/**
 * Wraps an async route handler so a rejected promise reaches Express's error
 * pipeline instead of becoming an unhandled rejection. Express 4 does not await
 * handlers (this is fixed in v5, which PLANNING.md §2 explicitly rules out).
 */
import type { NextFunction, Request, Response } from 'express';

type AsyncHandler = (req: Request, res: Response, next: NextFunction) => Promise<unknown>;

export function asyncHandler(fn: AsyncHandler) {
  return (req: Request, res: Response, next: NextFunction): void => {
    Promise.resolve(fn(req, res, next)).catch(next);
  };
}