// Comprehensive input validation
export const validateTokenAmount = (amount: string, decimals: number): boolean => {
  // Check if amount is a valid number
  if (!/^\d+(\.\d+)?$/.test(amount)) {
    return false;
  }
  
  // Check decimal places
  const parts = amount.split('.');
  if (parts[1] && parts[1].length > decimals) {
    return false;
  }
  
  // Check for negative values
  if (parseFloat(amount) <= 0) {
    return false;
  }
  
  return true;
};

// API route validation
export default async function handler(req: NextApiRequest, res: NextApiResponse) {
  const { amount, tokenAddress } = req.body;
  
  // Validate token address
  if (!ethers.utils.isAddress(tokenAddress)) {
    return res.status(400).json({ error: 'Invalid token address' });
  }
  
  // Validate amount
  if (!validateTokenAmount(amount, 18)) {
    return res.status(400).json({ error: 'Invalid amount' });
  }
  
  // Process request
  // ...
}

// next.config.js
const securityHeaders = [
  {
    key: 'Content-Security-Policy',
    value: `
      default-src 'self';
      script-src 'self' 'unsafe-eval' 'unsafe-inline' https://www.googletagmanager.com;
      style-src 'self' 'unsafe-inline' https://fonts.googleapis.com;
      font-src 'self' https://fonts.gstatic.com;
      img-src 'self' data: https: blob:;
      connect-src 'self' https://api.coingecko.com https://api.thegraph.com;
      frame-src 'self';
      object-src 'none';
      base-uri 'self';
      form-action 'self';
    `.replace(/\s{2,}/g, ' ').trim()
  }
];

// Sanitize user input before rendering
import DOMPurify from 'dompurify';

export const sanitizeInput = (input: string): string => {
  return DOMPurify.sanitize(input, {
    ALLOWED_TAGS: [],
    ALLOWED_ATTR: []
  });
};

// Generate and validate CSRF tokens
import { randomBytes } from 'crypto';

export const generateCSRFToken = (): string => {
  return randomBytes(32).toString('hex');
};

export const validateCSRFToken = (token: string, sessionToken: string): boolean => {
  return token === sessionToken;
};

// Validate wallet connections
export const validateWalletConnection = async (provider: any): Promise<boolean> => {
  try {
    // Check if provider is available
    if (!provider) {
      throw new Error('No wallet provider available');
    }
    
    // Request account access
    const accounts = await provider.request({ method: 'eth_requestAccounts' });
    
    if (!accounts || accounts.length === 0) {
      throw new Error('No accounts found');
    }
    
    // Validate account format
    const account = accounts[0];
    if (!ethers.utils.isAddress(account)) {
      throw new Error('Invalid account address');
    }
    
    return true;
  } catch (error) {
    console.error('Wallet validation failed:', error);
    return false;
  }
};

// Secure transaction signing
export const signTransactionSecurely = async (
  transaction: any,
  signer: any
): Promise<string> => {
  try {
    // Validate transaction parameters
    if (!transaction.to || !ethers.utils.isAddress(transaction.to)) {
      throw new Error('Invalid recipient address');
    }
    
    if (!transaction.value || transaction.value.lte(0)) {
      throw new Error('Invalid transaction value');
    }
    
    // Sign transaction
    const signedTx = await signer.signTransaction(transaction);
    
    // Validate signature
    const recoveredAddress = ethers.utils.recoverAddress(
      ethers.utils.hashMessage(transaction),
      signedTx
    );
    
    if (recoveredAddress !== await signer.getAddress()) {
      throw new Error('Invalid signature');
    }
    
    return signedTx;
  } catch (error) {
    console.error('Transaction signing failed:', error);
    throw error;
  }
};

// Secure RPC endpoint configuration
export const getSecureRPCConfig = (chainId: number) => {
  const configs = {
    1: { // Ethereum Mainnet
      url: process.env.NEXT_PUBLIC_ETHEREUM_RPC_URL,
      timeout: 30000,
      retries: 3
    },
    11155111: { // Sepolia
      url: process.env.NEXT_PUBLIC_SEPOLIA_RPC_URL,
      timeout: 30000,
      retries: 3
    }
  };
  
  return configs[chainId] || configs[1];
};

// Validate RPC requests
export const validateRPCRequest = (method: string, params: any[]): boolean => {
  const allowedMethods = [
    'eth_call',
    'eth_getBalance',
    'eth_getTransactionCount',
    'eth_sendRawTransaction',
    'eth_getTransactionReceipt'
  ];
  
  if (!allowedMethods.includes(method)) {
    return false;
  }
  
  // Validate parameters based on method
  switch (method) {
    case 'eth_call':
      return params.length >= 2 && ethers.utils.isAddress(params[0].to);
    case 'eth_getBalance':
      return params.length >= 1 && ethers.utils.isAddress(params[0]);
    default:
      return true;
  }
};

// Monitor suspicious transactions
export const monitorTransaction = async (tx: any): Promise<boolean> => {
  const riskFactors = [];
  
  // Check for large transactions
  if (tx.value.gt(ethers.utils.parseEther('100'))) {
    riskFactors.push('LARGE_TRANSACTION');
  }
  
  // Check for known malicious addresses
  if (await isKnownMaliciousAddress(tx.to)) {
    riskFactors.push('MALICIOUS_ADDRESS');
  }
  
  // Check for unusual gas usage
  if (tx.gasLimit.gt(500000)) {
    riskFactors.push('HIGH_GAS_USAGE');
  }
  
  // Alert if multiple risk factors
  if (riskFactors.length >= 2) {
    await alertSecurityTeam(tx, riskFactors);
    return false;
  }
  
  return true;
};

// Detect anomalous behavior
export const detectAnomalies = async (userAddress: string): Promise<string[]> => {
  const anomalies = [];
  
  // Check transaction frequency
  const recentTxs = await getRecentTransactions(userAddress, 24); // 24 hours
  if (recentTxs.length > 100) {
    anomalies.push('HIGH_TRANSACTION_FREQUENCY');
  }
  
  // Check for failed transactions
  const failedTxs = recentTxs.filter(tx => !tx.status);
  if (failedTxs.length > 10) {
    anomalies.push('MULTIPLE_FAILED_TRANSACTIONS');
  }
  
  // Check for unusual trading patterns
  const tradingPattern = await analyzeTradingPattern(userAddress);
  if (tradingPattern.riskScore > 0.8) {
    anomalies.push('SUSPICIOUS_TRADING_PATTERN');
  }
  
  return anomalies;
};

enum SecurityIncidentType {
  CRITICAL = 'CRITICAL',      // User funds at risk
  HIGH = 'HIGH',              // System compromise
  MEDIUM = 'MEDIUM',          // Data breach
  LOW = 'LOW'                 // Minor security issue
}

interface SecurityIncident {
  id: string;
  type: SecurityIncidentType;
  description: string;
  timestamp: Date;
  affectedUsers: string[];
  status: 'OPEN' | 'INVESTIGATING' | 'RESOLVED';
}