// express-402-paid-endpoint.js
//
// Drop-in example: a paid `/v1/inference` endpoint that charges $0.0125
// in USDC.e per call via AERE402 settlement on Chain 2800.
//
// Run:
//   yarn add express @aere/sdk-js ethers
//   FACILITATOR=0x... PAYEE=0x... PROVIDER_PRIVATE_KEY=0x... node express-402-paid-endpoint.js
//
// Then the agent-side does:
//   1. curl http://localhost:3000/v1/inference
//      → 402 with X-AERE402-Quote JSON header
//   2. agent EIP-712-signs the quote using its registered signing key
//   3. curl -H "X-AERE402-Sig: 0x.." -H "X-AERE402-AgentId: 1234" \
//          -H "X-AERE402-Quote: <original-quote-json>" \
//          http://localhost:3000/v1/inference
//      → 200 with the actual inference output, X-AERE402-TxHash header set

const express = require('express');
const { ethers } = require('ethers');
const { createAere402Middleware } = require('@aere/sdk-js');

const FACILITATOR = process.env.FACILITATOR;
const USDC_E      = process.env.USDC_E      ?? '0x0000000000000000000000000000000000000000';
const PAYEE       = process.env.PAYEE;
const PROVIDER_PK = process.env.PROVIDER_PRIVATE_KEY;
const RPC_URL     = process.env.RPC_URL     ?? 'https://rpc.aere.network';
const CHAIN_ID    = parseInt(process.env.CHAIN_ID ?? '2800', 10);

if (!FACILITATOR || !PAYEE || !PROVIDER_PK) {
  console.error('FACILITATOR, PAYEE, and PROVIDER_PRIVATE_KEY env vars required');
  process.exit(1);
}

const provider = new ethers.JsonRpcProvider(RPC_URL);
const providerWallet = new ethers.Wallet(PROVIDER_PK, provider);

// Real `settle()` ABI from AERE402Facilitator. Pulled minimal — just what we call.
const FAC_ABI = [
  'function settle(uint256 agentId, address token, address payee, uint256 amount, bytes32 resourceId, uint256 nonce, uint256 deadline, bytes signature) external',
];
const facContract = new ethers.Contract(FACILITATOR, FAC_ABI, providerWallet);

const charge = createAere402Middleware({
  facilitator: FACILITATOR,
  chainId: CHAIN_ID,
  token: USDC_E,
  payee: PAYEE,
  pricer: () => 12500n,                       // $0.0125 in USDC.e (6 decimals)
  submit: async (auth, signature) => {
    const tx = await facContract.settle(
      BigInt(auth.agentId),
      auth.token,
      auth.payee,
      BigInt(auth.amount),
      auth.resourceId,
      BigInt(auth.nonce),
      BigInt(auth.deadline),
      signature,
    );
    const rcpt = await tx.wait();
    return rcpt.hash;
  },
});

const app = express();

app.get('/v1/inference', charge, (req, res) => {
  // The middleware paid us — we can read req.aere402 for receipt info.
  const { txHash, auth } = req.aere402;
  console.log(`paid call: agent=${auth.agentId} amount=${auth.amount} tx=${txHash}`);
  res.json({
    output: 'Pretend this is an LLM completion.',
    aere402: { txHash, amountCharged: auth.amount, token: auth.token },
  });
});

const PORT = parseInt(process.env.PORT ?? '3000', 10);
app.listen(PORT, () => {
  console.log(`paid endpoint running at http://localhost:${PORT}/v1/inference`);
  console.log(`facilitator: ${FACILITATOR}`);
  console.log(`payee: ${PAYEE}`);
  console.log(`provider wallet: ${providerWallet.address}`);
});