from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models


class ExternalMapping(models.Model):
    """Maps internal entities to provider-specific IDs across namespaces."""

    provider_namespace = models.CharField(max_length=80)
    external_id = models.CharField(max_length=160)
    external_secondary_id = models.CharField(max_length=160, blank=True)

    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveBigIntegerField()
    content_object = GenericForeignKey("content_type", "object_id")

    # Raw payload is kept only for troubleshooting and parsing diagnostics.
    raw_payload = models.JSONField(default=dict, blank=True)
    last_seen_at = models.DateTimeField(auto_now=True)
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=["provider_namespace", "external_id"],
                name="uq_mapping_provider_external_id",
            ),
            models.UniqueConstraint(
                fields=["provider_namespace", "content_type", "object_id"],
                name="uq_mapping_provider_entity",
            ),
        ]
        indexes = [
            models.Index(fields=["provider_namespace", "external_id"]),
            models.Index(fields=["content_type", "object_id"]),
            models.Index(fields=["is_active"]),
        ]

    def __str__(self) -> str:
        return f"{self.provider_namespace}:{self.external_id}"