from datetime import UTC, datetime

from app import db


class SoftDeleteMixin:
    """Mixin that provides soft-delete functionality.

    Instead of removing rows from the database, records are marked with
    status='deleted' and a deleted_at timestamp. This preserves data
    integrity and supports audit/recovery use-cases.

    Usage:
        class MyModel(db.Model, SoftDeleteMixin):
            ...

        # Queries
        MyModel.active().filter_by(name="foo").all()

        # Soft-delete
        instance = db.session.get(MyModel, 1)
        instance.soft_delete()
        db.session.commit()

        # Restore
        instance.restore()
        db.session.commit()

    For relationship filtering:
        class Parent(db.Model, SoftDeleteMixin):
            children = db.relationship(
                "Child",
                primaryjoin="and_(Parent.id == Child.parent_id, "
                            "Child.status == 'active')",
                ...
            )
    """

    STATUS_ACTIVE = "active"
    STATUS_DELETED = "deleted"

    status = db.Column(
        db.String(20),
        default=STATUS_ACTIVE,
        nullable=False,
        index=True,
    )
    deleted_at = db.Column(db.DateTime, nullable=True)

    @classmethod
    def active(cls):
        """Return a query scoped to non-deleted records only.

        Usage:
            Board.active().filter_by(user_id=1).all()
            Card.active().order_by(Card.pos).all()
        """
        return cls.query.filter(cls.status == cls.STATUS_ACTIVE)

    @property
    def is_active(self):
        """Check if this record is active (not soft-deleted)."""
        return self.status == self.STATUS_ACTIVE

    def soft_delete(self):
        """Mark this record as deleted and cascade to child relationships.

        Every relationship defined with cascade="all, delete-orphan" or
        cascade="all" is considered a *soft-deletable child* and will also
        be soft-deleted recursively.
        """
        self._do_soft_delete()

    def _do_soft_delete(self):
        """Internal recursive soft-delete implementation."""
        now = datetime.now(UTC)

        # Soft-delete children from configured cascade relationships
        for prop in self.__mapper__.relationships:
            cascade = prop.cascade
            if cascade is None:
                continue

            # Only cascade to relationships that had delete/delete-orphan
            if not (cascade.delete or cascade.delete_orphan):
                continue

            # Get the related objects
            children = getattr(self, prop.key, None)
            if children is None:
                continue

            # Handle dynamic/lazy relationships (query-like)
            if hasattr(children, "all"):
                children = children.all()

            # Handle single (many-to-one / scalar) relationships
            if not isinstance(children, list):
                children = [children] if children else []

            for child in children:
                if isinstance(child, SoftDeleteMixin):
                    child._do_soft_delete()

        self.status = self.STATUS_DELETED
        self.deleted_at = now

    def restore(self):
        """Restore a soft-deleted record and cascade to children."""
        self._do_restore()

    def _do_restore(self):
        """Internal recursive restore implementation."""
        for prop in self.__mapper__.relationships:
            cascade = prop.cascade
            if cascade is None:
                continue

            if not (cascade.delete or cascade.delete_orphan):
                continue

            children = getattr(self, prop.key, None)
            if children is None:
                continue

            if hasattr(children, "all"):
                children = children.all()

            if not isinstance(children, list):
                children = [children] if children else []

            for child in children:
                if isinstance(child, SoftDeleteMixin):
                    child._do_restore()

        self.status = self.STATUS_ACTIVE
        self.deleted_at = None