/*
 * Copyright 2019, 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.
 */
import Foundation
import NIOHTTP1

/// Options to use for GRPC calls.
public struct CallOptions {
  /// Additional metadata to send to the service.
  public var customMetadata: HTTPHeaders

  /// The call timeout.
  public var timeout: GRPCTimeout

  /// Whether the call is cacheable.
  public var cacheable: Bool

  /// How IDs should be provided for requests. Defaults to `.autogenerated`.
  ///
  /// The request ID is used for logging and will be added to the headers of a call if
  /// `requestIDHeader` is specified.
  ///
  /// - Important: When setting `CallOptions` at the client level, `.userDefined` should __not__ be
  /// used otherwise each request will have the same ID.
  public var requestIDProvider: RequestIDProvider

  /// The name of the header to use when adding a request ID to a call, e.g. "x-request-id". If the
  /// value is `nil` (the default) then no additional header will be addded.
  ///
  /// Setting this value will add a request ID to the headers of the call these options are used
  /// with. The request ID will be provided by `requestIDProvider` and will also be used in log
  /// messages associated with the call.
  public var requestIDHeader: String?

  public init(
    customMetadata: HTTPHeaders = HTTPHeaders(),
    timeout: GRPCTimeout = GRPCTimeout.infinite,
    cacheable: Bool = false,
    requestIDProvider: RequestIDProvider = .autogenerated,
    requestIDHeader: String? = nil
  ) {
    self.customMetadata = customMetadata
    self.timeout = timeout
    self.cacheable = false
    self.requestIDProvider = requestIDProvider
    self.requestIDHeader = requestIDHeader
  }

  /// How Request IDs should be provided.
  public enum RequestIDProvider {
    /// Generate a new ID automatically.
    case autogenerated

    /// Specify an ID to be used.
    ///
    /// - Important: this should only be used when `CallOptions` are passed directly to the call.
    ///   If it is used for the default options on a client then all calls with have the same ID.
    case userDefined(String)

    func requestID() -> String {
      switch self {
      case .autogenerated:
        return UUID().uuidString

      case .userDefined(let id):
        return id
      }
    }
  }
}