from django import forms
from django.db.utils import OperationalError
from .models import FicheStatistique


class StatistiquesForm(forms.ModelForm):
    class Meta:
        model = FicheStatistique
        exclude = ["sujet"]


def get_year_range():
    qs = FicheStatistique.objects.filter(
                sujet__premiere_rencontre__isnull=False
            ).order_by(
                'sujet__premiere_rencontre'
            )

    def year(fiche):
        return fiche.sujet.premiere_rencontre.year

    # Need to call exists() in a try block
    # to avoid raising exception on first migration
    try:
        qs_is_not_empty = qs.exists()
    except OperationalError:
        qs_is_not_empty = False
        
    if qs_is_not_empty:
        return range(year(qs.first()), year(qs.last()) + 1)
    else:
        return ()


class SelectRangeForm(forms.Form):
    period = forms.ChoiceField(label="Année", choices=[(0, 'Tout')] + [(i, str(i)) for i in get_year_range()])