/*

 * 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

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package jdk.jshell.execution;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.PrintStream;

import java.lang.reflect.Method;

import java.net.Socket;

import java.util.HashMap;

import java.util.Map;

import java.util.function.Consumer;

import jdk.jshell.spi.ExecutionControl;

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

/**

 * The remote agent runs in the execution process (separate from the main JShell

 * process). This agent loads code over a socket from the main JShell process,

 * executes the code, and other misc, Specialization of

 * {@link DirectExecutionControl} which adds stop support controlled by

 * an external process. Designed to work with {@link JDIDefaultExecutionControl}.

 *

 * @author Jan Lahoda

 * @author Robert Field

 */

public class RemoteExecutionControl extends DirectExecutionControl implements ExecutionControl {

    /**

     * Launch the agent, connecting to the JShell-core over the socket specified

     * in the command-line argument.

     *

     * @param args standard command-line arguments, expectation is the socket

     * number is the only argument

     * @throws Exception any unexpected exception

     */

    public static void main(String[] args) throws Exception {

        String loopBack = null;

        Socket socket = new Socket(loopBack, Integer.parseInt(args[0]));

        InputStream inStream = socket.getInputStream();

        OutputStream outStream = socket.getOutputStream();

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

        chans.put("out", st -> System.setOut(new PrintStream(st, true)));

        chans.put("err", st -> System.setErr(new PrintStream(st, true)));

        forwardExecutionControlAndIO(new RemoteExecutionControl(), inStream, outStream, chans);

    }

    // These three variables are used by the main JShell process in interrupting

    // the running process.  Access is via JDI, so the reference is not visible

    // to code inspection.

    private boolean inClientCode; // Queried by the main process (in superclass)

    private boolean expectingStop; // Set by the main process

// Set by the main process

    // thrown by the main process via JDI:

    private final StopExecutionException stopException = new StopExecutionException();

    /**

     * Creates an instance, delegating loader operations to the specified

     * delegate.

     *

     * @param loaderDelegate the delegate to handle loading classes

     */

    public RemoteExecutionControl(LoaderDelegate loaderDelegate) {

        super(loaderDelegate);

    }

    /**

     * Create an instance using the default class loading.

     */

    public RemoteExecutionControl() {

    }

    @Override

    public void stop() throws EngineTerminationException, InternalException {

        // handled by JDI

    }

    // Overridden only so this stack frame is seen

    @Override

    protected String invoke(Method doitMethod) throws Exception {

        return super.invoke(doitMethod);

    }

    // Overridden only so this stack frame is seen

    @Override

    public String varValue(String className, String varName) throws RunException, EngineTerminationException, InternalException {

        return super.varValue(className, varName);

    }

    @Override

    protected String throwConvertedInvocationException(Throwable cause) throws RunException, InternalException {

        if (cause instanceof StopExecutionException) {

            expectingStop = false;

            throw new StoppedException();

        } else {

            return super.throwConvertedInvocationException(cause);

        }

    }

    @Override

    protected String throwConvertedOtherException(Throwable ex) throws RunException, InternalException {

        if (ex instanceof StopExecutionException ||

                 ex.getCause() instanceof StopExecutionException) {

            expectingStop = false;

            throw new StoppedException();

        }

        return super.throwConvertedOtherException(ex);

    }

    @Override

    protected void clientCodeEnter() {

        expectingStop = false;

        inClientCode = true;

    }

    @Override

    protected void clientCodeLeave() throws InternalException {

        inClientCode = false;

        while (expectingStop) {

            try {

                Thread.sleep(0);

            } catch (InterruptedException ex) {

                throw new InternalException("*** Sleep interrupted while waiting for stop exception: " + ex);

            }

        }

    }

    @SuppressWarnings("serial")             // serialVersionUID intentionally omitted

    private class StopExecutionException extends ThreadDeath {

        @Override

        public synchronized Throwable fillInStackTrace() {

            return this;

        }

    }

}