from typing import Callable, List
from .contracts import QuoteSnapshot, OrderEvent


class ToyVenueAdapter:
    """A tiny in-process adapter that exposes a simple order acceptance model.

    It accepts OrderEvent objects and updates an internal top-of-book. Deterministic
    behaviour is achieved by not using random jitter and relying on caller ordering.
    """

    def __init__(self, venue_id: str, initial_bid: float = 100.0, initial_ask: float = 100.5, asset: str = "TEST/USD"):
        self.venue_id = venue_id
        self.asset = asset
        self.initial_bid = initial_bid
        self.initial_ask = initial_ask
        self.best_bid = initial_bid
        self.best_ask = initial_ask
        self.listeners: List[Callable[[QuoteSnapshot], None]] = []

    def reset(self):
        self.best_bid = self.initial_bid
        self.best_ask = self.initial_ask

    def _normalize_book(self):
        if self.best_ask <= self.best_bid:
            midpoint = (self.best_bid + self.best_ask) / 2
            self.best_bid = round(midpoint - 0.005, 4)
            self.best_ask = round(midpoint + 0.005, 4)

    def on_snapshot(self, cb: Callable[[QuoteSnapshot], None]):
        self.listeners.append(cb)

    def publish_snapshot(self):
        snap = QuoteSnapshot(
            venue_id=self.venue_id,
            asset=self.asset,
            bids=[[self.best_bid, 100.0]],
            asks=[[self.best_ask, 100.0]],
        )
        for cb in list(self.listeners):
            cb(snap)

    def handle_order(self, order: OrderEvent) -> OrderEvent:
        # Very small deterministic matcher: marketable at top-of-book executes
        impact = round(max(order.size, 1.0) * 0.05, 4)
        if order.side == "buy" and order.price is None:
            order.status = "filled"
            self.best_bid = round(self.best_bid + impact, 4)
            self.best_ask = round(self.best_ask + impact, 4)
            self._normalize_book()
        elif order.side == "sell" and order.price is None:
            order.status = "filled"
            self.best_bid = round(self.best_bid - impact, 4)
            self.best_ask = round(self.best_ask - impact, 4)
            self._normalize_book()
        else:
            order.status = "accepted"
        # publish new snapshot deterministically
        self.publish_snapshot()
        return order