import { Directive } from '@angular/core';
import { AbstractControl, FormGroup, NG_VALIDATORS, ValidationErrors, Validator, ValidatorFn } from '@angular/forms';

export const fromYearAfterToYearValidator: ValidatorFn = (control: FormGroup): ValidationErrors | null => {
  const yearFrom = control.get('yearFrom');
  const yearTo = control.get('yearTo');

  return ((yearFrom && yearTo && (parseInt(yearFrom.value, 10) >  parseInt(yearTo.value, 10))) ? { 'fromYearAfterToYear': true } : null);
};

@Directive({
  selector: '[fromYearAfterToYear]',
  providers: [{ provide: NG_VALIDATORS, useExisting: FromYearAfterToYearValidatorDirective, multi: true }]
})
export class FromYearAfterToYearValidatorDirective implements Validator {
  validate(control: AbstractControl): ValidationErrors {
    return fromYearAfterToYearValidator(control)
  }
}