/*
 * Copyright 2006-2014 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.job.flow;

import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.batch.core.Job;
import org.springframework.batch.core.JobExecution;
import org.springframework.batch.core.JobExecutionException;
import org.springframework.batch.core.Step;
import org.springframework.batch.core.job.AbstractJob;
import org.springframework.batch.core.job.SimpleStepHandler;
import org.springframework.batch.core.step.StepHolder;
import org.springframework.batch.core.step.StepLocator;

/**
 * Implementation of the {@link Job} interface that allows for complex flows of
 * steps, rather than requiring sequential execution. In general, this job
 * implementation was designed to be used behind a parser, allowing for a
 * namespace to abstract away details.
 *
 * @author Dave Syer
 * @since 2.0
 */
public class FlowJob extends AbstractJob {

	protected Flow flow;

	private Map<String, Step> stepMap = new ConcurrentHashMap<String, Step>();

	private volatile boolean initialized = false;

	/**
	 * Create a {@link FlowJob} with null name and no flow (invalid state).
	 */
	public FlowJob() {
		super();
	}

	/**
	 * Create a {@link FlowJob} with provided name and no flow (invalid state).
	 */
	public FlowJob(String name) {
		super(name);
	}

	/**
	 * Public setter for the flow.
	 *
	 * @param flow the flow to set
	 */
	public void setFlow(Flow flow) {
		this.flow = flow;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public Step getStep(String stepName) {
		if (!initialized) {
			init();
		}
		return stepMap.get(stepName);
	}

	/**
	 * Initialize the step names
	 */
	private void init() {
		findSteps(flow, stepMap);
	}

	/**
	 * @param flow
	 * @param map
	 */
	private void findSteps(Flow flow, Map<String, Step> map) {

		for (State state : flow.getStates()) {
			if (state instanceof StepLocator) {
				StepLocator locator = (StepLocator) state;
				for (String name : locator.getStepNames()) {
					map.put(name, locator.getStep(name));
				}
			} else if (state instanceof StepHolder) {
				Step step = ((StepHolder) state).getStep();
				String name = step.getName();
				stepMap.put(name, step);
			}
			else if (state instanceof FlowHolder) {
				for (Flow subflow : ((FlowHolder) state).getFlows()) {
					findSteps(subflow, map);
				}
			}
		}

	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public Collection<String> getStepNames() {
		if (!initialized) {
			init();
		}
		return stepMap.keySet();
	}

	/**
	 * @see AbstractJob#doExecute(JobExecution)
	 */
	@Override
	protected void doExecute(final JobExecution execution) throws JobExecutionException {
		try {
			JobFlowExecutor executor = new JobFlowExecutor(getJobRepository(),
					new SimpleStepHandler(getJobRepository()), execution);
			executor.updateJobExecutionStatus(flow.start(executor).getStatus());
		}
		catch (FlowExecutionException e) {
			if (e.getCause() instanceof JobExecutionException) {
				throw (JobExecutionException) e.getCause();
			}
			throw new JobExecutionException("Flow execution ended unexpectedly", e);
		}
	}

}