"""assistant_messages.sources — keep an answer's citations with the answer

Revision ID: 518
Revises: 517

The answer card renders the mirrored Feishu docs the reply drew on, and the
employee taps 👍/👎 on that card. Handling the tap has to return a new card
(Feishu replaces the old one with whatever the callback answers), and the new
card was rebuilt from ``content`` alone — so **rating an answer deleted its
sources**. The links were never stored: they lived only in the turn that sent
the card.

Stored as JSON rather than a child table: it is a short, ordered, read-together
list (at most three ``{title, url}`` pairs — ``answer_card.MAX_DOC_LINKS``) that
nothing ever queries by, which is what JSON is for. Nullable with no backfill:
rows written before this column existed genuinely have no recorded sources, and
inventing an empty list for them would claim we know they had none.
"""
from alembic import op
import sqlalchemy as sa

revision = "518"
down_revision = "517"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.add_column(
        "assistant_messages",
        sa.Column("sources", sa.JSON(), nullable=True),
    )


def downgrade() -> None:
    op.drop_column("assistant_messages", "sources")