chain_subscribeNewHeads - Moonbeam RPC Method

async function indexBlocks(api, onBlock) {
  const unsub = await api.rpc.chain.subscribeNewHeads(async (header) => {
    const blockHash = header.hash;
    const [block, events] = await Promise.all([
      api.rpc.chain.getBlock(blockHash),
      api.query.system.events.at(blockHash)
    ]);

    const blockData = {
      number: header.number.toNumber(),
      hash: blockHash.toHex(),
      parentHash: header.parentHash.toHex(),
      extrinsicCount: block.block.extrinsics.length,
      eventCount: events.length,
      timestamp: Date.now()
    };

    await onBlock(blockData);
  });

  return unsub;
}

async function monitorBlockProduction(api, expectedBlockTimeMs = 6000) {
  let lastBlockTime = Date.now();
  const threshold = expectedBlockTimeMs * 3;

  const unsub = await api.rpc.chain.subscribeNewHeads((header) => {
    const now = Date.now();
    const elapsed = now - lastBlockTime;

    if (elapsed > threshold) {
      console.warn(
        `Block #${header.number}: ${elapsed}ms since last block (expected ~${expectedBlockTimeMs}ms)`
      );
    } else {
      console.log(`Block #${header.number}: ${elapsed}ms`);
    }

    lastBlockTime = now;
  });

  return unsub;
}

async function streamToClients(api, wss) {
  const unsub = await api.rpc.chain.subscribeNewHeads(async (header) => {
    const message = JSON.stringify({
      type: 'new_block',
      number: header.number.toNumber(),
      hash: header.hash.toHex(),
      parentHash: header.parentHash.toHex(),
      stateRoot: header.stateRoot.toHex()
    });

    wss.clients.forEach((client) => {
      if (client.readyState === 1) {
        client.send(message);
      }
    });
  });

  return unsub;
}