Buying over x402

import { toClientCardanoSigner } from "@x402/cardano";
import { ExactCardanoScheme } from "@x402/cardano/exact/client";
import { decodePaymentResponseHeader, wrapFetchWithPayment, x402Client } from "@x402/fetch";

const ESCROW = "addr_test1wzy842psthjj2llfv06tc38dtuqey8ve55n6gm6acprk9ksc7d963";

const signer = toClientCardanoSigner({
  mnemonic: process.env.BUYER_MNEMONIC!, // a fresh preprod test wallet
  network: "cardano:preprod",
  provider: { blockfrost: { baseUrl: "https://cardano-preprod.blockfrost.io/api/v0", projectId: process.env.BLOCKFROST_PROJECT_ID! } },
  validateCustomMasumiDeployment: (claim) => claim.payTo === ESCROW, // only pay into Simpuru's escrow
});

const client = x402Client.fromConfig({
  schemes: [{ network: "cardano:preprod", client: new ExactCardanoScheme(signer) }],
  // Pick the protected option, and only if it pays into Simpuru's escrow.
  policies: [(_v, reqs) => reqs.filter((r) => r.extra?.assetTransferMethod === "masumi" && r.payTo === ESCROW)],
  spendControls: {
    allowedAssets: [{ network: "cardano:preprod", asset: "lovelace", maxAmountPerPayment: "20000000" }],
  },
});

const pay = wrapFetchWithPayment(fetch, client);
const res = await pay("https://api.simpuru.xyz/listings/<id>/unlock");
const content = await res.text();
const tx = decodePaymentResponseHeader(res.headers.get("PAYMENT-RESPONSE")!).transaction;