cryptocurrencyexchangeplatform-vgi538/app/services/transaction.py

from sqlalchemy.orm import Session
from fastapi import HTTPException, status
from typing import List, Optional
from app.models.transaction import Transaction, FiatTransaction, TransactionStatus, TransactionType
from app.models.wallet import Wallet, FiatAccount  
from app.models.user import User
from app.schemas.transaction import TransactionCreate, FiatTransactionCreate
from app.services.wallet import WalletService
from app.utils.crypto import WalletFactory
from app.core.config import settings
import uuid
import hashlib


class TransactionService:
    def __init__(self, db: Session):
        self.db = db
        self.wallet_service = WalletService(db)

    def send_crypto(self, user: User, transaction_data: TransactionCreate) -> Transaction:
        # Get sender wallet
        from_wallet = self.wallet_service.get_wallet_by_id(transaction_data.from_wallet_id, user)
        if not from_wallet:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Wallet not found"
            )

        # Validate currency match
        if from_wallet.currency != transaction_data.currency:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Currency mismatch"
            )

        # Check balance
        if from_wallet.balance < transaction_data.amount:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Insufficient balance"
            )

        # Validate recipient address
        if not WalletFactory.verify_address(transaction_data.currency, transaction_data.to_address):
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invalid recipient address"
            )

        # Calculate fee (simplified - in production, use dynamic fee calculation)
        fee = self._calculate_transaction_fee(transaction_data.currency, transaction_data.amount)
        
        if from_wallet.balance < (transaction_data.amount + fee):
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Insufficient balance including fees"
            )

        try:
            # Create transaction record
            transaction = Transaction(
                user_id=user.id,
                from_wallet_id=from_wallet.id,
                amount=transaction_data.amount,
                fee=fee,
                currency=transaction_data.currency,
                transaction_type=TransactionType.SEND,
                status=TransactionStatus.PENDING,
                from_address=from_wallet.address,
                to_address=transaction_data.to_address,
                notes=transaction_data.notes
            )
            
            self.db.add(transaction)
            self.db.flush()  # Get the transaction ID

            # Sign and broadcast transaction
            signed_hash = self._sign_transaction(user, from_wallet, transaction)
            transaction.transaction_hash = signed_hash
            
            # Update wallet balance
            new_balance = from_wallet.balance - transaction_data.amount - fee
            self.wallet_service.update_wallet_balance(from_wallet.id, new_balance)
            
            # In production, you would broadcast to the network here
            # For now, we'll mark as confirmed
            transaction.status = TransactionStatus.CONFIRMED
            transaction.confirmations = 1
            
            self.db.commit()
            self.db.refresh(transaction)
            
            return transaction
            
        except Exception as e:
            self.db.rollback()
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Transaction failed: {str(e)}"
            )

    def receive_crypto(self, user: User, amount: float, currency: str, from_address: str, to_wallet_id: int) -> Transaction:
        # Get recipient wallet
        to_wallet = self.wallet_service.get_wallet_by_id(to_wallet_id, user)
        if not to_wallet:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Wallet not found"
            )

        # Create transaction record
        transaction = Transaction(
            user_id=user.id,
            to_wallet_id=to_wallet.id,
            amount=amount,
            currency=currency,
            transaction_type=TransactionType.RECEIVE,
            status=TransactionStatus.CONFIRMED,
            from_address=from_address,
            to_address=to_wallet.address,
            confirmations=1
        )
        
        self.db.add(transaction)
        
        # Update wallet balance
        new_balance = to_wallet.balance + amount
        self.wallet_service.update_wallet_balance(to_wallet.id, new_balance)
        
        self.db.commit()
        self.db.refresh(transaction)
        
        return transaction

    def deposit_fiat(self, user: User, transaction_data: FiatTransactionCreate) -> FiatTransaction:
        # Get fiat account
        fiat_account = self.db.query(FiatAccount).filter(
            FiatAccount.user_id == user.id,
            FiatAccount.currency == transaction_data.currency
        ).first()
        
        if not fiat_account:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Fiat account not found"
            )

        # Validate deposit limits
        if transaction_data.amount < settings.min_fiat_deposit:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Minimum deposit amount is {settings.min_fiat_deposit}"
            )
        
        if transaction_data.amount > settings.max_fiat_deposit:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Maximum deposit amount is {settings.max_fiat_deposit}"
            )

