// Signs an x402 payment for one site-report request and prints the PAYMENT-SIGNATURE header value (used by ../curl.sh).
// Usage: BUYER_PRIVATE_KEY=0x... node sign-payment.mjs <endpoint> '<json body>'
// It sends the request once without payment, reads the 402 terms and signs exactly those (USDC, scheme exact).
// Nothing is paid until you send the signature; an answer >= 400 to the paid request is never settled.
// MAX_PRICE_USD (default 1) refuses to sign anything more expensive. Needs @x402/fetch, @x402/evm and viem.
import { x402Client, x402HTTPClient } from '@x402/fetch';
import { registerExactEvmScheme } from '@x402/evm/exact/client';
import { privateKeyToAccount } from 'viem/accounts';

const [endpoint, body] = process.argv.slice(2);
const key = process.env.BUYER_PRIVATE_KEY;
const max = Number(process.env.MAX_PRICE_USD || 1);
if (!endpoint || !body || !key) { console.error('Usage: BUYER_PRIVATE_KEY=0x... node sign-payment.mjs <endpoint> <json body>'); process.exit(2); }

const res = await fetch(endpoint, { method: 'POST', headers: { 'content-type': 'application/json' }, body });
if (res.status !== 402) { console.error(`Expected 402 with payment terms, got ${res.status}: ${await res.text()}`); process.exit(1); }
const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(key) });
const http = new x402HTTPClient(client);
const terms = http.getPaymentRequiredResponse(name => res.headers.get(name), await res.json().catch(() => null));
const offer = terms.accepts?.[0];
const usd = Number(offer?.amount) / 1e6; // USDC has 6 decimals
if (!(usd > 0) || usd > max) { console.error(`Refusing to sign: the price is ${usd} USD, above MAX_PRICE_USD ${max}.`); process.exit(1); }
console.error(`Signing ${usd} USD (USDC) to ${offer.payTo} on ${offer.network}.`);
const headers = http.encodePaymentSignatureHeader(await client.createPaymentPayload(terms));
process.stdout.write(headers['PAYMENT-SIGNATURE'] || headers['X-PAYMENT']);