lostplaces-backend/lostplaces/lostplaces_app/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.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.name
        
@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 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 (models.Model):
    """
    Place defines a lost place (location, name, description etc.).
    """

    name = models.CharField(max_length=50)
    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='places'
    )
    location = models.CharField(max_length=50)
    latitude = models.FloatField(
        validators=[
            MinValueValidator(-90),
            MaxValueValidator(90)
        ]
    )
    longitude = models.FloatField(
        validators=[
            MinValueValidator(-180),
            MaxValueValidator(180)
        ]
    )
    description = models.TextField()

    tags = TaggableManager(blank=True)

    # Get center position of LP-geocoordinates.
    def average_latlon(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 / amount, longitude / amount)

        return (latitude, 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 (models.Model):
    """
    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='images'
    )
    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='images'
    )

    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
    )