import os

from django.contrib.auth.hashers import make_password
from django.core import validators
from django.core.mail import send_mail
from django.db import models
from django.utils.functional import cached_property
from django.utils.translation import ugettext_lazy as _

from orchestra.core import services

from . import settings


class SystemUserQuerySet(models.QuerySet):
    def create_user(self, username, password='', **kwargs):
        user = super(SystemUserQuerySet, self).create(username=username, **kwargs)
        user.set_password(password)
        user.save(update_fields=['password'])
        return user


class SystemUser(models.Model):
    """ System users """
    username = models.CharField(_("username"), max_length=64, unique=True,
            help_text=_("Required. 64 characters or fewer. Letters, digits and ./-/_ only."),
            validators=[
                validators.RegexValidator(r'^[\w.-]+$', _("Enter a valid username."))
            ])
    password = models.CharField(_("password"), max_length=128)
    account = models.ForeignKey('accounts.Account', verbose_name=_("Account"),
            related_name='systemusers')
    home = models.CharField(_("home"), max_length=256, blank=False,
            help_text=_("Starting location when login with this no-shell user."))
    directory = models.CharField(_("directory"), max_length=256, blank=True,
            help_text=_("Optional directory relative to user's home."))
    shell = models.CharField(_("shell"), max_length=32, choices=settings.SYSTEMUSERS_SHELLS,
            default=settings.SYSTEMUSERS_DEFAULT_SHELL)
    groups = models.ManyToManyField('self', blank=True,  symmetrical=False,
            help_text=_("A new group will be created for the user. "
                        "Which additional groups would you like them to be a member of?"))
#    is_main = models.BooleanField(_("is main"), default=False)
    is_active = models.BooleanField(_("active"), default=True,
            help_text=_("Designates whether this account should be treated as active. "
                        "Unselect this instead of deleting accounts."))
    
    objects = SystemUserQuerySet.as_manager()
    
    def __unicode__(self):
        return self.username
    
    @cached_property
    def active(self):
        try:
            return self.is_active and self.account.is_active
        except type(self).account.field.rel.to.DoesNotExist:
            return self.is_active
    
    @cached_property
    def is_main(self):
        # TODO on account delete
        # On account creation main_systemuser_id is still None
        if self.account.main_systemuser_id:
            return self.account.main_systemuser_id == self.pk
        return self.account.username == self.username
    
    @property
    def has_shell(self):
        return self.shell not in settings.SYSTEMUSERS_DISABLED_SHELLS
    
    def clean(self):
        if self.has_shell or self.is_main:
            self.home = self.get_base_home()
            self.directory = ''
    
    def set_password(self, raw_password):
        self.password = make_password(raw_password)
    
    def get_base_home(self):
        context = {
            'username': self.username,
        }
        return settings.SYSTEMUSERS_HOME % context
    
    def get_home(self):
        return os.path.join(
            self.home or self.get_base_home(),
            self.directory
        )


services.register(SystemUser)