package org.tanukisoftware.wrapper;

/*
 * Copyright (c) 1999, 2010 Tanuki Software, Ltd.
 * http://www.tanukisoftware.com
 * All rights reserved.
 *
 * This software is the proprietary information of Tanuki Software.
 * You shall use it only in accordance with the terms of the
 * license agreement you entered into with Tanuki Software.
 * http://wrapper.tanukisoftware.org/doc/english/licenseOverview.html
 * 
 * 
 * Portions of the Software have been derived from source code
 * developed by Silver Egg Technology under the following license:
 * 
 * Copyright (c) 2001 Silver Egg Technology
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without 
 * restriction, including without limitation the rights to use, 
 * copy, modify, merge, publish, distribute, sub-license, and/or 
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following 
 * conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 */

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * By default the WrapperSimpleApp will only wait for 2 seconds for the main
 *  method of the start class to complete.  This was done because the main
 *  methods of many applications never return.  It is possible to force the
 *  class to wait for the startup main method to complete by defining the
 *  following system property when launching the JVM (defaults to FALSE):
 *  -Dorg.tanukisoftware.wrapper.WrapperSimpleApp.waitForStartMain=TRUE
 * <p>
 * Using the waitForStartMain property will cause the startup to wait
 *  indefinitely.  This is fine if the main method will always return
 *  within a predefined period of time.  But if there is any chance that
 *  it could hang, then the maxStartMainWait property may be a better
 *  option.  It allows the 2 second wait time to be overridden. To wait
 *  for up to 5 minutes for the startup main method to complete, set
 *  the property to 300 as follows (defaults to 2 seconds):
 *  -Dorg.tanukisoftware.wrapper.WrapperSimpleApp.maxStartMainWait=300
 * <p>
 * It is possible to extend this class but make absolutely sure that any
 *  overridden methods call their super method or the class will fail to
 *  function correctly.  Most users will have no need to override this
 *  class.  Remember that if overridden, the main method will also need to
 *  be recreated in the child class to make sure that the correct instance
 *  is created.
 * <p>
 * NOTE - The main methods of many applications are designed not to
 *  return.  In these cases, you must either stick with the default 2 second
 *  startup timeout or specify a slightly longer timeout, using the
 *  maxStartMainWait property, to simulate the amount of time your application
 *  takes to start up.
 * <p>
 * WARNING - If the waitForStartMain is specified for an application
 *  whose start method never returns, the Wrapper will appear at first to be
 *  functioning correctly.  However the Wrapper will never enter a running
 *  state, this means that the Windows Service Manager and several of the
 *  Wrapper's error recovery mechanisms will not function correctly.
 *
 * @author Leif Mortenson <leif@tanukisoftware.com>
 */
public class WrapperSimpleApp
    implements WrapperListener, Runnable
{
    /** Info level log channel */
    private static WrapperPrintStream m_outInfo;
    
    /** Error level log channel */
    private static WrapperPrintStream m_outError;
    
    /** Debug level log channel */
    private static WrapperPrintStream m_outDebug;
    
    /**
     * Application's main method
     */
    private Method m_mainMethod;
    
    /**
     * Command line arguments to be passed on to the application
     */
    private String[] m_appArgs;
    
    /**
     * Gets set to true when the thread used to launch the application
     *  actuially starts.
     */
    private boolean m_mainStarted;
    
    /**
     * Gets set to true when the thread used to launch the application
     *  completes.
     */
    private boolean m_mainComplete;
    
    /**
     * Exit code to be returned if the application fails to start.
     */
    private Integer m_mainExitCode;
    
    /**
     * Flag used to signify that the start method has completed.
     */
    private boolean m_startComplete;
    
    /*---------------------------------------------------------------
     * Constructors
     *-------------------------------------------------------------*/
    /**
     * Creates an instance of a WrapperSimpleApp.
     *
     * @param args The full list of arguments passed to the JVM.
     */
    protected WrapperSimpleApp( String args[] )
    {
        
        // Initialize the WrapperManager class on startup by referencing it.
        Class wmClass = WrapperManager.class;
        
        // Set up some log channels
        m_outInfo = new WrapperPrintStream( System.out, "WrapperSimpleApp: " );
        m_outError = new WrapperPrintStream( System.out, "WrapperSimpleApp: " );
        m_outDebug = new WrapperPrintStream( System.out, "WrapperSimpleApp Debug: " );
        
