Helper Functions and Utilities

/**
 * Attaches custom parameters to a validator
 * @param params - Object containing parameter data
 * @param validator - Validator function to enhance
 * @returns ValidationRuleWithParams containing the validator and parameters
 */
function withParams<T = unknown>(params: object, validator: ValidationRule<T>): ValidationRuleWithParams;

import { helpers } from "@vuelidate/validators";

// Add custom parameters to a validator
const customMinLength = helpers.withParams(
  { type: "minLength", min: 5 },
  (value) => value && value.length >= 5
);

// Parameters are available in error messages
const customValidator = helpers.withParams(
  { 
    customParam: "special value",
    threshold: 100,
    validationType: "custom"
  },
  (value) => value > 100
);

// In validation rules
const validationRules = {
  description: {
    customLength: helpers.withParams(
      { min: 10, field: "description" },
      (value) => value && value.length >= 10
    )
  }
};

/**
 * Attaches custom error message to a validator
 * @param message - String message or function that returns message
 * @param validator - Validator function to enhance
 * @returns ValidationRuleWithParams containing the validator and message
 */
function withMessage<T = unknown>(
  message: string | ((params: MessageProps) => string),
  validator: ValidationRule<T>
): ValidationRuleWithParams;

import { helpers, required, minLength } from "@vuelidate/validators";

// Static custom message
const customRequired = helpers.withMessage(
  "This field is absolutely required!",
  required
);

// Dynamic message with parameters
const customMinLength = helpers.withMessage(
  (params) => `Minimum length is ${params.$params.min} characters`,
  minLength(5)
);

// Message accessing field data
const contextualMessage = helpers.withMessage(
  (params) => `The ${params.$property} field must be at least ${params.$params.min} characters long`,
  minLength(8)
);

// Complex conditional message
const smartMessage = helpers.withMessage(
  (params) => {
    const value = params.$model;
    const min = params.$params.min;
    const current = value ? value.length : 0;
    return `Field needs ${min - current} more characters (${current}/${min})`;
  },
  minLength(10)
);

// In validation rules
const validationRules = {
  username: {
    required: helpers.withMessage("Username cannot be empty", required),
    minLength: helpers.withMessage(
      "Username must be at least 3 characters long",
      minLength(3)
    )
  }
};

/**
 * Marks a validator as asynchronous
 * Used for validators that return Promises
 * @param validator - Async validator function
 * @returns Enhanced validator marked as async
 */
const withAsync: Function;

import { helpers } from "@vuelidate/validators";

// Async username availability check
const checkUsernameAvailability = helpers.withAsync(async (value) => {
  if (!value) return true; // Let required validator handle empty values
  
  const response = await fetch(`/api/check-username/${value}`);
  const result = await response.json();
  return result.available;
});

// Async email verification
const verifyEmailExists = helpers.withAsync(async (email) => {
  if (!email) return true;
  
  try {
    const response = await fetch('/api/verify-email', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ email })
    });
    const result = await response.json();
    return result.exists;
  } catch (error) {
    return false; // Fail validation on network error
  }
});

// Combining async with message
const asyncUsernameValidator = helpers.withMessage(
  "Username is not available",
  helpers.withAsync(checkUsernameAvailability)
);

// In validation rules
const validationRules = {
  username: {
    required,
    minLength: minLength(3),
    available: asyncUsernameValidator
  },
  email: {
    required,
    email,
    verified: helpers.withMessage(
      "Email address could not be verified",
      verifyEmailExists
    )
  }
};

/**
 * Applies validators to each element in an array
 * @param validators - Validation rules to apply to array elements
 * @returns Object with $validator and $message for array validation
 */
function forEach(validators: ValidationArgs): { 
  $validator: ValidationRule, 
  $message: () => string 
};

import { helpers, required, email, minLength } from "@vuelidate/validators";

// Validate array of emails
const emailListValidation = helpers.forEach({
  required,
  email
});

// Validate array of user objects
const userListValidation = helpers.forEach({
  name: { required, minLength: minLength(2) },
  email: { required, email },
  age: { required, minValue: minValue(18) }
});

