# 🔐 NovaLang Advanced Security & Blockchain

## Zero-Trust Security Model
```nova
@ZeroTrustSecurity
@Security(
    authentication: "oauth2",
    authorization: "rbac",
    encryption: "end-to-end"
)
class SecurePaymentService {
    
    @RequirePermission("payment.process")
    @AuditLog(level: "HIGH", includePayload: false)
    @RateLimit(requests: 10, window: "1m", scope: "user")
    @Encrypt(algorithm: "AES-256-GCM", keyRotation: "daily")
    async processPayment(
        @Validated @Encrypted payment: PaymentRequest,
        @AuthenticatedUser user: User
    ): Result<PaymentResponse, PaymentError> {
        
        // Multi-factor authentication check
        if (!await mfaService.verifyMFA(user, payment.mfaToken)) {
            return PaymentError.mfaRequired()
        }
        
        // Fraud detection
        let fraudScore = await fraudDetectionService.analyzePayment(payment, user)
        if (fraudScore > 0.8) {
            await alertService.sendFraudAlert(payment, user)
            return PaymentError.fraudDetected()
        }
        
        // Tokenize sensitive data
        let tokenizedPayment = await tokenizationService.tokenize(payment)
        
        // Process with external service
        let result = await paymentGateway.processPayment(tokenizedPayment)
        
        // Log successful transaction
        await auditService.logPaymentSuccess(payment.id, user.id)
        
        return PaymentResponse.success(result)
    }
    
    @DataMasking(fields: ["cardNumber", "cvv"])
    @AccessControl("admin")
    async getPaymentHistory(userId: string): List<PaymentRecord> {
        return await paymentRepository.findByUserId(userId)
    }
}
```

## Advanced Authentication & Authorization
```nova
@AuthenticationProvider
class MultiFactorAuthProvider {
    
    @Primary
    @OAuth2("google", "github", "microsoft")
    async authenticateWithOAuth2(
        @Token accessToken: string,
        @Provider provider: string
    ): Authentication {
        
        let userInfo = await oauth2Service.getUserInfo(provider, accessToken)
        let user = await userService.findOrCreateUser(userInfo)
        
        return Authentication.builder()
            .principal(user)
            .authorities(await authorityService.getUserAuthorities(user))
            .authenticated(true)
            .build()
    }
    
    @WebAuthn
    async authenticateWithBiometrics(
        @Credential credential: PublicKeyCredential
    ): Authentication {
        
        let verification = await webAuthnService.verifyCredential(credential)
        if (!verification.isValid()) {
            throw new AuthenticationException("Invalid biometric credential")
        }
        
        let user = await userService.findByCredentialId(credential.id)
        return createAuthentication(user)
    }
    
    @SAML2
    async authenticateWithSAML(
        @Assertion samlAssertion: Assertion
    ): Authentication {
        
        let validation = await samlService.validateAssertion(samlAssertion)
        if (!validation.isValid()) {
            throw new AuthenticationException("Invalid SAML assertion")
        }
        
        let user = await userService.findBySAMLAttributes(validation.attributes)
        return createAuthentication(user)
    }
}

@AuthorizationService
class RoleBasedAccessControl {
    
    @PreAuthorize("hasRole('ADMIN') or #userId == authentication.name")
    async getUserData(userId: string): UserData {
        return await userService.getUserData(userId)
    }
    
    @PostAuthorize("returnObject.owner == authentication.name")
    async getDocument(documentId: string): Document {
        return await documentService.getDocument(documentId)
    }
    
    @Secured(["ROLE_MANAGER", "ROLE_HR"])
    async getEmployeeReport(): EmployeeReport {
        return await reportService.generateEmployeeReport()
    }
    
    @AttributeBasedAccessControl
    async accessResource(
        @Subject user: User,
        @Resource resource: Resource,
        @Action action: string,
        @Environment environment: Map<string, any>
