import { AbstractControl, ValidationErrors, ValidatorFn } from '@angular/forms';
export declare class CustomValidators {
    /**
     * Validates that the control value contains only numeric characters (0-9).
     * Empty values are considered valid.
     *
     * @param control The form control to validate
     * @returns ValidationErrors with {number: true} if invalid, null if valid
     * @example
     * this.formGroup = this.fb.group({
     *   age: ['', [Validators.required, CustomValidators.onlyNumber]]
     * });
     */
    static onlyNumber(control: AbstractControl): ValidationErrors | null;
    /**
     * Validates that the control value is not composed of only whitespace characters.
     * Empty values are considered valid.
     *
     * @param control The form control to validate
     * @returns ValidationErrors with {whiteSpaceLine: true} if invalid, null if valid
     * @example
     * this.formGroup = this.fb.group({
     *   description: ['', [Validators.required, CustomValidators.hasWhiteSpaceLine]]
     * });
     */
    static hasWhiteSpaceLine(control: AbstractControl): ValidationErrors | null;
    /**
     * Validates that the control value exists within a provided list of valid values.
     * Empty values are considered valid.
     *
     * @param datalist Array of valid values to check against
     * @param customError Optional custom error key to return instead of the default that is 'valueNoExist'
     *                    If set to 'none', no error message will be returned.
     * @returns A validator function that returns an error object if invalid, empty object if valid
     * @example
     * const allowedCities = ['New York', 'London', 'Tokyo'];
     * this.formGroup = this.fb.group({
     *   city: ['', [Validators.required, CustomValidators.introducedValueExists(allowedCities)]]
     * });
     */
    static introducedValueExists(datalist: any[], customError?: string): ValidatorFn;
    /**
     * Validates that the control value does not start with a whitespace character.
     *
     * @param control The form control to validate
     * @returns ValidationErrors with {leadingWhiteSpaceLine: true} if invalid, null if valid
     * @example
     * this.formGroup = this.fb.group({
     *   username: ['', [Validators.required, CustomValidators.hasLeadingWhiteSpace]]
     * });
     */
    static hasLeadingWhiteSpace(control: AbstractControl): ValidationErrors | null;
    /**
     * Validates that the control value does not end with a whitespace character.
     *
     * @param control The form control to validate
     * @returns ValidationErrors with {trailingWhiteSpaceLine: true} if invalid, null if valid
     * @example
     * this.formGroup = this.fb.group({
     *   password: ['', [Validators.required, CustomValidators.hasTrailingWhiteSpace]]
     * });
     */
    static hasTrailingWhiteSpace(control: AbstractControl): ValidationErrors | null;
    /**
     * Validates that the size of the control value in bytes does not exceed the specified maximum.
     * Useful for validating file sizes or input lengths in bytes rather than characters.
     *
     * @param maxLength Maximum allowed size in bytes
     * @returns A validator function that returns {maxlength: true} if size exceeds limit
     * @example
     * // Validate that a file input doesn't exceed 5MB
     * this.formGroup = this.fb.group({
     *   fileUpload: ['', [Validators.required, CustomValidators.maxByte(1024)]]
     * });
     */
    static maxByte(maxLength: number): ValidatorFn;
}