/*

 * Copyright (c) 2015, 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

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 */

import java.lang.System.Logger.Level;

import java.util.concurrent.atomic.AtomicInteger;

abstract class WindowUpdateSender {

    final static boolean DEBUG = Utils.DEBUG;

    final System.Logger debug =

            Utils.getDebugLogger(this::dbgString, DEBUG);

    final int limit;

    final Http2Connection connection;

    final AtomicInteger received = new AtomicInteger(0);

    WindowUpdateSender(Http2Connection connection) {

        this(connection, connection.clientSettings.getParameter(SettingsFrame.INITIAL_WINDOW_SIZE));

    }

    WindowUpdateSender(Http2Connection connection, int initWindowSize) {

        this(connection, connection.getMaxReceiveFrameSize(), initWindowSize);

    }

    WindowUpdateSender(Http2Connection connection, int maxFrameSize, int initWindowSize) {

        this.connection = connection;

        int v0 = Math.max(0, initWindowSize - maxFrameSize);

        int v1 = (initWindowSize + (maxFrameSize - 1)) / maxFrameSize;

        v1 = v1 * maxFrameSize / 2;

        // send WindowUpdate heuristic:

        // - we got data near half of window size

        //   or

        // - remaining window size reached max frame size.

        limit = Math.min(v0, v1);

        debug.log(Level.DEBUG, "maxFrameSize=%d, initWindowSize=%d, limit=%d",

                maxFrameSize, initWindowSize, limit);

    }

    abstract int getStreamId();

    void update(int delta) {

        debug.log(Level.DEBUG, "update: %d", delta);

        if (received.addAndGet(delta) > limit) {

            synchronized (this) {

                int tosend = received.get();

                if( tosend > limit) {

                    received.getAndAdd(-tosend);

                    sendWindowUpdate(tosend);

                }

            }

        }

    }

    void sendWindowUpdate(int delta) {

        debug.log(Level.DEBUG, "sending window update: %d", delta);

        connection.sendUnorderedFrame(new WindowUpdateFrame(getStreamId(), delta));

    }

    String dbgString() {

        return "WindowUpdateSender(stream: " + getStreamId() + ")";

    }

}