"""Add parent_id for subtasks functionality

Revision ID: 006
Revises: 005
Create Date: 2025-06-18 17:00:00.000000

"""

from alembic import op
import sqlalchemy as sa

# revision identifiers, used by Alembic.
revision = "006"
down_revision = "005"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # Add parent_id column to todos table
    op.add_column(
        "todos",
        sa.Column("parent_id", sa.Integer(), nullable=True),
    )

    # Add foreign key constraint for self-referential relationship
    op.create_foreign_key(
        "fk_todos_parent_id",
        "todos",
        "todos",
        ["parent_id"],
        ["id"],
        ondelete="CASCADE",
    )

    # Add index for better performance
    op.create_index(op.f("ix_todos_parent_id"), "todos", ["parent_id"], unique=False)


def downgrade() -> None:
    op.drop_index(op.f("ix_todos_parent_id"), table_name="todos")
    op.drop_constraint("fk_todos_parent_id", "todos", type_="foreignkey")
    op.drop_column("todos", "parent_id")