from datetime import date
import os

from django.db import models, transaction
from django.conf import settings
from django.core.exceptions import ValidationError
from django.utils import timezone
from django.utils.encoding import python_2_unicode_compatible
from django.utils.translation import ugettext as _

from model_utils.models import TimeStampedModel

from passlib.hash import sha512_crypt
from passlib.utils import generate_password


class GroupManager(models.Manager):

    def get_next_gid(self):
        q = self.aggregate(models.Max('gid'))
        if q['gid__max'] is None:
            return settings.OSUSER_MINGID
        return max(settings.OSUSER_MINGID, q['gid__max'] + 1)


@python_2_unicode_compatible
class Group(TimeStampedModel, models.Model):
    groupname = models.CharField(
        _('Group name'), max_length=16, unique=True)
    gid = models.PositiveSmallIntegerField(
        _('Group ID'), unique=True, primary_key=True)
    descr = models.TextField(_('Description'), blank=True)
    passwd = models.CharField(
        _('Group password'), max_length=128, blank=True)

    objects = GroupManager()

    class Meta:
        verbose_name = _('Group')
        verbose_name_plural = _('Groups')

    def __str__(self):
        return '{0} ({1})'.format(self.groupname, self.gid)


class UserManager(models.Manager):

    def get_next_uid(self):
        q = self.aggregate(models.Max('uid'))
        if q['uid__max'] is None:
            return settings.OSUSER_MINUID
        return max(settings.OSUSER_MINUID, q['uid__max'] + 1)

    def get_next_username(self):
        count = 1
        usernameformat = "{0}{1:02d}"
        nextuser = usernameformat.format(settings.OSUSER_USERNAME_PREFIX,
                                         count)
        for user in self.values('username').filter(
            username__startswith=settings.OSUSER_USERNAME_PREFIX).order_by(
                'username'):
            if user == nextuser:
                count += 1
                nextuser = usernameformat.format(
                    settings.OSUSER_USERNAME_PREFIX, count)
            else:
                break
        return nextuser

    def create_user(self, username=None, password=None):
        uid = self.get_next_uid()
        gid = Group.objects.get_next_gid()
        if username is None:
            username = self.get_next_username()
        if password is None:
            password = generate_password()
        homedir = os.path.join(settings.OSUSER_HOME_BASEPATH, username)
        autocommit = transaction.get_autocommit()
        if autocommit:
            transaction.set_autocommit(False)
        group = Group.objects.create(groupname=username, gid=gid)
        user = self.create(username=username, group=group, uid=uid,
                           homedir=homedir,
                           shell=settings.OSUSER_DEFAULT_SHELL)
        shadow = Shadow.objects.create_shadow(user=user, password=password)
        user.save()
        shadow.save()
        transaction.commit()
        if autocommit:
            transaction.set_autocommit(True)
        return user


@python_2_unicode_compatible
class User(TimeStampedModel, models.Model):
    username = models.CharField(
        _('User name'), max_length=64, unique=True)
    uid = models.PositiveSmallIntegerField(
        _('User ID'), unique=True, primary_key=True)
    group = models.ForeignKey(Group, verbose_name=_('Group'))
    gecos = models.CharField(_('Gecos field'), max_length=128, blank=True)
    homedir = models.CharField(_('Home directory'), max_length=256)
    shell = models.CharField(_('Login shell'), max_length=64)

    objects = UserManager()

    class Meta:
        verbose_name = _('User')
        verbose_name_plural = _('Users')

    def __str__(self):
        return '{0} ({1})'.format(self.username, self.uid)


class ShadowManager(models.Manager):

    def create_shadow(self, user, password):
        changedays = (timezone.now().date() - date(1970, 1, 1)).days
        pwhash = sha512_crypt.encrypt(password)
        shadow = self.create(
            user=user, changedays=changedays,
            minage=0, maxage=None, gracedays=7,
            inactdays=30, expiredays=None, passwd=pwhash
        )
        shadow.save()
        return shadow


@python_2_unicode_compatible
class Shadow(TimeStampedModel, models.Model):
    user = models.OneToOneField(User, primary_key=True, verbose_name=_('User'))
    passwd = models.CharField(_('Encrypted password'), max_length=128)
    changedays = models.PositiveSmallIntegerField(
        _('Date of last change'),
        help_text=_('This is expressed in days since Jan 1, 1970'),
        blank=True, null=True)
    minage = models.PositiveSmallIntegerField(
        _('Minimum age'),
        help_text=_('Minimum number of days before the password can be'
                    ' changed'),
        blank=True, null=True)
    maxage = models.PositiveSmallIntegerField(
        _('Maximum age'),
        help_text=_('Maximum number of days after which the password has to'
                    ' be changed'),
        blank=True, null=True)
    gracedays = models.PositiveSmallIntegerField(
        _('Grace period'),
        help_text=_('The number of days before the password is going to'
                    ' expire'),
        blank=True, null=True)
    inactdays = models.PositiveSmallIntegerField(
        _('Inactivity period'),
        help_text=_('The number of days after the password has expired during'
                    ' which the password should still be accepted'),
        blank=True, null=True)
    expiredays = models.PositiveSmallIntegerField(
        _('Account expiration date'),
        help_text=_('The date of expiration of the account, expressed as'
                    ' number of days since Jan 1, 1970'),
        blank=True, null=True, default=None)

    objects = ShadowManager()

    class Meta:
        verbose_name = _('Shadow password')
        verbose_name_plural = _('Shadow passwords')

    def __str__(self):
        return 'for user {0}'.format(self.user)


@python_2_unicode_compatible
class AdditionalGroup(TimeStampedModel, models.Model):
    user = models.ForeignKey(User)
    group = models.ForeignKey(Group)

    class Meta:
        unique_together = ('user', 'group')
        verbose_name = _('Additional group')
        verbose_name_plural = _('Additional groups')

    def clean(self):
        if self.user.group == self.group:
            raise ValidationError(_(
                "You can not use a user's primary group."))

    def __str__(self):
        return '{0} in {1}'.format(self.user, self.group)