SegmentAllocator.php

<?php

declare(strict_types=1);

namespace App\Product\Quality;

use App\Entity\Product\Segment;
use Generator;
use InvalidArgumentException;
use Money\Money;

/**
 * @author Konstantin Grachev <me@grachevko.ru>
 */
final class SegmentAllocator
{
    private const ONE_HUNDRED_PERCENT = 100;
    /**
     * @var Money
     */
    private $current;

    /**
     * @var Money
     */
    private $next;

    /**
     * @var Segment
     */
    private $segment;

    /**
     * @var Generator
     */
    private $switcher;

    public function __construct(Money $sum, array $map)
    {
        $this->current = new Money(0, $sum->getCurrency());
        $this->next = new Money(0, $sum->getCurrency());

        $ratios = array_map(function ($item) {
            return $item['ratio'];
        }, $map);

        if (self::ONE_HUNDRED_PERCENT !== array_sum($ratios)) {
            throw new InvalidArgumentException(
                sprintf('Sum of ratios must be %s', self::ONE_HUNDRED_PERCENT)
            );
        }

        $parts = $sum->allocate($ratios);

        $this->switcher = call_user_func(function () use ($map, $parts) {
            foreach ($parts as $key => $part) {
                $this->next = $this->next->add($part);

                $this->segment = $map[$key]['segment'];

                yield;
            }
        });
        $this->switcher->current();
    }

    public function allocate(Money $money): Segment
    {
        $currency = $this->current->getCurrency();
        if (!$currency->equals($money->getCurrency())) {
            throw new InvalidArgumentException(
                sprintf('This instance of %s accept only %s currency.', __CLASS__, $currency->getCode())
            );
        }

        $this->increment($money);

        return $this->segment;
    }

    private function increment(Money $money): void
    {
        $this->current = $this->current->add($money);

        if ($this->current->greaterThan($this->next)) {
            $this->switcher->next();
        }
    }
}

SegmentAllocatorTest.php

<?php

declare(strict_types=1);

namespace App\Tests\Product\Quality;

use App\Entity\Product\Segment;
use App\Product\Quality\SegmentAllocator;
use InvalidArgumentException;
use Money\Currency;
use Money\Money;
use PHPUnit\Framework\TestCase;

/**
 * @author Konstantin Grachev <me@grachevko.ru>
 */
final class SegmentAllocatorTest extends TestCase
{
    public function testRatioSum(): void
    {
        $this->expectException(InvalidArgumentException::class);

        new SegmentAllocator(new Money(0, new Currency('RUB')), [
            ['ratio' => 99, 'segment' => Segment::medium()],
        ]);
    }

    public function testAllocate(): void
    {
        $currency = new Currency('RUB');

        $allocator = new SegmentAllocator(new Money(100, $currency), [
            ['ratio' => 25, 'segment' => Segment::eco()],
            ['ratio' => 25, 'segment' => Segment::medium()],
            ['ratio' => 25, 'segment' => Segment::high()],
            ['ratio' => 25, 'segment' => Segment::exclusive()],
        ]);

        $this->assertSame(Segment::eco()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::eco()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::medium()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::medium()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::medium()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::high()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::high()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::exclusive()->getName(), $allocator->allocate(new Money(10, $currency))->getName());
        $this->assertSame(Segment::exclusive()->getName(), $allocator->allocate(new Money(100, $currency))->getName());
    }
}