import mysql, { type Pool, type PoolConnection, type RowDataPacket } from "mysql2/promise";

let pool: Pool | undefined;

export function getPool(): Pool {
  if (!pool) {
    const databaseUrl = process.env.DATABASE_URL;
    if (!databaseUrl) throw new Error("DATABASE_URL is not set");
    const url = new URL(databaseUrl);
    pool = mysql.createPool({
      host: url.hostname,
      port: url.port ? Number(url.port) : 3306,
      user: decodeURIComponent(url.username),
      password: decodeURIComponent(url.password),
      database: decodeURIComponent(url.pathname.replace(/^\//, "")),
      connectionLimit: 10,
      dateStrings: true,
      timezone: "Z",
      charset: "utf8mb4",
      supportBigNumbers: true,
      multipleStatements: false,
    });
  }
  return pool;
}

export async function closePool(): Promise<void> {
  if (!pool) return;
  await pool.end();
  pool = undefined;
}

export async function withTransaction<T>(fn: (conn: PoolConnection) => Promise<T>): Promise<T> {
  const conn = await getPool().getConnection();
  try {
    await conn.beginTransaction();
    const result = await fn(conn);
    await conn.commit();
    return result;
  } catch (error) {
    await conn.rollback();
    throw error;
  } finally {
    conn.release();
  }
}

export type { RowDataPacket };