#!/usr/bin/env python
# -*- coding: utf-8 -*-
# File:        after.py
# Author:      Guilherme Victal <guilherme at victal.eti.br>
# Description: Generates regexes after a certain date
# License:     Vim license
# Website:     http://github.com/freitass/todo.txt-vim
# Version:     0.1

from datetime import date, timedelta, MAXYEAR


def _year_regex_after(year):
    if int(year) > MAXYEAR:
        return None

    year_regex = r'(\d+\d{%s}' % len(year)
    for idx, digit in enumerate(year):
        if digit != '9':
            regex = '|' + year[0:idx]
            regex += '9' if digit == '8' else '[%s-9]' % str(int(digit) + 1)
            if idx < len(year) - 1:
                regex += '\d{%s}' % (len(year) - (idx + 1))
            year_regex += regex

    year_regex += ')'
    return '-'.join((year_regex, r'\d{2}', r'\d{2}'))


def _month_regex_after(year, month):
    if month == '12':
        return None

    digit1, digit2 = month
    if digit1 == '1':
        month_regex = r'12' if month == '11' else r'1[12]'
    else:
        month_regex = r'1[0-2]'
        if digit2 != '9':
            if digit2 == '8':
                month_regex = r'(' + month_regex + r'|09)'
            else:
                month_regex = r'(' + month_regex + r'|0[%s-9])'
                month_regex = month_regex % str(int(digit2) + 1)
    return '-'.join((year, month_regex, r'\d{2}'))

def _day_regex_after(year, month, day):
    last_month_day = str((date(int(year), (int(month) + 1) % 12, 1) + - date.resolution).day)
    if day == last_month_day:
        return None
    day_regex = r'('
    digit1, digit2 = day
    last_digit1, last_digit2 = last_month_day
    if digit1 == last_digit1:
        day_regex = last_month_day if int(digit2) == int(last_digit2) - 1 else last_digit1 + r'[%s-%s]' % (str(int(digit2) + 1), last_digit2)
    else:
        day_regex = r'('
        day_regex += last_digit1 if int(digit1) == int(last_digit1) - 1 else r'[%s-%s]' % (str(int(digit1) + 1), last_digit1)
        day_regex +=r'\d'
        if digit2 < '9':
            day_regex += '|' + digit1
            day_regex += '9' if digit2 == '8' else r'[%s-9]' % str(int(digit2) + 1)

        day_regex += ')'
    return '-'.join((year, month, day_regex))


def regex_date_after(given_date):
    year, month, day = given_date.isoformat().split('-')

    year_regex = _year_regex_after(year)
    month_regex = _month_regex_after(year, month)
    day_regex = _day_regex_after(year, month, day)

    date_regex = '(' + year_regex if year_regex else '('
    date_regex += ('|' + month_regex) if month_regex else ''
    date_regex += ('|' + day_regex) if day_regex else ''
    date_regex += ')'
    return date_regex


def __main():
    import re
    date_regex = regex_date_after(date(1999,12,31))
    print(date_regex)
    pattern = re.compile(date_regex)


    d = date.today() + date.resolution
    assert pattern.match(date.strftime(d, '%Y-%m-%d')) is not None
    print(date.strftime(d, '%Y-%m-%d') + ' is okay')
    d += date.resolution

if __name__ == '__main__':
    __main()