from collections import deque
from decimal import Decimal

import pandas as pd

from shared.models import Candle, Signal, OrderSide
from strategies.base import BaseStrategy


class MacdStrategy(BaseStrategy):
    name: str = "macd"

    def __init__(self) -> None:
        self._fast_period: int = 12
        self._slow_period: int = 26
        self._signal_period: int = 9
        self._quantity: Decimal = Decimal("0.01")
        self._closes: deque[float] = deque(maxlen=500)
        self._prev_histogram: float | None = None

    @property
    def warmup_period(self) -> int:
        return self._slow_period + self._signal_period

    def configure(self, params: dict) -> None:
        self._fast_period = int(params.get("fast_period", 12))
        self._slow_period = int(params.get("slow_period", 26))
        self._signal_period = int(params.get("signal_period", 9))
        self._quantity = Decimal(str(params.get("quantity", "0.01")))

        if self._fast_period >= self._slow_period:
            raise ValueError(
                f"MACD fast_period must be < slow_period, "
                f"got fast={self._fast_period}, slow={self._slow_period}"
            )
        if self._fast_period < 2:
            raise ValueError(f"MACD fast_period must be >= 2, got {self._fast_period}")
        if self._slow_period < 2:
            raise ValueError(f"MACD slow_period must be >= 2, got {self._slow_period}")
        if self._signal_period < 2:
            raise ValueError(f"MACD signal_period must be >= 2, got {self._signal_period}")
        if self._quantity <= 0:
            raise ValueError(f"Quantity must be positive, got {self._quantity}")

    def reset(self) -> None:
        self._closes.clear()
        self._prev_histogram = None

    def on_candle(self, candle: Candle) -> Signal | None:
        self._closes.append(float(candle.close))

        if len(self._closes) < self.warmup_period:
            return None

        series = pd.Series(list(self._closes))

        fast_ema = series.ewm(span=self._fast_period, adjust=False).mean()
        slow_ema = series.ewm(span=self._slow_period, adjust=False).mean()
        macd_line = fast_ema - slow_ema
        signal_line = macd_line.ewm(span=self._signal_period, adjust=False).mean()
        histogram = macd_line - signal_line

        current_histogram = float(histogram.iloc[-1])
        signal = None

        if self._prev_histogram is not None:
            # Bullish crossover: histogram crosses from negative to positive
            if self._prev_histogram <= 0 and current_histogram > 0:
                signal = Signal(
                    strategy=self.name,
                    symbol=candle.symbol,
                    side=OrderSide.BUY,
                    price=candle.close,
                    quantity=self._quantity,
                    reason=f"MACD bullish crossover: histogram {self._prev_histogram:.6f} -> {current_histogram:.6f}",
                )
            # Bearish crossover: histogram crosses from positive to negative
            elif self._prev_histogram >= 0 and current_histogram < 0:
                signal = Signal(
                    strategy=self.name,
                    symbol=candle.symbol,
                    side=OrderSide.SELL,
                    price=candle.close,
                    quantity=self._quantity,
                    reason=f"MACD bearish crossover: histogram {self._prev_histogram:.6f} -> {current_histogram:.6f}",
                )

        self._prev_histogram = current_histogram
        return signal