"""
Internal Pine Script Backtester.

Translates the *intent* of Pine Script strategies into Python
and executes them against real historical data via yfinance.
This is NOT a full Pine Script parser — it maps the generated
template strategies to the existing BacktestEngine.

Produces TradingView-style performance metrics:
  - Net Profit, Gross Profit, Gross Loss
  - Max Drawdown, Profit Factor
  - Sharpe Ratio, Sortino Ratio
  - Win Rate, Average Win/Loss
  - Equity Curve, Monthly Returns
"""

from __future__ import annotations

import logging
import re
from typing import Any, Dict, List, Optional, Tuple

import numpy as np
import pandas as pd

logger = logging.getLogger(__name__)


class PineScriptBacktester:
    """
    Simulates Pine Script strategies using Python.

    For template-generated strategies, maps the strategy logic
    directly to pandas operations for accurate backtesting.
    """

    async def backtest(
        self,
        code: str,
        ticker: str = "SPY",
        period: str = "3y",
        initial_capital: float = 100_000,
        commission_pct: float = 0.1,
    ) -> Dict[str, Any]:
        """
        Run a backtest on Pine Script code.
        """
        from app.services.data_ingestion.yahoo import yahoo_adapter

        # Fetch data
        df = await yahoo_adapter.get_price_dataframe(ticker, period=period)
        if df.empty or len(df) < 50:
            raise ValueError(f"Insufficient data for {ticker}")

        # Detect strategy type from code and run appropriate backtest
        strategy_type = self._detect_strategy_type(code)
        params = self._extract_parameters(code)

        signals = self._generate_signals(df, strategy_type, params)
        results = self._simulate_trades(df, signals, initial_capital, commission_pct)

        return {
            "ticker": ticker,
            "period": period,
            "strategy_type": strategy_type,
            "initial_capital": initial_capital,
            **results,
        }

    def _detect_strategy_type(self, code: str) -> str:
        """Determine strategy type from Pine Script code keywords."""
        code_lower = code.lower()

        if "ta.supertrend" in code_lower:
            return "supertrend"
        if "ta.macd" in code_lower:
            return "macd"
        if "ta.rsi" in code_lower and "ta.stoch" in code_lower:
            return "stochastic_rsi"
        if "ta.rsi" in code_lower:
            return "rsi"
        if "ta.bb" in code_lower or "bollinger" in code_lower or "ta.stdev" in code_lower:
            return "bollinger"
        if "ta.vwap" in code_lower or "vwap" in code_lower:
            return "vwap"
        if "ichimoku" in code_lower or "donchian" in code_lower:
            return "ichimoku"
        if "z_score" in code_lower or "z-score" in code_lower:
            return "zscore"
        if "ema" in code_lower and code_lower.count("ta.ema") >= 3:
            return "ema_ribbon"
        if "crossover" in code_lower and "sma" in code_lower:
            return "sma_crossover"
        if "ta.atr" in code_lower and "trail" in code_lower:
            return "atr_trailing"
        if "request.security" in code_lower:
            return "multi_timeframe"

        return "sma_crossover"  # default

    def _extract_parameters(self, code: str) -> Dict[str, Any]:
        """Extract input parameters from Pine Script code."""
        params: Dict[str, Any] = {}

        # Match input.int(value, ...) and input.float(value, ...)
        int_matches = re.findall(r'(\w+)\s*=\s*input\.int\((\d+)', code)
        float_matches = re.findall(r'(\w+)\s*=\s*input\.float\(([\d.]+)', code)

        for name, val in int_matches:
            params[name] = int(val)
        for name, val in float_matches:
            params[name] = float(val)

        return params

    def _generate_signals(
        self,
        df: pd.DataFrame,
        strategy_type: str,
        params: Dict[str, Any],
    ) -> pd.Series:
        """
        Generate trading signals: +1 = buy, -1 = sell, 0 = hold.
        Maps each strategy type to Python logic.
        """
        close = df["Close"]
        high = df["High"]
        low = df["Low"]
        volume = df["Volume"] if "Volume" in df.columns else pd.Series(0, index=df.index)
        signals = pd.Series(0, index=df.index)

        if strategy_type == "sma_crossover":
            fast = params.get("fast_length", 20)
            slow = params.get("slow_length", 50)
            sma_fast = close.rolling(fast).mean()
            sma_slow = close.rolling(slow).mean()
            signals[sma_fast > sma_slow] = 1
            signals[sma_fast <= sma_slow] = -1

        elif strategy_type == "rsi":
            length = params.get("rsi_length", 14)
            oversold = params.get("oversold_level", 30)
            overbought = params.get("overbought_level", 70)
            delta = close.diff()
            gain = delta.where(delta > 0, 0).rolling(length).mean()
            loss = (-delta.where(delta < 0, 0)).rolling(length).mean()
            rs = gain / (loss + 1e-10)
            rsi = 100 - (100 / (1 + rs))
            signals[rsi < oversold] = 1
            signals[rsi > overbought] = -1

