<?php

if(!class_exists('BusinessDaysCalculator')) {    
    class BusinessDaysCalculator
    {
        const MONDAY    = 1;
        const TUESDAY   = 2;
        const WEDNESDAY = 3;
        const THURSDAY  = 4;
        const FRIDAY    = 5;
        const SATURDAY  = 6;
        const SUNDAY    = 7;

        /**
         * @param DateTime   $startDate       Date to start calculations from
         * @param DateTime[] $holidays        Array of holidays, holidays are no conisdered business days.
         * @param int[]      $nonBusinessDays Array of days of the week which are not business days.
         */
        public function __construct(DateTime $startDate, array $holidays, array $nonBusinessDays) {
            $this->date = $startDate;
            $this->holidays = $holidays;
            $this->nonBusinessDays = $nonBusinessDays;

            $this->assocHollyday();
        }

        public function assocHollyday() 
        {
            $this->holidays[] = new DateTime((date('Y')+1)."-01-01");
            $this->holidays[] = new DateTime(date('Y')."-01-01");
            $this->holidays[] = new DateTime(date('Y')."-05-01");
            $this->holidays[] = new DateTime(date('Y')."-05-08");
            $this->holidays[] = new DateTime(date('Y')."-07-14");
            $this->holidays[] = new DateTime(date('Y')."-08-15");
            $this->holidays[] = new DateTime(date('Y')."-11-11");
            $this->holidays[] = new DateTime(date('Y')."-12-25");
        }

        public function addBusinessDays($howManyDays) {
            $i = 0;
            while ($i < $howManyDays) {
                $this->date->modify("+1 day");
                if ($this->isBusinessDay($this->date)) {
                    $i++;
                }
            }
        }

        public function addDaysWithCheckLastDay($howManyDays) {
            $i = 0;
            while ($i < $howManyDays) {
                $this->date->modify("+1 day");
                $i++;
            }
            if (!$this->isBusinessDay($this->date)) {
                $this->date->modify("+1 day");
            }
        }

        public function getDate() {
            return $this->date;
        }

        private function isBusinessDay(DateTime $date) {
            if (in_array((int)$date->format('N'), $this->nonBusinessDays)) {
                return false; //Date is a nonBusinessDay.
            }
            foreach ($this->holidays as $day) {
                if ($date->format('Y-m-d') == $day->format('Y-m-d')) {
                    return false; //Date is a holiday.
                }
            }
            return true; //Date is a business day.
        }
    }
}