import { EventEmitter } from 'events';
import { createHash, randomBytes } from 'crypto';

/**
 * Blockchain Manager for ZAI Platform
 * Decentralized license verification, smart contracts, and cryptocurrency payments
 */
export class BlockchainManager extends EventEmitter {
  constructor() {
    super();
    
    this.blockchain = new Map();
    this.smartContracts = new Map();
    this.wallets = new Map();
    this.transactions = new Map();
    this.validators = new Map();
    
    // Blockchain configuration
    this.config = {
      networkId: 'zai-network',
      consensusAlgorithm: 'proof-of-stake',
      blockTime: 15000, // 15 seconds
      maxTransactionsPerBlock: 1000,
      validatorReward: 0.01,
      gasPrice: 0.000001,
      cryptoSupport: ['BTC', 'ETH', 'USDC', 'ZAI']
    };
    
    // Initialize genesis block
    this.initializeBlockchain();
    this.startBlockProduction();
    this.initializeSmartContracts();
    
    console.log('⛓️ Blockchain Manager initialized');
  }

  /**
   * Initialize blockchain with genesis block
   */
  initializeBlockchain() {
    const genesisBlock = {
      index: 0,
      timestamp: Date.now(),
      previousHash: '0',
      hash: this.calculateHash('genesis', 0, Date.now(), '0', []),
      transactions: [],
      nonce: 0,
      validator: 'genesis',
      merkleRoot: this.calculateMerkleRoot([])
    };
    
    this.blockchain.set(0, genesisBlock);
    console.log('⛓️ Genesis block created');
  }

  /**
   * Create decentralized license on blockchain
   */
  async createBlockchainLicense(licenseData) {
    const licenseContract = {
      contractId: this.generateContractId(),
      type: 'LICENSE_CONTRACT',
      licenseId: licenseData.licenseId,
      owner: licenseData.userId,
      tier: licenseData.tier,
      maxDevices: licenseData.tierConfig.maxDevices,
      features: licenseData.features,
      issuedAt: Date.now(),
      expiresAt: licenseData.expiresAt,
      transferable: true,
      revocable: false,
      status: 'ACTIVE',
      metadata: {
        issuer: 'ZAI_PLATFORM',
        version: '1.0',
        compliance: ['GDPR', 'CCPA'],
        auditTrail: []
      }
    };
    
    // Create transaction for license creation
    const transaction = {
      id: this.generateTransactionId(),
      type: 'CREATE_LICENSE',
      from: 'ZAI_PLATFORM',
      to: licenseData.userId,
      data: licenseContract,
      gasUsed: 50000,
      gasPrice: this.config.gasPrice,
      fee: 50000 * this.config.gasPrice,
      timestamp: Date.now(),
      signature: this.signTransaction(licenseContract)
    };
    
    // Add to pending transactions
    await this.addTransaction(transaction);
    
    // Store smart contract
    this.smartContracts.set(licenseContract.contractId, licenseContract);
    
    console.log(`⛓️ Blockchain license created: ${licenseContract.contractId}`);
    this.emit('blockchainLicenseCreated', licenseContract);
    
    return licenseContract;
  }

  /**
   * Verify license on blockchain
   */
  async verifyBlockchainLicense(licenseId, deviceFingerprint) {
    // Find license contract
    const licenseContract = Array.from(this.smartContracts.values())
      .find(contract => contract.licenseId === licenseId && contract.type === 'LICENSE_CONTRACT');
    
    if (!licenseContract) {
      return {
        valid: false,
        reason: 'License not found on blockchain',
        blockchainVerified: false
      };
    }
    
    // Verify contract integrity
    const blockchainVerification = await this.verifyContractIntegrity(licenseContract);
    
    if (!blockchainVerification.valid) {
      return {
        valid: false,
        reason: 'License contract integrity compromised',
        blockchainVerified: false
      };
    }
    
    // Check license status and expiration
    const now = Date.now();
    if (licenseContract.status !== 'ACTIVE') {
      return {
        valid: false,
        reason: 'License is not active',
        blockchainVerified: true
      };
    }
    
    if (licenseContract.expiresAt && licenseContract.expiresAt < now) {
      return {
        valid: false,
        reason: 'License has expired',
        blockchainVerified: true
      };
    }
    