        // Get the class name of the application
        if ( args.length < 1 )
        {
            showUsage();
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        
        // Look for the specified class by name
        Class mainClass;
        try
        {
            mainClass = Class.forName( args[0] );
        }
        catch ( ClassNotFoundException e )
        {
            m_outError.println( "Unable to locate the class " + args[0] + ": " + e );
            showUsage();
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        catch ( ExceptionInInitializerError e )
        {
            m_outError.println( "Class " + args[0] + " found but could not be initialized due to:" );
            e.printStackTrace( m_outError );
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        catch ( LinkageError e )
        {
            m_outError.println( "Class " + args[0] + " found but could not be initialized: " + e );
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        
        // Look for the main method
        try
        {
            // getDeclaredMethod will return any method named main in the specified class,
            //  while getMethod will only return public methods, but it will search up the
            //  inheritance path.
            m_mainMethod = mainClass.getMethod( "main", new Class[] { String[].class } );
        }
        catch ( NoSuchMethodException e )
        {
            m_outError.println(
                "Unable to locate a public static main method in class " + args[0] + ": " + e );
            showUsage();
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        catch ( SecurityException e )
        {
            m_outError.println(
                "Unable to locate a public static main method in class " + args[0] + ": " + e );
            showUsage();
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        
        // Make sure that the method is public and static
        int modifiers = m_mainMethod.getModifiers();
        if ( !( Modifier.isPublic( modifiers ) && Modifier.isStatic( modifiers ) ) )
        {
            m_outError.println(
                "The main method in class " + args[0] + " must be declared public and static." );
            showUsage();
            WrapperManager.stop( 1 );
            return;  // Will not get here
        }
        
        // Build the application args array
        String[] appArgs = new String[args.length - 1];
        System.arraycopy( args, 1, appArgs, 0, appArgs.length );
        
        // Start the application.  If the JVM was launched from the native
        //  Wrapper then the application will wait for the native Wrapper to
        //  call the application's start method.  Otherwise the start method
        //  will be called immediately.
        WrapperManager.start( this, appArgs );
        
        // This thread ends, the WrapperManager will start the application after the Wrapper has
        //  been properly initialized by calling the start method above.
    }
    
    /*---------------------------------------------------------------
     * Runnable Methods
     *-------------------------------------------------------------*/
    /**
     * Used to launch the application in a separate thread.
     */
    public void run()
    {
        // Notify the start method that the thread has been started by the JVM.
        synchronized( this )
        {
            m_mainStarted = true;
            notifyAll();
        }
        
        Throwable t = null;
        try
        {
            if ( WrapperManager.isDebugEnabled() )
            {
                m_outDebug.println( "invoking main method" );
            }
            m_mainMethod.invoke( null, new Object[] { m_appArgs } );
            if ( WrapperManager.isDebugEnabled() )
            {
                m_outDebug.println( "main method completed" );
            }
            
            synchronized(this)
            {
                // Let the start() method know that the main method returned, in case it is 
                //  still waiting.
                m_mainComplete = true;
                this.notifyAll();
            }
            
            return;
        }
        catch ( IllegalAccessException e )
        {
            t = e;
        }
        catch ( IllegalArgumentException e )
        {
            t = e;
        }
        catch ( InvocationTargetException e )
        {
            t = e.getTargetException();
            if ( t == null )
            {
                t = e;
            }
        }
        
        // If we get here, then an error was thrown.  If this happened quickly 
        // enough, the start method should be allowed to shut things down.
        m_outInfo.println();
        m_outError.println( "Encountered an error running main:" );

        // We should print a stack trace here, because in the case of an 
        // InvocationTargetException, the user needs to know what exception
        // their app threw.
        t.printStackTrace( m_outError );

        synchronized(this)
        {
            if ( m_startComplete )
            {
                // Shut down here.
                WrapperManager.stop( 1 );
                return; // Will not get here.
            }
            else
            {
                // Let start method handle shutdown.
                m_mainComplete = true;
                m_mainExitCode = new Integer( 1 );
                this.notifyAll();
                return;
            }
        }
    }
    
    /*---------------------------------------------------------------
     * WrapperListener Methods
     *-------------------------------------------------------------*/
    /**
     * The start method is called when the WrapperManager is signalled by the 
     *	native wrapper code that it can start its application.  This
     *	method call is expected to return, so a new thread should be launched
     *	if necessary.
     * If there are any problems, then an Integer should be returned, set to
     *	the desired exit code.  If the application should continue,
     *	return null.
     */
    public Integer start( String[] args )
    {
        // Decide whether or not to wait for the start main method to complete before returning.
        boolean waitForStartMain = WrapperSystemPropertyUtil.getBooleanProperty(
            WrapperSimpleApp.class.getName() + ".waitForStartMain", false );
        int maxStartMainWait = WrapperSystemPropertyUtil.getIntProperty(
            WrapperSimpleApp.class.getName() + ".maxStartMainWait", 2 );
        maxStartMainWait = Math.max( 1, maxStartMainWait ); 
        
