// agent-402-pqc-client.js
//
// Drop-in example: agent-side AERE402FacilitatorPQC client. The agent's spending
// authority is rooted in a quantum-durable Falcon key (an AereAgentDID); each payment
// is authorized by a cheap, short-lived, revocable secp256k1 SESSION key. Rotating or
// revoking the Falcon root instantly halts every downstream payment.
//
// The agent calls a paid endpoint, receives 402 + a PQC quote, signs the DID action
// digest with its SESSION key (a single ecrecover on-chain), and retries. The Falcon
// root is never touched on the payment hot path — it only ever issues sessions.
//
// Run:
//   yarn add ethers
//   SESSION_PRIVATE_KEY=0x... ENDPOINT=http://localhost:3000/v1/inference node agent-402-pqc-client.js
//
// Prereq: an AereAgentDID agent (Falcon root) exists, a session is issued for
// SESSION_PRIVATE_KEY's address (with scope + spend cap + expiry), and the agent's
// AERE402FacilitatorPQC vault is funded. The server issues the 402 quote; the agent only
// needs its session key here.

const { ethers } = require('ethers');

const SESSION_PK = process.env.SESSION_PRIVATE_KEY;
const ENDPOINT = process.env.ENDPOINT ?? 'http://localhost:3000/v1/inference';

if (!SESSION_PK) {
  console.error('SESSION_PRIVATE_KEY env required');
  process.exit(1);
}

// Domain tags — mirror the contracts exactly.
const PAYMENT_DOMAIN = ethers.keccak256(ethers.toUtf8Bytes('AERE402FacilitatorPQC.v1.payment'));
const ACTION_DOMAIN = ethers.keccak256(ethers.toUtf8Bytes('AereAgentDID.v1.action'));

// keccak256(abi.encode(PAYMENT_DOMAIN, chainId, facilitator, token, payee, resourceId, deadline))
function paymentActionHash(q) {
  const enc = ethers.AbiCoder.defaultAbiCoder().encode(
    ['bytes32', 'uint256', 'address', 'address', 'address', 'bytes32', 'uint256'],
    [PAYMENT_DOMAIN, q.chainId, q.facilitator, q.token, q.payee, q.resourceId, BigInt(q.deadline)],
  );
  return ethers.keccak256(enc);
}

// keccak256(abi.encode(ACTION_DOMAIN, chainId, did, sessionId, scope, actionHash, amount, actionNonce))
function actionDigest(q, actionHash) {
  const enc = ethers.AbiCoder.defaultAbiCoder().encode(
    ['bytes32', 'uint256', 'address', 'uint256', 'bytes32', 'bytes32', 'uint256', 'uint64'],
    [ACTION_DOMAIN, q.chainId, q.did, BigInt(q.sessionId), q.scope, actionHash, BigInt(q.amount), BigInt(q.actionNonce)],
  );
  return ethers.keccak256(enc);
}

const session = new ethers.SigningKey(SESSION_PK);

(async () => {
  console.log(`session ${ethers.computeAddress(session)} calling ${ENDPOINT}...`);

  // 1. Unpaid request.
  const r1 = await fetch(ENDPOINT);
  if (r1.status !== 402) {
    console.log(`unexpected status ${r1.status} on first call`);
    console.log(await r1.text());
    return;
  }
  const quoteJson = r1.headers.get('x-aere402pqc-quote');
  if (!quoteJson) throw new Error('server did not return X-AERE402PQC-Quote');
  const quote = JSON.parse(quoteJson);
  // quote = { chainId, facilitator, did, sessionId, scope, token, payee, amount,
  //           resourceId, deadline, actionNonce }
  console.log('  received quote:', quote);

  // 2. Derive the actionHash (binds the payment to THIS facilitator + terms) and the DID
  //    action digest the session key must sign.
  const actionHash = paymentActionHash(quote);
  const digest = actionDigest(quote, actionHash);

  // 3. Sign the raw digest with the SESSION key (canonical low-s; matches on-chain ecrecover).
  const signature = session.sign(digest).serialized;
  console.log(`  signed: ${signature.slice(0, 18)}...`);

  // 4. Retry with the signature. The provider POSTs
  //    settle(sessionId, scope, token, payee, amount, resourceId, deadline, signature)
  //    to AERE402FacilitatorPQC, which enforces the Falcon root lifecycle + scope + spend
  //    cap + this session signature + anti-replay in one call, then pays out.
  const r2 = await fetch(ENDPOINT, {
    headers: {
      'X-AERE402PQC-Sig': signature,
      'X-AERE402PQC-Quote': quoteJson,
    },
  });
  console.log(`  retry status: ${r2.status}`);
  console.log(`  tx hash:      ${r2.headers.get('x-aere402pqc-txhash')}`);
  console.log('  body:', await r2.json());
})();