"""``asset_items.status`` column default ``available`` → ``idle``.

The table has carried a DDL-level ``DEFAULT 'available'`` since the
original asset migration, while the ORM model, the intake path and every
return path use ``idle``. Nothing in the app relies on the column default
(every INSERT names the column), but it is the last place that still says
"the stock status is called `available`" — and one meaning with two names
is what produced the 「可用 / 闲置」 split and, in the same family, the
frozen ``in_stock`` row that migration 454 cleaned up.

Pure metadata change: existing rows are untouched (`available` stays a
readable legacy value; 0 rows carry it in prod as of 2026-08-07).

Revision ID: 455
Revises: 454
"""
from __future__ import annotations

import logging

import sqlalchemy as sa

from alembic import op

revision = "455"
down_revision = "454"
branch_labels = None
depends_on = None

logger = logging.getLogger("alembic.runtime.migration")


def _current_default(bind) -> str | None:
    return bind.execute(
        sa.text(
            "SELECT column_default FROM information_schema.columns "
            "WHERE table_schema = DATABASE() AND table_name = 'asset_items' "
            "AND column_name = 'status'"
        )
    ).scalar()


def upgrade() -> None:
    bind = op.get_bind()
    before = _current_default(bind)
    op.execute(
        sa.text("ALTER TABLE asset_items ALTER COLUMN status SET DEFAULT 'idle'")
    )
    logger.info(
        "migration 455: asset_items.status default %r -> 'idle'", before,
    )


def downgrade() -> None:
    op.execute(
        sa.text(
            "ALTER TABLE asset_items ALTER COLUMN status SET DEFAULT 'available'"
        )
    )