import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';

@Injectable()
export class GraphQLValidationMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    // Only handle POST requests
    if (
      req.method === 'POST' &&
      req.headers['content-type'] === 'application/json'
    ) {
      const { query, mutation, subscription } = req.body;

      // If none of these are present, return a custom error response
      if (!query && !mutation && !subscription) {
        return res.status(400).json({
          errors: [
            {
              message:
                'Must provide a valid GraphQL query, mutation, or subscription.',
            },
          ],
        });
      }
      // handle query only contain \n
      if (query.trim() === '') {
        return res.status(400).json({
          errors: [
            {
              message:
                'Must provide a valid GraphQL query, mutation, or subscription.',
            },
          ],
        });
      }
    }

    // Continue to the next middleware or GraphQL handler
    next();
  }
}