#!/usr/bin/env python3
# Copyright 2023 Florian Fischer
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program. If not, see <https://www.gnu.org/licenses/>.
"""simple script to generate a rough markdown map of a school year"""

import argparse
from datetime import datetime, timedelta
from pathlib import Path
import os
import re
import sys
import urllib
import typing as t

from bs4 import BeautifulSoup
import icalevents
from icalevents.icalevents import events
import requests

BAYERN = 1
ICAL_BASE_URL = 'https://www.schulferien.eu/downloads/ical4.php'

TEMPLATE_DIR = Path(
    os.environ['HOME']
) / 'Documents/MyDocuments/Work/Schule/Unterricht/templates'
TEMPLATE_FILE = 'map.tex'

LPP_BASE_URL = 'https://www.lehrplanplus.bayern.de/fachlehrplan/gymnasium'

WEEKLY_HOURS = {
    'mathematik': {
        5: 4,
        6: 4,
        7: 4,
        8: 3,
        9: 4,
        10: 3,
        11: 4
    },
    'informatik': {
        9: 2,
        10: 2,
        11: 2
    },
    'nt_gym': {
        6: 2,
        7: 2
    }
}


def die(msg: str, status=1):
    """Exit with status printing a msg to stderr"""
    print(msg, file=sys.stderr)
    sys.exit(status)


def default_year() -> int:
    """return the default year"""
    now = datetime.now()
    return now.year if now.month < 8 else now.year + 1


def get_holidays(land: int, year: int) -> list[icalevents.icalparser.Event]:
    """Get list of all holidays in a school year"""
    start_year = datetime(year=year - 1, month=1, day=1)
    end_year = datetime(year=year + 1, month=12, day=31)

    params = {'land': land, 'year': year, 'type': 1}
    uri_first_year = ICAL_BASE_URL + '?' + urllib.parse.urlencode(params)

    first_holidays = events(url=uri_first_year, start=start_year, end=end_year)

    params['year'] = year + 1
    uri_second_year = ICAL_BASE_URL + '?' + urllib.parse.urlencode(params)

    second_holidays = events(url=uri_second_year,
                             start=start_year,
                             end=end_year)

    first_summer = next(
        filter(lambda e: "Sommerferien" in e.summary, first_holidays))

    second_summer = next(
        filter(lambda e: "Sommerferien" in e.summary, second_holidays))

    return [
        h for h in first_holidays + second_holidays
        if h.start >= first_summer.start and h.start <= second_summer.start
    ]


def fmt_holiday(holiday: icalevents.icalparser.Event) -> str:
    """Return a formatted holiday description"""
    h_start = f'{holiday.start.date().strftime("%d.%m")}'
    h_end = f'{holiday.end.date().strftime("%d.%m")}'
    return f'{h_start}-{h_end} {holiday.summary}'


def get_public_holidays(land: int, start: datetime,
                        end: datetime) -> list[icalevents.icalparser.Event]:
    """Get list of all public holidays in the school year"""

    params = {'land': land, 'year': start.year, 'type': 0}
    uri_first_year = ICAL_BASE_URL + '?' + urllib.parse.urlencode(params)

    params['year'] = end.year
    uri_second_year = ICAL_BASE_URL + '?' + urllib.parse.urlencode(params)

    all_public_holidays = events(url=uri_first_year, start=start,
                                 end=end) + events(
                                     url=uri_second_year, start=start, end=end)

    return [
        e for e in all_public_holidays if e.start >= start and e.start <= end
    ]


class LehrplanSection:
    """Representation of a section of Lehrplanplus"""

    def __init__(self, num, summary, duration, subsections=None):
        self.num = num
        self.summary = summary
        self.duration = duration
        self.subsections = subsections or []

    def __str__(self):
        return f'{self.num}: {self.summary} ({self.duration}h) {self.subsections}'

    def __repr__(self):
        return (f'LehrplanSection({self.num}, {self.summary}, '
                f'{self.duration}h, {self.subsections})')


Lehrplan = list[LehrplanSection]

SUMMARY_RE = re.compile(r'(.*) \(ca\. ([1-9][0-9]*) Std\.\)')


def parse_section_html(section, summary_class: str) -> t.Tuple[str, str, int]:
    """Parse the html for a section from the Lehrplanplus webpage"""
    num = list(section.find(**{
        'class': 'head-absatz-num'
    }).children)[2].strip()

    summary = section.find(**{'class': summary_class}).string.strip()
    summary = summary.replace('\xa0', ' ')

    match = SUMMARY_RE.match(summary)
    if not match is None:
        summary = match.group(1)
        duration = int(match.group(2))
    else:
        die(f'summary: {summary} does not match our re')

    return num, summary, duration


def get_lehrplan(subject: str, form: str, form_type: str) -> Lehrplan:
    """Retrieve the sections and expected duration from lehrplanplus"""

    lpp_url = '/'.join([LPP_BASE_URL, form, subject])
    if form_type:
        lpp_url += f'/{form_type}'
    resp = requests.get(lpp_url, timeout=10)
    html = BeautifulSoup(resp.text)

