from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.db.models import Round

_ACTIVE_STATUSES = ("open", "closing", "drawing", "paying_out")


async def get_active_round(session: AsyncSession) -> Round | None:
    """The round currently in progress (in any non-closed state), if any. Rounds
    never overlap: a new round only opens once the previous one is fully closed
    (payout confirmed, or no participants to pay out)."""
    return await session.scalar(select(Round).where(Round.status.in_(_ACTIVE_STATUSES)).order_by(Round.id.desc()))


async def open_new_round_if_needed(session: AsyncSession) -> Round:
    """Returns the active round if one exists (whatever its status), otherwise
    opens a fresh one. Callers that need to attach a bet must additionally check
    the returned round's status == "open" — a round in closing/drawing/paying_out
    isn't accepting new bets, but a new round can't open until it's done."""
    active = await get_active_round(session)
    if active is not None:
        return active
    round_ = Round(status="open")
    session.add(round_)
    await session.flush()
    return round_