"""series_page pending staging: status + nullable page_number (#789 Phase 2)

Pages added from a post no longer append straight into the run — they land
'pending' with a NULL page_number, staged grouped by their source post so the
operator can drop junk (text-free alts, bumpers) and place the keepers into the
sequence. A page only gets a series-global page_number once it's 'placed'.

Revision ID: 0048
Revises: 0047
Create Date: 2026-06-11

"""
from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

revision: str = "0048"
down_revision: Union[str, None] = "0047"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column(
        "series_page",
        sa.Column(
            "status", sa.String(length=16), nullable=False,
            server_default="placed",
        ),
    )
    op.alter_column(
        "series_page", "page_number",
        existing_type=sa.Integer(), nullable=True,
    )


def downgrade() -> None:
    # Lossy: pending pages are unsorted staging rows with no order — drop them.
    op.execute("DELETE FROM series_page WHERE status = 'pending'")
    op.alter_column(
        "series_page", "page_number",
        existing_type=sa.Integer(), nullable=False,
    )
    op.drop_column("series_page", "status")
