"""Performance metrics for backtesting."""

from decimal import Decimal
from typing import Dict, List, Any, Optional
from src.trading.paper_trading import PaperTradingSimulator

class BacktestMetrics:
    """Calculates backtest performance metrics."""
    
    def calculate_metrics(
        self,
        simulator: PaperTradingSimulator,
        trades: List[Dict[str, Any]],
        initial_capital: Decimal,
        total_fees: Optional[Decimal] = None
    ) -> Dict[str, Any]:
        """Calculate backtest metrics, including fee-adjusted metrics.
        
        Args:
            simulator: Paper trading simulator
            trades: List of executed trades (may include 'fee' field)
            initial_capital: Initial capital
            total_fees: Total fees paid (if None, calculated from trades)
            
        Returns:
            Dictionary of metrics
        """
        final_value = simulator.get_portfolio_value()
        
        # Calculate total fees if not provided
        if total_fees is None:
            total_fees = sum(
                Decimal(str(trade.get('fee', 0))) for trade in trades
            )
        
        # Gross return (before fees)
        gross_return = ((final_value - initial_capital) / initial_capital) * 100 if initial_capital > 0 else 0
        
        # Net return (after fees) - fees are already deducted in simulator
        # But we calculate what return would be without fees for comparison
        value_without_fees = final_value + total_fees
        net_return = ((final_value - initial_capital) / initial_capital) * 100 if initial_capital > 0 else 0
        gross_return_without_fees = ((value_without_fees - initial_capital) / initial_capital) * 100 if initial_capital > 0 else 0
        
        # Fee impact
        fee_impact = gross_return_without_fees - net_return
        
        # Calculate win rate from trades
        win_rate = self._calculate_win_rate(trades)
        
        return {
            "initial_capital": float(initial_capital),
            "final_capital": float(final_value),
            "total_return": float(net_return),  # Net return (after fees)
            "gross_return": float(gross_return_without_fees),  # Gross return (before fees)
            "total_fees": float(total_fees),
            "fee_impact_percent": float(fee_impact),
            "fee_percentage": float((total_fees / initial_capital) * 100) if initial_capital > 0 else 0.0,
            "total_trades": len(trades),
            "win_rate": win_rate,
            "sharpe_ratio": 0.0,  # Placeholder - would need returns series
            "max_drawdown": 0.0,  # Placeholder - would need equity curve
        }
    
    def _calculate_win_rate(self, trades: List[Dict[str, Any]]) -> float:
        """Calculate win rate from trades.
        
        Args:
            trades: List of trades
            
        Returns:
            Win rate (0.0 to 1.0)
        """
        if len(trades) < 2:
            return 0.0
        
        # Simple approach: count buy-sell pairs
        # This is a simplified calculation - full implementation would track positions
        wins = 0
        total_pairs = 0
        
        # Group trades by symbol and calculate pairs
        # For now, return placeholder
        return 0.5