Gnosis Chain - Ethereum Sidechain

// Watch for transaction confirmation on Gnosis Chain
async function waitForTransaction(txHash) {
  const receipt = await provider.waitForTransaction(txHash, 1);

  // Gnosis Chain has 5-second blocks for fast confirmations
  console.log('Transaction confirmed in ~5 seconds');

  return receipt;
}

// Gas estimation on Gnosis Chain
const gasEstimate = await provider.estimateGas(tx);

// xDAI has predictable pricing (~$1.00)
const gasPrice = await provider.getGasPrice();
const costInXDAI = gasEstimate * gasPrice / BigInt(1e18);

console.log(`Transaction cost: ${costInXDAI} xDAI (~$${costInXDAI})`);

// Query events with automatic retry and pagination
async function getEvents(contract, eventName, fromBlock = 0) {
  const filter = contract.filters[eventName]();
  const events = [];
  const batchSize = 3000; // Gnosis Chain recommended batch size

  for (let i = fromBlock; i <= currentBlock; i += batchSize) {
    const batch = await contract.queryFilter(
      filter,
      i,
      Math.min(i + batchSize - 1, currentBlock)
    );
    events.push(...batch);
  }

  return events;
}

const batch = [
  { method: 'eth_blockNumber', params: [] },
  { method: 'eth_gasPrice', params: [] },
  { method: 'eth_getBalance', params: [address, 'latest'] }
];

const results = await provider.send(batch);

// Singleton pattern for provider
class GnosisProvider {
  static instance = null;

  static getInstance() {
    if (!this.instance) {
      this.instance = new JsonRpcProvider(
        'https://api-gnosis-mainnet.n.dwellir.com/YOUR_API_KEY'
      );
    }
    return this.instance;
  }
}

const cache = new Map();

async function getCachedBlockData(blockNumber) {
  const key = `block_${blockNumber}`;

  if (!cache.has(key)) {
    const block = await provider.getBlock(blockNumber);
    cache.set(key, block);
  }

  return cache.get(key);
}

// Check xDAI balance before transactions
const balance = await provider.getBalance(address);
const gasEstimate = await provider.estimateGas(tx);
const gasPrice = await provider.getGasPrice();
const totalRequired = gasEstimate * gasPrice + tx.value;

if (balance < totalRequired) {
  const shortage = ethers.formatEther(totalRequired - balance);
  throw new Error(`Need ${shortage} more xDAI`);
}

// Get current fee data
const feeData = await provider.getFeeData();

const tx = {
  to: recipient,
  value: amount,
  maxFeePerGas: feeData.maxFeePerGas,
  maxPriorityFeePerGas: feeData.maxPriorityFeePerGas,
  gasLimit: 21000n
};

async function callWithRetry(fn, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await fn();
    } catch (error) {
      if (error.code === 429 && i < maxRetries - 1) {
        await new Promise(r => setTimeout(r, 2 ** i * 1000));
      } else {
        throw error;
      }
    }
  }
}

// Before (Ethereum)
const provider = new JsonRpcProvider('https://eth-rpc.example.com');

// After (Gnosis Chain)
const provider = new JsonRpcProvider(
  'https://api-gnosis-mainnet.n.dwellir.com/YOUR_API_KEY'
);

// Smart contracts work identically
// Same tooling and libraries
// Note: Different chain ID (100)
// Note: Native token is xDAI (not ETH)
// Note: 5-second block times (faster than Ethereum)