import asyncio
from contextlib import asynccontextmanager


class UserLocks:
    """Per-user asyncio.Lock registry, shared by PLAY and WITHDRAW so a user can
    never have a bet-build and a withdrawal-build in flight at once (both would
    otherwise spend from the same UTXO set on the user's dedicated address).

    Single-process-only by design (an in-memory dict of asyncio.Lock) — this is an
    accepted MVP constraint; a multi-process deployment would need a DB or Redis
    lock instead (e.g. a Postgres advisory lock).
    """

    def __init__(self) -> None:
        self._locks: dict[int, asyncio.Lock] = {}

    @asynccontextmanager
    async def acquire(self, user_id: int):
        lock = self._locks.setdefault(user_id, asyncio.Lock())
        async with lock:
            yield