#pragma once

#include <memory>

#include "absl/status/statusor.h"

#include "absl/types/span.h"

#include "grpcpp/channel.h"

#include "grpcpp/client_context.h"

#include "grpcpp/support/sync_stream.h"

#include "src/proto/grpc/gcp/handshaker.grpc.pb.h"

#include "src/proto/grpc/gcp/handshaker.pb.h"

#include "src/proto/grpc/gcp/transport_security_common.pb.h"

namespace Envoy {

namespace Extensions {

namespace TransportSockets {

namespace Alts {

constexpr char ApplicationProtocol[] = "grpc";

constexpr char RecordProtocol[] = "ALTSRP_GCM_AES128_REKEY";

constexpr std::size_t MaxFrameSize = 1024 * 1024;

constexpr std::size_t MaxMajorRpcVersion = 2;

constexpr std::size_t MaxMinorRpcVersion = 1;

constexpr std::size_t MinMajorRpcVersion = 2;

constexpr std::size_t MinMinorRpcVersion = 1;

// Manages a bidirectional stream to the ALTS handshaker service. An AltsProxy

// instance is tied to a single ALTS handshake and must not be reused.

//

// WARNING: Several methods block the worker thread performing the ALTS

// handshake to make a gRPC call to the ALTS handshaker service. This can slow

// down or halt the proxy if the ALTS handshaker service is unavailable or

// experiencing high latency.

class AltsProxy {

public:

  static absl::StatusOr<std::unique_ptr<AltsProxy>>

  create(std::shared_ptr<grpc::Channel> handshaker_service_channel);

  ~AltsProxy();

  // Sends a StartClientHandshakeReq message to the ALTS handshaker service and

  // returns the response.

  //

  // WARNING: Blocks the worker thread performing the ALTS handshake to make a

  // gRPC call to the ALTS handshaker service. This can slow down or halt the

  // proxy if the ALTS handshaker service is unavailable or experiencing high

  // latency.

  absl::StatusOr<grpc::gcp::HandshakerResp> sendStartClientHandshakeReq();

  // Sends a StartServerHandshakeReq message to the ALTS handshaker service and

  // returns the response.

  //

  // WARNING: Blocks the worker thread performing the ALTS handshake to make a

  // gRPC call to the ALTS handshaker service. This can slow down or halt the

  // proxy if the ALTS handshaker service is unavailable or experiencing high

  // latency.

  absl::StatusOr<grpc::gcp::HandshakerResp>

  sendStartServerHandshakeReq(absl::Span<const uint8_t> in_bytes);

  // Sends a NextHandshakeMessageReq message to the ALTS handshaker service and

  // returns the response.

  //

  // WARNING: Blocks the worker thread performing the ALTS handshake to make a

  // gRPC call to the ALTS handshaker service. This can slow down or halt the

  // proxy if the ALTS handshaker service is unavailable or experiencing high

  // latency.

  absl::StatusOr<grpc::gcp::HandshakerResp>

  sendNextHandshakeReq(absl::Span<const uint8_t> in_bytes);

private:

  static void setRpcProtocolVersions(grpc::gcp::RpcProtocolVersions* rpc_protocol_versions);

  AltsProxy(

      std::unique_ptr<grpc::ClientContext> client_context,

      std::unique_ptr<grpc::gcp::HandshakerService::Stub> stub,

      std::unique_ptr<grpc::ClientReaderWriter<grpc::gcp::HandshakerReq, grpc::gcp::HandshakerResp>>

          stream);

  std::unique_ptr<grpc::ClientContext> client_context_ = nullptr;

  std::unique_ptr<grpc::gcp::HandshakerService::Stub> stub_;

  std::unique_ptr<grpc::ClientReaderWriter<grpc::gcp::HandshakerReq, grpc::gcp::HandshakerResp>>

      stream_ = nullptr;

};

} // namespace Alts

} // namespace TransportSockets

} // namespace Extensions

} // namespace Envoy