from django.contrib.auth import get_user_model
from django.utils.translation import ugettext_lazy as _
from django.core.validators import RegexValidator
from django.core.exceptions import FieldError
from django.db import models
from communication.models import SubscriptionMixin

User = get_user_model()


class Event(SubscriptionMixin, models.Model):
    title = models.CharField(
                    _("nom de l'évènement"),
                    max_length=200,
                )
    slug = models.SlugField(
                    _('identificateur'),
                    unique=True,
                    help_text=_("Seulement des lettres, des chiffres ou"
                                "les caractères '_' ou '-'."),
                )
    created_by = models.ForeignKey(
                    User,
                    related_name="created_events",
                    editable=False,
                )
    creation_date = models.DateTimeField(
                    _('date de création'),
                    auto_now_add=True,
                )
    description = models.TextField(_('description'))
    beginning_date = models.DateTimeField(_('date de début'))
    ending_date = models.DateTimeField(_('date de fin'))

    class Meta:
        verbose_name = _("évènement")
        verbose_name_plural = _("évènements")

    def __str__(self):
        return self.title


class EventSpecificMixin(models.Model):
    """Mixin allowing for event-specific models instances
    or not (depending on whether the event field is null)"""

    event = models.ForeignKey(
        'event.Event',
        verbose_name=_("évènement"),
        help_text=_("Si spécifié, l'instance du modèle "
                    "est spécifique à l'évènement en question"),
        blank=True,
        null=True
    )

    class Meta:
        abstract = True


class Place(EventSpecificMixin, models.Model):
    name = models.CharField(
                    _("nom du lieu"),
                    max_length=200,
                )
    description = models.TextField(blank=True)

    class Meta:
        verbose_name = _("lieu")
        verbose_name_plural = _("lieux")

    def __str__(self):
        return self.name


class ActivityTag(EventSpecificMixin, models.Model):
    name = models.CharField(
                    _("nom du tag"),
                    max_length=200,
                )
    is_public = models.BooleanField(
                    help_text=_("Sert à faire une distinction dans"
                                " l'affichage selon que cela soit"
                                " destiné au public ou à l'équipe"
                                " organisatrice"),
                )
    color_regex = RegexValidator(
                regex=r'^#(?:[0-9a-fA-F]{3}){1,2}$',
                message=_("La chaîne de caractère rentrée n'est pas"
                          " une couleur en hexadécimal."),
                )
    color = models.CharField(
                    _('couleur'),
                    max_length=7,
                    validators=[color_regex],
                    help_text=_("Rentrer une couleur en hexadécimal"),
                )

    class Meta:
        verbose_name = _("tag")
        verbose_name_plural = _("tags")

    def __str__(self):
        return self.name


class AbstractActivityTemplate(SubscriptionMixin, models.Model):
    title = models.CharField(
                    _("nom de l'activité"),
                    max_length=200,
                    blank=True,
                    null=True,
                )
    # FIXME: voir comment on traite l'héritage de `event`
    event = models.ForeignKey(Event)
    is_public = models.NullBooleanField(
                    blank=True,
                )
    has_perm = models.NullBooleanField(
                    blank=True,
                )
    min_perm = models.PositiveSmallIntegerField(
                    _('nombre minimum de permanents'),
                    blank=True,
                    null=True,
                )
    max_perm = models.PositiveSmallIntegerField(
                    _('nombre maximum de permanents'),
                    blank=True,
                    null=True,
                )
    description = models.TextField(
                    _('description'),
                    help_text=_("Public, Visible par tout le monde."),
                    blank=True,
                    null=True,
                )
    remarks = models.TextField(
                    _('remarques'),
                    help_text=_("Visible uniquement par les organisateurs"),
                    blank=True,
                    null=True,
                )
    tags = models.ManyToManyField(
                    ActivityTag,
                    blank=True,
                )
    place = models.ManyToManyField(
                    Place,
                    blank=True,
                )

    class Meta:
        abstract = True


class ActivityTemplate(AbstractActivityTemplate):
    class Meta:
        verbose_name = _("template activité")
        verbose_name_plural = _("templates activité")

    def __str__(self):
        return self.title


class Activity(AbstractActivityTemplate):
    parent = models.ForeignKey(
                    ActivityTemplate,
                    related_name="children",
                )
    staff = models.ManyToManyField(
                    User,
                    related_name="in_perm_activities",
                    blank=True,
                )

    beginning = models.DateTimeField(_("heure de début"))
    end = models.DateTimeField(_("heure de fin"))

    def get_herited(self, attrname):
        inherited_fields = [f.name for f in ActivityTemplate._meta.get_fields()]
        m2m_fields = [f.name for f in ActivityTemplate._meta.get_fields()
                      if f.many_to_many]
        attr = getattr(self, attrname)
        if attrname not in inherited_fields:
            raise FieldError(
                    _("%(attrname)s n'est pas un champ héritable"),
                    params={'attrname': attrname},
                )
        elif attrname in m2m_fields:
            if attr.exists():
                return attr
            else:
                return getattr(self.parent, attrname)
        elif attr is None:
            return getattr(self.parent, attrname)
        else:
            return attr

    class Meta:
        verbose_name = _("activité")
        verbose_name_plural = _("activités")

    def __str__(self):
        return self.get_herited('title')