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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.container.jdisc.metric;

import com.yahoo.component.annotation.Inject;
import com.yahoo.component.provider.ComponentRegistry;
import com.yahoo.container.jdisc.MetricConsumerFactory;
import com.yahoo.jdisc.application.MetricConsumer;


/**
 * The purpose of this class it to be the only provider for the MetricConsumer interface in a component
 * graph. This component is automatically registered in the graph by the config server. Configuring a different
 * MetricConsumer is done by registering one or more {@link MetricConsumerFactory} in the services-file.
 *
 * Because this class depends on the {@link ComponentRegistry} of {@link MetricConsumerFactory}, any added or removed
 * {@link MetricConsumerFactory} will cause this component to be reconfigured. Because {@link MetricProvider} depends on
 * this class, which means any component that uses Metric will be reconfigured. Any component that depends
 * directly on MetricConsumer will also be reconfigured.
 *
 * @author Simon Thoresen Hult
 */
public class MetricConsumerProvider {

    private final MetricConsumerFactory[] factories;

    @Inject
    public MetricConsumerProvider(ComponentRegistry factoryRegistry) {
        MetricConsumerFactory[] factories = new MetricConsumerFactory[factoryRegistry.getComponentCount()];
        factoryRegistry.allComponents().toArray(factories);
        this.factories = factories;
    }

    public MetricConsumer newInstance() {
        if (factories.length == 1) {
            return factories[0].newInstance();
        }
        MetricConsumer[] consumers = new MetricConsumer[factories.length];
        for (int i = 0; i < factories.length; ++i) {
            consumers[i] = factories[i].newInstance();
        }
        return new ForwardingMetricConsumer(consumers);
    }

}