ISA-Frontend/libs/ui/datepicker/src/lib/validators/date-bounds.validator.ts

import { AbstractControl, ValidationErrors, ValidatorFn } from '@angular/forms';
import { isValid, isBefore, isAfter } from 'date-fns';

/**
 * Validator function to check if a date value is within the specified bounds.
 *
 * This validator performs the following checks:
 * - If the control value is empty, the validation passes.
 * - If the date is invalid, a validation error with {invalidDate: true} is returned.
 * - If a minimum date is provided and the control date is before it, a validation error with {minDate: true} is returned.
 * - If a maximum date is provided and the control date is after it, a validation error with {maxDate: true} is returned.
 *
 * @param min - The minimum allowed date (inclusive). Optional.
 * @param max - The maximum allowed date (inclusive). Optional.
 * @returns A ValidatorFn that returns a ValidationErrors object if the date is out of bounds, otherwise null.
 */

// TODO: Utils Auslagern
export function dateBoundsValidator(min?: Date, max?: Date): ValidatorFn {
  return (control: AbstractControl): ValidationErrors | null => {
    const date: Date | null = control.value ?? null;
    if (!date) return null;

    if (!isValid(date)) return { invalidDate: true };
    if (min && isBefore(date, min)) return { minDate: true };
    if (max && isAfter(date, max)) return { maxDate: true };

    return null;
  };
}