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/*
 * Milyn - Copyright (C) 2006 - 2010
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License (version 2.1) as published
 * by the Free Software Foundation.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.
 * 
 * See the GNU Lesser General Public License for more details:
 * http://www.gnu.org/licenses/lgpl.txt
 */

package org.milyn.container.plugin;

import org.milyn.Smooks;
import org.milyn.SmooksException;
import org.milyn.assertion.AssertArgument;
import org.milyn.container.ExecutionContext;
import org.milyn.payload.ByteResult;
import org.milyn.payload.JavaResult;
import org.milyn.payload.StringResult;

import javax.xml.transform.Result;
import javax.xml.transform.Source;

/**
 * Processor class for an abstract payload type.
 *
 * This class can be used to ease Smooks integration with application
 * containers (for example ESBs).  It works out how to filter the supplied Object payload
 * through Smooks, to produce the desired {@link ResultType result type}.
 *
 * The "payload" object supplied to the {@link #process(Object, org.milyn.container.ExecutionContext)}
 * method can be one of type:
 * 
 * {@link String},
 * {@link Byte} array,
 * {@link java.io.Reader},
 * {@link java.io.InputStream},
 * {@link Source},
 * {@link SourceResult}, or
 * any Java user type (gets wrapped in a {@link org.milyn.payload.JavaSource}).
 * 
 *
 * The {@link SourceResult} payload type allows full control over the filter
 * {@link Source} and {@link Result}.
 *
 * @author Daniel Bevenius
 */
public class PayloadProcessor {

    private Smooks smooks;
    private ResultType resultType;
    private String javaResultBeanId;

    /**
     * Public constructor.
     * @param smooks The Smooks instance to be used.
     * @param resultType The required result type.
     */
    public PayloadProcessor(final Smooks smooks, final ResultType resultType) {
        AssertArgument.isNotNull(smooks, "smooks");
        AssertArgument.isNotNull(resultType, "resultType");
        this.smooks = smooks;
        this.resultType = resultType;
    }

    /**
     * Set the bean ID to be unpacked from a {@link JavaResult}.
     *
     * Only relevant for {@link ResultType#JAVA}.  If not specified, the
     * complete {@link org.milyn.payload.JavaResult#getResultMap() result Map}
     * will be returned as the result of the {@link #process(Object, org.milyn.container.ExecutionContext)}
     * method call.
     *
     * @param javaResultBeanId The bean ID to be unpacked.
     */
    public void setJavaResultBeanId(final String javaResultBeanId) {
        AssertArgument.isNotNullAndNotEmpty(javaResultBeanId, "javaResultBeanId");
        this.javaResultBeanId = javaResultBeanId;
    }

    public final Object process(final Object payload, final ExecutionContext executionContext) throws SmooksException {
        AssertArgument.isNotNull(payload, "payload");

        Source source;
        Result result;

        if (payload instanceof SourceResult) {
            SourceResult sourceResult = (SourceResult) payload;
            source = sourceResult.getSource();
            result = sourceResult.getResult();
        } else {
            source = SourceFactory.getInstance().createSource(payload);
            result = ResultFactory.getInstance().createResult(resultType);
        }

        // Filter it through Smooks...
        smooks.filterSource(executionContext, source, result);

        // Extract the result...
        if (result instanceof JavaResult) {
            if (javaResultBeanId != null) {
                return ((JavaResult) result).getResultMap().get(javaResultBeanId);
            } else {
                return ((JavaResult) result).getResultMap();
            }
        } else if (result instanceof StringResult) {
            return ((StringResult) result).getResult();
        } else if (result instanceof ByteResult) {
            return ((ByteResult) result).getResult();
        }

        return result;
    }
}