package org.apache.helix.participant.statemachine;
   
   /*
    * 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.
   */
  
  import java.lang.reflect.Method;
  import java.util.Arrays;
  
  import org.apache.helix.NotificationContext;
  import org.apache.helix.model.Message;
  
  
  /**
   * Finds the method in stateModel to generate
   * 
   * 
   */
  public class StateModelParser
  {
  
  	public Method getMethodForTransition(Class<? extends StateModel> clazz,
  	    String fromState, String toState, Class<?>[] paramTypes)
  	{
  		Method method = getMethodForTransitionUsingAnnotation(clazz, fromState,
  		    toState, paramTypes);
  		if (method == null)
  		{
  			method = getMethodForTransitionByConvention(clazz, fromState, toState,
  			    paramTypes);
  		}
  		return method;
  	}
  
  	/**
  	 * This class uses the method naming convention "onBecome" + toState + "From"
  	 * + fromState;
  	 * 
  	 * @param clazz
  	 * @param fromState
  	 * @param toState
  	 * @param paramTypes
  	 * @return Method if found else null
  	 */
  	public Method getMethodForTransitionByConvention(
  	    Class<? extends StateModel> clazz, String fromState, String toState,
  	    Class<?>[] paramTypes)
  	{
  		Method methodToInvoke = null;
  		String methodName = "onBecome" + toState + "From" + fromState;
  		if (fromState.equals("*"))
  		{
  			methodName = "onBecome" + toState;
  		}
  
  		Method[] methods = clazz.getMethods();
  		for (Method method : methods)
  		{
  			if (method.getName().equalsIgnoreCase(methodName))
  			{
  				Class<?>[] parameterTypes = method.getParameterTypes();
  				if (parameterTypes.length == 2
  				    && parameterTypes[0].equals(Message.class)
  				    && parameterTypes[1].equals(NotificationContext.class))
  				{
  					methodToInvoke = method;
  					break;
  				}
  			}
  		}
  		return methodToInvoke;
  
  	}
  
  	/**
  	 * This method uses annotations on the StateModel class. Use StateModelInfo
  	 * annotation to specify valid states and initial value use Transition to
  	 * specify "to" and "from" state
  	 * 
  	 * @param clazz
  	 *          , class which extends StateModel
  	 * @param fromState
  	 * @param toState
  	 * @param paramTypes
 	 * @return
 	 */
 	public Method getMethodForTransitionUsingAnnotation(
 	    Class<? extends StateModel> clazz, String fromState, String toState,
 	    Class<?>[] paramTypes)
 	{
 		StateModelInfo stateModelInfo = clazz.getAnnotation(StateModelInfo.class);
 		Method methodToInvoke = null;
 		if (stateModelInfo != null)
 		{
 			Method[] methods = clazz.getMethods();
 			if (methods != null)
 			{
 				for (Method method : methods)
 				{
 					Transition annotation = method.getAnnotation(Transition.class);
 					if (annotation != null)
 					{
 						boolean matchesFrom = "*".equals(annotation.from()) || annotation.from().equalsIgnoreCase(fromState);
 						boolean matchesTo = "*".equals(annotation.to()) || annotation.to().equalsIgnoreCase(toState);
 						boolean matchesParamTypes = Arrays.equals(paramTypes,
 						    method.getParameterTypes());
 						if (matchesFrom && matchesTo && matchesParamTypes)
 						{
 							methodToInvoke = method;
 							break;
 						}
 					}
 				}
 			}
 		}
 
 		return methodToInvoke;
 	}
 
 	/**
 	 * Get the initial state for the state model
 	 * 
 	 * @param clazz
 	 * @return
 	 */
 	public String getInitialState(Class<? extends StateModel> clazz)
 	{
 		StateModelInfo stateModelInfo = clazz.getAnnotation(StateModelInfo.class);
 		if (stateModelInfo != null)
 		{
 			return stateModelInfo.initialState();
 		}else{
 			return StateModel.DEFAULT_INITIAL_STATE;
 		}
 	}
 
 }