        elif strategy_type == "macd":
            fast = params.get("fast_len", 12)
            slow = params.get("slow_len", 26)
            sig = params.get("sig_len", 9)
            ema_fast = close.ewm(span=fast).mean()
            ema_slow = close.ewm(span=slow).mean()
            macd_line = ema_fast - ema_slow
            signal_line = macd_line.ewm(span=sig).mean()
            hist = macd_line - signal_line
            signals[(macd_line > signal_line) & (hist > 0)] = 1
            signals[macd_line < signal_line] = -1

        elif strategy_type == "bollinger":
            length = params.get("length", 20)
            mult = params.get("mult", 2.0)
            basis = close.rolling(length).mean()
            std = close.rolling(length).std()
            upper = basis + mult * std
            signals[close > upper] = 1
            signals[close < basis] = -1

        elif strategy_type == "supertrend":
            atr_len = params.get("atr_len", 10)
            factor = params.get("factor", 3.0)
            tr = pd.concat([
                high - low,
                abs(high - close.shift(1)),
                abs(low - close.shift(1))
            ], axis=1).max(axis=1)
            atr = tr.rolling(atr_len).mean()
            upper_band = (high + low) / 2 + factor * atr
            lower_band = (high + low) / 2 - factor * atr

            supertrend = pd.Series(0.0, index=df.index)
            direction = pd.Series(1, index=df.index)
            for i in range(1, len(df)):
                if close.iloc[i] > upper_band.iloc[i-1]:
                    direction.iloc[i] = 1
                elif close.iloc[i] < lower_band.iloc[i-1]:
                    direction.iloc[i] = -1
                else:
                    direction.iloc[i] = direction.iloc[i-1]
            signals[direction == 1] = 1
            signals[direction == -1] = -1

        elif strategy_type == "ema_ribbon":
            emas = [8, 13, 21, 34, 55]
            ema_vals = [close.ewm(span=e).mean() for e in emas]
            bullish = all(ema_vals[i].iloc[-1] > ema_vals[i+1].iloc[-1] for i in range(len(ema_vals)-1))
            for i in range(len(df)):
                if all(ema_vals[j].iloc[i] > ema_vals[j+1].iloc[i] for j in range(len(ema_vals)-1) if i < len(ema_vals[j])):
                    signals.iloc[i] = 1
                elif all(ema_vals[j].iloc[i] < ema_vals[j+1].iloc[i] for j in range(len(ema_vals)-1) if i < len(ema_vals[j])):
                    signals.iloc[i] = -1

        elif strategy_type == "zscore":
            lookback = params.get("lookback", 50)
            entry_z = params.get("entry_z", 2.0)
            mean = close.rolling(lookback).mean()
            std = close.rolling(lookback).std()
            z = (close - mean) / (std + 1e-10)
            signals[z < -entry_z] = 1
            signals[z > entry_z] = -1

        else:
            # Default: SMA crossover
            sma20 = close.rolling(20).mean()
            sma50 = close.rolling(50).mean()
            signals[sma20 > sma50] = 1
            signals[sma20 <= sma50] = -1

        return signals

    def _simulate_trades(
        self,
        df: pd.DataFrame,
        signals: pd.Series,
        initial_capital: float,
        commission_pct: float,
    ) -> Dict[str, Any]:
        """
        Simulate trading based on signals and compute all metrics.
        """
        close = df["Close"].values
        sig = signals.values
        n = len(close)

        # Track positions and equity
        position = 0  # 0 or 1
        entry_price = 0.0
        capital = initial_capital
        equity_curve = [initial_capital]
        trades: List[Dict[str, Any]] = []
        daily_returns: List[float] = [0.0]

        for i in range(1, n):
            if sig[i] == 1 and position == 0:
                # Buy
                shares = capital / close[i]
                commission = capital * (commission_pct / 100)
                capital -= commission
                entry_price = close[i]
                position = 1
                trades.append({
                    "type": "ENTRY",
                    "date": str(df.index[i].date()) if hasattr(df.index[i], 'date') else str(df.index[i]),
                    "price": round(close[i], 2),
                    "shares": round(shares, 4),
                })

            elif sig[i] == -1 and position == 1:
                # Sell
                ret = (close[i] - entry_price) / entry_price
                commission = capital * (1 + ret) * (commission_pct / 100)
                capital = capital * (1 + ret) - commission
                position = 0
                trades.append({
                    "type": "EXIT",
                    "date": str(df.index[i].date()) if hasattr(df.index[i], 'date') else str(df.index[i]),
                    "price": round(close[i], 2),
                    "pnl_pct": round(ret * 100, 2),
                    "pnl_abs": round(capital - equity_curve[-1], 2),
                })

