const { JsonRpcProvider } = require('ethers');
const { readDb, writeDb } = require('../storage');
const { getEthereumRpcUrls, createRoundRobinPicker } = require('../utils/rpc');

function startEvmWatcher({ notifyMerchant }) {
  const rpcUrls = getEthereumRpcUrls();
  if (!rpcUrls.length) {
    console.warn('[evmWatcher] No Ethereum RPC URLs configured. Skipping watcher.');
    return;
  }

  const pollInterval = Number(process.env.TX_POLL_INTERVAL_MS || 180000);
  const maxPerCycle = Number(process.env.MAX_TX_CHECK_PER_CYCLE || 20);
  const minConfirmations = Number(process.env.MIN_CONFIRMATIONS || 1);
  const pickRpcUrl = createRoundRobinPicker(rpcUrls);

  let running = false;

  async function poll() {
    if (running) return;
    running = true;
    try {
      const db = await readDb();
      const pending = db.txs.filter((tx) => tx.network === 'evm:ethereum' && tx.status === 'pending');
      if (pending.length === 0) {
        running = false;
        return;
      }

      const rpcUrl = pickRpcUrl();
      const provider = new JsonRpcProvider(rpcUrl);
      const latestBlock = await provider.getBlockNumber();
      const now = new Date().toISOString();
      const confirmedEvents = [];

      for (const tx of pending.slice(0, maxPerCycle)) {
        const receipt = await provider.getTransactionReceipt(tx.txHash);
        tx.lastCheckedAt = now;

        if (!receipt) continue;

        const confirmations = latestBlock - receipt.blockNumber + 1;
        tx.confirmations = confirmations;
        tx.updatedAt = now;

        if (receipt.status === 1 && confirmations >= minConfirmations) {
          tx.status = 'confirmed';
          const order = db.orders.find((item) => item.id === tx.orderId);
          if (order) {
            order.status = 'paid';
            order.updatedAt = now;
            confirmedEvents.push({ order, tx });
          }
        } else if (receipt.status === 0) {
          tx.status = 'failed';
        }
      }

      await writeDb(db);

      for (const event of confirmedEvents) {
        await notifyMerchant(event.order, event.tx);
      }
    } catch (error) {
      console.error('[evmWatcher] poll error', error.message);
    } finally {
      running = false;
    }
  }

  poll();
  setInterval(poll, pollInterval);
  console.log(`[evmWatcher] started with interval ${pollInterval}ms`);
}

module.exports = { startEvmWatcher };