// Copyright 2025 Google LLC
//
// 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

syntax = "proto3";

package google.firebase.fcm.connection.v1alpha1;

import "google/api/annotations.proto";
import "google/protobuf/timestamp.proto";

option go_package = "google.golang.org/genproto/googleapis/firebase/fcm/connection/v1alpha1;connection";
option java_multiple_files = true;
option java_package = "com.google.firebase.fcm.connection.v1alpha1";

// FCM's service to create client connections to send/receive messages.
service ConnectionApi {
  // Creates a streaming connection with FCM to send messages and their
  // respective ACKs.
  //
  // The client credentials need to be passed in the [gRPC
  // Metadata](https://grpc.io/docs/guides/concepts.html#metadata). The Format
  // of the header is:
  //   Key: "authorization"
  //   Value: "Checkin [client_id:secret]"
  //
  //
  // The project's API key also needs to be sent to authorize the project.
  // That can be set in the X-Goog-Api-Key Metadata header.
  rpc Connect(stream UpstreamRequest) returns (stream DownstreamResponse) {
  }
}

// Request sent to FCM from the connected client.
message UpstreamRequest {
  // The type of request the client is making to FCM.
  oneof request_type {
    // Message acknowledgement.
    Ack ack = 1;
  }
}

// Response sent to the connected client from FCM.
message DownstreamResponse {
  // The type of response FCM is sending to the client.
  oneof response_type {
    // Message sent to FCM via the [Send
    // API](https://firebase.google.com/docs/cloud-messaging/send-message)
    // targeting this client.
    Message message = 1;
  }
}

// Acknowledgement to indicate a client successfully received an FCM message.
//
// If a message is not acked, FCM will continously resend the message until
// it expires. Duplicate delivery in this case is working as intended.
message Ack {
  // Id of message being acknowledged
  string message_id = 1;
}

// Message created through the [Send
// API](https://firebase.google.com/docs/reference/fcm/rest/v1/projects.messages#resource-message).
message Message {
  // The identifier of the message. Used to ack the message.
  string message_id = 1;

  // Time the message was received in FCM.
  google.protobuf.Timestamp create_time = 2;

  // Expiry time of the message. Currently it is always 4 weeks.
  google.protobuf.Timestamp expire_time = 3;

  // The arbitrary payload set in the [Send
  // API](https://firebase.google.com/docs/reference/fcm/rest/v1/projects.messages#resource-message).
  map<string, string> data = 4;
}
