/*******************************************************************************
 * Copyright (c) 2007 SAS Institute.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     SAS Institute - initial API and implementation
 *******************************************************************************/
package org.simantics.utils.ui.internal.awt;

import java.awt.EventQueue;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.ControlAdapter;
import org.eclipse.swt.events.ControlEvent;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.events.FocusEvent;
import org.eclipse.swt.events.FocusListener;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.events.KeyListener;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class SwtFocusHandler implements FocusListener, KeyListener {

    private Composite       composite;
    private final Display   display;
    private AwtFocusHandler awtHandler;

    public SwtFocusHandler(Composite composite) {
        assert composite != null;
        assert Display.getCurrent() != null;     // On SWT event thread
        
        this.composite = composite;
        display = composite.getDisplay();
        composite.addFocusListener(this);
        composite.addKeyListener(this);
    }

    public void setAwtHandler(AwtFocusHandler handler) {
        assert handler != null;
        assert awtHandler == null;  // this method is meant to be called once
        assert composite != null;
        assert Display.getCurrent() != null;     // On SWT event thread        
        
        awtHandler = handler;
        
        // Dismiss Swing popups when the main window is moved. (It would be 
        // better to dismiss popups whenever the titlebar is clicked, but 
        // there does not seem to be a way.)
        final ControlAdapter controlAdapter = new ControlAdapter() {
            public void controlMoved(ControlEvent e) {
                assert awtHandler != null;
                awtHandler.postHidePopups();
            }
        };
        final Shell shell = composite.getShell();
        shell.addControlListener(controlAdapter);
        
        // Cleanup listeners on dispose
        composite.addDisposeListener(new DisposeListener() {
            public void widgetDisposed(DisposeEvent e) {
                // Remove listener from shell before nullifying awtHandler
                shell.removeControlListener(controlAdapter);
                awtHandler.dispose();
                awtHandler = null;
                composite = null;
            }
        });
    }
    
    void gainFocusNext() {
        traverse(SWT.TRAVERSE_TAB_NEXT);
    }
    
    void gainFocusPrevious() {
        traverse(SWT.TRAVERSE_TAB_PREVIOUS);
    }
    
    private void traverse(final int traversal) {
        //assert composite != null;
        if (composite == null)
            return;

        // Tab from the containing SWT component while 
        // running on the SWT thread
        Runnable r = new Runnable() {
            public void run() {
                composite.traverse(traversal);
            }
        };
        display.asyncExec(r);
    }

//    boolean hasFocus() {
//        assert composite != null;
//        
//        // This will return true if the composite has focus, or if any
//        // foreign (e.g. AWT) child of the composite has focus.
//        if (display.isDisposed()) {
//            return false;
//        }
//        final boolean[] result = new boolean[1];
//        display.syncExec(new Runnable() {
//            public void run() {
//                result[0] = (!composite.isDisposed() &&
//                             (display.getFocusControl() == composite));
//            }
//        });
//        return result[0];
//    }

    // ..................... Listener implementations
    
    public void focusGained(FocusEvent e) {
        assert awtHandler != null;
        assert Display.getCurrent() != null;     // On SWT event thread

        // System.out.println("Gained: " + e.toString() + " (" + e.widget.getClass().getName() + ")");
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                // composite DisposeListener may have nullified this meanwhile!
                // Not a bug.
                if (awtHandler != null)
                    awtHandler.gainFocus();
            }
        });
    }
    
    public void focusLost(FocusEvent e) {
        // System.out.println("Lost: " + e.toString() + " (" + e.widget.getClass().getName() + ")");
    }

    public void keyPressed(KeyEvent e) {
        assert Display.getCurrent() != null;     // On SWT event thread

        // If the embedded swing root pane has no components to receive focus, 
        // then there will be cases where the parent SWT composite will keep 
        // focus. (For example, when tabbing into the root pane container). 
        // By default, in these cases, the focus is swallowed by the Composite
        // and never escapes. This code allows tab and back-tab to do the 
        // proper traversal to other SWT components from the composite.
        // TODO: other keys?
        if (e.keyCode == SWT.TAB) {
            // TODO: In some cases, this gobbles up all the tabs, even from AWT children. Find a more selective way. 
            /*if (e.stateMask == SWT.NONE) {
                traverse(SWT.TRAVERSE_TAB_NEXT);
            } else if (e.stateMask == SWT.SHIFT) {
                traverse(SWT.TRAVERSE_TAB_PREVIOUS);
            }*/
        }
    }

    public void keyReleased(KeyEvent e) {
    }


}