<?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;

use Closure;
use Elastic\Apm\CustomErrorData;
use Elastic\Apm\DistributedTracingData;
use Elastic\Apm\ExecutionSegmentInterface;
use Elastic\Apm\Impl\BackendComm\SerializationUtil;
use Elastic\Apm\Impl\BreakdownMetrics\SelfTimeTracker as BreakdownMetricsSelfTimeTracker;
use Elastic\Apm\Impl\Log\Level as LogLevel;
use Elastic\Apm\Impl\Log\LogCategory;
use Elastic\Apm\Impl\Log\LoggableInterface;
use Elastic\Apm\Impl\Log\LoggableTrait;
use Elastic\Apm\Impl\Log\Logger;
use Elastic\Apm\Impl\Log\LoggerFactory;
use Elastic\Apm\Impl\Util\ClassNameUtil;
use Elastic\Apm\Impl\Util\IdGenerator;
use Elastic\Apm\Impl\Util\TextUtil;
use Elastic\Apm\Impl\Util\TimeUtil;
use Elastic\Apm\SpanInterface;
use Throwable;

/**
 * Code in this file is part of implementation internals and thus it is not covered by the backward compatibility.
 *
 * @internal
 */
abstract class ExecutionSegment implements ExecutionSegmentInterface, SerializableDataInterface, LoggableInterface
{
    use LoggableTrait;

    /** @var string */
    public $name;

    /** @var string */
    public $type;

    /** @var string */
    public $id;

    /** @var string */
    public $traceId;

    /** @var float UTC based and in microseconds since Unix epoch */
    public $timestamp;

    /** @var float In milliseconds with 3 decimal points */
    public $duration;

    /** @var ?string */
    public $outcome = null;

    /** @var ?Span */
    private $pendingCompositeChild = null;

    /** @var bool */
    protected $wasPropogatedViaDistributedTracing = false;

    /**
     * @var ?float
     *
     * Sample rate applied to the monitored service at the time where this transaction/span was recorded.
     * Allowed values are [0..1].
     * A sample rate < 1 indicates that not all spans are recorded.
     *
     * @link https://github.com/elastic/apm-server/blob/v7.10.0/docs/spec/transactions/transaction.json#L26
     * @link https://github.com/elastic/apm-server/blob/v7.10.0/docs/spec/spans/span.json#L45
     */
    public $sampleRate = null;

    /** @var bool */
    protected $isDiscarded = false;

    /** @var ?BreakdownMetricsSelfTimeTracker */
    protected $breakdownMetricsSelfTimeTracker = null;

    /** @var float */
    private $diffStartTimeWithSystemClockOnBeginInMicroseconds;

    /** @var float */
    private $systemClockBeginTime;

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

    /** @var Logger */
    private $logger;

    /** @var bool */
    private $isEnded = false;

    protected function __construct(
        Tracer $tracer,
        ?ExecutionSegment $parentExecutionSegment,
        string $traceId,
        string $name,
        string $type,
        ?float $sampleRate,
        ?float $timestampArg = null
    ) {
        $monotonicClockNow = $tracer->getClock()->getMonotonicClockCurrentTime();
        $systemClockNow = $tracer->getClock()->getSystemClockCurrentTime();

        $this->id = IdGenerator::generateId(Constants::EXECUTION_SEGMENT_ID_SIZE_IN_BYTES);

        $this->systemClockBeginTime = $systemClockNow;
        if ($timestampArg === null) {
            $this->timestamp = $systemClockNow;
        } elseif ($timestampArg <= $systemClockNow) {
            $this->timestamp = $timestampArg;
        } else {
            $this->timestamp = $systemClockNow;

            $localLogger = self::createLogger($tracer->loggerFactory());
            ($loggerProxy = $localLogger->ifDebugLevelEnabled(__LINE__, __FUNCTION__))
            && $loggerProxy->log(
                'Using systemClockNow for start time instead of timestampArg argument'
                . ' because timestampArg argument is later (further into the future) than systemClockNow',
                [
                    'systemClockNow' => $systemClockNow,
                    'timestampArg'   => $timestampArg,
                    'timestampArg - systemClockNow (seconds)'
                                     => TimeUtil::microsecondsToSeconds($timestampArg - $systemClockNow),
                    'id'             => $this->id,
                    'name'           => $name,
                    'type'           => $type,
                ]
            );
        }
        $this->diffStartTimeWithSystemClockOnBeginInMicroseconds = TimeUtil::calcDurationInMicrosecondsClampNegativeToZero($this->timestamp, $systemClockNow);
        $this->monotonicBeginTime = $monotonicClockNow;
        $this->traceId = $traceId;
        $this->setName($name);
        $this->setType($type);
        $this->sampleRate = $sampleRate;

