package org.vaadin.hene.expandingtextarea.widgetset.client.ui;
   
   import java.util.ArrayList;
   import java.util.List;
   
   import com.google.gwt.user.client.Element;
   import com.google.gwt.user.client.Event;
   import com.google.gwt.user.client.Timer;
   import com.vaadin.v7.client.ui.VTextArea;
  
  /**
   * Client side widget which communicates with the server. Messages from the
   * server are shown as HTML and mouse clicks are sent to the server.
   */
  public class VExpandingTextArea extends VTextArea {
  
      /** Set the CSS class name to allow styling. */
      public static final String CLASSNAME = "v-expandingtextarea";
      
      private static int REPEAT_INTERVAL = 400;
  
      private Integer maxRows = null;
  
      private final HeightObserver heightObserver;
  
      public VExpandingTextArea() {
          setStyleName(CLASSNAME);
          sinkEvents(Event.ONFOCUS | Event.ONFOCUS);
  
          heightObserver = new HeightObserver();
      }
  
      @Override
      public void onBrowserEvent(Event event) {
          super.onBrowserEvent(event);
          if (event.getTypeInt() == Event.ONFOCUS) {
              heightObserver.scheduleRepeating(REPEAT_INTERVAL);
              getElement().addClassName(CLASSNAME + "-focus");
          } else if (event.getTypeInt() == Event.ONBLUR) {
              heightObserver.cancel();
              getElement().removeClassName(CLASSNAME + "-focus");
          }
      }
  
      public void checkHeight() {
          int origRows = getRows(getElement());
  
          // Check if we have to increase textarea's height
          int rows = origRows;
          rows++;
          while ((maxRows == null || rows <= maxRows)
                  && getElement().getScrollHeight() > getOffsetHeight()) {
              setRows(rows++);
          }
  
          // Check if we can reduce textarea's height
          rows = getRows(getElement());
          while (rows > 1) {
              setRows(rows - 1);
              if (!(getElement().getScrollHeight() > getOffsetHeight())) {
                  rows -= 1;
                  continue;
              } else {
                  setRows(rows);
                  break;
              }
          }
  
          int updatedRowCount = getRows(getElement()) + 1;
          // Add stylename if we have reached maximum row number, so we can show a
          // scroll bar
          if (maxRows != null && updatedRowCount > maxRows) {
              addStyleName("max");
              updatedRowCount = updatedRowCount > maxRows ? maxRows
                      : updatedRowCount;
          } else {
              removeStyleName("max");
          }
  
          setRows(updatedRowCount);
  
          if (origRows != getRows(getElement())) {
          	for (HeightChangedListener listener : heightChangedListeners) {
          		listener.heightChanged(getRows(getElement()));
          	}
          }
      }
  
      public void setMaxRows(Integer maxRows) {
          this.maxRows = maxRows;
      }
  
      public int getRows() {
          return getRows(getElement());
      }
  
      private native int getRows(Element e)
      /*-{
      	try {
     		return e.rows;
     	} catch (e) {
     		return -1;
     	}
     }-*/;
 
     private class HeightObserver extends Timer {
 
         @Override
         public void run() {
             checkHeight();
         }
     }
 
     @Override
     protected void onDetach() {
         heightObserver.cancel();
         super.onDetach();
     }
     
     List<HeightChangedListener> heightChangedListeners = new ArrayList<VExpandingTextArea.HeightChangedListener>();
     
     public interface HeightChangedListener {
     	void heightChanged(int newHeight);
     }
     
     public void addHeightChangedListener(HeightChangedListener listener) {
     	heightChangedListeners.add(listener);
     }
     
     public void removeHeightChangedListener(HeightChangedListener listener) {
     	heightChangedListeners.remove(listener);
     }
 }