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):
        self.venue_id = venue_id
        self.best_bid = initial_bid
        self.best_ask = initial_ask
        self.listeners: List[Callable[[QuoteSnapshot], None]] = []

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

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

    def handle_order(self, order: OrderEvent) -> OrderEvent:
        # Very small deterministic matcher: marketable at top-of-book executes
        if order.side == "buy" and order.price is None:
            order.status = "filled"
            # naive mid update
            self.best_bid = max(self.best_bid, order.price or self.best_bid)
        elif order.side == "sell" and order.price is None:
            order.status = "filled"
            self.best_ask = min(self.best_ask, order.price or self.best_ask)
        else:
            order.status = "accepted"
        # publish new snapshot deterministically
        self.publish_snapshot()
        return order