from django.http import HttpRequest
from django.utils import timezone

from .models import AnoCenso

SESSION_KEY = "ano_censo"


def default_ano_censo() -> int:
    configured_year = (
        AnoCenso.objects.order_by("-ano")
        .values_list("ano", flat=True)
        .first()
    )
    return configured_year or timezone.localdate().year - 1


def available_anos_censo() -> list[int]:
    years = list(AnoCenso.objects.order_by("-ano").values_list("ano", flat=True))
    return years or [default_ano_censo()]


def get_selected_ano_censo(request: HttpRequest) -> int:
    raw_value = request.session.get(SESSION_KEY)
    try:
        selected_year = int(raw_value)
    except (TypeError, ValueError):
        selected_year = default_ano_censo()
        request.session[SESSION_KEY] = selected_year
        return selected_year

    if AnoCenso.objects.filter(ano=selected_year).exists():
        return selected_year

    selected_year = default_ano_censo()
    request.session[SESSION_KEY] = selected_year
    return selected_year


def set_selected_ano_censo(request: HttpRequest, ano_censo: int) -> None:
    if not AnoCenso.objects.filter(ano=ano_censo).exists():
        raise ValueError("Ano do censo nao cadastrado.")
    request.session[SESSION_KEY] = ano_censo