import { ValidatorFn, AbstractControl } from '@angular/forms/src/forms';
import { FormGroup, FormControl } from '@angular/forms/forms';

export function maxValue(max: Number): ValidatorFn {
  return (control: AbstractControl): { [key: string]: any } => {
    const input = control.value,
      isValid = input > max;
    if (isValid) {
      return { 'maxValue': { max } }
    } else {
      return null;
    }
  };
}

export function minValue(min: Number): ValidatorFn {
  return (control: AbstractControl): { [key: string]: any } => {
    const input = control.value,
      isValid = input < min;
    if (isValid) {
      return { 'minValue': { min } }
    } else {
      return null;
    }
  };
}

export function matchOtherValidator(otherControlName: string) {

  let thisControl: FormControl;
  let otherControl: FormControl;

  return function matchOtherValidate(control: FormControl) {

    if (!control.parent) {
      return null;
    }

    // Initializing the validator.
    if (!thisControl) {
      thisControl = control;
      otherControl = control.parent.get(otherControlName) as FormControl;
      if (!otherControl) {
        throw new Error('matchOtherValidator(): other control is not found in parent group');
      }
      otherControl.valueChanges.subscribe(() => {
        thisControl.updateValueAndValidity();
      });
    }

    if (!otherControl) {
      return null;
    }

    if (otherControl.value !== thisControl.value) {
      return {
        matchOther: true
      };
    }

    return null;

  }

}