chain_getHeader - Moonbeam RPC Method

async function estimateBlockTime(api, sampleSize = 10) {
  const latestHeader = await api.rpc.chain.getHeader();
  const latestNumber = latestHeader.number.toNumber();

  const oldHash = await api.rpc.chain.getBlockHash(latestNumber - sampleSize);
  const oldHeader = await api.rpc.chain.getHeader(oldHash);

  // Use timestamp from block digests or timestamp pallet
  const latestTimestamp = await api.query.timestamp.now();
  const apiAt = await api.at(oldHash);
  const oldTimestamp = await apiAt.query.timestamp.now();

  const timeDiff = latestTimestamp.toNumber() - oldTimestamp.toNumber();
  const avgBlockTime = timeDiff / sampleSize;

  console.log(`Average block time: ${avgBlockTime / 1000}s over ${sampleSize} blocks`);
  return avgBlockTime;
}

async function walkChain(api, startHash, depth = 5) {
  let currentHash = startHash || (await api.rpc.chain.getBlockHash());
  const headers = [];

  for (let i = 0; i < depth; i++) {
    const header = await api.rpc.chain.getHeader(currentHash);
    headers.push({
      number: header.number.toNumber(),
      hash: currentHash.toString(),
      parentHash: header.parentHash.toHex()
    });
    currentHash = header.parentHash;
  }

  return headers;
}

async function monitorBlocks(api, callback) {
  let lastNumber = 0;

  setInterval(async () => {
    const header = await api.rpc.chain.getHeader();
    const number = header.number.toNumber();

    if (number > lastNumber) {
      console.log(`New block #${number}`);
      callback(header);
      lastNumber = number;
    }
  }, 3000);
}