class ResourceUsageFormatter

final class ResourceUsageFormatter {
    
    /**
     * @psalm-var array<string,int>
     */
    private const SIZES = [
        'GB' => 1073741824,
        'MB' => 1048576,
        'KB' => 1024,
    ];
    public function resourceUsage(Duration $duration) : string {
        return sprintf('Time: %s, Memory: %s', $duration->asString(), $this->bytesToString(memory_get_peak_usage(true)));
    }
    
    /**
     * @throws TimeSinceStartOfRequestNotAvailableException
     */
    public function resourceUsageSinceStartOfRequest() : string {
        if (!isset($_SERVER['REQUEST_TIME_FLOAT'])) {
            throw new TimeSinceStartOfRequestNotAvailableException('Cannot determine time at which the request started because $_SERVER[\'REQUEST_TIME_FLOAT\'] is not available');
        }
        if (!is_float($_SERVER['REQUEST_TIME_FLOAT'])) {
            throw new TimeSinceStartOfRequestNotAvailableException('Cannot determine time at which the request started because $_SERVER[\'REQUEST_TIME_FLOAT\'] is not of type float');
        }
        return $this->resourceUsage(Duration::fromMicroseconds(1000000 * (microtime(true) - $_SERVER['REQUEST_TIME_FLOAT'])));
    }
    private function bytesToString(int $bytes) : string {
        foreach (self::SIZES as $unit => $value) {
            if ($bytes >= $value) {
                return sprintf('%.2f %s', $bytes / $value, $unit);
            }
        }
        // @codeCoverageIgnoreStart
        return $bytes . ' byte' . ($bytes !== 1 ? 's' : '');
        // @codeCoverageIgnoreEnd
    }

}