/*

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.jshell.execution;

import java.lang.reflect.Array;

import java.lang.reflect.Field;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import jdk.jshell.spi.ExecutionControl;

import jdk.jshell.spi.SPIResolutionException;

/**

 * An {@link ExecutionControl} implementation that runs in the current process.

 * May be used directly, or over a channel with

 * {@link Util#forwardExecutionControl(ExecutionControl, java.io.ObjectInput, java.io.ObjectOutput) }.

 *

 * @author Robert Field

 * @author Jan Lahoda

 */

public class DirectExecutionControl implements ExecutionControl {

    private final LoaderDelegate loaderDelegate;

    /**

     * Creates an instance, delegating loader operations to the specified

     * delegate.

     *

     * @param loaderDelegate the delegate to handle loading classes

     */

    public DirectExecutionControl(LoaderDelegate loaderDelegate) {

        this.loaderDelegate = loaderDelegate;

    }

    /**

     * Create an instance using the default class loading.

     */

    public DirectExecutionControl() {

        this(new DefaultLoaderDelegate());

    }

    @Override

    public void load(ClassBytecodes[] cbcs)

            throws ClassInstallException, NotImplementedException, EngineTerminationException {

        loaderDelegate.load(cbcs);

    }

    @Override

    public void redefine(ClassBytecodes[] cbcs)

            throws ClassInstallException, NotImplementedException, EngineTerminationException {

        throw new NotImplementedException("redefine not supported");

    }

    @Override

    public String invoke(String className, String methodName)

            throws RunException, InternalException, EngineTerminationException {

        Method doitMethod;

        try {

            Class<?> klass = findClass(className);

            doitMethod = klass.getDeclaredMethod(methodName, new Class<?>[0]);

            doitMethod.setAccessible(true);

        } catch (Throwable ex) {

            throw new InternalException(ex.toString());

        }

        try {

            clientCodeEnter();

            String result = invoke(doitMethod);

            System.out.flush();

            return result;

        } catch (RunException | InternalException | EngineTerminationException ex) {

            throw ex;

        } catch (SPIResolutionException ex) {

            return throwConvertedInvocationException(ex);

        } catch (InvocationTargetException ex) {

            return throwConvertedInvocationException(ex.getCause());

        } catch (Throwable ex) {

            return throwConvertedOtherException(ex);

        } finally {

            clientCodeLeave();

        }

    }

    @Override

    public String varValue(String className, String varName)

            throws RunException, EngineTerminationException, InternalException {

        Object val;

        try {

            Class<?> klass = findClass(className);

            Field var = klass.getDeclaredField(varName);

            var.setAccessible(true);

            val = var.get(null);

        } catch (Throwable ex) {

            throw new InternalException(ex.toString());

        }

        try {

            clientCodeEnter();

            return valueString(val);

        } catch (Throwable ex) {

            return throwConvertedInvocationException(ex);

        } finally {

            clientCodeLeave();

        }

    }

    @Override

    public void addToClasspath(String cp)

            throws EngineTerminationException, InternalException {

        loaderDelegate.addToClasspath(cp);

    }

    @Override

    public void setClasspath(String path)

            throws EngineTerminationException, InternalException {

        loaderDelegate.setClasspath(path);

    }

    /**

     * {@inheritDoc}

     * <p>

     * Not supported.

     */

    @Override

    public void stop()

            throws EngineTerminationException, InternalException {

        throw new NotImplementedException("stop: Not supported.");

    }

    @Override

    public Object extensionCommand(String command, Object arg)

            throws RunException, EngineTerminationException, InternalException {

        throw new NotImplementedException("Unknown command: " + command);

    }

    @Override

    public void close() {

    }

    /**

     * Finds the class with the specified binary name.

     *

     * @param name the binary name of the class

     * @return the Class Object

     * @throws ClassNotFoundException if the class could not be found

     */

    protected Class<?> findClass(String name) throws ClassNotFoundException {

        return loaderDelegate.findClass(name);

    }

    /**

     * Invoke the specified "doit-method", a static method with no parameters.

     * The {@link DirectExecutionControl#invoke(java.lang.String, java.lang.String) }

     * in this class will call this to invoke.

     *

     * @param doitMethod the Method to invoke

     * @return the value or null

     * @throws Exception any exceptions thrown by

     * {@link java.lang.reflect.Method#invoke(Object, Object...) }

     * or any {@link ExecutionControl.ExecutionControlException}

     * to pass-through.

     */

    protected String invoke(Method doitMethod) throws Exception {

        Object res = doitMethod.invoke(null, new Object[0]);

        return valueString(res);

    }

    /**

     * Converts the {@code Object} value from

     * {@link ExecutionControl#invoke(String, String)  } or

     * {@link ExecutionControl#varValue(String, String)   } to {@code String}.

     *

     * @param value the value to convert

     * @return the {@code String} representation

     */

    protected static String valueString(Object value) {

        if (value == null) {

            return "null";

        } else if (value instanceof String) {

            return "\"" + (String) value + "\"";

        } else if (value instanceof Character) {

            return "'" + value + "'";

        } else if (value.getClass().isArray()) {

            int len = Array.getLength(value);

            StringBuilder sb = new StringBuilder();

            sb.append(len);

            for (int i = 0; i < len; ++i) {

                sb.append(valueString(Array.get(value, i)));

                if (i < len - 1) {

                    sb.append(", ");

                }

            }

            sb.append(" }");

            return sb.toString();

        } else {

            return value.toString();

        }

    }

    /**

     * Converts incoming exceptions in user code into instances of subtypes of

     * {@link ExecutionControl.ExecutionControlException} and throws the

     * converted exception.

     *

     * @param cause the exception to convert

     * @return never returns as it always throws

     * @throws ExecutionControl.RunException for normal exception occurrences

     * @throws ExecutionControl.InternalException for internal problems

     */

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

        if (cause instanceof SPIResolutionException) {

            SPIResolutionException spire = (SPIResolutionException) cause;

            throw new ResolutionException(spire.id(), spire.getStackTrace());

        } else {

            throw new UserException(cause.getMessage(), cause.getClass().getName(), cause.getStackTrace());

        }

    }

    /**

     * Converts incoming exceptions in agent code into instances of subtypes of

     * {@link ExecutionControl.ExecutionControlException} and throws the

     * converted exception.

     *

     * @param ex the exception to convert

     * @return never returns as it always throws

     * @throws ExecutionControl.RunException for normal exception occurrences

     * @throws ExecutionControl.InternalException for internal problems

     */

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

        throw new InternalException(ex.toString());

    }

    /**

     * Marks entry into user code.

     *

     * @throws ExecutionControl.InternalException in unexpected failure cases

     */

    protected void clientCodeEnter() throws InternalException {

    }

    /**

     * Marks departure from user code.

     *

     * @throws ExecutionControl.InternalException in unexpected failure cases

     */

    protected void clientCodeLeave() throws InternalException {

    }

}