PriceMatrix.php

PriceMatrix.php

<?php

namespace App;

use App\Enums\Discount;
use Brick\Money\Money;
use Illuminate\Contracts\Support\Arrayable;
use InvalidArgumentException;
use WeakMap;

class PriceMatrix implements Arrayable
{
    public Money $raw;

    public readonly Money $vat;

    public Money $total;

    /**
     * The applied discounts.
     * The money value is the total 
     * when the discount was applied.
     * 
     * @var WeakMap<Discount, Money>
     */
    public readonly WeakMap $discounts;

    public function __construct($initialAmount = 0, string $currency = 'DKK')
    {
        $this->discounts = new WeakMap();

        if (is_numeric($initialAmount)) {
            $initialAmount = Money::of($initialAmount, $currency);
        }

        if ($initialAmount instanceof Money) {
            $initialAmount = $initialAmount->getAmount();
        }

        $this->raw = Money::of($initialAmount, $currency);
        $this->vat = Money::of($initialAmount->multipliedBy(0.25), $currency);
        $this->calculateTotal();
    }

    public function calculateTotal(): static
    {
        $this->total = Money::of(
            $this->raw->plus($this->vat)->getAmount(), 
            $this->raw->getCurrency()
        );

        return $this;
    }

    public function addDiscount(Discount $discount): static
    {
        $this->discounts[$discount] = $this->raw;

        $this->raw = $this->raw->minus(
            $discount->calculate($this->raw)
        );

        $this->calculateTotal();

        return $this;
    }

    public function subtractDiscount(Discount $discount): static
    {
        [$appliedDiscount, $rawAmount] = $this->findDiscount($discount);

        if ($appliedDiscount === null) {
            throw new InvalidArgumentException(
                sprintf(
                    "No %s Discount was applied.",
                    $discount->value
                )
            );
        }

        $this->raw = $rawAmount;
        $this->calculateTotal();

        unset($this->discounts[$appliedDiscount]);

        return $this;
    }

    public function findDiscount(Discount $discount): array
    {
        if (isset($this->discounts[$discount])) {
            return [$discount, $this->discounts[$discount]];
        }

        foreach ($this->discounts as $registeredDiscount => $rawAmount)
        {
            if ($registeredDiscount->value === $discount->value) {
                return [$registeredDiscount, $rawAmount];
            }
        }

        return [null, null];
    }

    public function toArray()
    {
        return [
            'raw' => $this->raw,
            'vat' => $this->vat,
            'total' => $this->total,
            'discounts' => iterator_to_array($this->discounts)
        ];
    }
}