text: // Copyright 2020 Google LLC
  //
  // 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
  //
  //     https://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.
  
  #ifndef CORE_V2_INTERNAL_ENCRYPTION_RUNNER_H_
  #define CORE_V2_INTERNAL_ENCRYPTION_RUNNER_H_
  
  #include <string>
  
  #include "core_v2/internal/client_proxy.h"
  #include "core_v2/internal/endpoint_channel.h"
  #include "core_v2/listeners.h"
  #include "platform_v2/base/byte_array.h"
  #include "platform_v2/public/scheduled_executor.h"
  #include "platform_v2/public/single_thread_executor.h"
  #include "securegcm/ukey2_handshake.h"
  
  namespace location {
  namespace nearby {
  namespace connections {
  
  // Encrypts a connection over UKEY2.
  //
  // NOTE: Stalled EndpointChannels will be disconnected after kTimeout.
  // This is to prevent unverified endpoints from maintaining an
  // indefinite connection to us.
  class EncryptionRunner {
   public:
    EncryptionRunner() = default;
    ~EncryptionRunner();
  
    struct ResultListener {
      // @EncryptionRunnerThread
      std::function<void(const std::string& endpoint_id,
                         std::unique_ptr<securegcm::UKey2Handshake> ukey2,
                         const std::string& auth_token,
                         const ByteArray& raw_auth_token)>
          on_success_cb =
              DefaultCallback<const std::string&,
                              std::unique_ptr<securegcm::UKey2Handshake>,
                              const std::string&, const ByteArray&>();
  
      // Encryption has failed. The remote_endpoint_id and channel are given so
      // that any pending state can be cleaned up.
      //
      // We return the EndpointChannel because, at this stage, simultaneous
      // connections are a possibility. Use this channel to verify that the state
      // you're cleaning up is for this EndpointChannel, and not state for another
      // channel to the same endpoint.
      //
      // @EncryptionRunnerThread
      std::function<void(const std::string& endpoint_id,
                         EndpointChannel* channel)>
          on_failure_cb = DefaultCallback<const std::string&, EndpointChannel*>();
    };
  
    // @AnyThread
    void StartServer(ClientProxy* client, const std::string& endpoint_id,
                     EndpointChannel* endpoint_channel,
                     ResultListener&& result_listener);
    // @AnyThread
    void StartClient(ClientProxy* client, const std::string& endpoint_id,
                     EndpointChannel* endpoint_channel,
                     ResultListener&& result_listener);
  
   private:
    ScheduledExecutor alarm_executor_;
    SingleThreadExecutor server_executor_;
    SingleThreadExecutor client_executor_;
  };
  
  }  // namespace connections
  }  // namespace nearby
  }  // namespace location
  
  #endif  // CORE_V2_INTERNAL_ENCRYPTION_RUNNER_H_
  