/*

 * Copyright (c) 1998, 2014, 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.jshell.execution;

import java.util.function.Consumer;

import com.sun.jdi.*;

import com.sun.jdi.event.*;

/**

 * Handler of Java Debug Interface events.

 * Adapted from jdb EventHandler.

 * Only exit and disconnect events processed.

 */

class JdiEventHandler implements Runnable {

    private final Thread thread;

    private volatile boolean connected = true;

    private boolean completed = false;

    private final VirtualMachine vm;

    private final Consumer<String> reportVMExit;

    /**

     * Creates an event handler. Start with {@code start()}.

     *

     * @param vm the virtual machine for which to handle events

     * @param reportVMExit callback to report exit/disconnect

     * (passed true if the VM has died)

     */

    JdiEventHandler(VirtualMachine vm, Consumer<String> reportVMExit) {

        this.vm = vm;

        this.reportVMExit = reportVMExit;

        this.thread = new Thread(this, "event-handler");

        this.thread.setDaemon(true);

    }

    /**

     * Starts the event handler.

     */

    void start() {

        thread.start();

    }

    synchronized void shutdown() {

        connected = false;  // force run() loop termination

        thread.interrupt();

        while (!completed) {

            try {wait();} catch (InterruptedException exc) {}

        }

    }

    @Override

    public void run() {

        EventQueue queue = vm.eventQueue();

        while (connected) {

            try {

                EventSet eventSet = queue.remove();

                boolean resumeStoppedApp = false;

                EventIterator it = eventSet.eventIterator();

                while (it.hasNext()) {

                    resumeStoppedApp |= handleEvent(it.nextEvent());

                }

                if (resumeStoppedApp) {

                    eventSet.resume();

                }

            } catch (InterruptedException exc) {

                // Do nothing. Any changes will be seen at top of loop.

            } catch (VMDisconnectedException discExc) {

                handleDisconnectedException();

                break;

            }

        }

        synchronized (this) {

            completed = true;

            notifyAll();

        }

    }

    private boolean handleEvent(Event event) {

        handleExitEvent(event);

        return true;

    }

    private void handleExitEvent(Event event) {

        if (event instanceof VMDeathEvent) {

            reportVMExit.accept("VM Died");

        } else if (event instanceof VMDisconnectEvent) {

            connected = false;

            reportVMExit.accept("VM Disconnected");

        } else {

            // ignore everything else

        }

    }

    private synchronized void handleDisconnectedException() {

        /*

         * A VMDisconnectedException has happened while dealing with

         * another event. We need to flush the event queue, dealing only

         * with exit events (VMDeath, VMDisconnect) so that we terminate

         * correctly.

         */

        EventQueue queue = vm.eventQueue();

        while (connected) {

            try {

                EventSet eventSet = queue.remove();

                EventIterator iter = eventSet.eventIterator();

                while (iter.hasNext()) {

                    handleExitEvent(iter.next());

                }

            } catch (InterruptedException exc) {

                // ignore

            } catch (InternalError exc) {

                // ignore

            }

        }

    }

}