/*
 * Copyright 2023, gRPC Authors 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.
 */

/// A namespace for request message types used by clients.
public enum ClientRequest {}

extension ClientRequest {
  /// A request created by the client for a single message.
  ///
  /// This is used for unary and server-streaming RPCs.
  ///
  /// See ``ClientRequest/Stream`` for streaming requests and ``ServerRequest/Single`` for the
  /// servers representation of a single-message request.
  ///
  /// ## Creating ``Single`` requests
  ///
  /// ```swift
  /// let request = ClientRequest.Single<String>(message: "Hello, gRPC!")
  /// print(request.metadata)  // prints '[:]'
  /// print(request.message)  // prints 'Hello, gRPC!'
  /// ```
  public struct Single<Message: Sendable>: Sendable {
    /// Caller-specified metadata to send to the server at the start of the RPC.
    ///
    /// Both gRPC Swift and its transport layer may insert additional metadata. Keys prefixed with
    /// "grpc-" are prohibited and may result in undefined behaviour. Transports may also insert
    /// their own metadata, you should avoid using key names which may clash with transport specific
    /// metadata. Note that transports may also impose limits in the amount of metadata which may
    /// be sent.
    public var metadata: Metadata

    /// The message to send to the server.
    public var message: Message

    /// Create a new single client request.
    ///
    /// - Parameters:
    ///   - message: The message to send to the server.
    ///   - metadata: Metadata to send to the server at the start of the request. Defaults to empty.
    public init(
      message: Message,
      metadata: Metadata = [:]
    ) {
      self.metadata = metadata
      self.message = message
    }
  }
}

extension ClientRequest {
  /// A request created by the client for a stream of messages.
  ///
  /// This is used for client-streaming and bidirectional-streaming RPCs.
  ///
  /// See ``ClientRequest/Single`` for single-message requests and ``ServerRequest/Stream`` for the
  /// servers representation of a streaming-message request.
  @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
  public struct Stream<Message: Sendable>: Sendable {
    /// Caller-specified metadata sent to the server at the start of the RPC.
    ///
    /// Both gRPC Swift and its transport layer may insert additional metadata. Keys prefixed with
    /// "grpc-" are prohibited and may result in undefined behaviour. Transports may also insert
    /// their own metadata, you should avoid using key names which may clash with transport specific
    /// metadata. Note that transports may also impose limits in the amount of metadata which may
    /// be sent.
    public var metadata: Metadata

    /// A closure which, when called, writes messages in the writer.
    ///
    /// The producer will only be consumed once by gRPC and therefore isn't required to be
    /// idempotent. If the producer throws an error then the RPC will be cancelled. Once the
    /// producer returns the request stream is closed.
    public var producer: @Sendable (RPCWriter<Message>) async throws -> Void

    /// Create a new streaming client request.
    ///
    /// - Parameters:
    ///   - messageType: The type of message contained in this request, defaults to `Message.self`.
    ///   - metadata: Metadata to send to the server at the start of the request. Defaults to empty.
    ///   - producer: A closure which writes messages to send to the server. The closure is called
    ///       at most once and may not be called.
    public init(
      of messageType: Message.Type = Message.self,
      metadata: Metadata = [:],
      producer: @escaping @Sendable (RPCWriter<Message>) async throws -> Void
    ) {
      self.metadata = metadata
      self.producer = producer
    }
  }
}

// MARK: - Conversion

@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
extension ClientRequest.Stream {
  @_spi(Testing)
  public init(single request: ClientRequest.Single<Message>) {
    self.init(metadata: request.metadata) {
      try await $0.write(request.message)
    }
  }
}