<?php

/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

declare(strict_types=1);

namespace Elastic\Apm\Impl\BreakdownMetrics;

use Elastic\Apm\Impl\Log\LoggableInterface;
use Elastic\Apm\Impl\Log\LoggableTrait;
use Elastic\Apm\Impl\Util\TimeUtil;

/**
 * An error or a logged error message captured by an agent occurring in a monitored service
 *
 * @link https://github.com/elastic/apm-server/blob/7.0/docs/spec/errors/error.json
 *
 * Code in this file is part of implementation internals and thus it is not covered by the backward compatibility.
 *
 * @internal
 */
class SelfTimeTracker implements LoggableInterface
{
    use LoggableTrait;

    /** @var float Monotonic time since some unspecified starting point in microseconds */
    private $currentSelfTimeSegmentBeginTime;

    /** @var int */
    private $runningChildrenCount = 0;

    /** @var float */
    private $accumulatedSelfTimeInMicroseconds = 0;

    public function __construct(float $monotonicClockNow)
    {
        $this->startTimer($monotonicClockNow);
    }

    public function onChildBegin(float $monotonicClockNow): void
    {
        if ($this->runningChildrenCount === 0) {
            $this->stopTimer($monotonicClockNow);
        }

        ++$this->runningChildrenCount;
    }

    public function onChildEnd(float $monotonicClockNow): void
    {
        --$this->runningChildrenCount;

        if ($this->runningChildrenCount === 0) {
            $this->startTimer($monotonicClockNow);
        }
    }

    public function end(float $monotonicClockNow): void
    {
        if ($this->runningChildrenCount === 0) {
            $this->stopTimer($monotonicClockNow);
        }
    }

    private function startTimer(float $monotonicClockNow): void
    {
        $this->currentSelfTimeSegmentBeginTime = $monotonicClockNow;
    }

    private function stopTimer(float $monotonicClockNow): void
    {
        $this->accumulatedSelfTimeInMicroseconds += TimeUtil::calcDurationInMicrosecondsClampNegativeToZero(
            $this->currentSelfTimeSegmentBeginTime,
            $monotonicClockNow
        );
    }

    public function accumulatedSelfTimeInMicroseconds(): float
    {
        return $this->accumulatedSelfTimeInMicroseconds;
    }
}