TypeScript-Backend-Template/src/middleware/validate.ts

import { Request, Response, NextFunction } from 'express';
import { ObjectSchema, ValidationError } from 'yup';
import ApiError from '../utils/helper/ApiError';
import { pick } from '../utils/handler/pick.handler';

/**
 * Validation middleware for Express routes.
 * @param schema - Validation schema object (Yup schema for request parts like params, query, body, etc.).
 * @returns Middleware function to validate request properties.
 */
const validate =
    (schema: Partial<Record<keyof Request, ObjectSchema<never>>>) =>
        (req: Request, res: Response, next: NextFunction): void => {
            // Define valid request keys explicitly
            const validRequestKeys = ['params', 'query', 'body', 'file', 'files'] as (keyof Request)[];

            // Extract the schemas for valid parts of the request
            const validSchema = pick(schema, validRequestKeys);

            // Extract the corresponding request properties
            const object = pick(req, Object.keys(validSchema) as (keyof Request)[]);

            // Validate each part of the request
            const promises = Object.keys(validSchema).map((key) =>
                validSchema[key as keyof Request]?.validate(object[key as keyof Request], { abortEarly: false })
            );

            // Process validation results
            Promise.all(promises)
                .then((validatedValues) => {
                    // Assign validated values back to the request object
                    validatedValues.forEach((value, index) => {
                        const key = Object.keys(validSchema)[index];
                        // Safely assign the validated value to the request object
                        req[key as keyof Request] = value; // Use `Request` here instead of `Request.ResBody`
                    });
                    next();
                })
                .catch((err: ValidationError) => {
                    // Collect and format error messages
                    const errorMessage = err.inner.map((detail) => detail.message).join(', ');
                    next(new ApiError(400, errorMessage));
                });
        };

export default validate;