/*
 * Copyright 2005 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.wamblee.xml;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.Document;
import org.wamblee.io.InputResource;

/**
 * XSLT utilities.
 */
public class XSLT {

    /**
     * Constructs the XSLT processor.
     * 
     */
    public XSLT() {
        // Empty.
    }

    /**
     * Transforms a DOM document into another DOM document using a given XSLT
     * transformation.
     * 
     * @param aDocument
     *            Document to transform.
     * @param aXslt
     *            XSLT to use.
     * @return Transformed document.
     * @throws IOException
     *             In case of problems reading resources.
     * @throws TransformerException
     *             In case transformation fails.
     */
    public Document transform(Document aDocument, InputResource aXslt)
            throws IOException, TransformerException {
        Source source = new DOMSource(aDocument);
        DOMResult result = new DOMResult();
        transform(source, result, aXslt);
        return (Document) result.getNode();
    }

    /**
     * Transforms a document using XSLT.
     * 
     * @param aDocument
     *            Document to transform.
     * @param aXslt
     *            XSLT to use.
     * @return Transformed document.
     * @throws IOException
     *             In case of problems reading resources.
     * @throws TransformerException
     *             In case transformation fails.
     */
    public Document transform(byte[] aDocument, InputResource aXslt)
            throws IOException, TransformerException {
        Source source = new StreamSource(new ByteArrayInputStream(aDocument));
        DOMResult result = new DOMResult();
        transform(source, result, aXslt);
        return (Document) result.getNode();
    }
    
    /**
     * Transforms a document to a text output. This supports XSLT transformations
     * that result in text documents. 
     * @param aDocument Document to transform.
     * @param aXslt XSL transformation. 
     * @return Transformed document.  
     */
    public String textTransform(byte[] aDocument, InputResource aXslt) throws IOException, TransformerException { 
        Source source = new StreamSource(new ByteArrayInputStream(aDocument));
        ByteArrayOutputStream os = new ByteArrayOutputStream(); 
        StreamResult result = new StreamResult(os);
        transform(source, result, aXslt);
        return new String(os.toByteArray());
    }

    /**
     * Transforms a document using XSLT.
     * 
     * @param aSource
     *            Document to transform.
     * @param aResult
     *            Result of the transformation.
     * @param aXslt
     *            XSLT to use.
     * @throws IOException
     *             In case of problems reading resources.
     * @throws TransformerException
     *             In case transformation fails.
     */
    public void transform(Source aSource, Result aResult, InputResource aXslt)
            throws IOException, TransformerException {
        InputStream xslt = null;
        try {
            xslt = aXslt.getInputStream();
            Source xsltSource = new StreamSource(xslt);
            Transformer transformer = TransformerFactory.newInstance()
                    .newTransformer(xsltSource);
            transformer.transform(aSource, aResult);
        } catch (TransformerConfigurationException e) {
            throw new RuntimeException(
                    "Configuration problem of XSLT transformation", e);
        } finally {
            if (xslt != null) {
                xslt.close();
            }
        }
    }
}