Type Checking Utilities

/**
 * Type guard that checks if a value is a string
 * @param value - Value to check
 * @returns true if value is a string, with type narrowing
 */
function isString(value: any): value is string;

/**
 * Checks if a string represents a CSS custom property (CSS variable)
 * @param value - String to check
 * @returns true if string matches var(--*) format
 */
function isCssVar(value: string): boolean;

/**
 * Type guard that checks if a value is a number
 * @param value - Value to check
 * @returns true if value is a number (excluding NaN), with type narrowing
 */
function isNumber(value: any): value is number;

/**
 * Checks if a value is not a number
 * @param value - Value to check
 * @returns true if value is not a valid number
 */
function isNotNumber(value: any): boolean;

/**
 * Checks if a value is numeric (number or numeric string)
 * @param value - Value to check
 * @returns true if value can be converted to a valid number
 */
function isNumeric(value: any): boolean;

import { isNumber, isNumeric, isNotNumber } from "@chakra-ui/utils";

// Type guard usage
function processValue(input: unknown) {
  if (isNumber(input)) {
    // TypeScript knows input is number here
    return input.toFixed(2);
  }
  return "Not a number";
}

// Numeric validation
const userInput = "42.5";
if (isNumeric(userInput)) {
  const num = parseFloat(userInput); // Safe to parse
}

// Filtering non-numbers
const mixedArray = [1, "hello", 2, null, 3];
const numbers = mixedArray.filter(item => !isNotNumber(item));

/**
 * Type guard that checks if a value is a plain object
 * @param value - Value to check
 * @returns true if value is a plain object, with type narrowing
 */
function isObject(value: any): value is Record<string, any>;

/**
 * Checks if an object has no enumerable properties
 * @param value - Value to check
 * @returns true if object is empty or not an object
 */
function isEmptyObject(value: any): boolean;

/**
 * Type guard that checks if a value is an array
 * @param value - Value to check
 * @returns true if value is an array, with type narrowing
 */
function isArray<T>(value: any): value is Array<T>;

/**
 * Checks if an array has no elements
 * @param value - Value to check
 * @returns true if array is empty or not an array
 */
function isEmptyArray(value: any): boolean;

/**
 * Type guard that checks if a value is a function
 * @param value - Value to check
 * @returns true if value is a function, with type narrowing
 */
function isFunction<T extends Function>(value: any): value is T;

/**
 * Type guard that checks if a value is null or undefined
 * @param value - Value to check
 * @returns true if value is null or undefined, with type narrowing
 */
function isNull(value: any): value is null;

/**
 * Type guard that checks if a value is undefined
 * @param value - Value to check
 * @returns true if value is undefined, with type narrowing
 */
function isUndefined(value: any): value is undefined;

/**
 * Checks if a value is defined (not null or undefined)
 * @param value - Value to check
 * @returns true if value is not null and not undefined
 */
function isDefined(value: any): boolean;

/**
 * Checks if a value is considered empty
 * Empty values include: null, undefined, empty string, empty array, empty object
 * @param value - Value to check
 * @returns true if value is considered empty
 */
function isEmpty(value: any): boolean;

/**
 * Type guard that checks if a value is a React ref object
 * @param val - Value to check
 * @returns true if value has a 'current' property
 */
function isRefObject(val: any): val is { current: any };

/**
 * Type guard that checks if a value is an input event
 * @param value - Value to check
 * @returns true if value is an event with HTMLInputElement target
 */
function isInputEvent(value: any): value is { target: HTMLInputElement };

import { 
  isObject, isArray, isEmpty, 
  isRefObject, isInputEvent 
} from "@chakra-ui/utils";

// Object validation
function processConfig(config: unknown) {
  if (isObject(config)) {
    // TypeScript knows config is Record<string, any>
    return config.setting || "default";
  }
}

// Array validation
function processItems(items: unknown) {
  if (isArray<string>(items)) {
    // TypeScript knows items is string[]
    return items.map(item => item.toUpperCase());
  }
}

// Emptiness checking
function validateInput(input: unknown): string | null {
  if (isEmpty(input)) {
    return null;
  }
  return String(input);
}

// React ref checking
function focusElement(ref: unknown) {
  if (isRefObject(ref) && ref.current?.focus) {
    ref.current.focus();
  }
}

// Event handling
function handleChange(event: unknown) {
  if (isInputEvent(event)) {
    // TypeScript knows event.target is HTMLInputElement
    console.log(event.target.value);
  }
}