import { Request, Response, NextFunction } from 'express';
import { ZodError } from 'zod';
import { logger } from '../utils/logger';

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

export function createError(message: string, statusCode: number, code: string): AppError {
  const err: AppError = new Error(message);
  err.statusCode = statusCode;
  err.code = code;
  return err;
}

export function errorHandler(
  err: AppError,
  _req: Request,
  res: Response,
  _next: NextFunction
): void {
  const timestamp = new Date().toISOString();

  if (err instanceof ZodError) {
    res.status(400).json({
      error: err.errors.map((e) => `${e.path.join('.')}: ${e.message}`).join('; '),
      code: 'VALIDATION_ERROR',
      timestamp,
    });
    return;
  }

  const statusCode = err.statusCode ?? 500;
  const code = err.code ?? 'INTERNAL_ERROR';

  if (statusCode >= 500) {
    logger.error({ err }, 'Unhandled server error');
  }

  res.status(statusCode).json({
    error: statusCode >= 500 ? 'An internal error occurred.' : err.message,
    code,
    timestamp,
  });
}