lostplaces-backend/django_lostplaces/lostplaces/models.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

'''
(Data)models which describe the structure of data to be saved into 
database.
'''

import os
import uuid

from django.urls import reverse
from django.db import models
from django.contrib.auth.models import User
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.core.validators import MaxValueValidator, MinValueValidator
from easy_thumbnails.fields import ThumbnailerImageField
from taggit.managers import TaggableManager

# Create your models here.

class Explorer(models.Model):
    """
    Profile that is linked to the a User.
    Every user has a profile.
    """
    
    user = models.OneToOneField(
        User,
        on_delete=models.CASCADE,
        related_name='explorer'
    )

    def __str__(self):
        return self.user.username
        
@receiver(post_save, sender=User)
def create_user_profile(sender, instance, created, **kwargs):
    if created:
        Explorer.objects.create(user=instance)

@receiver(post_save, sender=User)
def save_user_profile(sender, instance, **kwargs):
    instance.explorer.save()

class Taggable(models.Model):
    '''
    This abstract model represtens an object that is taggalble
    using django-taggit
    '''
    class Meta:
        abstract = True
        
    tags = TaggableManager(blank=True)
    
class Mapable(models.Model):
    '''
    This abstract model class represents an object that can be
    displayed on a map.
    '''
    class Meta:
        abstract = True
        
    name = models.CharField(max_length=50)
    latitude = models.FloatField(
        validators=[
            MinValueValidator(-90),
            MaxValueValidator(90)
        ]
    )
    longitude = models.FloatField(
        validators=[
            MinValueValidator(-180),
            MaxValueValidator(180)
        ]
    )

class Submittable(models.Model):
    '''
    This abstract model class represents an object that can be submitted by
    an explorer.
    '''
    class Meta:
        abstract = True

    submitted_when = models.DateTimeField(auto_now_add=True, null=True)
    submitted_by = models.ForeignKey(
        Explorer,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='%(class)s'
    )

class Voucher(models.Model):
    """
    Vouchers are authorization tokens to allow the registration of new users.
    A voucher has a code, a creation and a deletion date, which are all 
    positional. Creation date is being set automatically during voucher 
    creation. 
    """

    code = models.CharField(unique=True, max_length=30)
    created_when = models.DateTimeField(auto_now_add=True)
    expires_when = models.DateTimeField()

    def __str__(self):
        return "Voucher " + str(self.code)


class Place(Submittable, Taggable, Mapable):
    """
    Place defines a lost place (location, name, description etc.).
    """

    location = models.CharField(max_length=50)
    description = models.TextField()

    def get_absolute_url(self):
        return reverse('place_detail', kwargs={'pk': self.pk})
    

    @classmethod
    # Get center position of LP-geocoordinates.
    def average_latlon(cls, place_list):
        amount = len(place_list)
        # Init fill values to prevent None
        longitude = 0
        latitude = 0

        if amount > 0:
            for place in place_list:
                longitude += place.longitude
                latitude += place.latitude
            return {'latitude':latitude / amount, 'longitude': longitude / amount}

        return {'latitude': latitude, 'longitude': longitude}

    def __str__(self):
        return self.name


def generate_image_upload_path(instance, filename):
    """
    Callback for generating path for uploaded images.
    """

    return 'places/' + str(uuid.uuid4())+'.'+filename.split('.')[-1]


class PlaceImage (Submittable):
    """
    PlaceImage defines an image file object that points to a file in uploads/.
    Intermediate image sizes are generated as defined in SIZES.
    PlaceImage references a Place to which it belongs.
    """

    description = models.TextField(blank=True)
    filename = ThumbnailerImageField(upload_to=generate_image_upload_path)
    place = models.ForeignKey(
        Place,
        on_delete=models.CASCADE,
        related_name='placeimages'
    )
    
    def __str__(self):
        """
        Returning the name of the corresponding place + id 
        of this image as textual represntation of this instance
        """

        return ' '.join([self.place.name, str(self.pk)])

# These two auto-delete files from filesystem when they are unneeded:


@receiver(models.signals.post_delete, sender=PlaceImage)
def auto_delete_file_on_delete(sender, instance, **kwargs):
    """
    Deletes file from filesystem
    when corresponding `PlaceImage` object is deleted.
    """
    if instance.filename:
        if os.path.isfile(instance.filename.path):
            os.remove(instance.filename.path)


@receiver(models.signals.pre_save, sender=PlaceImage)
def auto_delete_file_on_change(sender, instance, **kwargs):
    """
    Deletes old file from filesystem
    when corresponding `PlaceImage` object is updated
    with new file.
    """
    if not instance.pk:
        return False

    try:
        old_file = PlaceImage.objects.get(pk=instance.pk).filename
    except PlaceImage.DoesNotExist:
        return False

    new_file = instance.filename
    if not old_file == new_file:
        if os.path.isfile(old_file.path):
            os.remove(old_file.path)


class ExternalLink(models.Model):
    url = models.URLField(max_length=200)
    label = models.CharField(max_length=100)
    submitted_by = models.ForeignKey(
        Explorer,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='external_links'
    )
    submitted_when = models.DateTimeField(auto_now_add=True, null=True)


class PhotoAlbum(ExternalLink):
    place = models.ForeignKey(
        Place,
        on_delete=models.CASCADE,
        related_name='photo_albums',
        null=True
    )