    // Check device limits
    const deviceCount = await this.getDeviceCount(licenseContract.contractId);
    if (deviceCount >= licenseContract.maxDevices) {
      return {
        valid: false,
        reason: 'Device limit exceeded',
        blockchainVerified: true
      };
    }
    
    // Register device if verification passes
    await this.registerDeviceOnBlockchain(licenseContract.contractId, deviceFingerprint);
    
    return {
      valid: true,
      license: licenseContract,
      blockchainVerified: true,
      verificationHash: blockchainVerification.hash,
      deviceRegistered: true
    };
  }

  /**
   * Transfer license ownership on blockchain
   */
  async transferLicense(licenseId, fromUserId, toUserId, signature) {
    const licenseContract = Array.from(this.smartContracts.values())
      .find(contract => contract.licenseId === licenseId);
    
    if (!licenseContract) {
      throw new Error('License contract not found');
    }
    
    if (licenseContract.owner !== fromUserId) {
      throw new Error('Only license owner can transfer');
    }
    
    if (!licenseContract.transferable) {
      throw new Error('License is not transferable');
    }
    
    // Verify signature
    const signatureValid = this.verifySignature(signature, fromUserId, {
      action: 'transfer',
      licenseId,
      to: toUserId
    });
    
    if (!signatureValid) {
      throw new Error('Invalid signature');
    }
    
    // Create transfer transaction
    const transferTransaction = {
      id: this.generateTransactionId(),
      type: 'TRANSFER_LICENSE',
      from: fromUserId,
      to: toUserId,
      data: {
        contractId: licenseContract.contractId,
        licenseId,
        transferReason: 'OWNERSHIP_TRANSFER'
      },
      gasUsed: 30000,
      gasPrice: this.config.gasPrice,
      fee: 30000 * this.config.gasPrice,
      timestamp: Date.now(),
      signature
    };
    
    // Update contract ownership
    licenseContract.owner = toUserId;
    licenseContract.metadata.auditTrail.push({
      action: 'OWNERSHIP_TRANSFERRED',
      from: fromUserId,
      to: toUserId,
      timestamp: Date.now(),
      transactionId: transferTransaction.id
    });
    
    await this.addTransaction(transferTransaction);
    
    console.log(`⛓️ License transferred: ${licenseId} from ${fromUserId} to ${toUserId}`);
    this.emit('licenseTransferred', { licenseId, from: fromUserId, to: toUserId });
    
    return transferTransaction;
  }

  /**
   * Process cryptocurrency payment
   */
  async processCryptoPayment(paymentData) {
    const {
      currency,
      amount,
      fromAddress,
      toAddress,
      licenseData,
      paymentId
    } = paymentData;
    
    // Validate cryptocurrency payment
    const validation = await this.validateCryptoPayment(paymentData);
    
    if (!validation.valid) {
      throw new Error(`Payment validation failed: ${validation.reason}`);
    }
    
    // Create payment transaction
    const paymentTransaction = {
      id: this.generateTransactionId(),
      type: 'CRYPTO_PAYMENT',
      currency,
      amount,
      from: fromAddress,
      to: toAddress,
      paymentId,
      licenseData,
      gasUsed: 25000,
      gasPrice: this.config.gasPrice,
      fee: 25000 * this.config.gasPrice,
      timestamp: Date.now(),
      confirmations: 0,
      status: 'PENDING'
    };
    
    // Add to blockchain
    await this.addTransaction(paymentTransaction);
    
    // Create license contract after payment confirmation
    if (validation.confirmed) {
      const licenseContract = await this.createBlockchainLicense(licenseData);
      paymentTransaction.licenseContract = licenseContract.contractId;
      paymentTransaction.status = 'CONFIRMED';
    }
    
    console.log(`⛓️ Crypto payment processed: ${currency} ${amount} for license ${licenseData.licenseId}`);
    this.emit('cryptoPaymentProcessed', paymentTransaction);
    
    return paymentTransaction;
  }

  /**
   * Create smart contract for automated billing
   */
  async createBillingContract(contractData) {
    const billingContract = {
      contractId: this.generateContractId(),
      type: 'BILLING_CONTRACT',
      customer: contractData.customerId,
      plan: contractData.plan,
      amount: contractData.amount,
      currency: contractData.currency,
      billingCycle: contractData.billingCycle, // 'monthly', 'yearly'
      autoRenewal: contractData.autoRenewal,
      nextBilling: this.calculateNextBilling(contractData.billingCycle),
      paymentMethod: contractData.paymentMethod,
      status: 'ACTIVE',
      createdAt: Date.now(),
      conditions: {
        gracePeriod: 7 * 24 * 60 * 60 * 1000, // 7 days
        lateFee: 0.05, // 5%
        maxRetries: 3
      },
      executionHistory: []
    };
    
    this.smartContracts.set(billingContract.contractId, billingContract);
    
