<?php
use PHPUnit\Framework\TestCase;

final class FormulaServiceTest extends TestCase
{
    private $formula;

    protected function setUp(): void
    {
        $this->formula = new FormulaService();
    }

    public function testPayrollFormulaHonorsPrecedenceAndVariables(): void
    {
        $value = $this->formula->calculate('basic_salary + overtime_hours * overtime_rate', array(
            'basic_salary' => 5000000,
            'overtime_hours' => 4,
            'overtime_rate' => 50000,
        ));
        self::assertSame(5200000.0, $value);
    }

    public function testProrataFormulaAndRounding(): void
    {
        self::assertSame(333333.33, $this->formula->calculate('salary / work_days', array(
            'salary' => 7000000,
            'work_days' => 21,
        )));
    }

    public function testUnknownVariableIsZeroForBackwardCompatibleFormula(): void
    {
        self::assertSame(1000.0, $this->formula->calculate('base + optional_bonus', array('base' => 1000)));
    }

    public function testRejectsDivisionByZero(): void
    {
        $this->expectException(BusinessException::class);
        $this->formula->calculate('salary / days', array('salary' => 1000, 'days' => 0));
    }

    public function testRejectsUnsafeTokens(): void
    {
        $this->expectException(BusinessException::class);
        $this->formula->calculate('system("whoami")', array());
    }
}