"""
Shared abstract base model.
Every model that needs audit trail inherits from TimeStampedModel.

Fields added:
  created_by  – FK to the user who created the record
  updated_by  – FK to the user who last updated it
  deleted_by  – FK to the user who soft-deleted it (null = not deleted)
  created_at  – auto timestamp on creation
  updated_at  – auto timestamp on every save
  deleted_at  – soft-delete timestamp (null = active)
"""
from django.db import models
from django.conf import settings


class TimeStampedModel(models.Model):
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True, blank=True,
        on_delete=models.SET_NULL,
        related_name='%(app_label)s_%(class)s_created',
    )
    updated_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True, blank=True,
        on_delete=models.SET_NULL,
        related_name='%(app_label)s_%(class)s_updated',
    )
    deleted_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True, blank=True,
        on_delete=models.SET_NULL,
        related_name='%(app_label)s_%(class)s_deleted',
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    deleted_at = models.DateTimeField(null=True, blank=True)

    class Meta:
        abstract = True

    @property
    def is_deleted(self):
        return self.deleted_at is not None

    def soft_delete(self, user=None):
        from django.utils import timezone
        self.deleted_at = timezone.now()
        self.deleted_by = user
        self.save(update_fields=['deleted_at', 'deleted_by', 'updated_at'])

    def restore(self):
        self.deleted_at = None
        self.deleted_by = None
        self.save(update_fields=['deleted_at', 'deleted_by', 'updated_at'])


class ActiveManager(models.Manager):
    """Default manager that hides soft-deleted rows."""
    def get_queryset(self):
        return super().get_queryset().filter(deleted_at__isnull=True)


class AllObjectsManager(models.Manager):
    """Manager that includes soft-deleted rows."""
    def get_queryset(self):
        return super().get_queryset()