#pragma once

#include <cstddef>

#include <memory>

#include <vector>

#include "absl/strings/string_view.h"

#include "absl/synchronization/mutex.h"

#include "grpcpp/channel.h"

namespace Envoy {

namespace Extensions {

namespace TransportSockets {

namespace Alts {

// Manages a pool of gRPC channels to the ALTS handshaker service.

class AltsChannelPool {

public:

  static std::unique_ptr<AltsChannelPool> create(absl::string_view handshaker_service_address);

  // Gets a channel to the ALTS handshaker service. The caller is responsible

  // for checking that the channel is non-null.

  std::shared_ptr<grpc::Channel> getChannel();

  std::size_t getChannelPoolSize() const;

private:

  explicit AltsChannelPool(const std::vector<std::shared_ptr<grpc::Channel>>& channel_pool);

  // Use round-robin to select channels from the pool.

  absl::Mutex mu_;

  std::size_t index_ ABSL_GUARDED_BY(mu_) = 0;

  std::vector<std::shared_ptr<grpc::Channel>> channel_pool_;

};

} // namespace Alts

} // namespace TransportSockets

} // namespace Extensions

} // namespace Envoy