import uuid
from pathlib import Path

from django.db import models
from django.db.models import Q
from django.db.models.functions import Lower


def product_image_upload_to(instance, filename):
    return f"commerce/products/{instance.product_id}/original/{Path(filename).name}"


def product_thumbnail_upload_to(instance, filename):
    return f"commerce/products/{instance.product_id}/thumbnails/{Path(filename).name}"


class ProductKind(models.TextChoices):
    PRODUCT = "product", "Товар"
    SERVICE = "service", "Услуга"
    BUNDLE = "bundle", "Комплект"


class Product(models.Model):
    """Canonical sellable or stockable SKU used by every data source."""

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    parent = models.ForeignKey(
        "self",
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name="variants",
        verbose_name="Родительский товар",
    )
    kind = models.CharField(
        "Тип",
        max_length=20,
        choices=ProductKind.choices,
        default=ProductKind.PRODUCT,
    )
    sku = models.CharField("Внутренний артикул", max_length=128, unique=True)
    name = models.CharField("Название", max_length=255)
    barcode = models.CharField("Штрихкод", max_length=64, blank=True, db_index=True)
    description = models.TextField("Описание", blank=True)
    is_active = models.BooleanField("Активен", default=True)
    created_at = models.DateTimeField("Создано", auto_now_add=True)
    updated_at = models.DateTimeField("Обновлено", auto_now=True)

    class Meta:
        verbose_name = "Товар"
        verbose_name_plural = "Товары"
        ordering = ["name", "sku"]
        constraints = [
            models.CheckConstraint(
                condition=~Q(parent=models.F("id")),
                name="commerce_product_not_own_parent",
            ),
            models.UniqueConstraint(
                Lower("sku"), name="commerce_product_sku_case_insensitive"
            ),
        ]
        indexes = [
            models.Index(
                fields=["is_active", "name"], name="commerce_product_active_name"
            ),
        ]

    def __str__(self):
        return f"{self.sku} — {self.name}"


class ProductImage(models.Model):
    """Locally stored image imported from an external product source."""

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    product = models.ForeignKey(
        Product,
        on_delete=models.CASCADE,
        related_name="images",
        verbose_name="Товар",
    )
    source = models.ForeignKey(
        "commerce.SourceSystem",
        on_delete=models.CASCADE,
        related_name="product_images",
        verbose_name="Источник",
    )
    external_id = models.CharField("Внешний ID", max_length=255)
    file = models.ImageField(
        "Оригинал",
        upload_to=product_image_upload_to,
        max_length=500,
    )
    thumbnail = models.ImageField(
        "Миниатюра",
        upload_to=product_thumbnail_upload_to,
        max_length=500,
        blank=True,
    )
    filename = models.CharField("Имя файла", max_length=255, blank=True)
    title = models.CharField("Название", max_length=255, blank=True)
    source_size = models.PositiveBigIntegerField("Размер в источнике", default=0)
    source_updated_at = models.DateTimeField(
        "Изменено в источнике",
        null=True,
        blank=True,
    )
    position = models.PositiveIntegerField("Позиция", default=0)
    is_primary = models.BooleanField("Основное", default=False)
    created_at = models.DateTimeField("Создано", auto_now_add=True)
    updated_at = models.DateTimeField("Обновлено", auto_now=True)

    class Meta:
        verbose_name = "Изображение товара"
        verbose_name_plural = "Изображения товаров"
        ordering = ["position", "created_at"]
        constraints = [
            models.UniqueConstraint(
                fields=["product", "source", "external_id"],
                name="commerce_product_image_identity",
            )
        ]
        indexes = [
            models.Index(
                fields=["product", "is_primary", "position"],
                name="commerce_product_image_order",
            )
        ]

    def __str__(self):
        return self.title or self.filename or self.external_id