/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache 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.apache.org/licenses/LICENSE-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.apache.myfaces.tobago.event;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.el.ValueExpression;
  import javax.faces.component.StateHolder;
  import javax.faces.component.UIComponentBase;
  import javax.faces.context.FacesContext;
  
  public class ValueExpressionTabChangeListener implements TabChangeListener, StateHolder {
  
    private static final Logger LOG = LoggerFactory.getLogger(ValueExpressionTabChangeListener.class);
  
    private String type;
    private ValueExpression valueExpression;
  
    public ValueExpressionTabChangeListener() {
    }
  
    public ValueExpressionTabChangeListener(String type, ValueExpression valueExpression) {
      this.type = type;
      this.valueExpression = valueExpression;
    }
  
    public void processTabChange(TabChangeEvent tabChangeEvent) {
      TabChangeListener handler = getTabChangeListener();
      if (handler != null) {
        handler.processTabChange(tabChangeEvent);
      } else {
        LOG.error("Ignoring TabChangeEvent. No TabChangeListener found.");
      }
    }
  
    public Object saveState(FacesContext context) {
      Object[] state = new Object[2];
      state[0] = UIComponentBase.saveAttachedState(context, valueExpression);
      state[1] = type;
      return state;
    }
  
    public void restoreState(FacesContext context, Object state) {
      Object[] values = (Object[]) state;
      valueExpression = (ValueExpression) UIComponentBase.restoreAttachedState(context, values[0]);
      type = (String) values[1];
  
    }
  
    public boolean isTransient() {
      return false;
    }
  
    public void setTransient(boolean newTransientValue) {
      // ignore
    }
  
    private TabChangeListener getTabChangeListener() {
      TabChangeListener handler = null;
      if (valueExpression != null) {
        Object obj = valueExpression.getValue(FacesContext.getCurrentInstance().getELContext());
        if (obj != null && obj instanceof TabChangeListener) {
          handler = (TabChangeListener) obj;
        }
      }
      if (handler == null && type != null) {
        handler = createTabChangeListener(type);
        if (handler != null && valueExpression != null) {
          valueExpression.setValue(FacesContext.getCurrentInstance().getELContext(), handler);
        }
      }
      return handler;
    }
  
    private TabChangeListener createTabChangeListener(String className) {
      try {
        Class clazz = getClass().getClassLoader().loadClass(className);
        return ((TabChangeListener) clazz.newInstance());
      } catch (Exception e) {
        LOG.error("", e);
      }
     return null;
   }
 }