Hip-904 account changes supporting pending airdrops

services/response_code.proto

@@ -1549,4 +1549,17 @@ enum ResponseCodeEnum {
     * The transaction attempted to use more than the allowed number of `PendingAirdropId`.
     */
     MAX_PENDING_AIRDROP_ID_EXCEEDED = 363;
+
+    /*
+    * A pending airdrop already exists for the specified NFT.
+    */
+    PENDING_NFT_AIRDROP_ALREADY_EXISTS = 364;
+
+    /*
+     * The identified account is sender for one or more pending airdrop(s)
+     * and cannot be deleted.<br/>
+     * Requester should cancel all pending airdrops before resending
+     * this transaction.
+     */
+    ACCOUNT_HAS_PENDING_AIRDROPS = 365;
 }

services/state/token/account.proto

@@ -203,6 +203,17 @@ message Account {
      * It will be null if if the account is not a contract or the contract has no storage mappings.
      */
     bytes first_contract_storage_key = 33;
+
+    /**
+     * A pending airdrop ID at the head of the linked list for this account
+     * from the account airdrops map.<br/>
+     * The account airdrops are connected by including the "next" and "previous"
+     * `PendingAirdropID` in each `AccountAirdrop` message.
+     * <p>
+     * This value SHALL NOT be empty if this account is "sender" for any
+     * pending airdrop, and SHALL be empty otherwise.
+     */
+    PendingAirdropId head_pending_airdrop_id = 34;
 }
 
 /**

services/state/token/account_pending_airdrop.proto

@@ -0,0 +1,70 @@
+syntax = "proto3";
+
+package proto;
+
+/*
+ * 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.
+ */
+
+import "basic_types.proto";
+
+option java_package = "com.hederahashgraph.api.proto.java";
+// <<<pbj.java_package = "com.hedera.hapi.node.state.token">>> This comment is special code for setting PBJ Compiler java package
+option java_multiple_files = true;
+
+
+/**
+ * A node within a doubly linked list of pending airdrop references.<br/>
+ * This internal state message forms the entries in a doubly-linked list
+ * of references to pending airdrop entries that are "owed" by a particular
+ * account as "sender".
+ *
+ * Each entry in this list MUST refer to an existing pending airdrop.<br/>
+ * The pending airdrop MUST NOT be claimed.<br/>
+ * The pending airdrop MUST NOT be canceled.<br/>
+ * The pending airdrop `sender` account's `head_pending_airdrop_id` field
+ * MUST match the `pending_airdrop_id` field in this message. 
+ *
+ * ### Record Stream Effects
+ * This value is not currently published in the record stream.
+ */
+message AccountPendingAirdrop {
+  /**
+   * The value of the current airdrop id. SHALL NOT be set for non fungible tokens
+   */
+  PendingAirdropValue pending_airdrop_value = 1;
+
+  /**
+   * A pending airdrop identifier.<br/>
+   * This identifies the specific pending airdrop that precedes this position
+   * within the doubly linked list of pending airdrops "owed" by the sending
+   * account associated with this account airdrop "list".
+   * <p>
+   * This SHALL match `pending_airdrop_id` if this is the only entry
+   * in the "list".
+   */
+  PendingAirdropId previous_airdrop = 2;
+
+  /**
+   * A pending airdrop identifier.<br/>
+   * This identifies the specific pending airdrop that follows this position
+   * within the doubly linked list of pending airdrops "owed" by the sending
+   * account associated with this account airdrop "list".
+   * <p>
+   * This SHALL match `pending_airdrop_id` if this is the only entry
+   * in the "list".
+   */
+  PendingAirdropId next_airdrop = 3;
+}