"""playlist synced_video_ids (S7: 3-way merge baseline for two-way YouTube sync)

The one-directional "local wins" push is replaced by a 3-way merge that classifies each item
against the last-synced state. That needs the raw ordered id set as a baseline, not just the
`synced_fingerprint` hash. Add a nullable `synced_video_ids` (JSON list) column; NULL on every
existing row means "no baseline yet" — the first merge then unions losslessly and records one.
Forward-only in practice (a downgrade just drops the column).
"""

from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

revision: str = "0075_playlist_sync_baseline"
down_revision: Union[str, None] = "0074_download_credentials"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column("playlists", sa.Column("synced_video_ids", sa.Text(), nullable=True))


def downgrade() -> None:
    op.drop_column("playlists", "synced_video_ids")