/**
    * This file Copyright (c) 2020 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.ui.vaadin.gwt.client.extension;
  
  import com.google.gwt.dom.client.Element;
  import com.google.gwt.dom.client.Style;
  import com.google.gwt.event.dom.client.KeyUpEvent;
  import com.google.gwt.event.shared.HandlerRegistration;
  import com.google.gwt.user.client.DOM;
  import com.google.gwt.user.client.ui.HasValue;
  import com.google.gwt.user.client.ui.Widget;
  import com.vaadin.client.ServerConnector;
  import com.vaadin.client.communication.StateChangeEvent;
  import com.vaadin.client.extensions.AbstractExtensionConnector;
  import com.vaadin.client.ui.AbstractComponentConnector;
  
  /**
   * Abstract client-side connector for adding counter of characters to text component.
   *
   * @param <T> component connector
   */
  public abstract class AbstractMaxLengthIndicatorExtensionConnector<T extends AbstractComponentConnector> extends AbstractExtensionConnector {
  
      public static final String MAXLENGTH_INDICATOR_STYLE_NAME = "maxlength-indicator";
  
      protected T textConnector;
      private Widget textWidget;
      private final Element indicatorElem = DOM.createDiv();
      private int maxLength = 0;
      private HandlerRegistration keyUpHandlerRegistration;
      private com.google.web.bindery.event.shared.HandlerRegistration parentStateChangeHandlerRegistration;
  
      abstract protected int getConnectorStateMaxLength();
      abstract protected String getConnectorStateText();
  
      @Override
      protected void extend(ServerConnector target) {
          textConnector = (T) target;
          textWidget = textConnector.getWidget();
  
          addHandlers();
          updateIndicatorFromParentState();
  
          textWidget.addAttachHandler(event -> {
              if (event.isAttached()) {
                  assembleAndAttach();
              }
          });
      }
  
      @Override
      public void onUnregister() {
          super.onUnregister();
          cleanUp();
      }
  
      private void cleanUp() {
          if (keyUpHandlerRegistration != null) {
              keyUpHandlerRegistration.removeHandler();
          }
          if (parentStateChangeHandlerRegistration != null) {
              parentStateChangeHandlerRegistration.removeHandler();
          }
          if (indicatorElem.hasParentElement()) {
              indicatorElem.removeFromParent();
          }
      }
  
     private void assembleAndAttach() {
         // We append indicator element to the text widget's parent element
         indicatorElem.addClassName(MAXLENGTH_INDICATOR_STYLE_NAME);
         textWidget.getElement().getParentElement().appendChild(indicatorElem);
     }
 
     private void addHandlers() {
         // One might think KeyPressEvent should be the "better" choice here.
         // However, when using KeyPressEvent, text field's value is not updated
         // and hence the displayed number of entered characters is always 1 too small.
         keyUpHandlerRegistration = textWidget.addDomHandler(event -> updateIndicatorValue(getInputValueLength()), KeyUpEvent.getType());
 
         // make sure to update maxLength when the property gets changed
         parentStateChangeHandlerRegistration = textConnector.addStateChangeHandler((StateChangeEvent.StateChangeHandler) stateChangeEvent -> {
             if (stateChangeEvent.hasPropertyChanged("maxLength") || stateChangeEvent.hasPropertyChanged("text")) {
                 updateIndicatorFromParentState();
             }
         });
     }
 
     private void updateIndicatorFromParentState() {
         maxLength = getConnectorStateMaxLength();
         String text = getConnectorStateText();
         updateIndicatorValue(text == null ? 0 : text.length());
         setIndicatorVisible(maxLength >= 0);
     }
 
     private void setIndicatorVisible(boolean isVisible) {
         if (isVisible) {
             indicatorElem.getStyle().clearDisplay();
         } else {
             indicatorElem.getStyle().setDisplay(Style.Display.NONE);
         }
     }
 
     private void updateIndicatorValue(int currentlyDisplayedCharactersAmount) {
         indicatorElem.setInnerHTML(currentlyDisplayedCharactersAmount + "/" + maxLength);
     }
 
     private int getInputValueLength() {
         return ((String)((HasValue)textWidget).getValue()).length();
     }
 
 
 }