"""Génération des créneaux d'un poste à partir des créneaux types (DayPart)."""

import datetime as dt

from sqlmodel import Session, select

from app.models import DayPart, Edition, Position, Shift
from app.validation.engine import day_boundary


def _dates(edition: Edition) -> list[dt.date]:
    span = (edition.end_date - edition.start_date).days
    return [edition.start_date + dt.timedelta(days=i) for i in range(span + 1)]


def _window(day: dt.date, part: DayPart, boundary: dt.time) -> tuple[dt.datetime, dt.datetime]:
    actual_day = day + dt.timedelta(days=1) if part.start_time < boundary else day
    start = dt.datetime.combine(actual_day, part.start_time)
    end_day = (
        actual_day if part.end_time > part.start_time else actual_day + dt.timedelta(days=1)
    )
    return start, dt.datetime.combine(end_day, part.end_time)


def generate_missing_shifts(
    session: Session, edition: Edition, position: Position
) -> int:
    """Crée, pour chaque jour de l'édition et chaque créneau type, un créneau à
    besoin 0/0 s'il n'existe pas déjà. Retourne le nombre créé."""
    day_parts = list(
        session.exec(select(DayPart).where(DayPart.edition_id == edition.id))
    )
    boundary = day_boundary(day_parts)
    existing = {
        (s.day_part_id, s.starts_at.date())
        for s in session.exec(
            select(Shift).where(Shift.position_id == position.id)
        )
    }
    created = 0
    for day in _dates(edition):
        for part in day_parts:
            start, end = _window(day, part, boundary)
            if (part.id, start.date()) in existing:
                continue
            session.add(
                Shift(
                    edition_id=edition.id,
                    position_id=position.id,
                    day_part_id=part.id,
                    starts_at=start,
                    ends_at=end,
                    min_staff=0,
                    ideal_staff=0,
                )
            )
            created += 1
    return created