"""Add subtask support with parent_task_id

Revision ID: 002
Revises: 001
Create Date: 2026-02-15 00:00:00.000000

"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision: str = '002'
down_revision: Union[str, None] = '001'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column('project_tasks', sa.Column('parent_task_id', sa.Integer(), nullable=True))
    op.create_foreign_key(
        'fk_project_tasks_parent_task_id',
        'project_tasks',
        'project_tasks',
        ['parent_task_id'],
        ['id'],
        ondelete='CASCADE'
    )
    op.create_index('ix_project_tasks_parent_task_id', 'project_tasks', ['parent_task_id'])


def downgrade() -> None:
    op.drop_index('ix_project_tasks_parent_task_id', table_name='project_tasks')
    op.drop_constraint('fk_project_tasks_parent_task_id', 'project_tasks', type_='foreignkey')
    op.drop_column('project_tasks', 'parent_task_id')