"""Add recurrence fields to calendar_events

Revision ID: 007
Revises: 006
Create Date: 2026-02-22 00:00:00.000000

"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision: str = '007'
down_revision: Union[str, None] = '006'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # parent_event_id: self-referential FK, nullable, ON DELETE CASCADE
    op.add_column(
        'calendar_events',
        sa.Column('parent_event_id', sa.Integer(), nullable=True)
    )
    op.create_foreign_key(
        'fk_calendar_events_parent_event_id',
        'calendar_events',
        'calendar_events',
        ['parent_event_id'],
        ['id'],
        ondelete='CASCADE',
    )

    # is_recurring: tracks whether this row is part of a recurring series
    op.add_column(
        'calendar_events',
        sa.Column(
            'is_recurring',
            sa.Boolean(),
            nullable=False,
            server_default='false',
        )
    )

    # original_start: the originally computed occurrence datetime (naive, no TZ)
    op.add_column(
        'calendar_events',
        sa.Column('original_start', sa.DateTime(), nullable=True)
    )


def downgrade() -> None:
    op.drop_column('calendar_events', 'original_start')
    op.drop_column('calendar_events', 'is_recurring')
    op.drop_constraint(
        'fk_calendar_events_parent_event_id',
        'calendar_events',
        type_='foreignkey',
    )
    op.drop_column('calendar_events', 'parent_event_id')