pdfbox-trunk/debugger/src/main/java/org/apache/pdfbox/debugger/ui/OSXAdapter.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
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 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
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/* 
 * This file includes code under the following terms:
 *
 *  Version: 2.0
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package org.apache.pdfbox.debugger.ui;

import java.awt.Desktop;
import java.io.File;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.StringTokenizer;
import java.util.List;

/**
 * Hooks existing preferences/about/quit functionality from an
 * existing Java app into handlers for the Mac OS X application menu.
 * Uses a Proxy object to dynamically implement the 
 * com.apple.eawt.ApplicationListener interface and register it with the
 * com.apple.eawt.Application object.  This allows the complete project
 * to be both built and run on any platform without any stubs or 
 * placeholders. Useful for developers looking to implement Mac OS X 
 * features while supporting multiple platforms with minimal impact.
 */
public class OSXAdapter implements InvocationHandler
{

    protected Object targetObject;
    protected Method targetMethod;
    protected String proxySignature;

    static Object macOSXApplication;
    
    private static boolean isMinJdk9()
    {
        // strategy from lucene-solr/lucene/core/src/java/org/apache/lucene/util/Constants.java
        String version = System.getProperty("java.specification.version");
        final StringTokenizer st = new StringTokenizer(version, ".");
        try
        {
            int major = Integer.parseInt(st.nextToken());
            int minor = 0;
            if (st.hasMoreTokens())
            {
                minor = Integer.parseInt(st.nextToken());
            }
            return major > 1 || (major == 1 && minor >= 9);
        }
        catch (NumberFormatException nfe)
        {
            // maybe some new numbering scheme in the 22nd century
            return true;
        }
    }

    // Pass this method an Object and Method equipped to perform application shutdown logic
    // The method passed should return a boolean stating whether or not the quit should occur
    public static void setQuitHandler(final Object target, final Method quitHandler)
    {
        if (isMinJdk9())
        {
            try
            {
                Desktop desktopObject = Desktop.getDesktop();
                Class<?> filesHandlerClass = Class.forName("java.awt.desktop.QuitHandler");
                final Method setQuitHandlerMethod = desktopObject.getClass().getMethod("setQuitHandler", filesHandlerClass);
                Object osxAdapterProxy = Proxy.newProxyInstance(OSXAdapter.class.getClassLoader(),
                        new Class[]
                        {
                            filesHandlerClass
                        }, new InvocationHandler()
                {
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args)
                            throws Throwable
                    {
                        if ("handleQuitRequestWith".equals(method.getName()))
                        {
                            // We just call our own quit handler
                            quitHandler.invoke(target);
                        }
                        return null;
                    }
                });
                setQuitHandlerMethod.invoke(desktopObject, osxAdapterProxy);
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
            return;
        }
        setHandler(new OSXAdapter("handleQuit", target, quitHandler));
    }

    // Pass this method an Object and Method equipped to display application info
    // They will be called when the About menu item is selected from the application menu
    public static void setAboutHandler(Object target, Method aboutHandler) {
        boolean enableAboutMenu = (target != null && aboutHandler != null);
        if (enableAboutMenu) {
            setHandler(new OSXAdapter("handleAbout", target, aboutHandler));
        }
        // If we're setting a handler, enable the About menu item by calling
        // com.apple.eawt.Application reflectively
        try {
            Method enableAboutMethod = macOSXApplication.getClass().getDeclaredMethod("setEnabledAboutMenu", boolean.class);
            enableAboutMethod.invoke(macOSXApplication, enableAboutMenu);
        } catch (Exception ex) {
            System.err.println("OSXAdapter could not access the About Menu");
            throw new RuntimeException(ex);
        }
    }

    // Pass this method an Object and a Method equipped to display application options
    // They will be called when the Preferences menu item is selected from the application menu
    public static void setPreferencesHandler(Object target, Method prefsHandler) {
        boolean enablePrefsMenu = (target != null && prefsHandler != null);
        if (enablePrefsMenu) {
            setHandler(new OSXAdapter("handlePreferences", target, prefsHandler));
        }
        // If we're setting a handler, enable the Preferences menu item by calling
        // com.apple.eawt.Application reflectively
        try {
            Method enablePrefsMethod = macOSXApplication.getClass().getDeclaredMethod("setEnabledPreferencesMenu", boolean.class);
            enablePrefsMethod.invoke(macOSXApplication, enablePrefsMenu);
        } catch (Exception ex) {
            System.err.println("OSXAdapter could not access the About Menu");
            throw new RuntimeException(ex);
        }
    }

