#!/usr/bin/env python3

import argparse
import datetime
import random
from string import Template
import sys


class SPTemplate(Template):
    delimiter = '%%'


def print_sp_template(template: SPTemplate, duration: str, names: list[str]):
    defs = [rf'\csdef{{name{i+1}}}{{{n}}}' for i, n in enumerate(names)]
    defs.append(rf'\csdef{{duration}}{{{duration}}}')
    print(template.substitute({'defs': '\n'.join(defs)}))


def main():
    """Entry point generating a random seating plan from students names"""

    parser = argparse.ArgumentParser()
    parser.add_argument('template')
    duration_group = parser.add_mutually_exclusive_group()
    duration_group.add_argument(
        '--duration',
        default=f'KW: {datetime.datetime.now().isocalendar()[1]}')
    duration_group.add_argument('--week', type=int)
    args = parser.parse_args()

    names = [line[:-1] for line in sys.stdin.readlines()]
    random.shuffle(names)

    duration = args.duration
    if args.week:
        # https://stackoverflow.com/questions/56163008/how-to-get-all-dates-of-week-based-on-week-number-in-python
        # Starts with knowing the day of the week
        week_day = datetime.datetime.now().isocalendar()[2]
        week_offset = args.week - datetime.datetime.now().isocalendar()[1]

        # Calculates Starting date (Sunday) for this case by subtracting
        # current date with time delta of the day of the week
        start_date = datetime.datetime.now() - datetime.timedelta(
            days=week_day) + datetime.timedelta(days=(week_offset * 7) + 1)

        # Prints the list of dates in a current week
        duration = (
            f'KW: {args.week}~~~{start_date.strftime("%d.%m")} - '
            f'{(start_date + datetime.timedelta(days=4)).strftime("%d.%m")}')

    with open(args.template, 'r', encoding='utf-8') as template_file:
        template = SPTemplate(template_file.read())
        print_sp_template(template, duration, names)


if __name__ == '__main__':
    main()