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 * Copyright (c) 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

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package jdk.jshell.execution;

import java.io.IOException;

import java.io.InputStream;

import java.io.ObjectInput;

import java.io.ObjectOutput;

import java.io.OutputStream;

import java.net.InetAddress;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.function.Consumer;

import com.sun.jdi.BooleanValue;

import com.sun.jdi.ClassNotLoadedException;

import com.sun.jdi.Field;

import com.sun.jdi.IncompatibleThreadStateException;

import com.sun.jdi.InvalidTypeException;

import com.sun.jdi.ObjectReference;

import com.sun.jdi.StackFrame;

import com.sun.jdi.ThreadReference;

import com.sun.jdi.VMDisconnectedException;

import com.sun.jdi.VirtualMachine;

import jdk.jshell.spi.ExecutionControl;

import jdk.jshell.spi.ExecutionEnv;

import static jdk.jshell.execution.Util.remoteInputOutput;

/**

 * The implementation of {@link jdk.jshell.spi.ExecutionControl} that the

 * JShell-core uses by default.

 * Launches a remote process -- the "remote agent".

 * Interfaces to the remote agent over a socket and via JDI.

 * Designed to work with {@link RemoteExecutionControl}.

 *

 * @author Robert Field

 * @author Jan Lahoda

 */

public class JdiDefaultExecutionControl extends JdiExecutionControl {

    private VirtualMachine vm;

    private Process process;

    private final String remoteAgent;

    private final Object STOP_LOCK = new Object();

    private boolean userCodeRunning = false;

    /**

     * Creates an ExecutionControl instance based on a JDI

     * {@code ListeningConnector} or {@code LaunchingConnector}.

     *

     * Initialize JDI and use it to launch the remote JVM. Set-up a socket for

     * commands and results. This socket also transports the user

     * input/output/error.

     *

     * @param env the context passed by

     * {@link jdk.jshell.spi.ExecutionControl#start(jdk.jshell.spi.ExecutionEnv) }

     * @param remoteAgent the remote agent to launch

     * @param isLaunch does JDI do the launch? That is, LaunchingConnector,

     * otherwise we start explicitly and use ListeningConnector

     * @param host explicit hostname to use, if null use discovered

     * hostname, applies to listening only (!isLaunch)

     * @return the channel

     * @throws IOException if there are errors in set-up

     */

    static ExecutionControl create(ExecutionEnv env, String remoteAgent,

            boolean isLaunch, String host, int timeout) throws IOException {

        try (final ServerSocket listener = new ServerSocket(0, 1, InetAddress.getLoopbackAddress())) {

            // timeout on I/O-socket

            listener.setSoTimeout(timeout);

            int port = listener.getLocalPort();

            // Set-up the JDI connection

            JdiInitiator jdii = new JdiInitiator(port,

                    env.extraRemoteVMOptions(), remoteAgent, isLaunch, host,

                    timeout, Collections.emptyMap());

            VirtualMachine vm = jdii.vm();

            Process process = jdii.process();

            List<Consumer<String>> deathListeners = new ArrayList<>();

            Util.detectJdiExitEvent(vm, s -> {

                for (Consumer<String> h : deathListeners) {

                    h.accept(s);

                }

            });

            // Set-up the commands/reslts on the socket.  Piggy-back snippet

            // output.

            Socket socket = listener.accept();

            // out before in -- match remote creation so we don't hang

            OutputStream out = socket.getOutputStream();

            Map<String, OutputStream> outputs = new HashMap<>();

            outputs.put("out", env.userOut());

            outputs.put("err", env.userErr());

            Map<String, InputStream> input = new HashMap<>();

            input.put("in", env.userIn());

            return remoteInputOutput(socket.getInputStream(), out, outputs, input,

                    (objIn, objOut) -> new JdiDefaultExecutionControl(env,

                                        objOut, objIn, vm, process, remoteAgent, deathListeners));

        }

    }

    /**

     * Create an instance.

