/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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 nokogiri.internals.c14n;

import java.io.OutputStream;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.w3c.dom.Node;

/**
 *
 * @author Christian Geuer-Pollmann
 */
public class Canonicalizer
{

  /** The output encoding of canonicalized data */
  public static final String ENCODING = "UTF8";

  /**
   * XPath Expression for selecting every node and continuous comments joined
   * in only one node
   */
  public static final String XPATH_C14N_WITH_COMMENTS_SINGLE_NODE =
    "(.//. | .//@* | .//namespace::*)";

  /**
   * The URL defined in XML-SEC Rec for inclusive c14n <b>without</b> comments.
   */
  public static final String ALGO_ID_C14N_OMIT_COMMENTS =
    "http://www.w3.org/TR/2001/REC-xml-c14n-20010315";
  /**
   * The URL defined in XML-SEC Rec for inclusive c14n <b>with</b> comments.
   */
  public static final String ALGO_ID_C14N_WITH_COMMENTS =
    ALGO_ID_C14N_OMIT_COMMENTS + "#WithComments";
  /**
   * The URL defined in XML-SEC Rec for exclusive c14n <b>without</b> comments.
   */
  public static final String ALGO_ID_C14N_EXCL_OMIT_COMMENTS =
    "http://www.w3.org/2001/10/xml-exc-c14n#";
  /**
   * The URL defined in XML-SEC Rec for exclusive c14n <b>with</b> comments.
   */
  public static final String ALGO_ID_C14N_EXCL_WITH_COMMENTS =
    ALGO_ID_C14N_EXCL_OMIT_COMMENTS + "WithComments";
  /**
   * The URI for inclusive c14n 1.1 <b>without</b> comments.
   */
  public static final String ALGO_ID_C14N11_OMIT_COMMENTS =
    "http://www.w3.org/2006/12/xml-c14n11";
  /**
   * The URI for inclusive c14n 1.1 <b>with</b> comments.
   */
  public static final String ALGO_ID_C14N11_WITH_COMMENTS =
    ALGO_ID_C14N11_OMIT_COMMENTS + "#WithComments";
  /**
   * Non-standard algorithm to serialize the physical representation for XML Encryption
   */
  public static final String ALGO_ID_C14N_PHYSICAL =
    "http://santuario.apache.org/c14n/physical";

  private static Map<String, Class<? extends CanonicalizerSpi>> canonicalizerHash = null;

  private final CanonicalizerSpi canonicalizerSpi;

  /**
   * Constructor Canonicalizer
   *
   * @param algorithmURI
   * @throws InvalidCanonicalizerException
   */
  private
  Canonicalizer(String algorithmURI) throws CanonicalizationException
  {
    try {
      Class<? extends CanonicalizerSpi> implementingClass =
        canonicalizerHash.get(algorithmURI);

      canonicalizerSpi = implementingClass.newInstance();
      canonicalizerSpi.reset = true;
    } catch (Exception e) {
      Object exArgs[] = { algorithmURI };
      throw new CanonicalizationException(
        "signature.Canonicalizer.UnknownCanonicalizer", exArgs, e
      );
    }
  }

  /**
   * Method getInstance
   *
   * @param algorithmURI
   * @return a Canonicalizer instance ready for the job
   * @throws InvalidCanonicalizerException
   */
  public static final Canonicalizer
  getInstance(String algorithmURI)
  throws CanonicalizationException
  {
    if (canonicalizerHash == null) {
      canonicalizerHash = new ConcurrentHashMap<String, Class<? extends CanonicalizerSpi>>();
      Canonicalizer.registerDefaultAlgorithms();
    }
    return new Canonicalizer(algorithmURI);
  }

