<?php
declare(strict_types=1);

namespace App\Domain\SLA;

final class SlaThresholdClassifier
{
    public const WITHIN_LIMIT = 'within_limit';
    public const WARNING = 'warning';
    public const CRITICAL = 'critical';
    public const EXCEEDED = 'exceeded';

    public function classify(float $usedHours, float $allocatedHours): string
    {
        if ($allocatedHours < 0) throw new \InvalidArgumentException('Allocated hours must not be negative.');
        $usedHours = max(0.0, $usedHours);
        if ($allocatedHours === 0.0) return $usedHours > 0.0 ? self::EXCEEDED : self::WITHIN_LIMIT;
        if ($usedHours > $allocatedHours) return self::EXCEEDED;
        $percentage = ($usedHours / $allocatedHours) * 100;
        return $percentage >= 90.0 ? self::CRITICAL : ($percentage >= 75.0 ? self::WARNING : self::WITHIN_LIMIT);
    }

    public function percentage(float $usedHours, float $allocatedHours): float
    {
        if ($allocatedHours < 0) throw new \InvalidArgumentException('Allocated hours must not be negative.');
        $usedHours = max(0.0, $usedHours);
        return $allocatedHours > 0.0 ? round(($usedHours / $allocatedHours) * 100, 2) : ($usedHours > 0.0 ? 100.0 : 0.0);
    }
}