// Validate array of strings with multiple rules
const tagListValidation = helpers.forEach({
  required,
  minLength: minLength(2),
  maxLength: maxLength(20),
  alphaNum
});

// In validation rules
const validationRules = {
  emailList: emailListValidation,
  
  userProfiles: userListValidation,
  
  tags: {
    ...tagListValidation,
    // Additional array-level validation
    minItems: (value) => value && value.length >= 1,
    maxItems: (value) => value && value.length <= 10
  }
};

// Example data structure
const formData = {
  emailList: ["user1@example.com", "user2@example.com"],
  userProfiles: [
    { name: "John", email: "john@example.com", age: 25 },
    { name: "Jane", email: "jane@example.com", age: 30 }
  ],
  tags: ["javascript", "vue", "validation"]
};

/**
 * Core required validation - checks if value exists and is not empty
 * @param value - Value to check
 * @returns true if value exists and is not empty
 */
function req(value: any): boolean;

/**
 * Calculates length of value (array, object, or string)
 * @param value - Value to measure
 * @returns Length as number
 */
function len(value: Array | Object | String): number;

/**
 * Creates validator from regular expression patterns
 * @param expr - One or more RegExp patterns
 * @returns Validator function that tests value against patterns
 */
function regex(...expr: RegExp[]): (value: any) => boolean;

import { helpers } from "@vuelidate/validators";

// Note: These are typically used internally, but can be used for custom validators

// Custom validator using req
const customRequired = (value) => helpers.req(value);

// Custom length validator using len
const exactLength = (expectedLength) => (value) => {
  return helpers.len(value) === expectedLength;
};

// Custom regex validator
const phonePattern = helpers.regex(/^\(\d{3}\)\s\d{3}-\d{4}$/);
const isValidPhone = phonePattern("(555) 123-4567"); // true

// Multiple regex patterns (must match all)
const strictPattern = helpers.regex(
  /^[a-zA-Z]/, // Must start with letter
  /[0-9]$/,    // Must end with number
  /^.{6,}$/    // Must be at least 6 characters
);

/**
 * Unwraps Vue ref to actual value
 * @param value - Value that might be a Vue ref
 * @returns Unwrapped value
 */
function unwrap(value: any): any;

/**
 * Checks if value is a function
 * @param val - Value to check
 * @returns true if value is a function
 */
function isFunction(val: any): boolean;

/**
 * Checks if value is an object
 * @param o - Value to check
 * @returns true if value is an object
 */
function isObject(o: any): boolean;

/**
 * Checks if value is truthy
 * @param prop - Value or function to check
 * @returns true if value is truthy
 */
function isTruthy(prop: Function | any): boolean;

/**
 * Checks if value is a Promise
 * @param object - Value to check
 * @returns true if value is a Promise
 */
function isPromise(object: any): boolean;

import { helpers, minLength, required } from "@vuelidate/validators";

// Combine multiple helpers for comprehensive custom validators
const advancedValidator = helpers.withMessage(
  "Field must be provided and meet length requirements",
  helpers.withParams(
    { customType: "advanced", minChars: 5 },
    (value) => helpers.req(value) && helpers.len(value) >= 5
  )
);

// Async validator with custom message and parameters
const asyncCustomValidator = helpers.withMessage(
  (params) => `Validation failed: ${params.$params.reason}`,
  helpers.withParams(
    { reason: "Server validation failed", type: "async" },
    helpers.withAsync(async (value) => {
      // Async validation logic
      return await serverValidation(value);
    })
  )
);

import { helpers } from "@vuelidate/validators";

// Factory for creating reusable custom validators
function createLengthValidator(min, max, fieldName) {
  return helpers.withMessage(
    `${fieldName} must be between ${min} and ${max} characters`,
    helpers.withParams(
      { min, max, fieldType: fieldName },
      (value) => {
        const length = helpers.len(value);
        return length >= min && length <= max;
      }
    )
  );
}

// Usage
const validationRules = {
  title: createLengthValidator(5, 100, "Title"),
  description: createLengthValidator(10, 500, "Description")
};