/*
 * Copyright (c) 2014, 2016, 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 com.sun.tools.sjavac.server;

import com.sun.tools.javac.main.Main.Result;
import com.sun.tools.sjavac.Log;

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 idleTimeout milliseconds after the last request is completed. 
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.
/**
 * 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 Result compile(String[] args) {
        startCall();
        try {
            return delegate.compile(args);
        } 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() {
                Log.setLogForCurrentThread(ServerMain.getErrorLog());
                toShutdown.shutdown("Server has been idle for " + (idleTimeout / 1000) + " seconds.");
            }
        };
        idlenessTimer.schedule(idlenessTimerTask, idleTimeout);
    }

    @Override
    public void shutdown() {
        idlenessTimer.cancel();
        delegate.shutdown();
    }

}