xyzshop/helper/mcard/amount_card.php

<?php
declare(strict_types=1);


namespace mcard;


class amount_card extends card
{
    public function usable(): bool
    {
        $state = $this->state();
        if ($state === STATE_OVER) {
            return false;
        }
        elseif ($state === STATE_USING)
        {
            $left = intval($this->left_amount() * 100);
            if ($left <= 0) {
                return false;
            }
            else {
                return true;
            }
        }
        else
        {
            return true;
        }
    }

    public function deduct(int $cent)
    {
        $left_cent = intval($this->left_amount() * 100 + 0.5);

        if ($left_cent > $cent)
        {
            $amount = $cent;
            $useup = false;
        }
        else
        {
            $amount = $left_cent;
            $useup = true;
        }

        return [$amount, $useup];
    }

    public function calc(int $cent)
    {
        $left_cent = intval($this->left_amount() * 100 + 0.5);

        if ($left_cent > $cent)
        {
            $amount = $cent;
            $useup = false;
        }
        else
        {
            $amount = $left_cent;
            $useup = true;
        }
        $price = round($amount * (1 - $this->discount()) / 100, 2);
        return [$amount, $useup,$price];
    }
}