eth_estimateGas - Estimate Transaction Gas

// Validate transaction before sending
async function validateTransaction(from, to, value, data) {
  try {
    const gasEstimate = await provider.estimateGas({
      from: from,
      to: to,
      value: value,
      data: data
    });
    
    // Check if account has enough balance
    const balance = await provider.getBalance(from);
    const feeData = await provider.getFeeData();
    const maxCost = value + (gasEstimate * feeData.maxFeePerGas);
    
    if (balance < maxCost) {
      return {
        valid: false,
        reason: 'Insufficient balance',
        required: ethers.formatEther(maxCost),
        available: ethers.formatEther(balance)
      };
    }
    
    return {
      valid: true,
      gasLimit: gasEstimate.toString(),
      estimatedFee: ethers.formatEther(gasEstimate * feeData.gasPrice)
    };
  } catch (error) {
    return {
      valid: false,
      reason: error.message
    };
  }
}

// Real-time gas price updates for UI
class GasPriceMonitor {
  constructor(provider) {
    this.provider = provider;
    this.listeners = [];
  }
  
  async getCurrentPrices() {
    const [feeData, block] = await Promise.all([
      this.provider.getFeeData(),
      this.provider.getBlock('latest')
    ]);
    
    return {
      slow: {
        maxFeePerGas: feeData.maxFeePerGas * 90n / 100n,
        maxPriorityFeePerGas: feeData.maxPriorityFeePerGas * 80n / 100n,
        estimatedTime: '2-5 minutes'
      },
      standard: {
        maxFeePerGas: feeData.maxFeePerGas,
        maxPriorityFeePerGas: feeData.maxPriorityFeePerGas,
        estimatedTime: '15-30 seconds'
      },
      fast: {
        maxFeePerGas: feeData.maxFeePerGas * 120n / 100n,
        maxPriorityFeePerGas: feeData.maxPriorityFeePerGas * 150n / 100n,
        estimatedTime: '5-15 seconds'
      },
      baseFee: block.baseFeePerGas
    };
  }
  
  async estimateForTransaction(tx, speed = 'standard') {
    const prices = await this.getCurrentPrices();
    const gasEstimate = await this.provider.estimateGas(tx);
    const settings = prices[speed];
    
    return {
      gasLimit: gasEstimate,
      ...settings,
      estimatedCost: ethers.formatEther(gasEstimate * settings.maxFeePerGas),
      maxCost: ethers.formatEther(gasEstimate * settings.maxFeePerGas)
    };
  }
}

// Optimize gas for batch operations
async function optimizeBatchTransactions(transactions) {
  const estimates = [];
  let totalGas = 0n;
  
  // Estimate individually
  for (const tx of transactions) {
    const estimate = await provider.estimateGas(tx);
    estimates.push(estimate);
    totalGas += estimate;
  }
  
  // Check if multicall is more efficient
  const multicallEstimate = await estimateMulticall(transactions);
  
  if (multicallEstimate < totalGas * 90n / 100n) {
    return {
      method: 'multicall',
      gasLimit: multicallEstimate,
      savings: ethers.formatUnits(totalGas - multicallEstimate, 'gwei')
    };
  }
  
  return {
    method: 'individual',
    gasLimits: estimates,
    totalGas: totalGas
  };
}