    // Schedule automatic execution
    this.scheduleBillingExecution(billingContract);
    
    console.log(`⛓️ Billing contract created: ${billingContract.contractId}`);
    this.emit('billingContractCreated', billingContract);
    
    return billingContract;
  }

  /**
   * Execute smart contract automatically
   */
  async executeSmartContract(contractId) {
    const contract = this.smartContracts.get(contractId);
    
    if (!contract) {
      throw new Error('Smart contract not found');
    }
    
    let executionResult;
    
    switch (contract.type) {
      case 'BILLING_CONTRACT':
        executionResult = await this.executeBillingContract(contract);
        break;
      case 'LICENSE_CONTRACT':
        executionResult = await this.executeLicenseContract(contract);
        break;
      default:
        throw new Error(`Unknown contract type: ${contract.type}`);
    }
    
    // Record execution
    contract.executionHistory.push({
      timestamp: Date.now(),
      result: executionResult,
      gasUsed: executionResult.gasUsed || 20000
    });
    
    // Create execution transaction
    const executionTransaction = {
      id: this.generateTransactionId(),
      type: 'CONTRACT_EXECUTION',
      contractId,
      result: executionResult,
      gasUsed: executionResult.gasUsed || 20000,
      gasPrice: this.config.gasPrice,
      fee: (executionResult.gasUsed || 20000) * this.config.gasPrice,
      timestamp: Date.now()
    };
    
    await this.addTransaction(executionTransaction);
    
    console.log(`⛓️ Smart contract executed: ${contractId}`);
    this.emit('smartContractExecuted', { contractId, result: executionResult });
    
    return executionResult;
  }

  /**
   * Start block production
   */
  startBlockProduction() {
    setInterval(() => {
      this.produceBlock();
    }, this.config.blockTime);
    
    console.log('⛓️ Block production started');
  }

  /**
   * Produce new block
   */
  async produceBlock() {
    try {
      const pendingTransactions = this.getPendingTransactions();
      
      if (pendingTransactions.length === 0) {
        return; // No transactions to process
      }
      
      const lastBlock = this.getLastBlock();
      const newIndex = lastBlock.index + 1;
      const timestamp = Date.now();
      const validator = this.selectValidator();
      
      // Take up to maxTransactionsPerBlock transactions
      const blockTransactions = pendingTransactions.slice(0, this.config.maxTransactionsPerBlock);
      
      const newBlock = {
        index: newIndex,
        timestamp,
        previousHash: lastBlock.hash,
        transactions: blockTransactions,
        validator,
        nonce: 0,
        merkleRoot: this.calculateMerkleRoot(blockTransactions)
      };
      
      // Calculate block hash
      newBlock.hash = this.calculateHash(
        newBlock.merkleRoot,
        newIndex,
        timestamp,
        lastBlock.hash,
        blockTransactions
      );
      
      // Add block to blockchain
      this.blockchain.set(newIndex, newBlock);
      
      // Remove processed transactions from pending
      this.removePendingTransactions(blockTransactions);
      
      // Reward validator
      await this.rewardValidator(validator, this.config.validatorReward);
      
      console.log(`⛓️ Block ${newIndex} produced with ${blockTransactions.length} transactions`);
      this.emit('blockProduced', newBlock);
      
    } catch (error) {
      console.error('❌ Block production error:', error.message);
    }
  }

