/*

 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.internal.net.http.common;

import java.net.http.HttpClient;

/**

 * A small class allowing to track how many operations are

 * left outstanding on an instance of HttpClient.

 */

public final class OperationTrackers {

    private OperationTrackers() {

        throw new InternalError("not instantiable");

    }

    /**

     * A tracker can return the current value of

     * operation counters maintained by an instance

     * of {@link Trackable}, such as an HttpClientImpl.

     */

    public interface Tracker {

        // The total number of outstanding operations

        long getOutstandingOperations();

        // The number of outstanding HTTP/1.1 operations.

        // A single HTTP/1.1 request may increment this counter

        // multiple times, so the value returned will be >= to

        // the number of active HTTP/1.1 connections, but will

        // still be 0 if there are no active connections.

        long getOutstandingHttpOperations();

        // The number of active HTTP/2 streams

        long getOutstandingHttp2Streams();

        // The number of active WebSockets

        long getOutstandingWebSocketOperations();

        // Whether the facade returned to the

        // user is still referenced

        boolean isFacadeReferenced();

        // The name of the object being tracked.

        String getName();

    }

    /**

     * Implemented by objects that maintain operation counters.

     */

    public interface Trackable {

        Tracker getOperationsTracker();

    }

    /**

     * Returns a tracker to track pending operations started on

     * an HttpClient instance. May return null if this isn't

     * an HttpClientImpl or HttpClientFacade.

     * @param client the HttpClient instance to track.

     * @return A tracker or null.

     */

    public static Tracker getTracker(HttpClient client) {

        if (client instanceof Trackable) {

            return ((Trackable)client).getOperationsTracker();

        } else {

            return null;

        }

    }

}