from django.db import models


class Library(models.Model):
    LIBRARY_NAME_MAX_LEN = 30

    library_name = models.CharField(
         max_length=LIBRARY_NAME_MAX_LEN,
         null=False,
         blank=False,
         verbose_name="Library Name"
    )

    def __str__(self):
        return self.library_name

    class Meta:
        verbose_name_plural = 'Library'


class Book(models.Model):
    TITLE_MAX_LEN = 30
    AUTHOR_MAX_LEN = 30
    DESCRIPTION_LEN = 300

    title = models.CharField(
        max_length=TITLE_MAX_LEN,
        null=False,
        blank=False,
    )

    pages = models.PositiveIntegerField(
        null=False,
        blank=False,
    )

    description = models.TextField(
        max_length=DESCRIPTION_LEN,
        null=False,
        blank=False,
    )

    author = models.CharField(
        max_length=AUTHOR_MAX_LEN,
        null=False,
        blank=False
    )

    library = models.ForeignKey(
        Library,
        on_delete=models.CASCADE,
        null=True,
        blank=True
    )

    def __str__(self):
        return self.title

    class Meta:
        verbose_name_plural = 'Book'