"""NL2SQL 安全 EXPLAIN 辅助函数。"""
from __future__ import annotations

from nl2sql.sql_security import ValidatedSql


def build_explain_sql(validated_sql: ValidatedSql) -> str:
    """只为已通过安全校验的 SELECT 构造 EXPLAIN 语句。"""
    if not isinstance(validated_sql, ValidatedSql):
        raise TypeError("EXPLAIN 只接受已校验 SQL")
    return f"EXPLAIN {validated_sql.sql}"