/*
 * Copyright 2003 Federal Chancellery Austria
 * MOA-SPSS has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */


package at.gv.egovernment.moa.spss.api.xmlbind;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;

import org.w3c.dom.Element;
import org.w3c.dom.traversal.NodeIterator;

import at.gv.egovernment.moa.spss.MOAApplicationException;
import at.gv.egovernment.moa.spss.api.SPSSFactory;
import at.gv.egovernment.moa.spss.api.common.Base64Transform;
import at.gv.egovernment.moa.spss.api.common.CanonicalizationTransform;
import at.gv.egovernment.moa.spss.api.common.EnvelopedSignatureTransform;
import at.gv.egovernment.moa.spss.api.common.ExclusiveCanonicalizationTransform;
import at.gv.egovernment.moa.spss.api.common.Transform;
import at.gv.egovernment.moa.spss.api.common.XPathFilter;
import at.gv.egovernment.moa.spss.api.common.XPathFilter2Transform;
import at.gv.egovernment.moa.spss.api.common.XPathTransform;
import at.gv.egovernment.moa.spss.api.common.XSLTTransform;
import at.gv.egovernment.moaspss.util.Constants;
import at.gv.egovernment.moaspss.util.DOMUtils;
import at.gv.egovernment.moaspss.util.XPathUtils;

/**
 * A parser to parse XMLDsig <code>Transform</code> DOM elements into their
 * MOA SPSS API representation.
 * 
 * @author Patrick Peck
 * @version $Id$
 */
public class TransformParser {
  //
  // XPath expressions for selecting information from the DOM tree
  //
  private static final String DSIG = Constants.DSIG_PREFIX + ":";
  private static final String DSIG_FILTER2 =
    Constants.DSIG_FILTER2_PREFIX + ":";
  private static final String XSLT = Constants.XSLT_PREFIX + ":";
  private static final String EC = Constants.DSIG_EC_PREFIX + ":";
  private static final String TRANSFORM_XPATH = DSIG + "Transform";
  private static final String XPATH_XPATH = DSIG + "XPath";
  private static final String XSLT_ELEMENT_XPATH = XSLT + "stylesheet";
  private static final String XPATH2_XPATH =
    (DSIG_FILTER2 + "XPath[@Filter=\"intersect\"] | ")
      + (DSIG_FILTER2 + "XPath[@Filter=\"subtract\"] | ")
      + (DSIG_FILTER2 + "XPath[@Filter=\"union\"]");
  private static final String INCLUSIVE_NAMESPACES_XPATH =
    EC + "InclusiveNamespaces";

  /**
   * The <code>SPSSFactory</code> to use for creating new API objects.
   */
  private SPSSFactory factory = SPSSFactory.getInstance();

  /**
   * Parse an XMLDsig <code>Transforms</code> DOM element.
   * 
   * @param transformsElem The <code>Transforms</code> DOM element to parse.
   * @return A <code>List</code> of <code>Transform</code> API objects 
   * containing the data from the individual <code>Transform</code> DOM
   * elements.
   * @throws MOAApplicationException An error occurred parsing the  
   * <code>Transforms</code> DOM element.
   */
  public List parseTransforms(Element transformsElem)
    throws MOAApplicationException {
    List transforms = new ArrayList();
    NodeIterator transformElems =
      XPathUtils.selectNodeIterator(transformsElem, TRANSFORM_XPATH);
    Element transformElem;
    Transform transform;

    while ((transformElem = (Element) transformElems.nextNode()) != null) {
      transform = parseTransform(transformElem);
      transforms.add(transform);
    }

    return transforms;
  }

  /**
   * Parse an XMLDsig <code>Transform</code> DOM element.
   * 
   * @param transformElem <code>Transform</code> DOM element to parse.
   * @return The <code>Transform</code> API object containing the data
   * from the <code>Transform</code> DOM element.
   * @throws MOAApplicationException An error occurred parsing the 
   * <code>Transform</code> DOM element.
   */
  public Transform parseTransform(Element transformElem)
    throws MOAApplicationException {

    String algorithmUri = transformElem.getAttribute("Algorithm");

    if (CanonicalizationTransform.CANONICAL_XML.equals(algorithmUri)
      || CanonicalizationTransform.CANONICAL_XML_WITH_COMMENTS.equals(
        algorithmUri)) {
      return factory.createCanonicalizationTransform(algorithmUri);
    } else if (
      ExclusiveCanonicalizationTransform.EXCLUSIVE_CANONICAL_XML.equals(
        algorithmUri)
        || ExclusiveCanonicalizationTransform
          .EXCLUSIVE_CANONICAL_XML_WITH_COMMENTS
          .equals(
          algorithmUri)) {
      return parseExclusiveC14nTransform(algorithmUri, transformElem);
    } else if (Base64Transform.BASE64_DECODING.equals(algorithmUri)) {
      return factory.createBase64Transform();
    } else if (
      EnvelopedSignatureTransform.ENVELOPED_SIGNATURE.equals(algorithmUri)) {
      return factory.createEnvelopedSignatureTransform();
    } else if (XPathTransform.XPATH.equals(algorithmUri)) {
      return parseXPathTransform(transformElem);
    } else if (XPathFilter2Transform.XPATH_FILTER2.equals(algorithmUri)) {
      return parseXPathFilter2Transform(transformElem);
    } else if (XSLTTransform.XSLT.equals(algorithmUri)) {
      return parseXSLTTransform(transformElem);
    } else {
      throw new MOAApplicationException("1108", new Object[] { algorithmUri });
    }
  }

