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/**
 * # Event Descriptor
 * Unique identifier for an event.
 *
 * Contains the hash of the event, the creator identifier, the birth round, and the generation.
 *
 * An event's descriptor is constructed individually by each node that receives a `GossipEvent`,
 * to uniquely identify that event. An event's descriptor isn't part of the `GossipEvent` itself,
 * since the descriptor contains the fields `hash` and `generation`, which can be computed locally.
 * Nodes receiving a `GossipEvent` have the required information to construct the event descriptor
 * immediately upon receiving the event, without needing to wait for the event to reach consensus.
 *
 * Aside from being a unique identifier for events that have been received through gossip,
 * the event descriptor contains the necessary information to describe an event's parents,
 * in the `parents` field of `GossipEvent`.
 *
 * ### Keywords
 * The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 * "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 * document are to be interpreted as described in [RFC2119](https://www.ietf.org/rfc/rfc2119).
 */
syntax = "proto3";

package com.hedera.hapi.platform.event;

/*
 * Hedera Network Services Protobuf
 *
 * Copyright (C) 2024 Hedera Hashgraph, 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.
 */

option java_package = "com.hedera.hapi.platform.event.legacy";
// <<>> This comment is special code for setting PBJ Compiler java package
option java_multiple_files = true;

/**
 * Unique identifier for an event.
 */
message EventDescriptor {
  /**
   * The hash of the event.

   * The hash SHALL be a SHA-384 hash.

   * The hash SHALL have the following inputs, in the specified order:

   * 1. The bytes of the `EventCore` protobuf

   * 2. The SHA-384 hash of each individual `EventTransaction`, in the order the transactions appear in the `event_transactions` field of the `GossipEvent` protobuf
   */
  bytes hash = 1;

  /**
   * The creator node identifier.

   * This SHALL be the unique identifier for the node that created the event.

   * This SHALL match the ID of the node as it appears in the address book.
   */
  int64 creator_node_id = 2;

  /**
   * The birth round of the event.

   * The birth round SHALL be the pending consensus round at the time the event is created.

   * The pending consensus round SHALL be **one greater** than the latest round to reach consensus.
   */
  int64 birth_round = 3;

  /**
  * The generation of the event.

  * This value SHALL be **one greater** than the _maximum_ generation of all parents.

  */
  int64 generation = 17; // This field is temporary until birth_round migration is complete. Field number 17 chosen to avoid polluting cheaper 1 byte field numbers 1-16
}