    ): AccessDecision {
        
        let policy = await policyService.getApplicablePolicy(resource, action)
        
        return PolicyEvaluator.builder()
            .subject(user)
            .resource(resource)
            .action(action)
            .environment(environment)
            .policy(policy)
            .evaluate()
    }
}
```

## Cryptocurrency & Blockchain Integration
```nova
@BlockchainService
class CryptocurrencyService {
    
    @BitcoinNetwork(network: "mainnet")
    private bitcoinClient: BitcoinClient
    
    @EthereumNetwork(network: "mainnet", infuraKey: "${infura.key}")
    private ethereumClient: EthereumClient
    
    @Wallet(type: "HD", mnemonic: "${wallet.mnemonic}")
    private wallet: HDWallet
    
    async createWallet(): WalletInfo {
        let newWallet = await HDWallet.generate()
        
        return WalletInfo.builder()
            .address(newWallet.getAddress())
            .publicKey(newWallet.getPublicKey())
            .mnemonic(newWallet.getMnemonic()) // Store securely
            .build()
    }
    
    @Transaction
    async sendBitcoin(
        @From fromAddress: string,
        @To toAddress: string,
        @Amount amount: BigDecimal,
        @FeeRate feeRate: BigDecimal
    ): TransactionResult {
        
        // Validate addresses
        if (!bitcoinClient.isValidAddress(fromAddress) || !bitcoinClient.isValidAddress(toAddress)) {
            throw new InvalidAddressException("Invalid Bitcoin address")
        }
        
        // Check balance
        let balance = await bitcoinClient.getBalance(fromAddress)
        if (balance < amount) {
            throw new InsufficientFundsException("Insufficient balance")
        }
        
        // Create and sign transaction
        let transaction = await bitcoinClient.createTransaction(fromAddress, toAddress, amount, feeRate)
        let signedTransaction = await wallet.signTransaction(transaction)
        
        // Broadcast transaction
        let txHash = await bitcoinClient.broadcastTransaction(signedTransaction)
        
        return TransactionResult.builder()
            .txHash(txHash)
            .amount(amount)
            .fee(transaction.fee)
            .confirmations(0)
            .build()
    }
    
    @EthereumContract("0x...")
    async interactWithSmartContract(
        @ContractAddress contractAddress: string,
        @Method methodName: string,
        @Parameters parameters: List<any>
    ): ContractResult {
        
        let contract = await ethereumClient.getContract(contractAddress)
        let result = await contract.callMethod(methodName, parameters)
        
        return ContractResult.of(result)
    }
}
```

## Smart Contract Development
```nova
@SmartContract(
    platform: "ethereum",
    compiler: "solidity-0.8.19"
)
class TokenContract {
    
    @State
    mapping(address => uint256) balances
    
    @State
    mapping(address => mapping(address => uint256)) allowances
    
    @State
    uint256 totalSupply
    
    @State
    string name
    
    @State
    string symbol
    
    @Constructor
    constructor(
        @Parameter name: string,
        @Parameter symbol: string,
        @Parameter initialSupply: uint256
    ) {
        this.name = name
        this.symbol = symbol
        this.totalSupply = initialSupply
        this.balances[msg.sender] = initialSupply
    }
    
    @PublicFunction
    @View
    balanceOf(@Parameter account: address): uint256 {
        return balances[account]
    }
    
    @PublicFunction
    transfer(
        @Parameter to: address,
        @Parameter amount: uint256
    ): boolean {
        require(to != address(0), "Transfer to zero address")
        require(balances[msg.sender] >= amount, "Insufficient balance")
        
        balances[msg.sender] -= amount
        balances[to] += amount
        
        emit Transfer(msg.sender, to, amount)
        return true
    }
    
    @PublicFunction
    approve(
        @Parameter spender: address,
        @Parameter amount: uint256
    ): boolean {
