Validation Chain Builders

/**
 * Creates validation chain for req.body fields
 * @param fields - Field name(s) to validate (supports nested paths and wildcards)
 * @param message - Default error message for failed validations
 * @returns ValidationChain for chaining validators and sanitizers
 */
function body(fields?: string | string[], message?: string): ValidationChain;

import { body } from "express-validator";

// Single field
body('email').isEmail();

// Multiple fields  
body(['name', 'email']).trim().notEmpty();

// Nested fields
body('user.profile.age').isInt({ min: 0 });

// Array elements
body('items.*.quantity').isInt({ min: 1 });

// With custom error message
body('password', 'Password must be at least 6 characters').isLength({ min: 6 });

/**
 * Creates validation chain for req.query fields
 * @param fields - Field name(s) to validate
 * @param message - Default error message for failed validations
 * @returns ValidationChain for chaining validators and sanitizers
 */
function query(fields?: string | string[], message?: string): ValidationChain;

import { query } from "express-validator";

// Query parameters
query('page').isInt({ min: 1 }).toInt();
query('limit').isInt({ min: 1, max: 100 }).toInt();
query('search').trim().escape();
query('sort').isIn(['name', 'date', 'price']);

/**
 * Creates validation chain for req.params fields
 * @param fields - Field name(s) to validate
 * @param message - Default error message for failed validations
 * @returns ValidationChain for chaining validators and sanitizers
 */
function param(fields?: string | string[], message?: string): ValidationChain;

import { param } from "express-validator";

// Route parameters
param('id').isUUID();
param('userId').isInt().toInt();
param('slug').isSlug();
param('category').isAlpha();

/**
 * Creates validation chain for req.headers fields
 * @param fields - Field name(s) to validate
 * @param message - Default error message for failed validations
 * @returns ValidationChain for chaining validators and sanitizers
 */
function header(fields?: string | string[], message?: string): ValidationChain;

import { header } from "express-validator";

// Request headers
header('authorization').notEmpty().matches(/^Bearer .+/);
header('content-type').equals('application/json');
header('x-api-key').isUUID();

/**
 * Creates validation chain for req.cookies fields
 * @param fields - Field name(s) to validate
 * @param message - Default error message for failed validations
 * @returns ValidationChain for chaining validators and sanitizers
 */
function cookie(fields?: string | string[], message?: string): ValidationChain;

import { cookie } from "express-validator";

// Cookies
cookie('sessionId').isUUID();
cookie('preferences').isJSON();
cookie('theme').isIn(['light', 'dark']);

/**
 * Creates validation chain that checks all request locations
 * @param fields - Field name(s) to validate
 * @param message - Default error message for failed validations
 * @returns ValidationChain for chaining validators and sanitizers
 */
function check(fields?: string | string[], message?: string): ValidationChain;

import { check } from "express-validator";

// Checks all locations for 'id' field
check('id').isUUID();

// Useful when field could be in multiple locations
check('token').notEmpty();

/**
 * Creates custom check function for specific locations
 * @param locations - Array of locations to check
 * @returns Function that creates ValidationChain for specified locations
 */
function buildCheckFunction(locations: Location[]): 
  (fields?: string | string[], message?: string) => ValidationChain;

import { buildCheckFunction } from "express-validator";

// Custom builder for body and query only
const checkBodyAndQuery = buildCheckFunction(['body', 'query']);

// Use the custom builder
checkBodyAndQuery('searchTerm').trim().notEmpty();

interface ValidationChain {
  // Conditional validation
  if(condition: (value: any, meta: Meta) => boolean): ValidationChain;
  optional(options?: { nullable?: boolean; checkFalsy?: boolean }): ValidationChain;
  
  // Error handling
  withMessage(message: string): ValidationChain;
  bail(): ValidationChain;
  
  // Negation
  not: ValidationChain;
  
  // Skip options
  skipUndefined(): ValidationChain;
  skipNull(): ValidationChain;
  skipEmpty(): ValidationChain;
}

// Nested object validation
body('user.profile.bio').isLength({ max: 500 });

// Array validation
body('products.*.price').isDecimal({ decimal_digits: '2' });

// Multiple field validation
body(['firstName', 'lastName']).trim().notEmpty();