        # Create fiat transaction
        transaction = FiatTransaction(
            account_id=fiat_account.id,
            amount=transaction_data.amount,
            currency=transaction_data.currency,
            transaction_type=TransactionType.DEPOSIT,
            status=TransactionStatus.PENDING,
            payment_method=transaction_data.payment_method,
            notes=transaction_data.notes,
            bank_reference=str(uuid.uuid4())
        )
        
        self.db.add(transaction)
        self.db.commit()
        self.db.refresh(transaction)
        
        return transaction

    def withdraw_fiat(self, user: User, transaction_data: FiatTransactionCreate) -> FiatTransaction:
        # Get fiat account
        fiat_account = self.db.query(FiatAccount).filter(
            FiatAccount.user_id == user.id,
            FiatAccount.currency == transaction_data.currency
        ).first()
        
        if not fiat_account:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Fiat account not found"
            )

        # Check balance
        if fiat_account.balance < transaction_data.amount:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Insufficient balance"
            )

        # Validate withdrawal limits
        if transaction_data.amount < settings.min_fiat_withdrawal:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Minimum withdrawal amount is {settings.min_fiat_withdrawal}"
            )
        
        if transaction_data.amount > settings.max_fiat_withdrawal:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Maximum withdrawal amount is {settings.max_fiat_withdrawal}"
            )

        # Create fiat transaction
        transaction = FiatTransaction(
            account_id=fiat_account.id,
            amount=transaction_data.amount,
            currency=transaction_data.currency,
            transaction_type=TransactionType.WITHDRAWAL,
            status=TransactionStatus.PENDING,
            payment_method=transaction_data.payment_method,
            notes=transaction_data.notes,
            bank_reference=str(uuid.uuid4())
        )
        
        self.db.add(transaction)
        
        # Update fiat account balance
        new_balance = fiat_account.balance - transaction_data.amount
        self.wallet_service.update_fiat_balance(fiat_account.id, new_balance)
        
        self.db.commit()
        self.db.refresh(transaction)
        
        return transaction

    def get_user_transactions(self, user: User, limit: int = 50, offset: int = 0) -> List[Transaction]:
        return self.db.query(Transaction).filter(
            Transaction.user_id == user.id
        ).order_by(Transaction.created_at.desc()).offset(offset).limit(limit).all()

    def get_user_fiat_transactions(self, user: User, limit: int = 50, offset: int = 0) -> List[FiatTransaction]:
        fiat_accounts = self.wallet_service.get_user_fiat_accounts(user)
        account_ids = [acc.id for acc in fiat_accounts]
        
        return self.db.query(FiatTransaction).filter(
            FiatTransaction.account_id.in_(account_ids)
        ).order_by(FiatTransaction.created_at.desc()).offset(offset).limit(limit).all()

    def get_transaction_by_id(self, transaction_id: int, user: User) -> Optional[Transaction]:
        return self.db.query(Transaction).filter(
            Transaction.id == transaction_id,
            Transaction.user_id == user.id
        ).first()

    def _sign_transaction(self, user: User, from_wallet: Wallet, transaction: Transaction) -> str:
        """Sign the transaction using the wallet's private key"""
        try:
            # Get private key
            private_key = self.wallet_service.get_private_key(from_wallet, user)
            
            # Prepare transaction data for signing
            transaction_data = {
                'from': from_wallet.address,
                'to': transaction.to_address,
                'amount': transaction.amount,
                'fee': transaction.fee,
                'nonce': transaction.id,
                'currency': transaction.currency
            }
            
            # Sign transaction
            signature = WalletFactory.sign_transaction(
                transaction.currency, 
                private_key, 
                transaction_data
            )
            
            # Generate transaction hash
            tx_hash = hashlib.sha256(
                f"{signature}_{transaction.id}_{transaction.from_address}_{transaction.to_address}".encode()
            ).hexdigest()
            
            return tx_hash
            
        except Exception as e:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Failed to sign transaction: {str(e)}"
            )

    def _calculate_transaction_fee(self, currency: str, amount: float) -> float:
        """Calculate transaction fee based on currency and amount"""
        # Simplified fee calculation - in production, use dynamic fee estimation
        fee_rates = {
            'BTC': 0.0001,  # Fixed fee
            'ETH': 0.002,   # 0.2% of amount
            'USDT': 0.001   # 0.1% of amount
        }
        
        if currency == 'BTC':
            return fee_rates['BTC']
        else:
            return amount * fee_rates.get(currency, 0.001)