        allowances[msg.sender][spender] = amount
        emit Approval(msg.sender, spender, amount)
        return true
    }
    
    @PublicFunction
    transferFrom(
        @Parameter from: address,
        @Parameter to: address,
        @Parameter amount: uint256
    ): boolean {
        require(allowances[from][msg.sender] >= amount, "Insufficient allowance")
        require(balances[from] >= amount, "Insufficient balance")
        
        balances[from] -= amount
        balances[to] += amount
        allowances[from][msg.sender] -= amount
        
        emit Transfer(from, to, amount)
        return true
    }
    
    @Event
    Transfer(from: address, to: address, value: uint256)
    
    @Event
    Approval(owner: address, spender: address, value: uint256)
}

// Auto-generates Solidity code:
/*
pragma solidity ^0.8.19;

contract TokenContract {
    mapping(address => uint256) private balances;
    mapping(address => mapping(address => uint256)) private allowances;
    uint256 private totalSupply;
    string private name;
    string private symbol;
    
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    
    constructor(string memory _name, string memory _symbol, uint256 _initialSupply) {
        name = _name;
        symbol = _symbol;
        totalSupply = _initialSupply;
        balances[msg.sender] = _initialSupply;
    }
    
    function balanceOf(address account) public view returns (uint256) {
        return balances[account];
    }
    
    function transfer(address to, uint256 amount) public returns (bool) {
        require(to != address(0), "Transfer to zero address");
        require(balances[msg.sender] >= amount, "Insufficient balance");
        
        balances[msg.sender] -= amount;
        balances[to] += amount;
        
        emit Transfer(msg.sender, to, amount);
        return true;
    }
}
*/
```

## DeFi Protocol Integration
```nova
@DeFiProtocol
class DecentralizedExchange {
    
    @UniswapV3Integration
    private uniswapRouter: UniswapV3Router
    
    @AaveIntegration
    private aaveLendingPool: AaveLendingPool
    
    @CompoundIntegration
    private compoundProtocol: CompoundProtocol
    
    @LiquidityPool
    async createLiquidityPool(
        @Token tokenA: ERC20Token,
        @Token tokenB: ERC20Token,
        @FeeRate fee: uint24,
        @InitialPrice sqrtPriceX96: uint160
    ): LiquidityPool {
        
        let poolAddress = await uniswapRouter.createPool(tokenA.address, tokenB.address, fee)
        await uniswapRouter.initialize(poolAddress, sqrtPriceX96)
        
        return LiquidityPool.builder()
            .address(poolAddress)
            .tokenA(tokenA)
            .tokenB(tokenB)
            .fee(fee)
            .build()
    }
    
    @Swap
    async swapTokens(
        @TokenIn tokenIn: ERC20Token,
        @TokenOut tokenOut: ERC20Token,
        @Amount amountIn: uint256,
        @MinAmountOut minAmountOut: uint256,
        @Deadline deadline: uint256
    ): SwapResult {
        
        // Get optimal route
        let route = await uniswapRouter.getOptimalRoute(tokenIn, tokenOut, amountIn)
        
        // Execute swap
        let swapParams = ExactInputParams.builder()
            .path(route.path)
            .recipient(msg.sender)
            .deadline(deadline)
            .amountIn(amountIn)
            .amountOutMinimum(minAmountOut)
            .build()
        
        let amountOut = await uniswapRouter.exactInput(swapParams)
        
        return SwapResult.builder()
            .amountIn(amountIn)
            .amountOut(amountOut)
            .route(route)
            .gasUsed(tx.gasUsed)
            .build()
    }
    
    @Lending
    async lendAsset(
        @Asset asset: ERC20Token,
        @Amount amount: uint256
    ): LendingResult {
        
        // Approve asset
        await asset.approve(aaveLendingPool.address, amount)
        
        // Deposit to Aave
        await aaveLendingPool.deposit(asset.address, amount, msg.sender, 0)
        
        // Get aToken address
