<?php 

class CreateComboNo{
    private $comboarr =  [
        'week'=>'BW002',
        'month'=>'EM002',
        'quarter'=>'EQ002',
        'half'=>'HY002',
        'year'=>'EY002'
    ];
    private $bwarr = [
        'week','month','week','month','week','quarter',
        'week','month','week','month','week','half',
        'week','month','week','month','week','quarter',
        'week','month','week','month','week','year'
    ];
    private $emarr = [
        'month','month','quarter','month','month','half',
        'month','month','quarter','month','month','year'
    ];
    private $combo;
    private $startdate;
    private $enddate;
    public function __construct($combo, $startdate, $enddate){
        $this->combo = $combo;
        $this->startdate = $startdate;
        $this->enddate = $enddate;
    }
    public function getComboNo(){
        $comboarr = (array) $this->combo === 'bw' ? $this->bwarr : $this->emarr;

        $startdate = new DateTime($this->startdate);
        $enddate = new DateTime($this->enddate);

        $interval =  date_diff($startdate, $enddate);

        $months = $interval->y * 12 + $interval->m;
        $months = $this->combo === 'bw' ? $months*2 : $months;

        $newarr = [];
        $idx = 0;
        $ori_first_month = date('m', strtotime($this->startdate));
        $first_day = date('Y-m-d', strtotime($this->startdate. ' + 3 days'));
        $new_first_month = date('m', strtotime($first_day));
        if($ori_first_month != $new_first_month){
            $first_day = date('Y-m-t', strtotime($this->startdate));
        }
        $scheduleDate =   new DateTime($first_day);
        for ($i = 0; $i < $months; $i++){  
            $newarr[] = [$this->comboarr[$comboarr[$idx]], $scheduleDate->format("Y-m-d")];
            $idx ++;
            $scheduleDate = $startdate->modify("+1 month");
            if($idx >= count($comboarr)){
                $idx = 0;
            }
        }
        return json_encode($newarr);
    }
}