// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// Over-the-wire message definitions used for the Helium synchronization
// protocol.

syntax = "proto3";

option optimize_for = LITE_RUNTIME;

package blimp.proto;

// Vector clock that is used to get the partial order of changes.
// This class is the proto definition of
// //blimp/net/helium/version_vector.h
message VersionVectorMessage {
  uint64 local_revision = 1;
  uint64 remote_revision = 2;
}

// Sample proto for test purposes.
message TestChangesetMessage {
  int32 value1 = 1;
  int32 value2 = 2;
}

// A union of serializable Changeset types. There will be one for each Helium
// Object that requires serialization.
message ChangesetMessage {
  oneof payload {
    // Sample message for the test
    TestChangesetMessage test = 1;
  };
}

// Message that encapsulates a change for a helium object. It contains
// information required to restore the object from the time specified in |from|
// until |to|.
//
// This is the main object that will be sent in the Helium transport
message HeliumMessage {
  // Identifies the local revision that this changeset applies to (relative
  // to the sender), and the remote revision that the local side most recently
  // received (i.e. an ACK, in effect).
  VersionVectorMessage from = 1;

  // Provides the local view of the vector-clock following application of
  // the changeset. This allows a single changeset to collate changes across
  // several revisions, following a break in connectivity, rather than simply
  // re-transmitting the lost changesets.
  VersionVectorMessage to = 2;

  // Identifies the Object to which this changeset applies.
  uint32 object_id = 3;

  // The changeset that contain the actual changes.
  ChangesetMessage change = 4;
}