<?php

declare(strict_types=1);

namespace OpenTelemetry\SDK\Metrics;

/**
 * Instrument type.
 *
 * Has to be type-hinted as `string|InstrumentType` to be forward compatible.
 */
final class InstrumentType
{
    public const COUNTER = 'Counter';
    public const UP_DOWN_COUNTER = 'UpDownCounter';
    public const HISTOGRAM = 'Histogram';
    /** @experimental */
    public const GAUGE = 'Gauge';

    public const ASYNCHRONOUS_COUNTER = 'AsynchronousCounter';
    public const ASYNCHRONOUS_UP_DOWN_COUNTER = 'AsynchronousUpDownCounter';
    public const ASYNCHRONOUS_GAUGE = 'AsynchronousGauge';

    private function __construct()
    {
    }
}