"""

Serialization

``django.core.serializers`` provides interfaces to converting Django

``QuerySet`` objects to and from "flat" data (i.e. strings).

"""

from decimal import Decimal

from django.db import models

class CategoryMetaDataManager(models.Manager):

    def get_by_natural_key(self, kind, name):

        return self.get(kind=kind, name=name)

class CategoryMetaData(models.Model):

    kind = models.CharField(max_length=10)

    name = models.CharField(max_length=10)

    value = models.CharField(max_length=10)

    objects = CategoryMetaDataManager()

    class Meta:

        unique_together = (("kind", "name"),)

    def __str__(self):

        return "[%s:%s]=%s" % (self.kind, self.name, self.value)

    def natural_key(self):

        return (self.kind, self.name)

class Category(models.Model):

    name = models.CharField(max_length=20)

    meta_data = models.ForeignKey(

        CategoryMetaData, models.SET_NULL, null=True, default=None

    )

    class Meta:

        ordering = ("name",)

    def __str__(self):

        return self.name

class Author(models.Model):

    name = models.CharField(max_length=20)

    class Meta:

        ordering = ("name",)

    def __str__(self):

        return self.name

class Article(models.Model):

    author = models.ForeignKey(Author, models.CASCADE)

    headline = models.CharField(max_length=50)

    pub_date = models.DateTimeField()

    categories = models.ManyToManyField(Category)

    meta_data = models.ManyToManyField(CategoryMetaData)

    class Meta:

        ordering = ("pub_date",)

    def __str__(self):

        return self.headline

class AuthorProfile(models.Model):

    author = models.OneToOneField(Author, models.CASCADE, primary_key=True)

    date_of_birth = models.DateField()

    def __str__(self):

        return "Profile of %s" % self.author

class Actor(models.Model):

    name = models.CharField(max_length=20, primary_key=True)

    class Meta:

        ordering = ("name",)

    def __str__(self):

        return self.name

class Movie(models.Model):

    actor = models.ForeignKey(Actor, models.CASCADE)

    title = models.CharField(max_length=50)

    price = models.DecimalField(max_digits=6, decimal_places=2, default=Decimal("0.00"))

    class Meta:

        ordering = ("title",)

    def __str__(self):

        return self.title

class Score(models.Model):

    score = models.FloatField()

class Team:

    def __init__(self, title):

        self.title = title

    def __str__(self):

        raise NotImplementedError("Not so simple")

    def to_string(self):

        return str(self.title)

class TeamField(models.CharField):

    def __init__(self):

        super().__init__(max_length=100)

    def get_db_prep_save(self, value, connection):

        return str(value.title)

    def to_python(self, value):

        if isinstance(value, Team):

            return value

        return Team(value)

    def from_db_value(self, value, expression, connection):

        return Team(value)

    def value_to_string(self, obj):

        return self.value_from_object(obj).to_string()

    def deconstruct(self):

        name, path, args, kwargs = super().deconstruct()

        del kwargs["max_length"]

        return name, path, args, kwargs

class Player(models.Model):

    name = models.CharField(max_length=50)

    rank = models.IntegerField()

    team = TeamField()

    def __str__(self):

        return "%s (%d) playing for %s" % (self.name, self.rank, self.team.to_string())

class BaseModel(models.Model):

    parent_data = models.IntegerField()

class ProxyBaseModel(BaseModel):

    class Meta:

        proxy = True

class ProxyProxyBaseModel(ProxyBaseModel):

    class Meta:

        proxy = True

class ComplexModel(models.Model):

    field1 = models.CharField(max_length=10)

    field2 = models.CharField(max_length=10)

    field3 = models.CharField(max_length=10)