/**
    * Copyright 2010 The Kuali Foundation Licensed under the
    * Educational Community 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.osedu.org/licenses/ECL-2.0
    *
    * Unless required by applicable law or agreed to in writing,
   * software 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.
   */
  
  package org.kuali.student.common.ui.client.widgets.focus;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import com.google.gwt.event.dom.client.BlurEvent;
  import com.google.gwt.event.dom.client.BlurHandler;
  import com.google.gwt.event.dom.client.FocusEvent;
  import com.google.gwt.event.dom.client.FocusHandler;
  import com.google.gwt.event.dom.client.HasBlurHandlers;
  import com.google.gwt.event.dom.client.HasFocusHandlers;
  import com.google.gwt.event.shared.GwtEvent;
  import com.google.gwt.event.shared.HandlerManager;
  import com.google.gwt.event.shared.HandlerRegistration;
  import com.google.gwt.event.shared.HasHandlers;
  import com.google.gwt.user.client.Command;
  import com.google.gwt.user.client.DeferredCommand;
  import com.google.gwt.user.client.ui.Widget;
  
  public class FocusGroup implements HasBlurHandlers, HasFocusHandlers, HasHandlers {
  	private static class SyntheticBlurEvent extends BlurEvent {
  		public SyntheticBlurEvent() {
  			// do nothing
  		}
  	}
  
  	private static class SyntheticFocusEvent extends FocusEvent {
  		public SyntheticFocusEvent() {
  			// do nothing
  		}
  	}
  
  	private final HandlerManager handlers;
  	private final Map<Widget, Boolean> focusTrackers = new HashMap<Widget, Boolean>();
  	private boolean focusEventPending = false;
  	private boolean suppressed = false;
  	
  	private boolean focused = false;
  
  	private final Command checkFocusState = new Command() {
  		@Override
  		public void execute() {
  			focusEventPending = false;
  			boolean nowFocused = false;
  			for (final Boolean b : focusTrackers.values()) {
  				if (b) {
  					nowFocused = true;
  					break;
  				}
  			}
  
  			if (!suppressed && (focused ^ nowFocused)) {
  				if (nowFocused) {
  					// we weren't focused, but now we are
  					//					FocusEvent.fireNativeEvent(lastFocusEvent, FocusGroup.this);
  					handlers.fireEvent(new SyntheticFocusEvent());
  				} else {
  					// we were focused, now we aren't
  					//					BlurEvent.fireNativeEvent(lastBlurEvent, FocusGroup.this);
  					handlers.fireEvent(new SyntheticBlurEvent());
  				}
  			}
  
  			focused = nowFocused;
  		}
  	};
  
  	public FocusGroup(final Widget parentWidget) {
  		this.handlers = new HandlerManager(parentWidget);
  	}
  
  	@Override
  	public HandlerRegistration addBlurHandler(final BlurHandler handler) {
  		return handlers.addHandler(BlurEvent.getType(), handler);
  	}
  
  	@Override
  	public HandlerRegistration addFocusHandler(final FocusHandler handler) {
  		return handlers.addHandler(FocusEvent.getType(), handler);
  	}
  
  	public void addWidget(final Widget w) {
  		if (w instanceof HasBlurHandlers) {
  			((HasBlurHandlers) w).addBlurHandler(new BlurHandler() {
 				@Override
 				public void onBlur(final BlurEvent event) {
 					focusTrackers.put(w, false);
 					queueCheckFocusState();
 				}
 			});
 		}
 		if (w instanceof HasFocusHandlers) {
 			((HasFocusHandlers) w).addFocusHandler(new FocusHandler() {
 				@Override
 				public void onFocus(final FocusEvent event) {
 					focusTrackers.put(w, true);
 					queueCheckFocusState();
 				}
 			});
 		}
 	}
 
 	@Override
 	public void fireEvent(final GwtEvent<?> event) {
 		handlers.fireEvent(event);
 	}
 
 	private void queueCheckFocusState() {
 		if (!focusEventPending) {
 			focusEventPending = true;
 			DeferredCommand.addCommand(checkFocusState);
 		}
 	}
 
 	public boolean isSuppressed() {
 		return suppressed;
 	}
 
 	public void setSuppressed(boolean suppressed) {
 		this.suppressed = suppressed;
 	}
 	
 	
 }