import type { ErrorRequestHandler, RequestHandler } from 'express';
import { ZodError } from 'zod';

export class AppError extends Error {
  public readonly statusCode: number;
  public readonly code: string;
  public readonly details?: unknown;

  constructor(statusCode: number, code: string, message: string, details?: unknown) {
    super(message);
    this.name = 'AppError';
    this.statusCode = statusCode;
    this.code = code;
    this.details = details;
  }
}

export const notFoundHandler: RequestHandler = (req, _res, next) => {
  next(new AppError(404, 'ROUTE_NOT_FOUND', `No route found for ${req.method} ${req.originalUrl}`));
};

export const errorHandler: ErrorRequestHandler = (error, _req, res, _next) => {
  if (error instanceof ZodError) {
    res.status(400).json({
      error: {
        code: 'VALIDATION_ERROR',
        message: 'Request validation failed.',
        details: error.flatten()
      }
    });
    return;
  }

  if (error instanceof AppError) {
    res.status(error.statusCode).json({
      error: {
        code: error.code,
        message: error.message,
        details: error.details
      }
    });
    return;
  }

  const message = error instanceof Error ? error.message : 'Unknown server error';
  res.status(500).json({
    error: {
      code: 'INTERNAL_SERVER_ERROR',
      message: process.env.NODE_ENV === 'production' ? 'Unexpected server error.' : message
    }
  });
};