from datetime import datetime, timedelta, timezone

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

from app.db.models import Round
from app.rounds.config import get_round_config

_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, or the lottery is paused for maintenance — in either 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.

    Pausing never touches a round already in progress: it only suppresses opening
    the *next* one, so the current round still closes, draws, and pays out the
    winner normally (see admin.py's /admin/pause and /admin/resume)."""
    active = await get_active_round(session)
    if active is not None:
        return active

    config = await get_round_config(session)
    if config.paused:
        return None

    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=config.round_cooldown_seconds):
            return None

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