            # Update equity
            if position == 1:
                current_equity = capital * (close[i] / entry_price) if entry_price > 0 else capital
            else:
                current_equity = capital

            daily_ret = (current_equity - equity_curve[-1]) / equity_curve[-1] if equity_curve[-1] > 0 else 0
            daily_returns.append(daily_ret)
            equity_curve.append(current_equity)

        # Close open position
        if position == 1:
            ret = (close[-1] - entry_price) / entry_price
            capital = capital * (1 + ret)

        # Compute metrics
        eq = np.array(equity_curve)
        rets = np.array(daily_returns)
        peak = np.maximum.accumulate(eq)
        drawdown = (eq - peak) / (peak + 1e-10)

        # Trade stats
        pnl_list = [t.get("pnl_pct", 0) for t in trades if t["type"] == "EXIT"]
        wins = [p for p in pnl_list if p > 0]
        losses = [p for p in pnl_list if p < 0]

        total_trades = len(pnl_list)
        win_rate = len(wins) / total_trades if total_trades > 0 else 0
        avg_win = np.mean(wins) if wins else 0
        avg_loss = np.mean(losses) if losses else 0

        net_profit = eq[-1] - initial_capital
        net_profit_pct = (eq[-1] / initial_capital - 1) * 100
        gross_profit = sum(p for p in pnl_list if p > 0)
        gross_loss = abs(sum(p for p in pnl_list if p < 0))
        profit_factor = gross_profit / (gross_loss + 1e-10) if gross_loss > 0 else float("inf")
        max_drawdown = float(np.min(drawdown)) * 100

        # Annualized metrics
        trading_days = len(rets) - 1
        ann_factor = 252 / max(trading_days, 1)
        ann_return = ((eq[-1] / initial_capital) ** ann_factor - 1) * 100 if trading_days > 0 else 0

        daily_std = np.std(rets[1:]) if len(rets) > 1 else 0
        sharpe = (np.mean(rets[1:]) / (daily_std + 1e-10)) * np.sqrt(252) if daily_std > 0 else 0

        downside = rets[rets < 0]
        downside_std = np.std(downside) if len(downside) > 0 else 0
        sortino = (np.mean(rets[1:]) / (downside_std + 1e-10)) * np.sqrt(252) if downside_std > 0 else 0

        # Monthly returns
        dates = df.index
        monthly_returns = {}
        month_start_eq = equity_curve[0]
        for i in range(1, len(equity_curve)):
            if i < len(dates):
                month_key = dates[i].strftime("%Y-%m") if hasattr(dates[i], 'strftime') else str(dates[i])[:7]
                if i > 0 and (i == len(equity_curve) - 1 or
                    (i < len(dates) and hasattr(dates[i], 'month') and
                     (dates[i].month != dates[i-1].month if i > 0 and hasattr(dates[i-1], 'month') else False))):
                    prev_key = dates[i-1].strftime("%Y-%m") if hasattr(dates[i-1], 'strftime') else str(dates[i-1])[:7]
                    monthly_returns[prev_key] = round((equity_curve[i] / month_start_eq - 1) * 100, 2) if month_start_eq > 0 else 0
                    month_start_eq = equity_curve[i]

        # Downsample equity curve for response size
        eq_len = len(equity_curve)
        step = max(1, eq_len // 250)
        sampled_equity = [
            {"index": i, "equity": round(equity_curve[i], 2)}
            for i in range(0, eq_len, step)
        ]

        return {
            "net_profit": round(net_profit, 2),
            "net_profit_pct": round(net_profit_pct, 2),
            "gross_profit_pct": round(gross_profit, 2),
            "gross_loss_pct": round(gross_loss, 2),
            "profit_factor": round(profit_factor, 4),
            "max_drawdown_pct": round(max_drawdown, 2),
            "sharpe_ratio": round(sharpe, 4),
            "sortino_ratio": round(sortino, 4),
            "annualized_return_pct": round(ann_return, 2),
            "total_trades": total_trades,
            "win_rate": round(win_rate, 4),
            "avg_win_pct": round(avg_win, 2),
            "avg_loss_pct": round(avg_loss, 2),
            "max_consecutive_wins": _max_consecutive(pnl_list, positive=True),
            "max_consecutive_losses": _max_consecutive(pnl_list, positive=False),
            "equity_curve": sampled_equity,
            "trades": trades[-50:],  # last 50 trades
            "monthly_returns": monthly_returns,
            "final_equity": round(eq[-1], 2),
            "trading_days": trading_days,
        }


def _max_consecutive(values: list, positive: bool = True) -> int:
    """Count max consecutive wins or losses."""
    max_count = 0
    current = 0
    for v in values:
        if (positive and v > 0) or (not positive and v < 0):
            current += 1
            max_count = max(max_count, current)
        else:
            current = 0
    return max_count


# Module singleton
pine_backtester = PineScriptBacktester()