     *

     * @param cmdout the output for commands

     * @param cmdin the input for responses

     */

    private JdiDefaultExecutionControl(ExecutionEnv env,

            ObjectOutput cmdout, ObjectInput cmdin,

            VirtualMachine vm, Process process, String remoteAgent,

            List<Consumer<String>> deathListeners) {

        super(cmdout, cmdin);

        this.vm = vm;

        this.process = process;

        this.remoteAgent = remoteAgent;

        // We have now succeeded in establishing the connection.

        // If there is an exit now it propagates all the way up

        // and the VM should be disposed of.

        deathListeners.add(s -> env.closeDown());

        deathListeners.add(s -> disposeVM());

     }

    @Override

    public String invoke(String classname, String methodname)

            throws RunException,

            EngineTerminationException, InternalException {

        String res;

        synchronized (STOP_LOCK) {

            userCodeRunning = true;

        }

        try {

            res = super.invoke(classname, methodname);

        } finally {

            synchronized (STOP_LOCK) {

                userCodeRunning = false;

            }

        }

        return res;

    }

    /**

     * Interrupts a running remote invoke by manipulating remote variables

     * and sending a stop via JDI.

     *

     * @throws EngineTerminationException the execution engine has terminated

     * @throws InternalException an internal problem occurred

     */

    @Override

    public void stop() throws EngineTerminationException, InternalException {

        synchronized (STOP_LOCK) {

            if (!userCodeRunning) {

                return;

            }

            vm().suspend();

            try {

                OUTER:

                for (ThreadReference thread : vm().allThreads()) {

                    // could also tag the thread (e.g. using name), to find it easier

                    for (StackFrame frame : thread.frames()) {

                        if (remoteAgent.equals(frame.location().declaringType().name()) &&

                                (    "invoke".equals(frame.location().method().name())

                                || "varValue".equals(frame.location().method().name()))) {

                            ObjectReference thiz = frame.thisObject();

                            Field inClientCode = thiz.referenceType().fieldByName("inClientCode");

                            Field expectingStop = thiz.referenceType().fieldByName("expectingStop");

                            Field stopException = thiz.referenceType().fieldByName("stopException");

                            if (((BooleanValue) thiz.getValue(inClientCode)).value()) {

                                thiz.setValue(expectingStop, vm().mirrorOf(true));

                                ObjectReference stopInstance = (ObjectReference) thiz.getValue(stopException);

                                vm().resume();

                                debug("Attempting to stop the client code...\n");

                                thread.stop(stopInstance);

                                thiz.setValue(expectingStop, vm().mirrorOf(false));

                            }

                            break OUTER;

                        }

                    }

                }

            } catch (ClassNotLoadedException | IncompatibleThreadStateException | InvalidTypeException ex) {

                throw new InternalException("Exception on remote stop: " + ex);

            } finally {

                vm().resume();

            }

        }

    }

    @Override

    public void close() {

        super.close();

        disposeVM();

    }

    private synchronized void disposeVM() {

        try {

            if (vm != null) {

                vm.dispose(); // This could NPE, so it is caught below

                vm = null;

            }

        } catch (VMDisconnectedException ex) {

            // Ignore if already closed

        } catch (Throwable ex) {

            debug(ex, "disposeVM");

        } finally {

            if (process != null) {

                process.destroy();

                process = null;

            }

        }

    }

    @Override

    protected synchronized VirtualMachine vm() throws EngineTerminationException {

        if (vm == null) {

            throw new EngineTerminationException("VM closed");

        } else {

            return vm;

        }

    }

    /**

     * Log debugging information. Arguments as for {@code printf}.

     *

     * @param format a format string as described in Format string syntax

     * @param args arguments referenced by the format specifiers in the format

     * string.

     */

    private static void debug(String format, Object... args) {

        // Reserved for future logging

    }

    /**

     * Log a serious unexpected internal exception.

     *

     * @param ex the exception

     * @param where a description of the context of the exception

     */

    private static void debug(Throwable ex, String where) {

        // Reserved for future logging

    }

}