"""DOC-003: Dokument-Versionierung - vorgaenger_id verkettet Versionen.

Revision ID: 0027_dokument_versionierung
Revises: 0026_dokumenttyp
Create Date: 2026-09-08
"""
from typing import Sequence, Union

from alembic import op

revision: str = "0027_dokument_versionierung"
down_revision: Union[str, None] = "0026_dokumenttyp"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.execute(
        "ALTER TABLE dokument ADD COLUMN vorgaenger_id UUID REFERENCES dokument(id)"
    )
    op.execute("CREATE INDEX ix_dokument_vorgaenger_id ON dokument (vorgaenger_id)")


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS ix_dokument_vorgaenger_id")
    op.execute("ALTER TABLE dokument DROP COLUMN vorgaenger_id")