chore: add util

Author: ruijialin-avalabs

examples/p-chain/etna/utils/addSignatureToAllCred.ts

@@ -0,0 +1,18 @@
+import { secp256k1, type UnsignedTx } from '../../../../src';
+
+export const addSigToAllCreds = async (
+  unsignedTx: UnsignedTx,
+  privateKey: Uint8Array,
+) => {
+  const unsignedBytes = unsignedTx.toBytes();
+  const publicKey = secp256k1.getPublicKey(privateKey);
+
+  if (!unsignedTx.hasPubkey(publicKey)) {
+    return;
+  }
+  const signature = await secp256k1.sign(unsignedBytes, privateKey);
+
+  for (let i = 0; i < unsignedTx.getCredentials().length; i++) {
+    unsignedTx.addSignatureAt(signature, i, 0);
+  }
+};