import logging
from datetime import datetime, timezone

from sqlalchemy import select
from sqlalchemy.orm import Session

from app.db.models import Reminder, User
from app.reminders.completion import ReminderCompletionHandler
from app.reminders.notify import bump_notify_seq

logger = logging.getLogger(__name__)


def _utcnow() -> datetime:
    return datetime.now(timezone.utc)


def get_due_reminders(db: Session, user_id: int) -> list[Reminder]:
    now = _utcnow()
    stmt = (
        select(Reminder)
        .where(
            Reminder.user_id == user_id,
            Reminder.enabled.is_(True),
            Reminder.completed_at.is_(None),
            Reminder.due_at <= now,
        )
        .order_by(Reminder.due_at.asc())
    )
    rows = list(db.scalars(stmt).all())
    return [row for row in rows if not (row.last_fired_at and row.last_fired_at >= row.due_at)]


async def process_due_reminders(db: Session) -> int:
    users = db.scalars(select(User).where(User.is_active.is_(True))).all()
    total = 0
    for user in users:
        due = get_due_reminders(db, user.id)
        if not due:
            continue
        handler = ReminderCompletionHandler(db, user.id)
        for row in due:
            await handler.process(row)
        total += len(due)

    if total:
        db.commit()
        bump_notify_seq(db)
        logger.info("Reminders fired: %d", total)
    return total