        // Decide the maximum number of times to loop waiting for the main start method.
        int maxLoops;
        if ( waitForStartMain )
        {
            maxLoops = Integer.MAX_VALUE;
            if ( WrapperManager.isDebugEnabled() )
            {
                m_outDebug.println(
                    "start(args) Will wait indefinitely for the main method to complete." );
            }
        }
        else
        {
            maxLoops = maxStartMainWait; // 1s loops.
            if ( WrapperManager.isDebugEnabled() )
            {
                m_outDebug.println( "start(args) Will wait up to " + maxLoops
                    + " seconds for the main method to complete." );
            }
        }
        
        Thread mainThread = new Thread( this, "WrapperSimpleAppMain" );
        synchronized(this)
        {
            m_appArgs = args;
            mainThread.start();
            
            // To avoid problems with the main thread starting slowly on heavily loaded systems,
            //  do not continue until the thread has actually started.
            while ( !m_mainStarted )
            {
                try
                {
                    this.wait( 1000 );
                }
                catch ( InterruptedException e )
                {
                    // Continue.
                }
            }
            
            // Wait for startup main method to complete.
            int loops = 0;
            while ( ( loops < maxLoops ) && ( !m_mainComplete ) )
            {
                try
                {
                    this.wait( 1000 );
                }
                catch ( InterruptedException e )
                {
                    // Continue.
                }
                
                if ( !m_mainComplete )
                {
                    // If maxLoops is large then this could take a while.  Notify the
                    //  WrapperManager that we are still starting so it doesn't give up.
                    WrapperManager.signalStarting( 5000 );
                }
                
                loops++;
            }
            
            // Always set the flag stating that the start method completed.  This is needed
            //  so the run method can decide whether or not it needs to be responsible for
            //  shutting down the JVM in the event of an exception thrown by the start main
            //  method.
            m_startComplete = true;
            
            // The main exit code will be null unless an error was thrown by the start
            //  main method.
            if ( WrapperManager.isDebugEnabled() )
            {
                m_outDebug.println( "start(args) end.  Main Completed=" + m_mainComplete
                    + ", exitCode=" + m_mainExitCode );
            }
            return m_mainExitCode;
        }
    }
    
    /**
     * Called when the application is shutting down.
     */
    public int stop( int exitCode )
    {
        if ( WrapperManager.isDebugEnabled() )
        {
            m_outDebug.println( "stop(" + exitCode + ")" );
        }
        
        // Normally an application will be asked to shutdown here.  Standard Java applications do
        //  not have shutdown hooks, so do nothing here.  It will be as if the user hit CTRL-C to
        //  kill the application.
        return exitCode;
    }
    
    /**
     * Called whenever the native wrapper code traps a system control signal
     *  against the Java process.  It is up to the callback to take any actions
     *  necessary.  Possible values are: WrapperManager.WRAPPER_CTRL_C_EVENT, 
     *    WRAPPER_CTRL_CLOSE_EVENT, WRAPPER_CTRL_LOGOFF_EVENT, or 
     *    WRAPPER_CTRL_SHUTDOWN_EVENT
     */
    public void controlEvent( int event )
    {
        if ( ( event == WrapperManager.WRAPPER_CTRL_LOGOFF_EVENT )
            && ( WrapperManager.isLaunchedAsService() || WrapperManager.isIgnoreUserLogoffs() ) )
        {
            // Ignore
            m_outInfo.println( "User logged out.  Ignored." );
        }
        else
        {
            if ( WrapperManager.isDebugEnabled() )
            {
                m_outDebug.println( "controlEvent(" + event + ") Stopping" );
            }
            WrapperManager.stop( 0 );
            // Will not get here.
        }
    }
    
    /*---------------------------------------------------------------
     * Methods
     *-------------------------------------------------------------*/
    /**
     * Displays application usage
     */
    protected void showUsage()
    {
        // Show this output without headers.
        System.out.println();
        System.out.println(
            "WrapperSimpleApp Usage:" );
        System.out.println(
            "  java org.tanukisoftware.wrapper.WrapperSimpleApp {app_class} [app_arguments]" );
        System.out.println();
        System.out.println(
            "Where:" );
        System.out.println(
            "  app_class:      The fully qualified class name of the application to run." );
        System.out.println(
            "  app_arguments:  The arguments that would normally be passed to the" );
        System.out.println(
            "                  application." );
    }
    
    /*---------------------------------------------------------------
     * Main Method
     *-------------------------------------------------------------*/
    /**
     * Used to Wrapper enable a standard Java application.  This main
     *  expects the first argument to be the class name of the application
     *  to launch.  All remaining arguments will be wrapped into a new
     *  argument list and passed to the main method of the specified
     *  application.
     *
     * @param args Arguments passed to the application.
     */
    public static void main( String args[] )
    {
        new WrapperSimpleApp( args );
    }
}

