/*
 * Copyright  1999-2004 The Apache Software Foundation.
 *
 *  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.apache.xml.security.transforms;

import java.io.IOException;
import java.io.OutputStream;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.xml.security.c14n.CanonicalizationException;
import org.apache.xml.security.c14n.InvalidCanonicalizerException;
import org.apache.xml.security.signature.XMLSignatureInput;
import org.xml.sax.SAXException;

/**
 * Base class which all Transform algorithms extend. The common methods that
 * have to be overridden are the 
 * {@link #enginePerformTransform(XMLSignatureInput, Transform)} method.
 *
 * @author Christian Geuer-Pollmann
 */
public abstract class TransformSpi {
    /**
     * For API compatibility not thread safe.
     * @deprecated
     */
    protected Transform _transformObject = null;
    /**
     * Set the transform object. 
     * Depeprecated For API compatibility.
     * @param transform the Transform
     * @deprecated
     */
    protected void setTransform(Transform transform) {
        this._transformObject = transform;
    }
    /**
     * The mega method which MUST be implemented by the Transformation Algorithm.
     *
     * @param input {@link XMLSignatureInput} as the input of transformation
     * @param os where to output this transformation.
     * @param _transformObject the Transform
     * @return {@link XMLSignatureInput} as the result of transformation
     * @throws CanonicalizationException
     * @throws IOException
     * @throws InvalidCanonicalizerException
     * @throws ParserConfigurationException
     * @throws SAXException
     * @throws TransformationException
     */
    protected XMLSignatureInput enginePerformTransform(
        XMLSignatureInput input, OutputStream os, Transform _transformObject)
        throws IOException,
               CanonicalizationException, InvalidCanonicalizerException,
               TransformationException, ParserConfigurationException,
               SAXException {
        return enginePerformTransform(input, _transformObject);
    }
    /**
     * The mega method which MUST be implemented by the Transformation Algorithm.
     * In order to be compatible with preexisting Transform implementations, 
     * by default this implementation invokes the deprecated, thread-unsafe
     * methods. Subclasses should override this with a thread-safe 
     * implementation.
     * 
     * @param input {@link XMLSignatureInput} as the input of transformation
     * @param _transformObject the Transform
     * @return {@link XMLSignatureInput} as the result of transformation
     * @throws CanonicalizationException
     * @throws IOException
     * @throws InvalidCanonicalizerException
     * @throws ParserConfigurationException
     * @throws SAXException
     * @throws TransformationException
     */
    protected XMLSignatureInput enginePerformTransform(
        XMLSignatureInput input, Transform _transformObject)
        throws IOException,
               CanonicalizationException, InvalidCanonicalizerException,
               TransformationException, ParserConfigurationException,
               SAXException {
	//Default implementation overide with a much better
	try {
		TransformSpi tmp = (TransformSpi) getClass().newInstance();
	    tmp.setTransform(_transformObject);
	    return tmp.enginePerformTransform(input);
	} catch (InstantiationException e) {
	    throw new TransformationException("",e);
	} catch (IllegalAccessException e) {
	    throw new TransformationException("",e);
	}
    }

    /**
     * The mega method which MUST be implemented by the Transformation Algorithm.
     * @deprecated
     * @param input {@link XMLSignatureInput} as the input of transformation
     * @return {@link XMLSignatureInput} as the result of transformation
     * @throws CanonicalizationException
     * @throws IOException
     * @throws InvalidCanonicalizerException
     * @throws ParserConfigurationException
     * @throws SAXException
     * @throws TransformationException
     */
    protected XMLSignatureInput enginePerformTransform(
        XMLSignatureInput input)
        throws IOException,
               CanonicalizationException, InvalidCanonicalizerException,
               TransformationException, ParserConfigurationException,
               SAXException {
	throw new UnsupportedOperationException();
    }
    /**
     * Returns the URI representation of <code>Transformation algorithm</code>
     *
     * @return the URI representation of <code>Transformation algorithm</code>
     */
    protected abstract String engineGetURI();
}
