<?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) {
            $first_day = date('Y-m-d', strtotime($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 = $scheduleDate->modify("+1 month");
            if ($idx >= count($comboarr)) {
                $idx = 0;
            }
        }
        return json_encode($newarr);
    }
}