from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.utils.text import slugify
from apps.core.history import TrackedModel
import pghistory


@pghistory.track()
class SlugHistory(models.Model):
    """
    Model for tracking slug changes across all models that use slugs.
    Uses generic relations to work with any model.
    """

    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.CharField(
        max_length=50
    )  # Using CharField to work with our custom IDs
    content_object = GenericForeignKey("content_type", "object_id")

    old_slug = models.SlugField(max_length=200)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        indexes = [
            models.Index(fields=["content_type", "object_id"]),
            models.Index(fields=["old_slug"]),
        ]
        verbose_name_plural = "Slug histories"
        ordering = ["-created_at"]

    def __str__(self):
        return f"Old slug '{self.old_slug}' for {self.content_object}"


class SluggedModel(TrackedModel):
    """
    Abstract base model that provides slug functionality with history tracking.
    """

    name = models.CharField(max_length=200)
    slug = models.SlugField(max_length=200, unique=True)

    class Meta(TrackedModel.Meta):
        abstract = True

    def save(self, *args, **kwargs):
        # Get the current instance from DB if it exists
        if self.pk:
            try:
                old_instance = self.__class__.objects.get(pk=self.pk)
                # If slug has changed, save the old one to history
                if old_instance.slug != self.slug:
                    SlugHistory.objects.create(
                        content_type=ContentType.objects.get_for_model(self),
                        object_id=getattr(self, self.get_id_field_name()),
                        old_slug=old_instance.slug,
                    )
            except self.__class__.DoesNotExist:
                pass

        # Generate slug if not set
        if not self.slug:
            self.slug = slugify(self.name)

        super().save(*args, **kwargs)

    def get_id_field_name(self):
        """
        Returns the name of the read-only ID field for this model.
        Should be overridden by subclasses.
        """
        raise NotImplementedError(
            "Subclasses of SluggedModel must implement get_id_field_name()"
        )

    @classmethod
    def get_by_slug(cls, slug):
        """
        Get an object by its current or historical slug.
        Returns (object, is_old_slug) tuple.
        """
        try:
            # Try to get by current slug first
            return cls.objects.get(slug=slug), False
        except cls.DoesNotExist:
            # Check pghistory first if available
            try:
                import pghistory.models

                history_entries = pghistory.models.Events.objects.filter(
                    pgh_model=f"{cls._meta.app_label}.{cls._meta.model_name}", slug=slug
                ).order_by("-pgh_created_at")

                if history_entries:
                    history_entry = history_entries.first()
                    if history_entry:
                        return cls.objects.get(id=history_entry.pgh_obj_id), True
            except (ImportError, AttributeError):
                pass

            # Try to find in manual slug history as fallback
            history = (
                SlugHistory.objects.filter(
                    content_type=ContentType.objects.get_for_model(cls),
                    old_slug=slug,
                )
                .order_by("-created_at")
                .first()
            )

            if history:
                return (
                    cls.objects.get(**{cls().get_id_field_name(): history.object_id}),
                    True,
                )

            raise cls.DoesNotExist(f"{cls.__name__} with slug '{slug}' does not exist")