class StreamFactory

final class StreamFactory implements MetricFactoryInterface {
    public function createAsynchronousObserver(MetricRegistryInterface $registry, ResourceInfo $resource, InstrumentationScopeInterface $instrumentationScope, Instrument $instrument, int $timestamp, iterable $views) : array {
        $streams = [];
        $dedup = [];
        foreach ($views as [
            $view,
            $registration,
        ]) {
            if ($view->aggregation === null) {
                continue;
            }
            $dedupId = $this->streamId($view->aggregation, $view->attributeKeys);
            if (($streamId = $dedup[$dedupId] ?? null) === null) {
                $stream = new AsynchronousMetricStream($view->aggregation, $timestamp);
                $streamId = $registry->registerAsynchronousStream($instrument, $stream, new MetricAggregatorFactory($this->attributeProcessor($view->attributeKeys), $view->aggregation));
                $streams[$streamId] = $stream;
                $dedup[$dedupId] = $streamId;
            }
            $this->registerSource($view, $instrument, $instrumentationScope, $resource, $streams[$streamId], $registry, $registration, $streamId);
        }
        return array_keys($streams);
    }
    public function createSynchronousWriter(MetricRegistryInterface $registry, ResourceInfo $resource, InstrumentationScopeInterface $instrumentationScope, Instrument $instrument, int $timestamp, iterable $views, ?ExemplarFilterInterface $exemplarFilter = null) : array {
        $streams = [];
        $dedup = [];
        foreach ($views as [
            $view,
            $registration,
        ]) {
            if ($view->aggregation === null) {
                continue;
            }
            $dedupId = $this->streamId($view->aggregation, $view->attributeKeys);
            if (($streamId = $dedup[$dedupId] ?? null) === null) {
                $stream = new SynchronousMetricStream($view->aggregation, $timestamp);
                $streamId = $registry->registerSynchronousStream($instrument, $stream, new MetricAggregator($this->attributeProcessor($view->attributeKeys), $view->aggregation, $this->createExemplarReservoir($view->aggregation, $exemplarFilter)));
                $streams[$streamId] = $stream;
                $dedup[$dedupId] = $streamId;
            }
            $this->registerSource($view, $instrument, $instrumentationScope, $resource, $streams[$streamId], $registry, $registration, $streamId);
        }
        return array_keys($streams);
    }
    private function attributeProcessor(?array $attributeKeys) : ?AttributeProcessorInterface {
        return $attributeKeys !== null ? new FilteredAttributeProcessor($attributeKeys) : null;
    }
    private function createExemplarReservoir(AggregationInterface $aggregation, ?ExemplarFilterInterface $exemplarFilter) : ?ExemplarReservoirInterface {
        if (!$exemplarFilter) {
            return null;
        }
        if ($aggregation instanceof ExplicitBucketHistogramAggregation && $aggregation->boundaries) {
            $exemplarReservoir = new HistogramBucketReservoir($aggregation->boundaries);
        }
        else {
            $exemplarReservoir = new FixedSizeReservoir();
        }
        return new FilteredReservoir($exemplarReservoir, $exemplarFilter);
    }
    private function registerSource(ViewProjection $view, Instrument $instrument, InstrumentationScopeInterface $instrumentationScope, ResourceInfo $resource, MetricStreamInterface $stream, MetricCollectorInterface $metricCollector, MetricRegistrationInterface $metricRegistration, int $streamId) : void {
        $provider = new StreamMetricSourceProvider($view, $instrument, $instrumentationScope, $resource, $stream, $metricCollector, $streamId);
        $metricRegistration->register($provider, $provider);
    }
    private function streamId(AggregationInterface $aggregation, ?array $attributeKeys) : string {
        return $this->trySerialize($aggregation) . serialize($attributeKeys);
    }
    private function trySerialize(object $object) {
        try {
            return serialize($object);
        } catch (Throwable) {
        }
        return spl_object_id($object);
    }

}