from django.db import models
from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin, UserManager, Group
from django.utils.translation import ugettext_lazy as _
from django.utils import timezone
from django.core import validators
from django.core.exceptions import ValidationError
from datetime import datetime

class User(AbstractBaseUser, PermissionsMixin):
    """
    Defines the base user class, useable in every app

    This is almost the same as the auth module AbstractUser since it inherits from it,
    but some fields are required, and the username is generated automatically with the
    name of the user (see generate_username()).

    Added field: nick_name, date_of_birth
    Required fields: email, first_name, last_name, date_of_birth
    """
    username = models.CharField(
        _('username'),
        max_length=254,
        unique=True,
        help_text=_('Required. 254 characters or fewer. Letters, digits and @/./+/-/_ only.'),
        validators=[
            validators.RegexValidator(
                r'^[\w.@+-]+$',
                _('Enter a valid username. This value may contain only '
                  'letters, numbers ' 'and @/./+/-/_ characters.')
            ),
        ],
        error_messages={
            'unique': _("A user with that username already exists."),
        },
    )
    first_name = models.CharField(_('first name'), max_length=30)
    last_name = models.CharField(_('last name'), max_length=30)
    email = models.EmailField(_('email address'), unique=True)
    date_of_birth = models.DateTimeField(_('date of birth'))
    nick_name = models.CharField(max_length=30, blank=True)
    is_staff = models.BooleanField(
        _('staff status'),
        default=False,
        help_text=_('Designates whether the user can log into this admin site.'),
    )
    is_active = models.BooleanField(
        _('active'),
        default=True,
        help_text=_(
            'Designates whether this user should be treated as active. '
            'Unselect this instead of deleting accounts.'
        ),
    )
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)

    objects = UserManager()

    USERNAME_FIELD = 'username'
    REQUIRED_FIELDS = ['email', 'first_name', 'last_name', 'date_of_birth']

    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')

    def __str__(self):
        return self.username

    def get_full_name(self):
        """
        Returns the first_name plus the last_name, with a space in between.
        """
        full_name = '%s %s' % (self.first_name, self.last_name)
        return full_name.strip()

    def get_short_name(self):
        "Returns the short name for the user."
        return self.first_name

    def get_display_name(self):
        """
        Returns the display name of the user.
        A nickname if possible, otherwise, the full name
        """
        if self.nick_name != "":
            return self.nick_name
        return self.get_full_name()

    def email_user(self, subject, message, from_email=None, **kwargs):
        """
        Sends an email to this User.
        """
        send_mail(subject, message, from_email, [self.email], **kwargs)

    def generate_username(self):
        """
        Generates a unique username based on the first and last names.
        For example: Guy Carlier gives gcarlier, and gcarlier1 if the first one exists
        Returns the generated username
        """
        user_name = str(self.first_name[0]+self.last_name).lower()
        un_set = [u.username for u in User.objects.all()]
        if user_name in un_set:
            i = 1
            while user_name+str(i) in un_set:
                i += 1
            user_name += str(i)
        self.username = user_name
        return user_name


class Page(models.Model):
    """
    The page class to build a Wiki
    Each page may have a parent and it's URL is of the form my.site/page/<grd_pa>/<parent>/<mypage>
    It has an ID field, but don't use it, since it's only there for DB part, and because compound primary key is
    awkward!
    Prefere querying pages with Page.get_page_by_full_name()

    Be careful with the full_name attribute: this field may not be valid until you call save(). It's made for fast
    query, but don't rely on it when playing with a Page object, use get_full_name() instead!
    """
    name = models.CharField(_('page name'), max_length=30, blank=False)
# TODO: move title and content to PageRev class with a OneToOne field
    title = models.CharField(_("page title"), max_length=255, blank=True)
    content = models.TextField(_("page content"), blank=True)
    revision = models.PositiveIntegerField(_("current revision"), default=1)
    is_locked = models.BooleanField(_("page mutex"), default=False)
    parent = models.ForeignKey('self', related_name="children", null=True, blank=True, on_delete=models.SET_NULL)
    # Attention: this field may not be valid until you call save(). It's made for fast query, but don't rely on it when
    # playing with a Page object, use get_full_name() instead!
    full_name = models.CharField(_('page name'), max_length=255, blank=True)

    owner_group = models.ForeignKey(Group, related_name="owned_pages", default=1)
    edit_group = models.ForeignKey(Group, related_name="editable_pages", default=1)
    view_group = models.ForeignKey(Group, related_name="viewable_pages", default=1)

    class Meta:
        unique_together = ('name', 'parent')
        permissions = (
            #("can_edit", "Can edit the page"),
            #("can_view", "Can view the page"),
        )

    @staticmethod
    def get_page_by_full_name(name):
        """
        Quicker to get a page with that method rather than building the request every time
        """
        return Page.objects.filter(full_name=name).first()

    def __init__(self, *args, **kwargs):
        super(Page, self).__init__(*args, **kwargs)

    def clean(self):
        """
        Cleans up only the name for the moment, but this can be used to make any treatment before saving the object
        """
        if '/' in self.name:
            self.name = self.name.split('/')[-1]
        if Page.objects.exclude(pk=self.pk).filter(full_name=self.get_full_name()).exists():
            raise ValidationError(
                _('Duplicate page'),
                code='duplicate',
            )
        super(Page, self).clean()

    def save(self, *args, **kwargs):
        self.full_clean()
        # This reset the full_name just before saving to maintain a coherent field quicker for queries than the
        # recursive method
        # It also update all the children to maintain correct names
        self.full_name = self.get_full_name()
        for c in self.children.all():
            c.save()
        super(Page, self).save(*args, **kwargs)

    def __str__(self):
        return self.get_full_name()

    def get_full_name(self):
        """
        Computes the real full_name of the page based on its name and its parent's name
        You can and must rely on this function when working on a page object that is not freshly fetched from the DB
        (For example when treating a Page object coming from a form)
        """
        if self.parent is None:
            return self.name
        return '/'.join([self.parent.get_full_name(), self.name])

    def get_display_name(self):
        return self.get_full_name()