#pragma once

#include "source/common/grpc/typed_async_client.h"

namespace Envoy {

namespace Config {

// Oversees communication for gRPC xDS implementations (parent to both SotW xDS and delta

// xDS variants). Reestablishes the gRPC channel when necessary, and provides rate limiting of

// requests.

template <class RequestProto, class ResponseProto>

class GrpcStreamInterface : public Grpc::AsyncStreamCallbacks<ResponseProto> {

public:

  // Attempt to establish a new gRPC stream to the xDS server.

  virtual void establishNewStream() PURE;

  // Returns true if the gRPC stream is available and messages can be sent over it.

  virtual bool grpcStreamAvailable() const PURE;

  // Sends a request to the xDS server over the stream.

  virtual void sendMessage(const RequestProto& request) PURE;

  // Updates the control_plane_stats `pending_requests` value. Note that the

  // update will not be taken into effect if the size is 0, and the

  // `pending_request` value was not set previously to non-zero value.

  // This is done to avoid updating the queue's length until the first

  // meaningful value is given.

  virtual void maybeUpdateQueueSizeStat(uint64_t size) PURE;

  // Returns true if a message can be sent from the rate-limiting perspective.

  // The rate-limiting counters may be updated by this method.

  virtual bool checkRateLimitAllowsDrain() PURE;

  // Intentionally close the gRPC stream and reset to the pre-establishNewStream() state.

  // Prevents the retry timer from reconnecting.

  virtual void closeStream() PURE;

};

template <class RequestProto, class ResponseProto>

using GrpcStreamInterfacePtr = std::unique_ptr<GrpcStreamInterface<RequestProto, ResponseProto>>;

} // namespace Config

} // namespace Envoy