from datetime import datetime, timedelta, timezone

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

from app.config import settings
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 | None:
    """Returns the active round if one exists (whatever its status). Otherwise
    opens a fresh one, unless the last closed round's cooldown (ROUND_COOLDOWN_SECONDS)
    hasn't elapsed yet — in which case returns None. 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

    last_closed = await session.scalar(select(Round).where(Round.status == "closed").order_by(Round.id.desc()))
    if last_closed is not None and last_closed.closed_at is not None:
        closed_at = last_closed.closed_at.replace(tzinfo=timezone.utc)
        if datetime.now(timezone.utc) < closed_at + timedelta(seconds=settings.round_cooldown_seconds):
            return None

    round_ = Round(status="open")
    session.add(round_)
    await session.flush()
    return round_