from django.db import models
from django.core.exceptions import ValidationError
from django.utils.translation import gettext as _

class Visitor(models.Model):
    """
    Stores information about a visitor of this application.
    No personal information is gathered, the name is optional and can be anything.
    The name has to be unique, tho.
    """
    session_id = models.CharField(
        _('A cookie set by this application to identify a visitor by session'),
        max_length=50
    )
    name = models.CharField(
        _('Human readable, self assigned name of the visitor'),
        null=True,
        default=None,
        max_length=50,
        unique=True
    )


class Gallery(models.Model):
    """
    A gallery is a collection of multiple images.
    It must be 
    """
    title = models.CharField(
        _('Optional title for this gallery'),
        null=True,
        max_length=100
    )
    private = models.BooleanField(
        _('Wether the gallery is vsibile publicly or to certain users only'),
        default=False,
        blank=True
    )
    access_code = models.CharField(
        _('Code to access private galleries'),
        null=True,
        max_length=32
    )

    created_by = models.ForeignKey(
        Visitor,
        verbose_name=_('Visitor who created the gallery'),
        related_name='created_galleries',
        on_delete=models.CASCADE
    )
        
    visitors = models.ManyToManyField(
        Visitor,
        verbose_name=_('Visitors that a part of this gallery'),
        related_name='linked_galleries'
    )

    def clean(self):
        if self.private and access_code is None:
            raise ValidationErrorr('Private gallery needs an access code')
        if len(self.visitors.all()) > 10:
            raise ValidationError('Gallery can not have more than 10 visitors assigned')


class Image(models.Model):
    """
    An image contains the path to the image file and several information
    like description, uploader and affiliation to galleries.
    """
    description = models.TextField(
        _('An optional description of the Image'),
        null=True
    )
    image_file = models.ImageField(
        _('File of the image'),
        upload_to='web_galleries/uploads/'
    )

    private = models.BooleanField(
        _('Wether this image is visible publicly or to certain users only'),
        default=False,
        blank=True
    )
    access_code = models.CharField(
        _('Code to access private images'),
        null=True,
        max_length=32
    )

    uploaded_by = models.ForeignKey(
        Visitor,
        verbose_name=_('Which visitor uploaded this picture'),
        null=True,
        related_name='uploaded_images',
        on_delete=models.SET_NULL
    )
    uploaded_when = models.DateTimeField(
        _('When this picture was uploaded'),
        auto_now_add=True
    )

    galleries = models.ManyToManyField(
        Gallery,
        verbose_name=_('What galleries this image is in'),
        related_name='images'
    )