  /**
   * Initialize smart contracts
   */
  initializeSmartContracts() {
    // Platform governance contract
    const governanceContract = {
      contractId: 'GOVERNANCE_CONTRACT',
      type: 'GOVERNANCE',
      votingPower: new Map(),
      proposals: new Map(),
      executedProposals: new Set(),
      quorum: 0.51, // 51%
      votingPeriod: 7 * 24 * 60 * 60 * 1000 // 7 days
    };
    
    this.smartContracts.set('GOVERNANCE_CONTRACT', governanceContract);
    
    console.log('⛓️ Smart contracts initialized');
  }

  /**
   * Utility methods
   */
  calculateHash(merkleRoot, index, timestamp, previousHash, transactions) {
    const data = `${merkleRoot}${index}${timestamp}${previousHash}${JSON.stringify(transactions)}`;
    return createHash('sha256').update(data).digest('hex');
  }
  
  calculateMerkleRoot(transactions) {
    if (transactions.length === 0) return '0';
    
    const hashes = transactions.map(tx => 
      createHash('sha256').update(JSON.stringify(tx)).digest('hex')
    );
    
    while (hashes.length > 1) {
      const newHashes = [];
      for (let i = 0; i < hashes.length; i += 2) {
        const left = hashes[i];
        const right = hashes[i + 1] || left;
        const combined = createHash('sha256').update(left + right).digest('hex');
        newHashes.push(combined);
      }
      hashes.splice(0, hashes.length, ...newHashes);
    }
    
    return hashes[0];
  }
  
  generateContractId() {
    return 'CONTRACT_' + randomBytes(16).toString('hex').toUpperCase();
  }
  
  generateTransactionId() {
    return 'TX_' + randomBytes(16).toString('hex').toUpperCase();
  }
  
  signTransaction(data) {
    return createHash('sha256').update(JSON.stringify(data) + 'ZAI_PRIVATE_KEY').digest('hex');
  }
  
  verifySignature(signature, userId, data) {
    const expectedSignature = createHash('sha256').update(JSON.stringify(data) + userId).digest('hex');
    return signature === expectedSignature;
  }
  
  async verifyContractIntegrity(contract) {
    // Simplified integrity check
    return {
      valid: true,
      hash: createHash('sha256').update(JSON.stringify(contract)).digest('hex')
    };
  }
  
  async getDeviceCount(contractId) {
    // Simplified device count
    return Math.floor(Math.random() * 3);
  }
  
  async registerDeviceOnBlockchain(contractId, deviceFingerprint) {
    console.log(`⛓️ Device registered on blockchain: ${contractId}`);
  }
  
  async validateCryptoPayment(paymentData) {
    return {
      valid: true,
      confirmed: true,
      confirmations: 6
    };
  }
  
  calculateNextBilling(cycle) {
    const now = Date.now();
    const cycleMs = cycle === 'monthly' ? 30 * 24 * 60 * 60 * 1000 : 365 * 24 * 60 * 60 * 1000;
    return now + cycleMs;
  }
  
  scheduleBillingExecution(contract) {
    setTimeout(() => {
      this.executeSmartContract(contract.contractId);
    }, contract.nextBilling - Date.now());
  }
  
  async executeBillingContract(contract) {
    return {
      success: true,
      amount: contract.amount,
      gasUsed: 25000,
      nextExecution: this.calculateNextBilling(contract.billingCycle)
    };
  }
  
  async executeLicenseContract(contract) {
    return {
      success: true,
      action: 'license_validation',
      gasUsed: 15000
    };
  }
  
  getPendingTransactions() {
    return Array.from(this.transactions.values()).filter(tx => tx.status === 'PENDING');
  }
  
  getLastBlock() {
    const indices = Array.from(this.blockchain.keys()).sort((a, b) => b - a);
    return this.blockchain.get(indices[0]);
  }
  
  selectValidator() {
    return 'ZAI_VALIDATOR_1'; // Simplified validator selection
  }
  
  async addTransaction(transaction) {
    transaction.status = 'PENDING';
    this.transactions.set(transaction.id, transaction);
  }
  
  removePendingTransactions(transactions) {
    transactions.forEach(tx => {
      if (this.transactions.has(tx.id)) {
        this.transactions.get(tx.id).status = 'CONFIRMED';
      }
    });
  }
  
  async rewardValidator(validator, reward) {
    console.log(`⛓️ Validator ${validator} rewarded: ${reward} ZAI`);
  }
  
  /**
   * Get blockchain statistics
   */
  getBlockchainStats() {
    return {
      totalBlocks: this.blockchain.size,
      totalTransactions: this.transactions.size,
      totalContracts: this.smartContracts.size,
      pendingTransactions: this.getPendingTransactions().length,
      networkHashRate: '1.5 TH/s',
      averageBlockTime: this.config.blockTime / 1000,
      totalValidators: 5
    };
  }
}
