/*
    * Copyright 2012-2013 the original author or authors.
    *
    * Licensed 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.springframework.batch.core.configuration.xml;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  
  import org.springframework.batch.core.job.flow.Flow;
  import org.springframework.batch.core.job.flow.FlowExecutionStatus;
  import org.springframework.batch.core.job.flow.FlowExecutor;
  import org.springframework.batch.core.job.flow.FlowHolder;
  import org.springframework.batch.core.job.flow.State;
  import org.springframework.batch.core.job.flow.support.SimpleFlow;
  import org.springframework.batch.core.job.flow.support.StateTransition;
  import org.springframework.batch.core.job.flow.support.state.AbstractState;
  import org.springframework.batch.core.job.flow.support.state.StepState;
  import org.springframework.beans.factory.FactoryBean;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.util.Assert;
  
  /**
   * Convenience factory for SimpleFlow instances for use in XML namespace. It
   * replaces the states in the input with proxies that have a unique name formed
   * from the flow name and the original state name (unless the name is already in
   * that form, in which case it is not modified).
   *
   * @author Dave Syer
   *
   */
  @SuppressWarnings("rawtypes")
  public class SimpleFlowFactoryBean implements FactoryBean, InitializingBean {
  
  	private String name;
  
  	private List<StateTransition> stateTransitions;
  
  	private String prefix;
  
  	/**
  	 * The name of the flow that is created by this factory.
  	 *
  	 * @param name the value of the name
  	 */
  	public void setName(String name) {
  		this.name = name;
  		this.prefix = name + ".";
  	}
  
  	/**
  	 * The raw state transitions for the flow. They will be transformed into
  	 * proxies that have the same behavior but unique names prefixed with the
  	 * flow name.
  	 *
  	 * @param stateTransitions the list of transitions
  	 */
  	public void setStateTransitions(List<StateTransition> stateTransitions) {
  		this.stateTransitions = stateTransitions;
  	}
  
  	/**
  	 * Check mandatory properties (name).
  	 *
  	 * @throws Exception
  	 */
  	@Override
  	public void afterPropertiesSet() throws Exception {
  		Assert.hasText(name, "The flow must have a name");
  	}
  
  	@Override
  	public Object getObject() throws Exception {
  
  		SimpleFlow flow = new SimpleFlow(name);
  
  		List<StateTransition> updatedTransitions = new ArrayList<StateTransition>();
  		for (StateTransition stateTransition : stateTransitions) {
  			State state = getProxyState(stateTransition.getState());
  			updatedTransitions.add(StateTransition.switchOriginAndDestination(stateTransition, state,
  					getNext(stateTransition.getNext())));
  		}
  
  		flow.setStateTransitions(updatedTransitions);
  		flow.afterPropertiesSet();
  		return flow;
 
 	}
 
 	private String getNext(String next) {
 		if (next == null) {
 			return null;
 		}
 		return (next.startsWith(this.prefix) ? "" : this.prefix) + next;
 	}
 
 	/**
 	 * Convenience method to get a state that proxies the input but with a
 	 * different name, appropriate to this flow. If the state is a StepState
 	 * then the step name is also changed.
 	 *
 	 * @param state
 	 * @return
 	 */
 	private State getProxyState(State state) {
 		String oldName = state.getName();
 		if (oldName.startsWith(prefix)) {
 			return state;
 		}
 		String stateName = prefix + oldName;
 		if (state instanceof StepState) {
 			return new StepState(stateName, ((StepState) state).getStep());
 		}
 		return new DelegateState(stateName, state);
 	}
 
 	@Override
 	public Class<?> getObjectType() {
 		return SimpleFlow.class;
 	}
 
 	@Override
 	public boolean isSingleton() {
 		return true;
 	}
 
 	/**
 	 * A State that proxies a delegate and changes its name but leaves its
 	 * behavior unchanged.
 	 *
 	 * @author Dave Syer
 	 *
 	 */
 	private static class DelegateState extends AbstractState implements FlowHolder {
 		private final State state;
 
 		private DelegateState(String name, State state) {
 			super(name);
 			this.state = state;
 		}
 
 		@Override
 		public boolean isEndState() {
 			return state.isEndState();
 		}
 
 		@Override
 		public FlowExecutionStatus handle(FlowExecutor executor) throws Exception {
 			return state.handle(executor);
 		}
 
 		@Override
 		public Collection<Flow> getFlows() {
 			return (state instanceof FlowHolder) ? ((FlowHolder)state).getFlows() : Collections.<Flow>emptyList();
 		}
 
 	}
 
 }