def __aenter__(self):
        """Starts an asynchronous context manager.

        Returns:
          Channel the channel that was instantiated.
        """

    @abc.abstractmethod
    async def __aexit__(self, exc_type, exc_val, exc_tb):
        """Finishes the asynchronous context manager by closing the channel.

        Still active RPCs will be cancelled.
        """

    @abc.abstractmethod
    async def close(self, grace: Optional[float] = None):
        """Closes this Channel and releases all resources held by it.

        This method immediately stops the channel from executing new RPCs in
        all cases.

        If a grace period is specified, this method waits until all active
        RPCs are finished or until the grace period is reached. RPCs that haven't
        been terminated within the grace period are aborted.
        If a grace period is not specified (by passing None for grace),
        all existing RPCs are cancelled immediately.

        This method is idempotent.
        """

    @abc.abstractmethod
    def get_state(
        self, try_to_connect: bool = False
    ) -> grpc.ChannelConnectivity:
        """Checks the connectivity state of a channel.

        This is an EXPERIMENTAL API.

        If the channel reaches a stable connectivity state, it is guaranteed
        that the return value of this function will eventually converge to that
        state.

        Args:
          try_to_connect: a bool indicate whether the Channel should try to
            connect to peer or not.

        Returns: A ChannelConnectivity object.
        """

    @abc.abstractmethod
    async def wait_for_state_change(
        self,
        last_observed_state: grpc.ChannelConnectivity,
    ) -> None:
        """Waits for a change in connectivity state.

        This is an EXPERIMENTAL API.

        The function blocks until there is a change in the channel connectivity
        state from the "last_observed_state". If the state is already
        different, this function will return immediately.

        There is an inherent race between the invocation of
        "Channel.wait_for_state_change" and "Channel.get_state". The state can
        change arbitrary many times during the race, so there is no way to
        observe every state transition.

        If there is a need to put a timeout for this function, please refer to
        "asyncio.wait_for".

        Args:
          last_observed_state: A grpc.ChannelConnectivity object representing
            the last known state.
        """

    @abc.abstractmethod
    async def channel_ready(self) -> None:
        """Creates a coroutine that blocks until the Channel is READY."""

    @abc.abstractmethod
    def unary_unary(
        self,
        method: str,
        request_serializer: Optional[SerializingFunction] = None,
        response_deserializer: Optional[DeserializingFunction] = None,
        _registered_method: Optional[bool] = False,
    ) -> UnaryUnaryMultiCallable:
        """Creates a UnaryUnaryMultiCallable for a unary-unary method.

        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None
            is passed.
          _registered_method: Implementation Private. Optional: A bool representing
            whether the method is registered.

        Returns:
          A UnaryUnaryMultiCallable value for the named unary-unary method.
        """

    @abc.abstractmethod
    def unary_stream(
        self,
        method: str,
        request_serializer: Optional[SerializingFunction] = None,
        response_deserializer: Optional[DeserializingFunction] = None,
        _registered_method: Optional[bool] = False,
    ) -> UnaryStreamMultiCallable:
        """Creates a UnaryStreamMultiCallable for a unary-stream method.

        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None
            is passed.
          _registered_method: Implementation Private. Optional: A bool representing
            whether the method is registered.

        Returns:
          A UnarySteramMultiCallable value for the named unary-stream method.
        """

    @abc.abstractmethod
    def stream_unary(
        self,
        method: str,
        request_serializer: Optional[SerializingFunction] = None,
        response_deserializer: Optional[DeserializingFunction] = None,
        _registered_method: Optional[bool] = False,
    ) -> StreamUnaryMultiCallable:
        """Creates a StreamUnaryMultiCallable for a stream-unary method.

        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None
            is passed.
          _registered_method: Implementation Private. Optional: A bool representing
            whether the method is registered.

        Returns:
          A StreamUnaryMultiCallable value for the named stream-unary method.
        """

    @abc.abstractmethod
    def stream_stream(
        self,
        method: str,
        request_serializer: Optional[SerializingFunction] = None,
        response_deserializer: Optional[DeserializingFunction] = None,
        _registered_method: Optional[bool] = False,
    ) -> StreamStreamMultiCallable:
        """Creates a StreamStreamMultiCallable for a stream-stream method.

        Args:
          method: The name of the RPC method.
          request_serializer: Optional :term:`serializer` for serializing the request
            message. Request goes unserialized in case None is passed.
          response_deserializer: Optional :term:`deserializer` for deserializing the
            response message. Response goes undeserialized in case None
            is passed.
          _registered_method: Implementation Private. Optional: A bool representing
            whether the method is registered.

        Returns:
          A StreamStreamMultiCallable value for the named stream-stream method.
        """
