/*
 * Copyright 2012 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.item.data;

import java.lang.reflect.InvocationTargetException;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.adapter.AbstractMethodInvokingDelegator.InvocationTargetThrowableWrapper;
import org.springframework.batch.item.adapter.DynamicMethodInvocationException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.data.repository.CrudRepository;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.MethodInvoker;

/**
 * <p>
 * A {@link org.springframework.batch.item.ItemReader} wrapper for a
 * {@link org.springframework.data.repository.CrudRepository} from Spring Data.
 * </p>
 *
 * <p>
 * It depends on {@link org.springframework.data.repository.CrudRepository#saveAll(Iterable)}
 * method to store the items for the chunk.  Performance will be determined by that
 * implementation more than this writer.
 * </p>
 *
 * <p>
 * As long as the repository provided is thread-safe, this writer is also thread-safe once
 * properties are set (normal singleton behavior), so it can be used in multiple concurrent
 * transactions.
 * </p>
 *
 * @author Michael Minella
 * @since 2.2
 */
public class RepositoryItemWriter<T> implements ItemWriter<T>, InitializingBean {

	protected static final Log logger = LogFactory.getLog(RepositoryItemWriter.class);

	private CrudRepository<T, ?> repository;

	private String methodName;

	/**
	 * Specifies what method on the repository to call.  This method must the type of
	 * object passed to this writer as the <em>sole</em> argument.
	 *
	 * @param methodName
	 */
	public void setMethodName(String methodName) {
		this.methodName = methodName;
	}

	/**
	 * Set the {@link org.springframework.data.repository.CrudRepository} implementation
	 * for persistence
	 *
	 * @param repository the Spring Data repository to be set
	 */
	public void setRepository(CrudRepository<T, ?> repository) {
		this.repository = repository;
	}

	/**
	 * Write all items to the data store via a Spring Data repository.
	 *
	 * @see org.springframework.batch.item.ItemWriter#write(java.util.List)
	 */
	@Override
	public void write(List<? extends T> items) throws Exception {
		if(!CollectionUtils.isEmpty(items)) {
			doWrite(items);
		}
	}

	/**
	 * Performs the actual write to the repository.  This can be overriden by
	 * a subclass if necessary.
	 *
	 * @param items the list of items to be persisted.
	 */
	protected void doWrite(List<? extends T> items) throws Exception {
		if (logger.isDebugEnabled()) {
			logger.debug("Writing to the repository with " + items.size() + " items.");
		}

		MethodInvoker invoker = createMethodInvoker(repository, methodName);

		for (T object : items) {
			invoker.setArguments(new Object [] {object});
			doInvoke(invoker);
		}
	}

	/**
	 * Check mandatory properties - there must be a repository.
	 */
	@Override
	public void afterPropertiesSet() throws Exception {
		Assert.state(repository != null, "A CrudRepository implementation is required");
	}


	private Object doInvoke(MethodInvoker invoker) throws Exception{
		try {
			invoker.prepare();
		}
		catch (ClassNotFoundException e) {
			throw new DynamicMethodInvocationException(e);
		}
		catch (NoSuchMethodException e) {
			throw new DynamicMethodInvocationException(e);
		}

		try {
			return invoker.invoke();
		}
		catch (InvocationTargetException e) {
			if (e.getCause() instanceof Exception) {
				throw (Exception) e.getCause();
			}
			else {
				throw new InvocationTargetThrowableWrapper(e.getCause());
			}
		}
		catch (IllegalAccessException e) {
			throw new DynamicMethodInvocationException(e);
		}
	}

	private MethodInvoker createMethodInvoker(Object targetObject, String targetMethod) {
		MethodInvoker invoker = new MethodInvoker();
		invoker.setTargetObject(targetObject);
		invoker.setTargetMethod(targetMethod);
		return invoker;
	}
}