  /**
   * Parse an exclusive canonicalization type of transform.
   * 
   * @param algorithmUri The algorithm URI of the canonicalization algorithm.
   * @param transformElem The <code>Transform</code> DOM element to parse.
   * @return An <code>ExclusiveCanonicalizationTransform</code> API object
   * containing the data from the <code>transformElem</code>.
   */
  private Transform parseExclusiveC14nTransform(
    String algorithmUri,
    Element transformElem)
    {

    Element inclusiveNamespacesElem =
      (Element) XPathUtils.selectSingleNode(
        transformElem,
        INCLUSIVE_NAMESPACES_XPATH);

    List inclusiveNamespaces = new ArrayList();
    if (inclusiveNamespacesElem != null)
    {
      StringTokenizer tokenizer = new StringTokenizer(inclusiveNamespacesElem.getAttribute("PrefixList"));
      while (tokenizer.hasMoreTokens()) 
      {
        inclusiveNamespaces.add(tokenizer.nextToken());
      }
    }
    return factory.createExclusiveCanonicalizationTransform(
      algorithmUri,
      inclusiveNamespaces);
  }

  /**
   * Parse an <code>XPath</code> type of <code>Transform</code>.
   * 
   * @param transformElem The <code>Transform</code> DOM element to parse.
   * @return The <code>Transform</code> API object representation of the
   * <code>Transform</code> DOM element.
   * @throws MOAApplicationException An error occurred parsing the 
   * <code>Transform</code> DOM element.
   */
  private Transform parseXPathTransform(Element transformElem)
    throws MOAApplicationException {
    Element xPathElem =
      (Element) XPathUtils.selectSingleNode(transformElem, XPATH_XPATH);
    Map nsDecls;

    if (xPathElem == null) {
      throw new MOAApplicationException("2202", null);
    }

    nsDecls = DOMUtils.getNamespaceDeclarations(xPathElem);
    nsDecls.remove("");

    return factory.createXPathTransform(DOMUtils.getText(xPathElem), nsDecls);
  }

  /**
   * Parse an <code>XPathFilter2</code> type of <code>Transform</code>.
   * 
   * @param transformElem The <code>Transform</code> DOM element to parse.
   * @return The <code>Transform</code> API object representation of the
   * <code>Transform</code> DOM element.
   * @throws MOAApplicationException An error occurred parsing the 
   * <code>Transform</code> DOM element.
   */
  private Transform parseXPathFilter2Transform(Element transformElem)
    throws MOAApplicationException {
    List filters = new ArrayList();
    NodeIterator iter =
      XPathUtils.selectNodeIterator(transformElem, XPATH2_XPATH);
    Element filterElem;

    while ((filterElem = (Element) iter.nextNode()) != null) {
      String filterAttr = filterElem.getAttribute("Filter");
      String filterType;
      String expression;
      Map nsDecls;

      if (filterAttr.equals("intersect")) {
        filterType = XPathFilter.INTERSECT_TYPE;
      } else if (filterAttr.equals("subtract")) {
        filterType = XPathFilter.SUBTRACT_TYPE;
      } else {
        filterType = XPathFilter.UNION_TYPE;
      }

      expression = DOMUtils.getText(filterElem);
      nsDecls = DOMUtils.getNamespaceDeclarations(filterElem);
      nsDecls.remove("");
      filters.add(factory.createXPathFilter(filterType, expression, nsDecls));
    }
    if (filters.size() == 0) {
      throw new MOAApplicationException("2216", null);
    }

    return factory.createXPathFilter2Transform(filters);
  }

  /**
   * Parse an <code>XSLT</code> type of <code>Transform</code>.
   * 
   * @param transformElem The <code>Transform</code> DOM element to parse.
   * @return The <code>Transform</code> API object representation of the
   * <code>Transform</code> DOM element.
   * @throws MOAApplicationException An error occurred parsing the 
   * <code>Transform</code> DOM element.
   */
  private Transform parseXSLTTransform(Element transformElem)
    throws MOAApplicationException {
    Element xsltElem =
      (Element) XPathUtils.selectSingleNode(transformElem, XSLT_ELEMENT_XPATH);

    if (xsltElem == null) {
      throw new MOAApplicationException("2215", null);
    }

    return factory.createXSLTTransform(xsltElem);
  }

}