  /**
   * Method register
   *
   * @param algorithmURI
   * @param implementingClass
   * @throws CanonicalizationException
   */
  @SuppressWarnings("unchecked")
  public static void
  register(String algorithmURI, String implementingClass)
  throws CanonicalizationException, ClassNotFoundException
  {
    // check whether URI is already registered
    Class<? extends CanonicalizerSpi> registeredClass =
      canonicalizerHash.get(algorithmURI);

    if (registeredClass != null)  {
      Object exArgs[] = { algorithmURI, registeredClass };
      throw new CanonicalizationException("algorithm.alreadyRegistered", exArgs);
    }

    canonicalizerHash.put(
      algorithmURI, (Class<? extends CanonicalizerSpi>)Class.forName(implementingClass)
    );
  }

  /**
   * Method register
   *
   * @param algorithmURI
   * @param implementingClass
   * @throws CanonicalizationException
   */
  public static void
  register(String algorithmURI, Class<? extends CanonicalizerSpi> implementingClass)
  throws CanonicalizationException
  {
    // check whether URI is already registered
    Class<? extends CanonicalizerSpi> registeredClass = canonicalizerHash.get(algorithmURI);

    if (registeredClass != null)  {
      Object exArgs[] = { algorithmURI, registeredClass };
      throw new CanonicalizationException("algorithm.alreadyRegistered", exArgs);
    }

    canonicalizerHash.put(algorithmURI, implementingClass);
  }

  /**
   * This method registers the default algorithms.
   */
  private static void
  registerDefaultAlgorithms()
  {
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N_OMIT_COMMENTS,
                          Canonicalizer20010315OmitComments.class);
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N_WITH_COMMENTS,
                          Canonicalizer20010315WithComments.class);
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N_EXCL_OMIT_COMMENTS,
                          Canonicalizer20010315ExclOmitComments.class);
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N_EXCL_WITH_COMMENTS,
                          Canonicalizer20010315ExclWithComments.class);
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N11_OMIT_COMMENTS,
                          Canonicalizer11_OmitComments.class);
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N11_WITH_COMMENTS,
                          Canonicalizer11_WithComments.class);
    canonicalizerHash.put(Canonicalizer.ALGO_ID_C14N_PHYSICAL,
                          CanonicalizerPhysical.class);
  }

  /**
   * Method getURI
   *
   * @return the URI defined for this c14n instance.
   */
  public final String
  getURI()
  {
    return canonicalizerSpi.engineGetURI();
  }

  /**
   * Method getIncludeComments
   *
   * @return true if the c14n respect the comments.
   */
  public boolean
  getIncludeComments()
  {
    return canonicalizerSpi.engineGetIncludeComments();
  }

  /**
   * Canonicalizes the subtree rooted by <CODE>node</CODE>.
   *
   * @param node The node to canonicalize
   * @return the result of the c14n.
   *
   * @throws CanonicalizationException
   */
  public byte[]
  canonicalizeSubtree(Node node, CanonicalFilter filter) throws CanonicalizationException
  {
    return canonicalizerSpi.engineCanonicalizeSubTree(node, filter);
  }

  /**
   * Canonicalizes the subtree rooted by <CODE>node</CODE>.
   *
   * @param node
   * @param inclusiveNamespaces
   * @return the result of the c14n.
   * @throws CanonicalizationException
   */
  public byte[]
  canonicalizeSubtree(Node node, String inclusiveNamespaces, CanonicalFilter filter)
  throws CanonicalizationException
  {
    return canonicalizerSpi.engineCanonicalizeSubTree(node, inclusiveNamespaces, filter);
  }

  /**
   * Sets the writer where the canonicalization ends.  ByteArrayOutputStream
   * if none is set.
   * @param os
   */
  public void
  setWriter(OutputStream os)
  {
    canonicalizerSpi.setWriter(os);
  }

  /**
   * Returns the name of the implementing {@link CanonicalizerSpi} class
   *
   * @return the name of the implementing {@link CanonicalizerSpi} class
   */
  public String
  getImplementingCanonicalizerClass()
  {
    return canonicalizerSpi.getClass().getName();
  }

  /**
   * Set the canonicalizer behaviour to not reset.
   */
  public void
  notReset()
  {
    canonicalizerSpi.reset = false;
  }

}