add server as sponsor example

examples/typescript-esm/package.json

@@ -6,12 +6,13 @@
   "type": "module",
   "scripts": {
     "build": "pnpm _build:esm",
-    "_build:esm": "tsup simple_transfer.ts simple_sponsored_transaction.ts simple_digital_asset.ts multisig_v2.ts front_to_back_txn.ts --platform node --format esm --dts --out-dir dist",
+    "_build:esm": "tsup simple_transfer.ts sponsored_transactions/simple_sponsored_transaction.ts sponsored_transactions/server_as_sponsor.ts simple_digital_asset.ts multisig_v2.ts sponsored_transactions/server_signs_and_submit.ts --platform node --format esm --dts --out-dir dist",
     "simple_transfer": "ts-node --esm dist/simple_transfer.js",
-    "simple_sponsored_transaction": "ts-node --esm dist/simple_sponsored_transaction.js",
+    "simple_sponsored_transaction": "ts-node --esm dist/sponsored_transactions/simple_sponsored_transaction.js",
     "simple_digital_asset": "pnpm run build && ts-node --esm dist/simple_digital_asset.js",
     "multisig_v2": "pnpm run build && ts-node --esm dist/multisig_v2.js",
-    "front_to_back_txn": "pnpm run build && ts-node dist/front_to_back_txn.js",
+    "server_signs_and_submit": "pnpm run build && ts-node dist/sponsored_transactions/server_signs_and_submit.js",
+    "server_as_sponsor": "pnpm run build && ts-node dist/sponsored_transactions/server_as_sponsor.js",
     "test": "run-s build simple_transfer simple_sponsored_transaction"
   },
   "keywords": [],

examples/typescript-esm/sponsored_transactions/server_as_sponsor.ts

@@ -0,0 +1,112 @@
+/* eslint-disable no-console */
+
+/**
+ * This example demostrates how one can use an external server
+ * as a sponsor to sign a transaction to eventually pay the gas fees.
+ *
+ * A server (for example, frontend) generates a transaction, have it serialized and send
+ * it to another server (for example, backend) to deserialize and signs as the sponsor,
+ * then sends it back to the other server (the frontend server) to submit the transaction.
+ */
+
+import {
+  Account,
+  AccountAuthenticator,
+  Aptos,
+  AptosConfig,
+  Deserializer,
+  Network,
+  NetworkToNetworkName,
+  RawTransaction,
+} from "@aptos-labs/ts-sdk";
+
+const INITIAL_BALANCE = 100_000_000;
+const TRANSFER_AMOUNT = 100;
+
+// Default to devnet, but allow for overriding
+const APTOS_NETWORK: Network = NetworkToNetworkName[process.env.APTOS_NETWORK] || Network.DEVNET;
+// Setup the client
+const config = new AptosConfig({ network: APTOS_NETWORK });
+const aptos = new Aptos(config);
+
+// The sponsor server gets the serialized transaction to sign as the fee payer
+const sendToTheSponsorServer = async (rawTransactionBytes: Uint8Array) => {
+  const sponsor = Account.generate();
+  console.log(`Sponsor's address is: ${sponsor.accountAddress}`);
+  await aptos.fundAccount({ accountAddress: sponsor.accountAddress, amount: INITIAL_BALANCE });
+
+  // deserialize raw transaction
+  const deserializer = new Deserializer(rawTransactionBytes);
+  const rawTransaction = RawTransaction.deserialize(deserializer);
+
+  // Sponsor signs
+  const sponsorAuth = aptos.transaction.signAsFeePayer({
+    signer: sponsor,
+    transaction: { rawTransaction, feePayerAddress: sponsor.accountAddress },
+  });
+
+  const sponsorAuthBytes = sponsorAuth.bcsToBytes();
+
+  return { sponsorAuthBytes, feepayerAddress: sponsor.accountAddress };
+};
+
+const example = async () => {
+  // Create two accounts
+  const alice = Account.generate();
+  const bob = Account.generate();
+
+  console.log("=== Addresses ===\n");
+  console.log(`Alice's address is: ${alice.accountAddress}`);
+  console.log(`Bob's address is: ${bob.accountAddress}`);
+
+  // Fund the accounts
+  console.log("\n=== Funding accounts ===\n");
+
+  await aptos.faucet.fundAccount({
+    accountAddress: alice.accountAddress,
+    amount: INITIAL_BALANCE,
+  });
+
+  console.log("\n=== Accounts funded ===\n");
+
+  const transaction = await aptos.transaction.build.simple({
+    sender: alice.accountAddress,
+    withFeePayer: true,
+    data: {
+      function: "0x1::aptos_account::transfer",
+      functionArguments: [bob.accountAddress, TRANSFER_AMOUNT],
+    },
+  });
+
+  // Alice signs
+  const senderAuth = aptos.transaction.sign({ signer: alice, transaction });
+
+  // Serialize data
+  /**
+   * the generated `transaction` is of a simple type and can't be
+   * bcs serialized. Therefore we serialize the `rawTransaction` and
+   * send it to the server.
+   */
+  const rawTransactionBytes = transaction.rawTransaction.bcsToBytes();
+
+  // Send the transaction to the sponsor server to sign
+  const { sponsorAuthBytes, feepayerAddress } = await sendToTheSponsorServer(rawTransactionBytes);
+
+  // deserialize fee payer authenticator
+  const deserializer3 = new Deserializer(sponsorAuthBytes);
+  const feePayerAuthenticator = AccountAuthenticator.deserialize(deserializer3);
+
+  const response = await aptos.transaction.submit.simple({
+    transaction: {
+      rawTransaction: transaction.rawTransaction,
+      feePayerAddress: feepayerAddress,
+    },
+    senderAuthenticator: senderAuth,
+    feePayerAuthenticator,
+  });
+
+  const executedTransaction = await aptos.waitForTransaction({ transactionHash: response.hash });
+  console.log("executed transaction", executedTransaction.hash);
+};
+
+example();

examples/typescript-esm/tsconfig.json

@@ -14,10 +14,8 @@
     "target": "es2020",
     "pretty": true
   },
-  "include": [
-    "*.ts"
-  ],
+  "include": ["*.ts", "sponsored_transactions/*.ts"],
   "paths": {
-    "@aptos/*": "../..",
+    "@aptos/*": "../.."
   }
 }