/*

 * 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.io.IOException;

import java.io.ObjectInput;

import java.io.ObjectOutput;

import jdk.jshell.JShellException;

import jdk.jshell.spi.ExecutionControl;

import static jdk.jshell.execution.ExecutionControlForwarder.NULL_MARKER;

import static jdk.jshell.execution.RemoteCodes.*;

/**

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

 * execution engine SPI which streams requests to a remote agent where

 * execution takes place.

 *

 * @author Robert Field

 * @since 9

 */

public class StreamingExecutionControl implements ExecutionControl {

    private final ObjectOutput out;

    private final ObjectInput in;

    /**

     * Creates an instance.

     *

     * @param out the output for commands

     * @param in the input for command responses

     */

    public StreamingExecutionControl(ObjectOutput out, ObjectInput in) {

        this.out = out;

        this.in = in;

    }

    @Override

    public void load(ClassBytecodes[] cbcs)

            throws ClassInstallException, NotImplementedException, EngineTerminationException {

        try {

            // Send a load command to the remote agent.

            writeCommand(CMD_LOAD);

            out.writeObject(cbcs);

            out.flush();

            // Retrieve and report results from the remote agent.

            readAndReportClassInstallResult();

        } catch (IOException ex) {

            throw new EngineTerminationException("Exception writing remote load: " + ex);

        }

    }

    @Override

    public void redefine(ClassBytecodes[] cbcs)

            throws ClassInstallException, NotImplementedException, EngineTerminationException {

        try {

            // Send a load command to the remote agent.

            writeCommand(CMD_REDEFINE);

            out.writeObject(cbcs);

            out.flush();

            // Retrieve and report results from the remote agent.

            readAndReportClassInstallResult();

        } catch (IOException ex) {

            throw new EngineTerminationException("Exception writing remote redefine: " + ex);

        }

    }

    @Override

    public String invoke(String classname, String methodname)

            throws RunException, EngineTerminationException, InternalException {

        try {

            // Send the invoke command to the remote agent.

            writeCommand(CMD_INVOKE);

            out.writeUTF(classname);

            out.writeUTF(methodname);

            out.flush();

            // Retrieve and report results from the remote agent.

            readAndReportExecutionResult();

            String result = in.readUTF();

            return result;

        } catch (IOException ex) {

            throw new EngineTerminationException("Exception writing remote invoke: " + ex);

        }

    }

    @Override

    public String varValue(String classname, String varname)

            throws RunException, EngineTerminationException, InternalException {

        try {

            // Send the variable-value command to the remote agent.

            writeCommand(CMD_VAR_VALUE);

            out.writeUTF(classname);

            out.writeUTF(varname);

            out.flush();

            // Retrieve and report results from the remote agent.

            readAndReportExecutionResult();

            String result = in.readUTF();

            return result;

        } catch (IOException ex) {

            throw new EngineTerminationException("Exception writing remote varValue: " + ex);

        }

    }

    @Override

    public void addToClasspath(String path)

            throws EngineTerminationException, InternalException {

        try {

            // Send the classpath addition command to the remote agent.

            writeCommand(CMD_ADD_CLASSPATH);

            out.writeUTF(path);

            out.flush();

            // Retrieve and report results from the remote agent.

            readAndReportClassSimpleResult();

        } catch (IOException ex) {

            throw new EngineTerminationException("Exception writing remote add to classpath: " + ex);

        }

    }

    @Override

    public void stop()

            throws EngineTerminationException, InternalException {

        try {

            // Send the variable-value command to the remote agent.

            writeCommand(CMD_STOP);

            out.flush();

        } catch (IOException ex) {

            throw new EngineTerminationException("Exception writing remote stop: " + ex);

        }

    }

    @Override

    public Object extensionCommand(String command, Object arg)

            throws RunException, EngineTerminationException, InternalException {

        try {

            writeCommand(command);

            out.writeObject(arg);

            out.flush();

            // Retrieve and report results from the remote agent.

            readAndReportExecutionResult();

            Object result = in.readObject();

            return result;

        } catch (IOException | ClassNotFoundException ex) {

            throw new EngineTerminationException("Exception transmitting remote extensionCommand: "

                    + command + " -- " + ex);

        }

    }

    /**

     * Closes the execution engine. Send an exit command to the remote agent.

