#    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
import re

from django.utils import timezone

def get_current_week():
    return timezone.now().isocalendar()[:2]

def get_current_or_next_week():
    year, week, day = timezone.now().isocalendar()
    if day >= 6:
        year, week, _ = (timezone.now() + datetime.timedelta(weeks=1)).isocalendar()

    return year, week

def get_week(year, week):
    start = timezone.make_aware(datetime.datetime.strptime(
        "{0}-W{1:02d}-1".format(year, week), "%Y-W%W-%w"))
    end = start + datetime.timedelta(weeks=1)

    return start, end

def group_courses(courses):
    grouped_courses = []
    for i, course in enumerate(courses):
        if i == 0 or courses[i - 1].begin.day != course.begin.day:
            grouped_courses.append([course])
        else:
            grouped_courses[-1].append(course)

    return grouped_courses

def parse_group(name):
    # Explication de la regex
    #
    # ^(.+?)\s+((CM(\w))|(TD(\w)(\d))|(TP(\w)(\d)(\d)))?(\s+\(.+\))?$
    # ^                                                               début de la ligne
    #  (.+?)                                                          correspond à au moins un caractère
    #       \s+                                                       un ou plusieurs espaces
    #          ((CM(\w))|                                             correspond à CM suivi d'une lettre ou…
    #                    (TD(\w)(\d))|                                … à TD suivi d’une lettre et d'un chiffre ou…
    #                                 (TP(\w)(\d)(\d))                … à TP suivi d’une lettre et de deux chiffres
    #                                                 )?              groupe optionnel
    #                                                   (\s+          un ou plusieurs espaces
    #                                                       \(.+\))   un ou plusieurs caractères quelconques entre parenthèses
    #                                                              ?  groupe optionnel
    #                                                               $ fin de la ligne
    group_regex = re.compile(r"^(.+?)\s+((CM(\w))|(TD(\w)(\d))|(TP(\w)(\d)(\d)))?(\s+\(.+\))?$")
    search = group_regex.search(name)
    if search is None:
        return name, None, None, None

    parts = search.groups()
    if parts[1] is None:       # Pas de groupe précis indiqué
        return parts[0], None, None, None
    elif parts[2] is not None: # Groupe de CM
        return parts[0], parts[3], None, None
    elif parts[4] is not None: # Groupe de TD
        return parts[0], parts[5], parts[6], None
    elif parts[7] is not None: # Groupe de TP
        return parts[0], parts[8], parts[9], parts[10]