import {
  ArgumentsHost,
  Catch,
  ExceptionFilter,
  HttpException,
  HttpStatus,
} from '@nestjs/common';
import { Response } from 'express';

/**
 * Normalizes every thrown error into the API contract's error shape:
 *   { error: { code, message, status } }
 * See docs/01-ANALYSIS-ARCHITECTURE-DB-API-MIGRATION.md section 4.
 */
@Catch()
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();

    let status = HttpStatus.INTERNAL_SERVER_ERROR;
    let code = 'INTERNAL_ERROR';
    let message = 'حدث خطأ غير متوقع، الرجاء المحاولة لاحقًا.';

    if (exception instanceof HttpException) {
      status = exception.getStatus();
      const body = exception.getResponse();
      if (typeof body === 'string') {
        message = body;
      } else if (typeof body === 'object' && body !== null) {
        const anyBody = body as Record<string, unknown>;
        message = (anyBody.message as string) ?? message;
        code = (anyBody.code as string) ?? codeFromStatus(status);
      }
    }

    response.status(status).json({
      error: { code, message, status },
    });
  }
}

function codeFromStatus(status: number): string {
  switch (status) {
    case 400:
      return 'BAD_REQUEST';
    case 401:
      return 'UNAUTHORIZED';
    case 403:
      return 'FORBIDDEN';
    case 404:
      return 'NOT_FOUND';
    case 409:
      return 'CONFLICT';
    case 429:
      return 'RATE_LIMITED';
    default:
      return 'INTERNAL_ERROR';
  }
}