import re
from datetime import datetime

from django.db import models
from django.core.validators import MinLengthValidator
from django.core.exceptions import ValidationError


def validate_rfc(value):
    l = 4
    if len(value)==12:
        l = 3
    s = value[0:l]
    r = re.match('[A-ZÑ&]{%s}' % l, s)
    if not r:
        raise ValidationError('Caracteres inválidos al inicio del RFC')

    s = value[-3:]
    r = re.match('[A-Z0-9]{3}', s)
    if not r:
        raise ValidationError('Caracteres inválidos al final del RFC')

    s = value[l:l+6]
    r = re.match('[0-9]{6}', s)
    msg = 'Fecha inválida en el RFC'
    if not r:
        raise ValidationError(msg)

    try:
        datetime.strptime(s,"%y%m%d")
    except:
        raise ValidationError(msg)


class RFCField(models.CharField):
    description = 'Field to RFC of México'
    default_validators = [MinLengthValidator(12), validate_rfc]

    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = 13
        super().__init__(*args, **kwargs)

    def to_python(self, value):
        return value.upper()


class Clients(models.Model):
    rfc = RFCField('RFC', unique=True)
    token = models.CharField('Token', max_length=100)
    key = models.TextField('Key', default='', blank=True)
    cer = models.TextField('Cer', default='', blank=True)
    serial_number = models.CharField('Fiel Serie', default='', blank=True, max_length=100)
    date_from = models.DateTimeField('Desde', null=True, blank=True)
    date_to = models.DateTimeField('Hasta', null=True, blank=True)

    class Meta:
        ordering = ['rfc']
        verbose_name = 'Cliente'
        verbose_name_plural = 'Clientes'

    def __str__(self):
        return self.rfc