import type { Request, Response, NextFunction } from "express";

interface AppError extends Error {
  statusCode?: number;
  details?: unknown;
}

/** Create a typed error with status code. */
export function createError(message: string, statusCode: number, details?: unknown): AppError {
  const err: AppError = new Error(message);
  err.statusCode = statusCode;
  err.details = details;
  return err;
}

/** Express error-handling middleware — must be mounted last. */
export function errorHandler(
  err: AppError,
  _req: Request,
  res: Response,
  _next: NextFunction,
): void {
  const status = err.statusCode || 500;
  const isDev = process.env.NODE_ENV !== "production";

  console.error(`[ERROR] ${status} ${err.message}`, isDev ? err.stack : "");

  res.status(status).json({
    error: err.message || "Internal server error",
    ...(err.details ? { details: err.details } : {}),
    ...(isDev && err.stack ? { stack: err.stack } : {}),
  });
}