// Igneum testnet faucet. POST /api/faucet {address} sends 10 IGN of testnet coin to that address: once per address per
// day, once per IP per day. The key is only in the Vercel env (FAUCET_KEY), the node in FAUCET_RPC; without either the
// faucet answers "not open yet" and sends nothing. Rate limits live in the Neon table faucet_grants (the same HTTP SQL
// pattern as api/log.mjs). Zero dependencies: the transaction is signed by site/lib/eth.mjs.
// Prepared on the devnet (chain id 4463) on 5 October 2026; the public testnet (4462) gets its own key and RPC.
import { signTransaction, addressOf, isAddress, toWei } from '../lib/eth.mjs';

export const AMOUNT_IGN = 10;
export const WINDOW_HOURS = 24;

export function neon(url) {
  if (!url) throw new Error('DATABASE_URL is not set');
  const host = new URL(url).hostname.replace('-pooler', '');
  return async (query, params = []) => {
    const r = await fetch(`https://${host}/sql`, {
      method: 'POST',
      headers: { 'Neon-Connection-String': url, 'Content-Type': 'application/json' },
      body: JSON.stringify({ query, params }),
    });
    const j = await r.json();
    if (!r.ok) throw new Error(j.message || JSON.stringify(j));
    return j;
  };
}

export function rpcClient(url, fetchImpl = fetch) {
  let id = 0;
  return async (method, params = []) => {
    const r = await fetchImpl(url, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ jsonrpc: '2.0', id: ++id, method, params }) });
    const j = await r.json();
    if (j.error) throw new Error(`${method}: ${j.error.message || JSON.stringify(j.error)}`);
    return j.result;
  };
}

async function readBody(req) {
  if (req.body !== undefined && req.body !== null) {
    if (typeof req.body === 'string') return JSON.parse(req.body);
    if (Buffer.isBuffer(req.body)) return JSON.parse(req.body.toString('utf8'));
    return req.body;
  }
  const chunks = [];
  for await (const c of req) chunks.push(c);
  return JSON.parse(Buffer.concat(chunks).toString('utf8') || '{}');
}

export function clientIp(req) {
  const fwd = req.headers['x-forwarded-for'];
  const first = (Array.isArray(fwd) ? fwd[0] : fwd || '').split(',')[0].trim();
  return first || String(req.headers['x-real-ip'] || req.socket?.remoteAddress || '').trim() || 'unknown';
}

// The handler, with its dependencies injectable for the tests: {env, sql, rpc}. `sql` is (query, params) -> {rows},
// `rpc` is (method, params) -> result. The default export wires the real ones from the environment.
export function createHandler({ env = process.env, sql, rpc } = {}) {
  return async function handler(req, res) {
    res.setHeader('Cache-Control', 'no-store');
    if (req.method !== 'POST') { res.setHeader('Allow', 'POST'); return res.status(405).json({ ok: false, error: 'method not allowed' }); }
    const key = env.FAUCET_KEY, rpcUrl = env.FAUCET_RPC;
    const chainId = Number(env.FAUCET_CHAIN_ID || 4463);
    if (!key || !/^0x[0-9a-fA-F]{64}$/.test(key) || !rpcUrl) {
      return res.status(503).json({ ok: false, error: 'The faucet is not open yet. It opens with the public testnet.' });
    }
    let body;
    try { body = await readBody(req); } catch { return res.status(400).json({ ok: false, error: 'bad json' }); }
    const address = String(body.address || '').trim();
    if (!isAddress(address)) return res.status(400).json({ ok: false, error: 'That is not an address. It is 0x followed by 40 hex characters.' });
    const to = address.toLowerCase();
    const ip = clientIp(req);
    try {
      sql = sql || neon(env.DATABASE_URL);
      const recent = await sql(
        `SELECT address, ip FROM faucet_grants WHERE created_at > now() - interval '${WINDOW_HOURS} hours' AND (address = $1 OR ip = $2)`,
        [to, ip],
      );
      const rows = recent.rows || [];
      if (rows.some(r => r.address === to)) return res.status(429).json({ ok: false, error: `This address had its ${AMOUNT_IGN} IGN in the last ${WINDOW_HOURS} hours. Come back tomorrow.` });
      if (rows.some(r => r.ip === ip)) return res.status(429).json({ ok: false, error: `This connection had its ${AMOUNT_IGN} IGN in the last ${WINDOW_HOURS} hours. Come back tomorrow.` });
      // reserve the grant first, so two requests in the same second cannot both pass the count
      const ins = await sql('INSERT INTO faucet_grants (address, ip, amount_wei, chain_id) VALUES ($1, $2, $3, $4) RETURNING id', [to, ip, toWei(AMOUNT_IGN).toString(), chainId]);
      const grantId = Number(ins.rows[0].id);
      try {
        rpc = rpc || rpcClient(rpcUrl);
        const from = addressOf(key);
        const [nonceHex, block, tipHex] = await Promise.all([
          rpc('eth_getTransactionCount', [from, 'pending']),
          rpc('eth_getBlockByNumber', ['latest', false]),
          rpc('eth_maxPriorityFeePerGas').catch(() => '0x3b9aca00'), // 1 gwei when the node has no tip oracle
        ]);
        const baseFee = BigInt(block?.baseFeePerGas || '0x3b9aca00');
        const tip = BigInt(tipHex || '0x3b9aca00');
        const value = toWei(AMOUNT_IGN);
        let gas = 21000n;
        try { gas = BigInt(await rpc('eth_estimateGas', [{ from, to, value: '0x' + value.toString(16) }])); } catch { /* the plain-transfer default */ }
        const tx = { chainId, nonce: BigInt(nonceHex), maxPriorityFeePerGas: tip, maxFeePerGas: baseFee * 2n + tip, gas, to, value, data: '0x' };
        const signed = signTransaction(tx, key);
        const hash = await rpc('eth_sendRawTransaction', [signed.raw]);
        await sql('UPDATE faucet_grants SET tx_hash = $1 WHERE id = $2', [hash, grantId]);
        return res.status(200).json({ ok: true, tx: hash, amount: String(AMOUNT_IGN), chainId, to });
      } catch (e) {
        await sql('DELETE FROM faucet_grants WHERE id = $1', [grantId]).catch(() => {});
        return res.status(502).json({ ok: false, error: `The node did not take the transaction: ${String(e.message || e).slice(0, 200)}` });
      }
    } catch (e) {
      return res.status(500).json({ ok: false, error: String(e.message || e).slice(0, 200) });
    }
  };
}

export default createHandler();