/**
 * 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.IOException;
import java.io.OutputStream;
import java.util.Iterator;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;


import org.w3c.dom.Attr;
import org.w3c.dom.Comment;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.ProcessingInstruction;

/**
 * Serializes the physical representation of the subtree. All the attributes
 * present in the subtree are emitted. The attributes are sorted within an element,
 * with the namespace declarations appearing before the regular attributes.
 * This algorithm is not a true canonicalization since equivalent subtrees
 * may produce different output. It is therefore unsuitable for digital signatures.
 * This same property makes it ideal for XML Encryption Syntax and Processing,
 * because the decrypted XML content will share the same physical representation
 * as the original XML content that was encrypted.
 */
public class CanonicalizerPhysical extends CanonicalizerBase
{

  private final SortedSet<Attr> result = new TreeSet<Attr>(COMPARE);

  /**
   * Constructor Canonicalizer20010315
   */
  public
  CanonicalizerPhysical()
  {
    super(true);
  }

  /**
   * Always throws a CanonicalizationException.
   *
   * @param xpathNodeSet
   * @param inclusiveNamespaces
   * @return none it always fails
   * @throws CanonicalizationException always
   */
  public byte[]
  engineCanonicalizeXPathNodeSet(Set<Node> xpathNodeSet, String inclusiveNamespaces, CanonicalFilter filter)
  throws CanonicalizationException
  {

    /** $todo$ well, should we throw UnsupportedOperationException ? */
    throw new CanonicalizationException("c14n.Canonicalizer.UnsupportedOperation");
  }

  /**
   * Always throws a CanonicalizationException.
   *
   * @param rootNode
   * @param inclusiveNamespaces
   * @return none it always fails
   * @throws CanonicalizationException
   */
  @Override
  public byte[]
  engineCanonicalizeSubTree(Node rootNode, String inclusiveNamespaces, CanonicalFilter filter)
  throws CanonicalizationException
  {

    /** $todo$ well, should we throw UnsupportedOperationException ? */
    throw new CanonicalizationException("c14n.Canonicalizer.UnsupportedOperation");
  }

  /**
   * Returns the Attr[]s to be output for the given element.
   * <br>
   * The code of this method is a copy of {@link #handleAttributes(Element,
   * NameSpaceSymbTable)},
   * whereas it takes into account that subtree-c14n is -- well -- subtree-based.
   * So if the element in question isRoot of c14n, it's parent is not in the
   * node set, as well as all other ancestors.
   *
   * @param element
   * @param ns
   * @return the Attr[]s to be output
   * @throws CanonicalizationException
   */
  @Override
  protected Iterator<Attr>
  handleAttributesSubtree(Element element, NameSpaceSymbTable ns)
  throws CanonicalizationException
  {
    if (!element.hasAttributes()) {
      return null;
    }

    // result will contain all the attrs declared directly on that element
    final SortedSet<Attr> result = this.result;
    result.clear();

    if (element.hasAttributes()) {
      NamedNodeMap attrs = element.getAttributes();
      int attrsLength = attrs.getLength();

      for (int i = 0; i < attrsLength; i++) {
        Attr attribute = (Attr) attrs.item(i);
        result.add(attribute);
      }
    }

    return result.iterator();
  }

  /**
   * Returns the Attr[]s to be output for the given element.
   *
   * @param element
   * @param ns
   * @return the Attr[]s to be output
   * @throws CanonicalizationException
   */
  @Override
  protected Iterator<Attr>
  handleAttributes(Element element, NameSpaceSymbTable ns)
  throws CanonicalizationException
  {

    /** $todo$ well, should we throw UnsupportedOperationException ? */
    throw new CanonicalizationException("c14n.Canonicalizer.UnsupportedOperation");
  }

  @Override
  protected void
  handleParent(Element e, NameSpaceSymbTable ns)
  {
    // nothing to do
  }

  /** @inheritDoc */
  @Override
  public final String
  engineGetURI()
  {
    return Canonicalizer.ALGO_ID_C14N_PHYSICAL;
  }

  /** @inheritDoc */
  @Override
  public final boolean
  engineGetIncludeComments()
  {
    return true;
  }

  @Override
  protected void
  outputPItoWriter(ProcessingInstruction currentPI,
                   OutputStream writer, int position) throws IOException
  {
    // Processing Instructions before or after the document element are not treated specially
    super.outputPItoWriter(currentPI, writer, NODE_NOT_BEFORE_OR_AFTER_DOCUMENT_ELEMENT);
  }

  @Override
  protected void
  outputCommentToWriter(Comment currentComment,
                        OutputStream writer, int position) throws IOException
  {
    // Comments before or after the document element are not treated specially
    super.outputCommentToWriter(currentComment, writer, NODE_NOT_BEFORE_OR_AFTER_DOCUMENT_ELEMENT);
  }

}
