/**********************************************
    * Copyright (C) 2010 Lukas Laag
    * This file is part of svgreal.
    * 
    * svgreal is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    * 
   * svgreal 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 for more details.
   * 
   * You should have received a copy of the GNU General Public License
   * along with svgreal.  If not, see http://www.gnu.org/licenses/
   **********************************************/
  package org.vectomatic.svg.edit.client.gxt.widget;
  
  import org.vectomatic.dom.svg.OMSVGGElement;
  import org.vectomatic.dom.svg.OMSVGMatrix;
  import org.vectomatic.dom.svg.OMSVGPoint;
  import org.vectomatic.dom.svg.OMSVGSVGElement;
  import org.vectomatic.dom.svg.utils.DOMHelper;
  import org.vectomatic.dom.svg.utils.SVGPrefixResolver;
  import org.vectomatic.svg.edit.client.AppBundle;
  import org.vectomatic.svg.edit.client.SvgrealApp;
  import org.vectomatic.svg.edit.client.engine.SVGProcessor;
  import org.vectomatic.svg.edit.client.event.HasRotationHandlers;
  import org.vectomatic.svg.edit.client.event.RotationEvent;
  import org.vectomatic.svg.edit.client.event.RotationHandler;
  
  import com.google.gwt.core.client.GWT;
  import com.google.gwt.event.dom.client.MouseDownEvent;
  import com.google.gwt.event.dom.client.MouseDownHandler;
  import com.google.gwt.event.dom.client.MouseEvent;
  import com.google.gwt.event.dom.client.MouseMoveEvent;
  import com.google.gwt.event.dom.client.MouseMoveHandler;
  import com.google.gwt.event.dom.client.MouseUpEvent;
  import com.google.gwt.event.dom.client.MouseUpHandler;
  import com.google.gwt.event.shared.EventHandler;
  import com.google.gwt.event.shared.GwtEvent;
  import com.google.gwt.event.shared.HandlerRegistration;
  
  /**
   * An compass widget implemented using an SVG image.
   * @author laaglu
   */
  public class Compass implements HasRotationHandlers {
  	private static final String COMPASS_PREFIX="compass";
  	protected boolean rotate;
  	protected int angle;
  	protected OMSVGSVGElement compass;
  	protected OMSVGGElement textGroup;
  	
  	/**
  	 * Constructor.
  	 */
  	public Compass() {
  		compass = AppBundle.INSTANCE.compass().getSvg();
  		textGroup = (OMSVGGElement)DOMHelper.evaluateXPath(compass, ".//svg:g[@id='textGroup']", new SVGPrefixResolver()).next();
  		SVGProcessor.normalizeIds(compass, COMPASS_PREFIX);
  		compass.addMouseDownHandler(new MouseDownHandler()  {
  			@Override
  			public void onMouseDown(MouseDownEvent event) {
  				rotate = true;
  				DOMHelper.setCaptureElement(compass, null);
  				event.preventDefault();
  				event.stopPropagation();
  			}
  		});
  		compass.addMouseMoveHandler(new MouseMoveHandler() {
  			@Override
  			public void onMouseMove(MouseMoveEvent event) {
  				if (rotate) {
  					OMSVGPoint p = getLocalCoordinates(event).substract(compass.createSVGPoint(50,50));
  					GWT.log(p.getDescription() + " " + Float.toString(-p.getY() / p.length()));
  					double a = Math.acos(-p.getY() / p.length());
  					if (p.getX() < 0) {
  						a = 2 * Math.PI - a;
  					}
  					setRotation((((int)toDeg(a)) / 6) * 6);
  					event.preventDefault();
  					event.stopPropagation();
  				}
  			}
  		});
  		compass.addMouseUpHandler(new MouseUpHandler() {
  			@Override
  			public void onMouseUp(MouseUpEvent event) {
  				if (rotate) {
  					rotate = false;
  					DOMHelper.releaseCaptureElement();
  					event.preventDefault();
  					event.stopPropagation();
  				}
  			}
  		});
  	}
 	
 	public void setRotation(int angle) {
 		this.angle = angle;
 		textGroup.getTransform().getBaseVal().getItem(0).setRotate(angle, 50, 50);
 		fireEvent(new RotationEvent(angle)); 
 	}
 	
 	public OMSVGSVGElement getSvgElement() {
 		return compass;
 	}
 
 	private static final float toDeg(double rad) {
 		return (float)(rad * 180 / Math.PI);
 	}
 
     /**
      * Returns the coordinates of a mouse event, converted
      * to the compass coordinate system
      * @param e
      * A mouse event
      * @return
      * The coordinates of the mouse event, converted
      * to the compass coordinate system
      */
     public OMSVGPoint getLocalCoordinates(MouseEvent<? extends EventHandler> e) {
         OMSVGPoint p = compass.createSVGPoint(e.getClientX(), e.getClientY());
         OMSVGMatrix m = compass.getScreenCTM().inverse();
         return p.matrixTransform(m);
     }
     
 	@Override
 	public void fireEvent(GwtEvent<?> event) {
 		SvgrealApp.getApp().getEventBus().fireEventFromSource(event, this);
 	}
 
 	@Override
 	public HandlerRegistration addRotationHandler(RotationHandler handler) {
 		return SvgrealApp.getApp().getEventBus().addHandlerToSource(RotationEvent.getType(), this, handler);
 	}
 }