        if ($this->containingTransaction()->getConfig()->breakdownMetrics()) {
            $this->breakdownMetricsSelfTimeTracker = new BreakdownMetricsSelfTimeTracker($monotonicClockNow);
            if ($parentExecutionSegment !== null) {
                /**
                 * If breakdownMetrics config is true then all transaction's spans
                 * breakdownMetricsSelfTimeTracker should not be null
                 *
                 * Local variable to workaround PHPStan not having a way to declare that
                 * $parentExecutionSegment->breakdownMetricsSelfTimeTracker is not null
                 *
                 * @var BreakdownMetricsSelfTimeTracker $parentBreakdownMetricsSelfTimeTracker
                 */
                $parentBreakdownMetricsSelfTimeTracker = $parentExecutionSegment->breakdownMetricsSelfTimeTracker;
                $parentBreakdownMetricsSelfTimeTracker->onChildBegin($monotonicClockNow);
            }
        }

        $this->logger = self::createLogger($tracer->loggerFactory())->addContext('this', $this);
        ($loggerProxy = $this->logger->ifDebugLevelEnabled(__LINE__, __FUNCTION__))
        && $loggerProxy->log(
            'Exiting...',
            [
                'systemClockNow' => $systemClockNow,
                'timestampArg'   => $timestampArg,
                'systemClockNow - timestampArg (seconds)'
                                 => TimeUtil::microsecondsToSeconds($systemClockNow - $timestampArg),
            ]
        );
    }

    protected static function createLogger(LoggerFactory $loggerFactory): Logger
    {
        return $loggerFactory->loggerForClass(LogCategory::PUBLIC_API, __NAMESPACE__, __CLASS__, __FILE__);
    }

    public function isSampled(): bool
    {
        return $this->containingTransaction()->isSampled();
    }

    /**
     * @return Transaction
     */
    abstract public function containingTransaction(): Transaction;

    /**
     * @return ExecutionSegment|null
     */
    abstract public function parentExecutionSegment(): ?ExecutionSegment;

    public function getName(): string
    {
        return $this->name;
    }

    public function getType(): string
    {
        return $this->type;
    }

    /**
     * Begins a new span with this execution segment as the new span's parent,
     * runs the provided callback as the new span and automatically ends the new span.
     *
     * @param string      $name      New span's name
     * @param string      $type      New span's type
     * @param Closure     $callback  Callback to execute as the new span
     * @param string|null $subtype   New span's subtype
     * @param string|null $action    New span's action
     * @param float|null  $timestamp Start time of the new span
     * @param int         $numberOfStackFramesToSkip
     *
     * @return mixed The return value of $callback
     *
     * @template        T
     * @phpstan-param   Closure(SpanInterface $newSpan): T $callback
     * @phpstan-return  T
     *
     * @phpstan-param 0|positive-int $numberOfStackFramesToSkip
     *
     * @see             SpanInterface
     *
     * @noinspection    PhpDocMissingThrowsInspection
     */
    protected function captureChildSpanImpl(
        string $name,
        string $type,
        Closure $callback,
        ?string $subtype,
        ?string $action,
        ?float $timestamp,
        int $numberOfStackFramesToSkip
    ) {
        $newSpan = $this->beginChildSpan(
            $name,
            $type,
            $subtype,
            $action,
            $timestamp
        );
        try {
            return $callback($newSpan);
        } catch (Throwable $throwable) {
            $newSpan->createErrorFromThrowable($throwable);
            /** @noinspection PhpUnhandledExceptionInspection */
            throw $throwable;
        } finally {
            // Since endSpanEx was not called directly it should not be kept in the stack trace
            $newSpan->endSpanEx(/* numberOfStackFramesToSkip: */ $numberOfStackFramesToSkip + 1);
        }
    }

    /**
     * @param ErrorExceptionData $errorExceptionData
     *
     * @return ?string
     */
    abstract public function dispatchCreateError(ErrorExceptionData $errorExceptionData): ?string;

