"""asset_software_catalog — add long-text ``description`` column.

The catalog already has ``remark`` (备注) and ``license_info`` (License 信息),
but both are short-form TEXT fields the admin uses for one-liners. Some
software needs a genuinely long write-up — onboarding guide, what it's for,
internal policy, links — that doesn't belong in 备注. This adds a dedicated
「详细介绍」 field.

MEDIUMTEXT (16MB) rather than TEXT (64KB): the field is meant to hold long
content, and a worst-case 20K-char utf8mb4 value (the Pydantic cap) is up to
80KB, which overflows TEXT. MEDIUMTEXT removes the worry entirely.

Idempotent — re-run is a no-op via INFORMATION_SCHEMA check.

Revision ID: 328
Revises: 327
"""
# ruff: noqa: I001
from __future__ import annotations

import sqlalchemy as sa
from sqlalchemy.dialects.mysql import MEDIUMTEXT
from alembic import op

revision = "328"
down_revision = "327"
branch_labels = None
depends_on = None

TABLE = "asset_software_catalog"
COLUMN = "description"


def _column_exists(bind, table: str, column: str) -> bool:
    rows = bind.execute(
        sa.text(
            "SELECT COUNT(*) FROM information_schema.COLUMNS "
            "WHERE TABLE_SCHEMA = DATABASE() "
            "AND TABLE_NAME = :t AND COLUMN_NAME = :c"
        ),
        {"t": table, "c": column},
    ).scalar()
    return bool(rows)


def upgrade() -> None:
    bind = op.get_bind()
    if _column_exists(bind, TABLE, COLUMN):
        return
    op.add_column(TABLE, sa.Column(COLUMN, MEDIUMTEXT(), nullable=True))


def downgrade() -> None:
    bind = op.get_bind()
    if not _column_exists(bind, TABLE, COLUMN):
        return
    op.drop_column(TABLE, COLUMN)