from __future__ import annotations

from app.broker.base import Broker, Fill
from app.models import OrderSide, utcnow


class PaperBroker(Broker):
    """Simulated fills against a reference price, with fees and slippage.

    Buys fill slightly above and sells slightly below the reference price to
    approximate adverse slippage.
    """

    def __init__(self, fee_bps: float = 10.0, slippage_bps: float = 5.0) -> None:
        self.fee_bps = fee_bps
        self.slippage_bps = slippage_bps

    def _fee(self, notional: float) -> float:
        return abs(notional) * self.fee_bps / 10_000

    def fill(self, symbol: str, side: OrderSide, qty: float, ref_price: float) -> Fill:
        """Synchronous fill used by the backtester (same model as buy/sell)."""
        direction = 1 if side == OrderSide.BUY else -1
        price = ref_price * (1 + direction * self.slippage_bps / 10_000)
        return Fill(
            symbol=symbol,
            side=side,
            qty=qty,
            price=price,
            fee=self._fee(qty * price),
            ts=utcnow(),
        )

    async def buy(self, symbol: str, qty: float, ref_price: float) -> Fill:
        return self.fill(symbol, OrderSide.BUY, qty, ref_price)

    async def sell(self, symbol: str, qty: float, ref_price: float) -> Fill:
        return self.fill(symbol, OrderSide.SELL, qty, ref_price)