/**
 * 从旧库直连读取数据，返回与 loadLegacyDump 一致的结构。
 * 仅 migrate.ts 的 --from-db 模式使用。
 */

import mysql from 'mysql2/promise';
import { LEGACY_COLUMNS, type LegacyTable } from './columns';
import type { LegacyRows } from './load';
import type { SqlValue } from './parser';

export async function loadLegacyDb(url: string): Promise<LegacyRows> {
  if (!url) throw new Error('缺少 LEGACY_DATABASE_URL');
  const conn = await mysql.createConnection(url);
  try {
    const result = {} as LegacyRows;
    for (const table of Object.keys(LEGACY_COLUMNS) as LegacyTable[]) {
      const [rows] = await conn.query(`SELECT * FROM \`${table}\``);
      result[table] = (rows as Record<string, unknown>[]).map((row) => {
        const obj: Record<string, SqlValue> = {};
        for (const col of LEGACY_COLUMNS[table]) {
          const v = row[col];
          obj[col] = v === null || v === undefined ? null : (v as SqlValue);
        }
        return obj;
      });
    }
    return result;
  } finally {
    await conn.end();
  }
}