"""Alembic 迁移共享工具（仅用于 versions/ 下的迁移脚本）。"""

from __future__ import annotations

import sqlalchemy as sa
from alembic import op


def table_exists(table_name: str) -> bool:
    bind = op.get_bind()
    return table_name in sa.inspect(bind).get_table_names()


def has_column(table_name: str, column_name: str) -> bool:
    if not table_exists(table_name):
        return False
    bind = op.get_bind()
    columns = sa.inspect(bind).get_columns(table_name)
    return any(column["name"] == column_name for column in columns)


def add_column_if_missing(table_name: str, column: sa.Column) -> bool:
    """若列不存在则 add_column；返回是否执行了添加。"""
    if has_column(table_name, column.name):
        return False
    op.add_column(table_name, column)
    return True


def drop_column_if_exists(table_name: str, column_name: str) -> bool:
    if not has_column(table_name, column_name):
        return False
    op.drop_column(table_name, column_name)
    return True