from decimal import Decimal

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


class VwapStrategy(BaseStrategy):
    name: str = "vwap"

    def __init__(self) -> None:
        self._deviation_threshold: float = 0.002
        self._quantity: Decimal = Decimal("0.01")
        self._cumulative_tp_vol: float = 0.0
        self._cumulative_vol: float = 0.0
        self._candle_count: int = 0
        self._was_below_vwap: bool = False
        self._was_above_vwap: bool = False

    @property
    def warmup_period(self) -> int:
        return 30

    def configure(self, params: dict) -> None:
        self._deviation_threshold = float(params.get("deviation_threshold", 0.002))
        self._quantity = Decimal(str(params.get("quantity", "0.01")))

        if self._deviation_threshold <= 0:
            raise ValueError(
                f"VWAP deviation_threshold must be > 0, got {self._deviation_threshold}"
            )
        if self._quantity <= 0:
            raise ValueError(f"Quantity must be positive, got {self._quantity}")

    def reset(self) -> None:
        self._cumulative_tp_vol = 0.0
        self._cumulative_vol = 0.0
        self._candle_count = 0
        self._was_below_vwap = False
        self._was_above_vwap = False

    def on_candle(self, candle: Candle) -> Signal | None:
        high = float(candle.high)
        low = float(candle.low)
        close = float(candle.close)
        volume = float(candle.volume)

        typical_price = (high + low + close) / 3.0
        self._cumulative_tp_vol += typical_price * volume
        self._cumulative_vol += volume
        self._candle_count += 1

        if self._candle_count < self.warmup_period:
            return None

        if self._cumulative_vol == 0.0:
            return None

        vwap = self._cumulative_tp_vol / self._cumulative_vol
        if vwap == 0.0:
            return None
        deviation = (close - vwap) / vwap

        if deviation < -self._deviation_threshold:
            self._was_below_vwap = True
        if deviation > self._deviation_threshold:
            self._was_above_vwap = True

        # Mean reversion from below: was below VWAP, now back near it
        if self._was_below_vwap and abs(deviation) <= self._deviation_threshold:
            self._was_below_vwap = False
            return Signal(
                strategy=self.name,
                symbol=candle.symbol,
                side=OrderSide.BUY,
                price=candle.close,
                quantity=self._quantity,
                reason=f"VWAP mean reversion BUY: deviation {deviation:.4f} within threshold {self._deviation_threshold}",
            )

        # Mean reversion from above: was above VWAP, now back near it
        if self._was_above_vwap and abs(deviation) <= self._deviation_threshold:
            self._was_above_vwap = False
            return Signal(
                strategy=self.name,
                symbol=candle.symbol,
                side=OrderSide.SELL,
                price=candle.close,
                quantity=self._quantity,
                reason=f"VWAP mean reversion SELL: deviation {deviation:.4f} within threshold {self._deviation_threshold}",
            )

        return None