// Copyright 2021 Lightbend Inc.

// gRPC interface for common messages and services for value-based Entity user functions.

syntax = "proto3";

package akkaserverless.component.valueentity;

option go_package = "github.com/lightbend/akkaserverless-go-sdk/akkaserverless/entity;entity";
option java_package = "com.akkaserverless.protocol";

import "akkaserverless/component/component.proto";
import "akkaserverless/component/entity/entity.proto";
import "google/protobuf/any.proto";

// Service that the SDK (in the user function) implements to make value
// entities available to the proxy
service ValueEntities {
  // One stream will be established per active entity. Once established, the
  // first message sent will be Init, which contains the entity ID, and, a state
  // if the entity has previously persisted one. Once the Init message is sent,
  // one to many commands are sent to the entity. Each request coming in leads
  // to a new command being sent to the entity. The entity is expected to reply
  // to each command with exactly one reply message. The entity should process
  // commands and reply to commands in the order they came in. When processing a
  // command the entity can read and persist (update or delete) the state.
  rpc Handle(stream ValueEntityStreamIn) returns (stream ValueEntityStreamOut);
}

// Input message type for the gRPC stream in.
message ValueEntityStreamIn {
  oneof message {
    ValueEntityInit init = 1;
    entity.Command command = 2;
  }
}

// The init message. This will always be the first message sent to the entity
// when it is loaded.
message ValueEntityInit {
  // The name of the service that implements this entity.
  string service_name = 1;
  // The id of the entity.
  string entity_id = 2;
  // The initial state of the entity.
  ValueEntityInitState state = 3;
}

// The state of the entity when it is first activated.
message ValueEntityInitState {
  // The value of the entity state, if the entity has already been created.
  google.protobuf.Any value = 1;
}

// Output message type for the gRPC stream out.
message ValueEntityStreamOut {
  oneof message {
    ValueEntityReply reply = 1;
    Failure failure = 2;
  }
}

// A reply to a command.
message ValueEntityReply {
  // The command being replied to
  int64 command_id = 1;
  // The action to take for the client response
  ClientAction client_action = 2;
  // Any side effects to perform
  repeated SideEffect side_effects = 3;
  // The action to take on the value entity
  ValueEntityAction state_action = 4;
}

// An action to take for changing the entity state.
message ValueEntityAction {
  oneof action {
    ValueEntityUpdate update = 1;
    ValueEntityDelete delete = 2;
  }
}

// An action which updates the persisted value of the Value entity. If the
// entity is not yet persisted, it will be created.
message ValueEntityUpdate {
  // The value to set.
  google.protobuf.Any value = 1;
}

// An action which deletes the persisted value of the Value entity.
message ValueEntityDelete {}