/*

 * Copyright 2007 Sun Microsystems, Inc.  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.

 *

 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package test.java.awt.regtesthelpers.process;

import java.io.*;

/** This class is created to solve interprocess communication problems.

 *  When you need to write a regression test which should verify inter jvm

 *  behavior such as DnD data transfer, Clipboard data transfer, focus

 *  transfer etc., you could use the next scenario:

 *

 *  1. Write an implementation for the parent JVM, using applet test.

 *  2. Write an implimentation for the child JVM or native application, using

 *     main() function.

 *  3. Execute child process using  ProcessCommunicator.executeChildProcess()

 *     method.

 *  4. You can decide whetherthe test is passed on the basis of

 *     ProcessResults class data.

 *

 *  Note: The class is not thread safe. You should access its methods only from the same

 *        thread.

 */

public class ProcessCommunicator {

    private static final String javaHome = System.getProperty("java.home", "");

    private static final String javaPath = javaHome + File.separator + "bin" +

            File.separator + "java ";

    private static String command = "";

    private ProcessCommunicator() {}

    /** The same as {#link #executeChildProcess(Class,String)} except

     *  the {@code classPathArgument} parameter. The class path

     *  parameter is for the debug purposes

     *

     *  @param classToExecute is passed to the child JVM

     *  @param classPathArguments class path for the child JVM

     *  @param args arguments that will be passed to the executed class

     *  @return results of the executed {@code Process}

     */

    public static ProcessResults executeChildProcess(final Class classToExecute,

                           final String classPathArguments, final String [] args)

    {

        try {

            String command = buildCommand(classToExecute, classPathArguments, args);

            Process process = Runtime.getRuntime().exec(command);

            return doWaitFor(process);

        } catch (IOException e) {

            throw new RuntimeException(e);

        }

    }

    /** Executes child {code Process}

     *

     * @param classToExecute class to be executed as a child java process

     * @param args args to be passed in to the child process

     * @return results of the executed {@code Process}

     */

    public static ProcessResults executeChildProcess(final Class classToExecute,

                           final String [] args)

    {

        return executeChildProcess(classToExecute, " ", args);

    }

    /**

     * Waits for a process and return its results.

     * This is a workaround for <code>Process.waitFor()</code> never returning.

     *

     * @return results of the executed {@code Process}

     */

    private static ProcessResults doWaitFor(final Process p) {

        ProcessResults pres = new ProcessResults();

        final InputStream in;

        final InputStream err;

        try {

            in = p.getInputStream();

            err = p.getErrorStream();

            boolean finished = false;

            while (!finished) {

                try {

                    while (in.available() > 0) {

                        pres.appendToStdOut((char)in.read());

                    }

                    while (err.available() > 0) {

                        pres.appendToStdErr((char)err.read());

                    }

                    // Ask the process for its exitValue. If the process

                    // is not finished, an IllegalThreadStateException

                    // is thrown. If it is finished, we fall through and

                    // the variable finished is set to true.

                    pres.setExitValue(p.exitValue());

                    finished  = true;

                }

                catch (IllegalThreadStateException e) {

                    // Process is not finished yet;

                    // Sleep a little to save on CPU cycles

                    Thread.currentThread().sleep(500);

                }

            }

            if (in != null) in.close();

            if (err != null) err.close();

        }

        catch (Throwable e) {

            System.err.println("doWaitFor(): unexpected exception");

            e.printStackTrace();

        }

        return pres;

    }

    /** Builds command on the basis of the passed class name,

     *  class path and arguments.

     *

     * @param classToExecute with class will be executed in the new JVM

     * @param classPathArguments java class path (only for test purposes)

     * @param args arguments for the new application. This could be used

     *             to pass some information from the parnent to child JVM.

     * @return command to execute the {@code Process}

     */

    private static String buildCommand(final Class classToExecute,

                         final String classPathArguments, final String [] args)

    {

        StringBuilder commandBuilder = new StringBuilder();

        for (String argument:args) {

            commandBuilder.append(" ").append(argument);

        }

        command = commandBuilder.toString();

        return command;

    }

    /** Could be used for the debug purposes.

     *

      * @return command that was build to execute the child process

     */

    public static String getExecutionCommand () {

        return command;

    }

}