    /**
     * @param ?CustomErrorData $customErrorData
     * @param ?Throwable       $throwable
     * @param int              $numberOfStackFramesToSkip
     *
     * @return ?string
     *
     * @phpstan-param 0|positive-int $numberOfStackFramesToSkip
     */
    private function createError(?CustomErrorData $customErrorData, ?Throwable $throwable, int $numberOfStackFramesToSkip): ?string
    {
        return $this->dispatchCreateError(ErrorExceptionData::build($this->containingTransaction()->tracer(), $customErrorData, /* phpErrorData */ null, $throwable, $numberOfStackFramesToSkip + 1));
    }

    /** @inheritDoc */
    public function createErrorFromThrowable(Throwable $throwable): ?string
    {
        return $this->createError(/* customErrorData: */ null, $throwable, /* numberOfStackFramesToSkip */ 1);
    }

    /** @inheritDoc */
    public function createCustomError(CustomErrorData $customErrorData): ?string
    {
        return $this->createError($customErrorData, /* throwable: */ null, /* numberOfStackFramesToSkip */ 1);
    }

    public function beforeMutating(): bool
    {
        if (!$this->isEnded) {
            return false;
        }

        if ($this->isDiscarded) {
            return true;
        }

        ($loggerProxy = $this->logger->ifWarningLevelEnabled(__LINE__, __FUNCTION__))
        && $loggerProxy->includeStackTrace()->log('A mutating method has been called on already ended event');

        return true;
    }

    /** @inheritDoc */
    public function isNoop(): bool
    {
        return false;
    }

    /** @inheritDoc */
    public function getId(): string
    {
        return $this->id;
    }

    /** @inheritDoc */
    public function getTimestamp(): float
    {
        return $this->timestamp;
    }

    /** @inheritDoc */
    public function getTraceId(): string
    {
        return $this->traceId;
    }

    /** @inheritDoc */
    public function setName(string $name): void
    {
        if ($this->beforeMutating()) {
            return;
        }

        $this->name = Tracer::limitKeywordString($name);
    }

    /** @inheritDoc */
    public function setType(string $type): void
    {
        if ($this->beforeMutating()) {
            return;
        }

        $this->type = TextUtil::isEmptyString($type)
            ? Constants::EXECUTION_SEGMENT_TYPE_DEFAULT
            : Tracer::limitKeywordString($type);
    }

    /** @inheritDoc */
    public function getDistributedTracingData(): ?DistributedTracingData
    {
        return $this->getDistributedTracingDataInternal();
    }

    /**
     * Returns distributed tracing data
     */
    abstract public function getDistributedTracingDataInternal(): ?DistributedTracingDataInternal;

    /** @inheritDoc */
    public function injectDistributedTracingHeaders(Closure $headerInjector): void
    {
        /** @noinspection PhpDeprecationInspection */
        $distTracingData = $this->getDistributedTracingData();
        if ($distTracingData !== null) {
            $distTracingData->injectHeaders($headerInjector);
        }
    }

    public static function isValidOutcome(?string $outcome): bool
    {
        return $outcome === null
               || $outcome === Constants::OUTCOME_SUCCESS
               || $outcome === Constants::OUTCOME_FAILURE
               || $outcome === Constants::OUTCOME_UNKNOWN;
    }

    /** @inheritDoc */
    public function setOutcome(?string $outcome): void
    {
        if (!self::isValidOutcome($outcome)) {
            ($loggerProxy = $this->logger->ifErrorLevelEnabled(__LINE__, __FUNCTION__))
            && $loggerProxy->log('Given outcome value is invalid', ['outcome' => $outcome]);
            return;
        }

        $this->outcome = $outcome;
    }

    /** @inheritDoc */
    public function getOutcome(): ?string
    {
        return $this->outcome;
    }

    /** @inheritDoc */
    public function discard(): void
    {
        if ($this->beforeMutating()) {
            return;
        }

