#    Copyright (C) 2017  Alban Gruin
#
#    celcatsanitizer is free software: you can redistribute it and/or modify
#    it under the terms of the GNU Affero General Public License as published
#    by the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    celcatsanitizer is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU Affero General Public License for more details.
#
#    You should have received a copy of the GNU Affero General Public License
#    along with celcatsanitizer.  If not, see <http://www.gnu.org/licenses/>.

import datetime

from django.core.management.base import BaseCommand
from django.db import transaction
from django.db.models import Min
from django.utils import timezone

from edt.models import Course, Timetable
from edt.utils import get_week
from ._private import delete_courses_in_week, get_events, get_update_date, get_weeks, get_xml

@transaction.atomic
def process_timetable_week(timetable, soup, weeks_in_soup, force, year=None, week=None):
    today = timezone.make_aware(datetime.datetime.now())

    # On récupère la mise à jour la plus ancienne dans les cours de l’emploi du temps
    # commençant à partir de maintenant
    last_update_date = Course.objects.filter(timetable=timetable, begin__gte=today)
    if year is not None and week is not None:
        # Si jamais on traite une semaine spécifique, on limite les cours sélectionnés
        # à ceux qui commencent entre le début du traitement et la fin de la semaine
        _, end = get_week(year, week)
        last_update_date = last_update_date.filter(begin__lt=end)

    last_update_date = last_update_date.aggregate(Min("last_update")) \
                       ["last_update__min"]

    # Date de mise à jour de Celcat, utilisée à des fins de statistiques
    new_update_date = get_update_date(soup)

    # On ne fait pas la mise à jour si jamais la dernière date de MàJ est plus récente
    # que celle indiquée par Celcat.
    # Attention, le champ last_update de la classe Course représente l’heure à laquelle
    # le cours a été inséré dans la base de données, et non pas la date indiquée par
    # Celcat.
    if not force and last_update_date is not None and new_update_date is not None and \
       last_update_date >= new_update_date:
        return

    if year is not None and week is not None:
        # On efface la semaine à partir de maintenant si jamais
        # on demande le traitement d’une seule semaine
        delete_courses_in_week(timetable, year, week, today)
    else:
        # Sinon, on efface tous les cours à partir de maintenant.
        # Précisément, on prend la plus grande valeur entre la première semaine
        # présente dans Celcat et maintenant.
        delete_from = max(min(weeks_in_soup.values()), today) # Vraiment utile ?
        Course.objects.filter(timetable=timetable, begin__gte=delete_from).delete()

    # Tous les cours commençant sur la période traitée
    # sont parsés, puis enregistrés dans la base de données.
    for course in get_events(timetable, soup, weeks_in_soup, today, year, week):
        course.save()

    # On renseigne la date de mise à jour de Celcat, à des fins de statistiques
    timetable.last_update_date = new_update_date
    timetable.save()

def process_timetable(timetable, force, year=None, weeks=None):
    soup = get_xml(timetable.url)
    weeks_in_soup = get_weeks(soup)

    if year is not None and weeks is not None:
        for week in weeks:
            process_timetable_week(timetable, soup, weeks_in_soup, force, year, week)
    else:
        process_timetable_week(timetable, soup, weeks_in_soup, force)


class Command(BaseCommand):
    help = "Fetches registered celcat timetables"

    def add_arguments(self, parser):
        parser.add_argument("--all", const=True, default=False, action="store_const")
        parser.add_argument("--force", const=True, default=False, action="store_const")
        parser.add_argument("--week", type=int, choices=range(1, 54), nargs="+")
        parser.add_argument("--year", type=int, nargs=1)

    def handle(self, *args, **options):
        year = None
        errcount = 0

        if options["all"]:
            weeks = None
        elif options["week"] is None:
            _, week, day = timezone.now().isocalendar()
            if day >= 6:
                year, week, _ = (timezone.now() + datetime.timedelta(weeks=1)).isocalendar()
            weeks = [week]
        else:
            weeks = options["week"]

        if not options["all"]:
            if options["year"] is None and year is None:
                year = timezone.now().year
            elif year is None:
                year = options["year"][0]

        for timetable in Timetable.objects.all():
            self.stdout.write("Processing {0}".format(timetable))

            try:
                process_timetable(timetable, options["force"], year, weeks)
            except Exception as exc:
                self.stderr.write(
                    self.style.ERROR("Failed to process {0}: {1}".format(timetable, exc)))
                errcount += 1

        if errcount == 0:
            self.stdout.write(self.style.SUCCESS("Done."))
        else:
            self.stdout.write(self.style.ERROR("Done with {0} errors.".format(errcount)))