71 lines
2.0 KiB
Python
71 lines
2.0 KiB
Python
import random
|
|
import string
|
|
from uuid import uuid4
|
|
|
|
from django.db import models
|
|
from django.utils import timezone
|
|
|
|
|
|
def generate_isbn() -> str:
|
|
"""
|
|
Generate a random ISBN number.
|
|
|
|
Returns:
|
|
A 13-digit string.
|
|
|
|
"""
|
|
digits = string.digits
|
|
return "".join(random.choice(digits) for _ in range(13))
|
|
|
|
|
|
class BookQuerySet(models.QuerySet):
|
|
"""
|
|
QuerySet class for books.
|
|
|
|
"""
|
|
|
|
def available(self) -> models.QuerySet:
|
|
"""
|
|
Get books available for a loan.
|
|
|
|
Excludes books with at least a loan whose `borrowed` field is `True`.
|
|
Given the constraints, only one loan for a book can have the `borrowed` status
|
|
to `True`.
|
|
|
|
"""
|
|
return self.exclude(loans__borrowed=True)
|
|
|
|
def late_returns(self) -> models.QuerySet:
|
|
"""
|
|
Get books that should have been returned by now.
|
|
|
|
"""
|
|
now = timezone.now()
|
|
return self.filter(loans__expected_return__lt=now, borrowed=True)
|
|
|
|
|
|
class Book(models.Model):
|
|
"""
|
|
Description of a book.
|
|
|
|
"""
|
|
|
|
uuid = models.UUIDField(default=uuid4, db_index=True, verbose_name="UUID")
|
|
isbn = models.CharField(max_length=64, default=generate_isbn, blank=False, verbose_name="ISBN")
|
|
name = models.CharField(max_length=128, blank=False, verbose_name="name")
|
|
description = models.TextField(blank=True, verbose_name="description")
|
|
registration_date = models.DateTimeField(auto_now_add=True, verbose_name="creation date")
|
|
year = models.PositiveIntegerField(default=1950, null=True, db_index=True, verbose_name="published")
|
|
authors = models.ManyToManyField("library.Author", related_name="books", verbose_name="authors")
|
|
genre = models.ForeignKey(
|
|
"library.Genre", on_delete=models.SET_NULL, null=True, related_name="books", verbose_name="genre"
|
|
)
|
|
objects = BookQuerySet.as_manager()
|
|
|
|
class Meta:
|
|
verbose_name = "book"
|
|
verbose_name_plural = "books"
|
|
|
|
def __str__(self):
|
|
return f"{self.name} ({self.isbn})"
|