        $this->isDiscarded = true;
        $this->end();
    }

    public static function calcDurationInMicroseconds(
        float $systemClockBeginTime,
        float $monotonicBeginTime,
        float $systemClockEndTime,
        float $monotonicEndTime,
        LoggerFactory $loggerFactory
    ): float {
        $monotonicDurationInMicroseconds = TimeUtil::calcDurationInMicrosecondsClampNegativeToZero(
            $monotonicBeginTime,
            $monotonicEndTime
        );
        $systemClockDurationInMicroseconds = TimeUtil::calcDurationInMicrosecondsClampNegativeToZero(
            $systemClockBeginTime,
            $systemClockEndTime
        );
        /** @var ?Logger $logger */
        $logger = null;
        $logLevel = LogLevel::TRACE;
        if ($loggerFactory->isEnabledForLevel($logLevel)) {
            $logger = self::createLogger($loggerFactory);
            $monotonicMinusSystemDurationInSeconds = TimeUtil::microsecondsToSeconds(
                $systemClockDurationInMicroseconds - $monotonicDurationInMicroseconds
            );
            $logger->addAllContext(
                [
                    'systemClockDurationInMicroseconds'     => $systemClockDurationInMicroseconds,
                    'monotonicDurationInMicroseconds'       => $monotonicDurationInMicroseconds,
                    'monotonicMinusSystemDurationInSeconds' => $monotonicMinusSystemDurationInSeconds,
                    'systemClockBeginTime'                  => $systemClockBeginTime,
                    'monotonicBeginTime'                    => $monotonicBeginTime,
                    'systemClockEndTime'                    => $systemClockEndTime,
                    'monotonicEndTime'                      => $monotonicEndTime,
                ]
            );
        }
        if ($monotonicDurationInMicroseconds >= $systemClockDurationInMicroseconds) {
            $durationInMicroseconds = $monotonicDurationInMicroseconds;
            $logger && ($loggerProxy = $logger->ifLevelEnabled($logLevel, __LINE__, __FUNCTION__))
            && $loggerProxy->log('Using monotonic clock duration');
        } else {
            $durationInMicroseconds = $systemClockDurationInMicroseconds;
            $logger && ($loggerProxy = $logger->ifLevelEnabled($logLevel, __LINE__, __FUNCTION__))
            && $loggerProxy->log(
                'Using system clock duration instead of monotonic clock duration'
                . ' because system clock duration is larger'
            );
        }

        return $durationInMicroseconds;
    }

    protected function endExecutionSegment(?float $durationArg = null): bool
    {
        if ($this->isDiscarded) {
            $this->isEnded = true;
            return false;
        }

        if ($this->beforeMutating()) {
            return false;
        }

        $this->flushPendingCompositeChild();

        $clock = $this->containingTransaction()->tracer()->getClock();
        $monotonicEndTime = $clock->getMonotonicClockCurrentTime();
        $systemClockEndTime = $clock->getSystemClockCurrentTime();

        if ($durationArg === null) {
            $durationAfterBeginInMicroseconds = self::calcDurationInMicroseconds(
                $this->systemClockBeginTime,
                $this->monotonicBeginTime,
                $systemClockEndTime,
                $monotonicEndTime,
                $this->containingTransaction()->tracer()->loggerFactory()
            );
            $this->duration = TimeUtil::microsecondsToMilliseconds(
                $this->diffStartTimeWithSystemClockOnBeginInMicroseconds + $durationAfterBeginInMicroseconds
            );
        } else {
            $this->duration = $durationArg;
        }

        if ($this->breakdownMetricsSelfTimeTracker !== null && !$this->containingTransaction()->hasEnded()) {
            $this->updateBreakdownMetricsOnEnd($monotonicEndTime);
        }

        $this->isEnded = true;

        ($loggerProxy = $this->logger->ifDebugLevelEnabled(__LINE__, __FUNCTION__))
        && $loggerProxy->log(ClassNameUtil::fqToShort(get_class($this)) . ' ended', ['durationArg' => $durationArg]);

        return true;
    }

    /**
     * @param float $monotonicClockNow
     *
     * @return void
     */
    abstract protected function updateBreakdownMetricsOnEnd(float $monotonicClockNow): void;

    protected function doUpdateBreakdownMetricsOnEnd(
        float $monotonicClockNow,
        string $spanType,
        ?string $spanSubtype
    ): void {
        /**
         * @var BreakdownMetricsSelfTimeTracker $breakdownMetricsSelfTimeTracker
         *
         * doUpdateBreakdownMetricsOnEnd is called only if breakdownMetricsSelfTimeTracker is not null
         */
        $breakdownMetricsSelfTimeTracker = $this->breakdownMetricsSelfTimeTracker;

        $breakdownMetricsSelfTimeTracker->end($monotonicClockNow);
        $this->containingTransaction()->addSpanSelfTime(
            $spanType,
            $spanSubtype,
            $breakdownMetricsSelfTimeTracker->accumulatedSelfTimeInMicroseconds()
        );

