import uuid

from django.db import models


class SourceSystem(models.Model):
    """External system that supplies observations and business events."""

    code = models.SlugField("Код", max_length=64, unique=True)
    name = models.CharField("Название", max_length=128)
    is_active = models.BooleanField("Активен", default=True)
    metadata = models.JSONField("Настройки без секретов", default=dict, blank=True)
    created_at = models.DateTimeField("Создано", auto_now_add=True)
    updated_at = models.DateTimeField("Обновлено", auto_now=True)

    class Meta:
        verbose_name = "Источник данных"
        verbose_name_plural = "Источники данных"
        ordering = ["name"]

    def __str__(self):
        return self.name


class SourceRecord(models.Model):
    """Latest source payload retained with provenance for repeatable imports."""

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    source = models.ForeignKey(
        SourceSystem,
        on_delete=models.PROTECT,
        related_name="records",
        verbose_name="Источник",
    )
    entity_type = models.CharField("Тип объекта", max_length=64)
    external_id = models.CharField("Внешний ID", max_length=255)
    payload = models.JSONField("Исходные данные", default=dict)
    payload_hash = models.CharField("Хеш данных", max_length=64, editable=False)
    source_updated_at = models.DateTimeField(
        "Изменено в источнике", null=True, blank=True
    )
    received_at = models.DateTimeField("Получено", auto_now=True)
    created_at = models.DateTimeField("Создано", auto_now_add=True)

    class Meta:
        verbose_name = "Исходная запись"
        verbose_name_plural = "Исходные записи"
        constraints = [
            models.UniqueConstraint(
                fields=["source", "entity_type", "external_id"],
                name="commerce_source_record_identity",
            )
        ]
        indexes = [
            models.Index(
                fields=["source", "entity_type", "source_updated_at"],
                name="commerce_source_record_sync",
            )
        ]

    def __str__(self):
        return f"{self.source.code}:{self.entity_type}:{self.external_id}"


class ProductBinding(models.Model):
    """Maps an external product/offer identifier to the canonical product."""

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    product = models.ForeignKey(
        "commerce.Product",
        on_delete=models.CASCADE,
        related_name="bindings",
        verbose_name="Товар",
    )
    source = models.ForeignKey(
        SourceSystem,
        on_delete=models.PROTECT,
        related_name="product_bindings",
        verbose_name="Источник",
    )
    external_id = models.CharField("Внешний ID", max_length=255)
    external_sku = models.CharField(
        "Артикул в источнике", max_length=128, blank=True, db_index=True
    )
    is_primary = models.BooleanField("Основная привязка", default=False)
    created_at = models.DateTimeField("Создано", auto_now_add=True)
    updated_at = models.DateTimeField("Обновлено", auto_now=True)

    class Meta:
        verbose_name = "Привязка товара"
        verbose_name_plural = "Привязки товаров"
        constraints = [
            models.UniqueConstraint(
                fields=["source", "external_id"],
                name="commerce_binding_source_external",
            )
        ]
        indexes = [
            models.Index(
                fields=["source", "external_sku"],
                name="commerce_binding_source_sku",
            )
        ]

    def __str__(self):
        return f"{self.product.sku} ← {self.source.code}:{self.external_id}"