/*
 * Copyright 2021, 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.
 */

internal protocol ConnectionManagerConnectivityDelegate {
  /// The state of the connection changed.
  ///
  /// - Parameters:
  ///   - connectionManager: The connection manager reporting the change of state.
  ///   - oldState: The previous `ConnectivityState`.
  ///   - newState: The current `ConnectivityState`.
  func connectionStateDidChange(
    _ connectionManager: ConnectionManager,
    from oldState: _ConnectivityState,
    to newState: _ConnectivityState
  )

  /// The connection is quiescing.
  ///
  /// - Parameters:
  ///   - connectionManager: The connection manager whose connection is quiescing.
  func connectionIsQuiescing(_ connectionManager: ConnectionManager)
}

internal protocol ConnectionManagerHTTP2Delegate {
  /// An HTTP/2 stream was opened.
  ///
  /// - Parameters:
  ///   - connectionManager: The connection manager reporting the opened stream.
  func streamOpened(_ connectionManager: ConnectionManager)

  /// An HTTP/2 stream was closed.
  ///
  /// - Parameters:
  ///   - connectionManager: The connection manager reporting the closed stream.
  func streamClosed(_ connectionManager: ConnectionManager)

  /// The connection received a SETTINGS frame containing SETTINGS_MAX_CONCURRENT_STREAMS.
  ///
  /// - Parameters:
  ///   - connectionManager: The connection manager which received the settings update.
  ///   - maxConcurrentStreams: The value of SETTINGS_MAX_CONCURRENT_STREAMS.
  func receivedSettingsMaxConcurrentStreams(
    _ connectionManager: ConnectionManager,
    maxConcurrentStreams: Int
  )
}

// This mirrors `ConnectivityState` (which is public API) but adds `Error` as associated data
// to a few cases.
internal enum _ConnectivityState: Sendable {
  case idle(Error?)
  case connecting
  case ready
  case transientFailure(Error)
  case shutdown

  /// Returns whether this state is the same as the other state (ignoring any associated data).
  internal func isSameState(as other: _ConnectivityState) -> Bool {
    switch (self, other) {
    case (.idle, .idle),
      (.connecting, .connecting),
      (.ready, .ready),
      (.transientFailure, .transientFailure),
      (.shutdown, .shutdown):
      return true
    default:
      return false
    }
  }
}

extension ConnectivityState {
  internal init(_ state: _ConnectivityState) {
    switch state {
    case .idle:
      self = .idle
    case .connecting:
      self = .connecting
    case .ready:
      self = .ready
    case .transientFailure:
      self = .transientFailure
    case .shutdown:
      self = .shutdown
    }
  }
}