writeside.proto

syntax = "proto3";

package chief_of_state.v1;

option csharp_namespace = "Namely.ChiefOfState.V1";
option go_package = "chief_of_state/v1;chiefofstatev1";
option java_multiple_files = true;
option java_outer_classname = "CosWriteSideHandlerProto";
option java_package = "com.namely.protobuf.chiefofstate.v1";

import "chief_of_state/v1/common.proto";
import "google/protobuf/any.proto";

// Defines the interface that will be implemented by any application that
// wants to keeps its events and state with ChiefOfState. So an application will
// implement the gRPC server while ChiefOfState will make use the client side to
// interact.
service WriteSideHandlerService {
  // Processes every command sent by ChiefOfState and return either a response
  // containing an event to persist or a simple reply.
  rpc HandleCommand(HandleCommandRequest) returns (HandleCommandResponse);
  // Processes every event sent by ChiefOfState by applying the event to the
  // current state to return a new state.
  rpc HandleEvent(HandleEventRequest) returns (HandleEventResponse);
}

// HandleCommandRequest
message HandleCommandRequest {
  // the command to handle
  google.protobuf.Any command = 1;
  // the aggregate state at the moment of handling the command. This is the
  // state before the command being handled.
  google.protobuf.Any prior_state = 2;
  // the prior event meta data. This is the event meta data of the last event
  // before this command
  chief_of_state.v1.MetaData prior_event_meta = 3;
}

// HandleCommandResponse
message HandleCommandResponse {
  // An event to append to the journal. If not set, COS
  // will treat this command as a no-op.
  google.protobuf.Any event = 1;
}

// HandleEventRequest
message HandleEventRequest {
  // the event to handle
  google.protobuf.Any event = 1;
  // the state before the event is being handled.
  google.protobuf.Any prior_state = 2;
  // the meta data of this event
  chief_of_state.v1.MetaData event_meta = 3;
}

// HandleEventResponse contains the resulting state
// after the event has been handled
message HandleEventResponse {
  // resulting state after the event has been handled
  google.protobuf.Any resulting_state = 1;
}