from __future__ import unicode_literals

from django.contrib.auth.models import User
from django.db import models
from django.utils.encoding import python_2_unicode_compatible


@python_2_unicode_compatible
class Book(models.Model):
    title = models.CharField(max_length=50)
    year = models.PositiveIntegerField(null=True, blank=True)
    author = models.ForeignKey(User, verbose_name="Verbose Author", related_name='books_authored', blank=True, null=True)
    contributors = models.ManyToManyField(User, verbose_name="Verbose Contributors", related_name='books_contributed', blank=True, null=True)
    is_best_seller = models.NullBooleanField(default=0)
    date_registered = models.DateField(null=True)
    no = models.IntegerField(verbose_name='number', blank=True, null=True)  # This field is intentionally 2 characters long. See #16080.

    def __str__(self):
        return self.title


@python_2_unicode_compatible
class Department(models.Model):
    code = models.CharField(max_length=4, unique=True)
    description = models.CharField(max_length=50, blank=True, null=True)

    def __str__(self):
        return self.description


@python_2_unicode_compatible
class Employee(models.Model):
    department = models.ForeignKey(Department, to_field="code")
    name = models.CharField(max_length=100)

    def __str__(self):
        return self.name