    // Pass this method an Object and a Method equipped to handle document events from the Finder
    // Documents are registered with the Finder via the CFBundleDocumentTypes dictionary in the 
    // application bundle's Info.plist
    public static void setFileHandler(Object target, Method fileHandler)
    {
        if (isMinJdk9())
        {
            try
            {
                Desktop desktopObject = Desktop.getDesktop();
                Class<?> filesHandlerClass = Class.forName("java.awt.desktop.OpenFilesHandler");
                Method setOpenFileHandlerMethod = desktopObject.getClass().getMethod("setOpenFileHandler", filesHandlerClass);
                Object osxAdapterProxy = Proxy.newProxyInstance(OSXAdapter.class.getClassLoader(),
                        new Class[]
                        {
                            filesHandlerClass
                        }, new OSXAdapter("openFiles", target, fileHandler)
                {
                    // Override OSXAdapter.callTarget to send information on the
                    // file to be opened
                    @Override
                    public boolean callTarget(Object openFilesEvent)
                    {
                        if (openFilesEvent != null)
                        {
                            try
                            {
                                Method getFilesMethod = openFilesEvent.getClass().getDeclaredMethod("getFiles",
                                        (Class[]) null);
                                @SuppressWarnings("unchecked")
                                List<File> files = (List<File>) getFilesMethod.invoke(openFilesEvent,
                                        (Object[]) null);
                                this.targetMethod.invoke(this.targetObject, files.get(0).getAbsolutePath());
                            }
                            catch (Exception ex)
                            {
                                throw new RuntimeException(ex);
                            }
                        }
                        return true;
                    }
                });
                setOpenFileHandlerMethod.invoke(desktopObject, osxAdapterProxy);
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
            return;
        }
        /* JDK <= 1.8, using Apple classes */
        setHandler(new OSXAdapter("handleOpenFile", target, fileHandler) {
            // Override OSXAdapter.callTarget to send information on the
            // file to be opened
            @Override
            public boolean callTarget(Object appleEvent) {
                if (appleEvent != null) {
                    try {
                        Method getFilenameMethod = appleEvent.getClass().getDeclaredMethod("getFilename", (Class[])null);
                        String filename = (String) getFilenameMethod.invoke(appleEvent, (Object[])null);
                        this.targetMethod.invoke(this.targetObject, filename);
                    } catch (Exception ex) {
                        throw new RuntimeException(ex);
                    }
                }
                return true;
            }
        });
    }

    // setHandler creates a Proxy object from the passed OSXAdapter and adds it as an ApplicationListener
    public static void setHandler(OSXAdapter adapter) {
        try {
            Class<?> applicationClass = Class.forName("com.apple.eawt.Application");
            if (macOSXApplication == null) {
                macOSXApplication = applicationClass.getDeclaredConstructor((Class[])null).newInstance((Object[])null);
            }
            Class<?> applicationListenerClass = Class.forName("com.apple.eawt.ApplicationListener");
            Method addListenerMethod = applicationClass.getDeclaredMethod("addApplicationListener", applicationListenerClass);
            // Create a proxy object around this handler that can be reflectively added as an Apple ApplicationListener
            Object osxAdapterProxy = Proxy.newProxyInstance(OSXAdapter.class.getClassLoader(), new Class[]{applicationListenerClass}, adapter);
            addListenerMethod.invoke(macOSXApplication, osxAdapterProxy);
        } catch (ClassNotFoundException cnfe) {
            System.err.println("This version of Mac OS X does not support the Apple EAWT.  ApplicationEvent handling has been disabled (" + cnfe + ")");
        } catch (Exception ex) {  // Likely a NoSuchMethodException or an IllegalAccessException loading/invoking eawt.Application methods
            System.err.println("Mac OS X Adapter could not talk to EAWT:");
            throw new RuntimeException(ex);
        }
    }

    // Each OSXAdapter has the name of the EAWT method it intends to listen for (handleAbout, for example),
    // the Object that will ultimately perform the task, and the Method to be called on that Object
    protected OSXAdapter(String proxySignature, Object target, Method handler) {
        this.proxySignature = proxySignature;
        this.targetObject = target;
        this.targetMethod = handler;
    }

    // Override this method to perform any operations on the event 
    // that comes with the various callbacks
    // See setFileHandler above for an example
    public boolean callTarget(Object appleEvent) throws InvocationTargetException, IllegalAccessException {
        Object result = targetMethod.invoke(targetObject, (Object[])null);
        if (result == null) {
            return true;
        }
        return Boolean.parseBoolean(result.toString());
    }

    // InvocationHandler implementation
    // This is the entry point for our proxy object; it is called every time an ApplicationListener method is invoked
    public Object invoke (Object proxy, Method method, Object[] args) throws Throwable {
        if (isCorrectMethod(method, args)) {
            boolean handled = callTarget(args[0]);
            setApplicationEventHandled(args[0], handled);
        }
        // All of the ApplicationListener methods are void; return null regardless of what happens
        return null;
    }

    // Compare the method that was called to the intended method when the OSXAdapter instance was created
    // (e.g. handleAbout, handleQuit, handleOpenFile, etc.)
    protected boolean isCorrectMethod(Method method, Object[] args) {
        return (targetMethod != null && proxySignature.equals(method.getName()) && args.length == 1);
    }

    // It is important to mark the ApplicationEvent as handled and cancel the default behavior
    // This method checks for a boolean result from the proxy method and sets the event accordingly
    protected void setApplicationEventHandled(Object event, boolean handled) {
        if (event != null) {
            try {
                Method setHandledMethod = event.getClass().getDeclaredMethod("setHandled", boolean.class);
                // If the target method returns a boolean, use that as a hint
                setHandledMethod.invoke(event, handled);
            } catch (Exception ex) {
                System.err.println("OSXAdapter was unable to handle an ApplicationEvent: " + event);
                throw new RuntimeException(ex);
            }
        }
    }
}
