/*

 * Copyright (c) 2014, 2015, 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

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 */

package com.sun.tools.sjavac.server;

import java.io.Writer;

import java.util.Timer;

import java.util.TimerTask;

/**

 * An sjavac implementation that keeps track of idleness and shuts down the

 * given Terminable upon idleness timeout.

 *

 * An idleness timeout kicks in {@code idleTimeout} milliseconds after the last

 * request is completed.

 *

 *  <p><b>This is NOT part of any supported API.

 *  If you write code that depends on this, you do so at your own risk.

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class IdleResetSjavac implements Sjavac {

    private final Sjavac delegate;

    private final Terminable toShutdown;

    private final Timer idlenessTimer = new Timer();

    private final long idleTimeout;

    private int outstandingCalls = 0;

    // Class invariant: idlenessTimerTask != null <-> idlenessTimerTask is scheduled

    private TimerTask idlenessTimerTask;

    public IdleResetSjavac(Sjavac delegate,

                            Terminable toShutdown,

                            long idleTimeout) {

        this.delegate = delegate;

        this.toShutdown = toShutdown;

        this.idleTimeout = idleTimeout;

        scheduleTimeout();

    }

    @Override

    public int compile(String[] args, Writer out, Writer err) {

        startCall();

        try {

            return delegate.compile(args, out, err);

        } finally {

            endCall();

        }

    }

    private synchronized void startCall() {

        // Was there no outstanding calls before this call?

        if (++outstandingCalls == 1) {

            // Then the timer task must have been scheduled

            if (idlenessTimerTask == null)

                throw new IllegalStateException("Idle timeout already cancelled");

            // Cancel timeout task

            idlenessTimerTask.cancel();

            idlenessTimerTask = null;

        }

    }

    private synchronized void endCall() {

        if (--outstandingCalls == 0) {

            // No more outstanding calls. Schedule timeout.

            scheduleTimeout();

        }

    }

    private void scheduleTimeout() {

        if (idlenessTimerTask != null)

            throw new IllegalStateException("Idle timeout already scheduled");

        idlenessTimerTask = new TimerTask() {

            public void run() {

                toShutdown.shutdown("Server has been idle for " + (idleTimeout / 1000) + " seconds.");

            }

        };

        idlenessTimer.schedule(idlenessTimerTask, idleTimeout);

    }

    @Override

    public void shutdown() {

        idlenessTimer.cancel();

        delegate.shutdown();

    }

}