     */

    @Override

    public void close() {

        try {

            writeCommand(CMD_CLOSE);

            out.flush();

        } catch (IOException ex) {

            // ignore;

        }

    }

    private void writeCommand(String cmd) throws IOException {

        out.writeInt(COMMAND_PREFIX);

        out.writeUTF(cmd);

    }

    /**

     * Read a UTF or a null encoded as a null marker.

     * @return a string or null

     * @throws IOException passed through from readUTF()

     */

    private String readNullOrUTF() throws IOException {

        String s = in.readUTF();

        return s.equals(NULL_MARKER) ? null : s;

    }

    /**

     * Reports results from a remote agent command that does not expect

     * exceptions.

     */

    private void readAndReportClassSimpleResult() throws EngineTerminationException, InternalException {

        try {

            int status = in.readInt();

            switch (status) {

                case RESULT_SUCCESS:

                    return;

                case RESULT_NOT_IMPLEMENTED: {

                    String message = in.readUTF();

                    throw new NotImplementedException(message);

                }

                case RESULT_INTERNAL_PROBLEM: {

                    String message = in.readUTF();

                    throw new InternalException(message);

                }

                case RESULT_TERMINATED: {

                    String message = in.readUTF();

                    throw new EngineTerminationException(message);

                }

                default: {

                    throw new EngineTerminationException("Bad remote result code: " + status);

                }

            }

        } catch (IOException ex) {

            throw new EngineTerminationException(ex.toString());

        }

    }

    /**

     * Reports results from a remote agent command that does not expect

     * exceptions.

     */

    private void readAndReportClassInstallResult() throws ClassInstallException,

            NotImplementedException, EngineTerminationException {

        try {

            int status = in.readInt();

            switch (status) {

                case RESULT_SUCCESS:

                    return;

                case RESULT_NOT_IMPLEMENTED: {

                    String message = in.readUTF();

                    throw new NotImplementedException(message);

                }

                case RESULT_CLASS_INSTALL_EXCEPTION: {

                    String message = in.readUTF();

                    boolean[] loaded = (boolean[]) in.readObject();

                    throw new ClassInstallException(message, loaded);

                }

                case RESULT_TERMINATED: {

                    String message = in.readUTF();

                    throw new EngineTerminationException(message);

                }

                default: {

                    throw new EngineTerminationException("Bad remote result code: " + status);

                }

            }

        } catch (IOException | ClassNotFoundException ex) {

            throw new EngineTerminationException(ex.toString());

        }

    }

    /**

     * Reports results from a remote agent command that expects runtime

     * exceptions.

     *

     * @return true if successful

     * @throws IOException if the connection has dropped

     * @throws JShellException {@link jdk.jshell.EvalException}, if a user

     * exception was encountered on invoke;

     * {@link jdk.jshell.UnresolvedReferenceException}, if an unresolved

     * reference was encountered

     * @throws java.lang.ClassNotFoundException

     */

    private void readAndReportExecutionResult() throws RunException,

            EngineTerminationException, InternalException {

        try {

            int status = in.readInt();

            switch (status) {

                case RESULT_SUCCESS:

                    return;

                case RESULT_NOT_IMPLEMENTED: {

                    String message = in.readUTF();

                    throw new NotImplementedException(message);

                }

                case RESULT_USER_EXCEPTION: {

                }

                case RESULT_CORRALLED: {

                    // An unresolved reference was encountered.

                }

                case RESULT_STOPPED: {

                    // Execution was aborted by the stop()

                    throw new StoppedException();

                }

                case RESULT_INTERNAL_PROBLEM: {

                    // An internal error has occurred.

                    String message = in.readUTF();

                    throw new InternalException(message);

                }

                case RESULT_TERMINATED: {

                    String message = in.readUTF();

                    throw new EngineTerminationException(message);

                }

                default: {

                    throw new EngineTerminationException("Bad remote result code: " + status);

                }

            }

        } catch (IOException | ClassNotFoundException ex) {

            throw new EngineTerminationException(ex.toString());

        }

    }

}