        let aTokenAddress = await aaveLendingPool.getReserveData(asset.address).aTokenAddress
        
        return LendingResult.builder()
            .asset(asset)
            .amount(amount)
            .aTokenAddress(aTokenAddress)
            .apy(await aaveLendingPool.getReserveData(asset.address).currentLiquidityRate)
            .build()
    }
    
    @Borrowing
    async borrowAsset(
        @Asset asset: ERC20Token,
        @Amount amount: uint256,
        @InterestRateMode rateMode: uint256
    ): BorrowingResult {
        
        // Check borrowing capacity
        let (totalCollateral, totalDebt, availableBorrows, , , ) = 
            await aaveLendingPool.getUserAccountData(msg.sender)
        
        require(amount <= availableBorrows, "Insufficient borrowing capacity")
        
        // Borrow asset
        await aaveLendingPool.borrow(asset.address, amount, rateMode, 0, msg.sender)
        
        return BorrowingResult.builder()
            .asset(asset)
            .amount(amount)
            .interestRate(await aaveLendingPool.getReserveData(asset.address).currentVariableBorrowRate)
            .build()
    }
}
```

## NFT & Web3 Integration
```nova
@NFTContract(standard: "ERC721")
class DigitalArtNFT {
    
    @State
    mapping(uint256 => string) tokenURIs
    
    @State
    mapping(uint256 => address) creators
    
    @State
    mapping(uint256 => uint256) royalties // Basis points (e.g., 500 = 5%)
    
    @State
    uint256 nextTokenId = 1
    
    @PublicFunction
    @Payable
    mintNFT(
        @Parameter to: address,
        @Parameter metadataURI: string,
        @Parameter royaltyBps: uint256
    ): uint256 {
        require(royaltyBps <= 1000, "Royalty too high") // Max 10%
        
        let tokenId = nextTokenId++
        
        _safeMint(to, tokenId)
        tokenURIs[tokenId] = metadataURI
        creators[tokenId] = msg.sender
        royalties[tokenId] = royaltyBps
        
        emit NFTMinted(tokenId, to, msg.sender, metadataURI)
        
        return tokenId
    }
    
    @PublicFunction
    @View
    tokenURI(@Parameter tokenId: uint256): string {
        require(_exists(tokenId), "Token does not exist")
        return tokenURIs[tokenId]
    }
    
    @PublicFunction
    @View
    royaltyInfo(
        @Parameter tokenId: uint256,
        @Parameter salePrice: uint256
    ): (address, uint256) {
        require(_exists(tokenId), "Token does not exist")
        
        let royaltyAmount = (salePrice * royalties[tokenId]) / 10000
        return (creators[tokenId], royaltyAmount)
    }
    
    @Event
    NFTMinted(tokenId: uint256, to: address, creator: address, metadataURI: string)
}

@Web3Service
class NFTMarketplace {
    
    @IPFSStorage
    private ipfsService: IPFSService
    
    async uploadMetadata(
        @Metadata metadata: NFTMetadata
    ): string {
        
        // Upload image to IPFS
        let imageHash = await ipfsService.upload(metadata.image)
        
        // Create metadata JSON
        let metadataJson = {
            "name": metadata.name,
            "description": metadata.description,
            "image": `ipfs://${imageHash}`,
            "attributes": metadata.attributes,
            "external_url": metadata.externalUrl
        }
        
        // Upload metadata to IPFS
        let metadataHash = await ipfsService.uploadJson(metadataJson)
        
        return `ipfs://${metadataHash}`
    }
    
    @MarketplaceFunction
    async listNFT(
        @NFTContract contractAddress: address,
        @TokenId tokenId: uint256,
        @Price price: uint256,
        @Duration duration: uint256
    ): ListingResult {
        
        let nftContract = ERC721(contractAddress)
        
        // Verify ownership
        require(nftContract.ownerOf(tokenId) == msg.sender, "Not token owner")
        
        // Create listing
        let listingId = await createListing(contractAddress, tokenId, price, duration)
        
        emit NFTListed(listingId, contractAddress, tokenId, msg.sender, price)
        
        return ListingResult.of(listingId)
    }
}
```
