// Copyright 2021 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package p2p;

import "gogoproto/gogo.proto";

option(gogoproto.sizer_all) = true;
// Use generated code to lower performance overhead.
option(gogoproto.marshaler_all) = true;
option(gogoproto.unmarshaler_all) = true;

service CDCPeerToPeer {
  // A bidirectional stream from the sender (client) to the receiver (server)
  // The send direction is used to carry the serialized payload, and the
  // reply direction is used to receive ACKs (progress information) from the server.
  rpc SendMessage(stream MessagePacket) returns (stream SendMessageResponse);
}

// MessageEntry represents a single message.
message MessageEntry {
  // topic is used to separate messages into order-guaranteed logical streams.
  string topic = 1;

  // serialized payload. The format and schema is defined by the business logic
  // using the peer-to-peer mechanism.
  bytes content = 2;

  // monotonically increase.
  int64 sequence = 3;
}

// Metadata associated with one client-server bidirectional stream.
message StreamMeta {
  // fields required for correctness
  string sender_id = 1;
  string receiver_id = 2;
  int64 epoch = 3; // monotonically increasing between two given node processes.

  // fields required for compatibility check
  string client_version = 50;

  // fields for metrics, logging, debugging, etc.
  string sender_advertised_addr = 100;
}

message MessagePacket {
  StreamMeta meta = 1;

  // multiple messages can be batched.
  repeated MessageEntry entries = 2;
}

message Ack {
  string topic = 1;

  // the sequence of an already processed message.
  // Must be monotonically increasing for a given topic and two given node processes.
  int64 last_seq = 2;
}

enum ExitReason {
  UNKNOWN = 0;
  OK = 1;
  CONGESTED = 2;
  CAPTURE_SUICIDE = 3;
  STALE_CONNECTION = 4;
  DUPLICATE_CONNECTION = 5;
  CAPTURE_ID_MISMATCH = 6;
}

message SendMessageResponse {
  repeated Ack ack = 1;
  ExitReason exit_reason = 2;
  string error_message = 3;
}