<?php

namespace Tests\App\Services;

use App\Services\FeeCalculationService;
use CodeIgniter\Test\CIUnitTestCase;

class FeeCalculationServiceTest extends CIUnitTestCase
{
    public function testRefundReversesLatestTuitionTierFirst(): void
    {
        $fees = $this->refundFeeStack(3, 2, 380.0, 280.0);

        $this->assertSame([280.0], $fees);
    }

    public function testRefundKeepsReversingAdditionalFeesBeforeFirstStudentFee(): void
    {
        $fees = $this->refundFeeStack(3, 0, 380.0, 280.0);

        $this->assertSame([280.0, 280.0, 380.0], $fees);
    }

    public function testSingleStudentWithdrawalRefundsFirstStudentFee(): void
    {
        $fees = $this->refundFeeStack(1, 0, 380.0, 280.0);

        $this->assertSame([380.0], $fees);
    }

    /**
     * @return array<int,float>
     */
    private function refundFeeStack(
        int $originalStudentCount,
        int $remainingStudentCount,
        float $firstStudentFee,
        float $additionalStudentFee
    ): array {
        $method = new \ReflectionMethod(FeeCalculationService::class, 'reverseTuitionRefundFeeStack');
        $method->setAccessible(true);

        return $method->invoke(
            new FeeCalculationService(),
            $originalStudentCount,
            $remainingStudentCount,
            $firstStudentFee,
            $additionalStudentFee
        );
    }
}