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from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
from django.db import models
class Author(models.Model):
name = models.CharField(max_length=50, unique=True)
favorite_books = models.ManyToManyField(
"Book",
related_name="preferred_by_authors",
related_query_name="preferred_by_authors",
)
content_type = models.ForeignKey(ContentType, models.CASCADE, null=True)
object_id = models.PositiveIntegerField(null=True)
content_object = GenericForeignKey()
class Editor(models.Model):
name = models.CharField(max_length=255)
class Book(models.Model):
AVAILABLE = "available"
RESERVED = "reserved"
RENTED = "rented"
STATES = (
(AVAILABLE, "Available"),
(RESERVED, "reserved"),
(RENTED, "Rented"),
)
title = models.CharField(max_length=255)
author = models.ForeignKey(
Author,
models.CASCADE,
related_name="books",
related_query_name="book",
)
editor = models.ForeignKey(Editor, models.CASCADE)
generic_author = GenericRelation(Author)
state = models.CharField(max_length=9, choices=STATES, default=AVAILABLE)
class Borrower(models.Model):
name = models.CharField(max_length=50, unique=True)
class Reservation(models.Model):
NEW = "new"
STOPPED = "stopped"
STATES = (
(NEW, "New"),
(STOPPED, "Stopped"),
)
borrower = models.ForeignKey(
Borrower,
models.CASCADE,
related_name="reservations",
related_query_name="reservation",
)
book = models.ForeignKey(
Book,
models.CASCADE,
related_name="reservations",
related_query_name="reservation",
)
state = models.CharField(max_length=7, choices=STATES, default=NEW)
class RentalSession(models.Model):
NEW = "new"
STOPPED = "stopped"
STATES = (
(NEW, "New"),
(STOPPED, "Stopped"),
)
borrower = models.ForeignKey(
Borrower,
models.CASCADE,
related_name="rental_sessions",
related_query_name="rental_session",
)
book = models.ForeignKey(
Book,
models.CASCADE,
related_name="rental_sessions",
related_query_name="rental_session",
)
state = models.CharField(max_length=7, choices=STATES, default=NEW)
class Seller(models.Model):
name = models.CharField(max_length=255)
class Currency(models.Model):
currency = models.CharField(max_length=3)
class ExchangeRate(models.Model):
rate_date = models.DateField()
from_currency = models.ForeignKey(
Currency,
models.CASCADE,
related_name="rates_from",
)
to_currency = models.ForeignKey(
Currency,
models.CASCADE,
related_name="rates_to",
)
rate = models.DecimalField(max_digits=6, decimal_places=4)
class BookDailySales(models.Model):
book = models.ForeignKey(Book, models.CASCADE, related_name="daily_sales")
sale_date = models.DateField()
currency = models.ForeignKey(Currency, models.CASCADE)
seller = models.ForeignKey(Seller, models.CASCADE)
sales = models.DecimalField(max_digits=10, decimal_places=2)
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