        $parentExecutionSegment = $this->parentExecutionSegment();
        if ($parentExecutionSegment !== null) {
            /**
             * doUpdateBreakdownMetricsOnEnd is called only if breakdownMetricsSelfTimeTracker is not null
             *
             * Local variable to workaround PHPStan not having a way to declare that
             * $parentExecutionSegment->breakdownMetricsSelfTimeTracker is not null
             *
             * @var BreakdownMetricsSelfTimeTracker $parentBreakdownMetricsSelfTimeTracker
             */
            $parentBreakdownMetricsSelfTimeTracker = $parentExecutionSegment->breakdownMetricsSelfTimeTracker;
            $parentBreakdownMetricsSelfTimeTracker->onChildEnd($monotonicClockNow);
        }
    }

    protected function onChildSpanAboutToStart(Span $child): void
    {
    }

    protected function onChildSpanEnded(Span $child): void
    {
        $shouldSendEndedSpanImmediately = false;

        if ($this->containingTransaction()->isSpanCompressionEnabled()) {
            if (!$this->tryToCompressChild($child)) {
                $this->flushPendingCompositeChild();
                $shouldSendEndedSpanImmediately = true;
            }
        } else {
            $shouldSendEndedSpanImmediately = true;
        }

        if ($shouldSendEndedSpanImmediately) {
            $this->containingTransaction()->tracer()->sendSpanToApmServer($child);
        }
    }

    private function tryToCompressChild(Span $child): bool
    {
        ($loggerProxy = $this->logger->ifTraceLevelEnabled(__LINE__, __FUNCTION__))
        && $loggerProxy->log('Entered', ['child' => $child]);

        if ($this->hasEnded()) {
            ($loggerProxy = $this->logger->ifTraceLevelEnabled(__LINE__, __FUNCTION__))
            && $loggerProxy->log('Exiting - not going to compress because this execution segment already ended');
            return false;
        }

        if (!$child->isCompressionEligible()) {
            ($loggerProxy = $this->logger->ifTraceLevelEnabled(__LINE__, __FUNCTION__))
            && $loggerProxy->log('Exiting - not going to compress because this execution segment already ended');
            return false;
        }

        if ($this->pendingCompositeChild === null) {
            $this->pendingCompositeChild = $child;
            ($loggerProxy = $this->logger->ifTraceLevelEnabled(__LINE__, __FUNCTION__))
            && $loggerProxy->log('Exiting - set pendingCompositeChild to child', ['child' => $child]);
            return true;
        }

        if ($this->pendingCompositeChild->tryToAddToCompress($child)) {
            ($loggerProxy = $this->logger->ifTraceLevelEnabled(__LINE__, __FUNCTION__))
            && $loggerProxy->log('Exiting - added to pendingCompositeChild', ['child' => $child]);
            return true;
        }

        /**
         * Flush and re-try from the given child
         */
        $this->flushPendingCompositeChild();
        return $this->tryToCompressChild($child);
    }

    private function flushPendingCompositeChild(): void
    {
        if ($this->pendingCompositeChild === null) {
            return;
        }

        $this->containingTransaction()->tracer()->sendSpanToApmServer($this->pendingCompositeChild);
        $this->pendingCompositeChild = null;
    }

    /** @inheritDoc */
    public function hasEnded(): bool
    {
        return $this->isEnded;
    }

    /** @inheritDoc */
    public function jsonSerialize()
    {
        $result = [];

        SerializationUtil::addNameValue('name', $this->name, /* ref */ $result);
        SerializationUtil::addNameValue('type', $this->type, /* ref */ $result);
        SerializationUtil::addNameValue('id', $this->id, /* ref */ $result);
        SerializationUtil::addNameValue('trace_id', $this->traceId, /* ref */ $result);
        $timestamp = SerializationUtil::adaptTimestamp($this->timestamp);
        SerializationUtil::addNameValue('timestamp', $timestamp, /* ref */ $result);
        SerializationUtil::addNameValue('duration', $this->duration, /* ref */ $result);
        SerializationUtil::addNameValueIfNotNull('outcome', $this->outcome, /* ref */ $result);
        SerializationUtil::addNameValueIfNotNull('sample_rate', $this->sampleRate, /* ref */ $result);

        return SerializationUtil::postProcessResult($result);
    }

    /**
     * @return array<string>
     */
    protected static function propertiesExcludedFromLog(): array
    {
        return ['tracer'];
    }
}