    lehrplan: Lehrplan = []
    top_level_sections = html.find_all(**{'class': 'headline_lvl1'})
    for section in top_level_sections:
        num, summary, duration = parse_section_html(section,
                                                    'head-absatz-title-short')
        lehrplan.append(LehrplanSection(num, summary, duration))

    second_level_sections = html.find_all(**{'class': 'headline_lvl2'})
    for section in second_level_sections:
        num, summary, duration = parse_section_html(section,
                                                    'head-absatz-title-long')
        lehrplan[int(num.split('.')[0]) - 1].subsections.append(
            LehrplanSection(num, summary, duration))

    return lehrplan


def gen_section_iter(lehrplan, inter_section_buffer_duration: int):
    """Create an iterator returning the current section"""
    end_section_buffer = LehrplanSection('', 'Puffer', 0)
    inter_section_buffer = LehrplanSection('', 'Puffer',
                                           inter_section_buffer_duration)

    _sections = []
    for s in lehrplan:
        if not s.subsections:
            _sections.append(s)
        else:
            _sections.extend(s.subsections)

    # Add buffer sections to the lehrplan
    sections = []
    for s in _sections:
        sections.append(s)
        if inter_section_buffer_duration:
            sections.append(inter_section_buffer)

    sections.append(end_section_buffer)

    next_section_in = sections[0].duration
    cur = 0

    def _section_iter(weekly_hours, total_hours) -> list[LehrplanSection]:
        nonlocal cur
        if cur == len(sections) - 1:
            return sections[-1]

        nonlocal next_section_in
        # advance section
        if total_hours > next_section_in + (weekly_hours -
                                            next_section_in % weekly_hours):
            cur += 1
            next_section_in += sections[cur].duration

        return sections[cur]

    return _section_iter


def gen_latex_table(
    weekly_hours: int,
    lehrplan: Lehrplan,
    school_holidays: list[icalevents.icalparser.Event],
    public_holidays: list[icalevents.icalparser.Event],  # # pylint: disable=unused-argument
    inter_section_buffer: int) -> list[str]:
    """generate a latex table matching lehrplan section on calendar weeks"""

    rows: list[str] = []

    lehrplan.append(LehrplanSection('', 'Puffer', 0))

    start = school_holidays[0].end
    end = school_holidays[-1].start

    holiday_iter = iter(school_holidays[1:])
    next_holiday = next(holiday_iter)

    section_iter = gen_section_iter(lehrplan, inter_section_buffer)
    total_hours = 0

    week_iter = start + timedelta(days=1)
    while week_iter < end:
        if week_iter > next_holiday.start:
            rows.append(
                rf'\Holiday{{{week_iter.isocalendar().week}}}{{{fmt_holiday(next_holiday)}}} \\'
            )
            week_iter = next_holiday.end + timedelta(days=1)
            next_holiday = next(holiday_iter)
            continue

        lp_section = section_iter(weekly_hours, total_hours)

        rows.append(
            f'{week_iter.isocalendar().week} & {lp_section.num} & {lp_section.summary} \\\\'
        )

        week_iter += timedelta(days=7)
        total_hours += weekly_hours

    return rows


def print_map(rows: list[str], template_path: Path, outfile):
    """Print the template including the generated table"""
    with open(template_path, 'r', encoding='utf-8') as template_file:
        template = template_file.readlines()

    template_prefix = template[:-8]
    template_suffix = template[-2:]

    print(''.join(template_prefix), file=outfile, end='')
    print('\n'.join(rows), file=outfile)
    print(''.join(template_suffix), file=outfile)


def main():
    """Create a rough map template for a certain school year"""
    parser = argparse.ArgumentParser()
    parser.add_argument('subject')
    parser.add_argument('form', type=int)
    parser.add_argument(
        '--form-type',
        help='type of the form used by LPP',
    )
    parser.add_argument('--template-dir')
    parser.add_argument('--year', default=default_year())
    parser.add_argument('--land', default=BAYERN)
    parser.add_argument('-o', '--output', default=sys.stdout)
    parser.add_argument('-b', '--inter-section-buffer', type=int)

    args = parser.parse_args()

    school_holidays = get_holidays(args.land, args.year)
    public_holidays = get_public_holidays(args.land, school_holidays[0].end,
                                          school_holidays[-1].start)

    weekly_hours = WEEKLY_HOURS[args.subject][args.form]
    lehrplan = get_lehrplan(args.subject, str(args.form), args.form_type)
    if not lehrplan:
        print('WARNING: empty lehrplan', file=sys.stderr)

    rows = gen_latex_table(weekly_hours, lehrplan, school_holidays,
                           public_holidays, args.inter_section_buffer)

    if args.template_dir:
        template_path = Path(args.template_dir) / TEMPLATE_FILE
    else:
        template_path = TEMPLATE_DIR / TEMPLATE_FILE

    if args.output != sys.stdout:
        with open(args.output, 'w', encoding='utf-8') as outfile:
            print_map(rows, template_path, outfile)
    else:
        print_map(rows, template_path, args.output)


if __name__ == '__main__':
    main()