Gasless sends

import { toHex } from "viem";

const AUSD = "0xa9012a055bd4e0eDfF8Ce09f960291C09D5322dC";

async function signTransfer(account, { to, value, validBefore }) {
  const message = {
    from: account.address,
    to,
    value,
    validAfter: 0n,
    validBefore,
    nonce: toHex(crypto.getRandomValues(new Uint8Array(32))), // random, once
  };
  const signature = await account.signTypedData({
    domain: { name: "Agora Dollar", version: "1", chainId: 10143, verifyingContract: AUSD },
    types: {
      TransferWithAuthorization: [
        { name: "from", type: "address" },
        { name: "to", type: "address" },
        { name: "value", type: "uint256" },
        { name: "validAfter", type: "uint256" },
        { name: "validBefore", type: "uint256" },
        { name: "nonce", type: "bytes32" },
      ],
    },
    primaryType: "TransferWithAuthorization",
    message,
  });
  // the API takes every bigint as a string
  return {
    ...message,
    value: String(message.value),
    validAfter: "0",
    validBefore: String(message.validBefore),
    signature,
  };
}

const authorization = await signTransfer(account, {
  to: mom,
  value: 5_000_000n, // 5 AUSD
  validBefore: BigInt(Math.floor(Date.now() / 1000) + 3600),
});
await post("/sends", { authorization }, session);