/*
 * 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.signature;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.xml.security.algorithms.SignatureAlgorithm;
import org.apache.xml.security.c14n.CanonicalizationException;
import org.apache.xml.security.c14n.Canonicalizer;
import org.apache.xml.security.c14n.InvalidCanonicalizerException;
import org.apache.xml.security.exceptions.XMLSecurityException;
import org.apache.xml.security.utils.Constants;
import org.apache.xml.security.utils.XMLUtils;
import org.apache.xml.security.transforms.params.InclusiveNamespaces;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

/**
 * Handles <code>&lt;ds:SignedInfo&gt;</code> elements
 * This <code>SignedInfo<code> element includes the canonicalization algorithm,
 * a signature algorithm, and one or more references.
 *
 * @author Christian Geuer-Pollmann
 */
public class SignedInfo extends Manifest {

    /** Field _signatureAlgorithm */
    private SignatureAlgorithm _signatureAlgorithm = null;

    /** Field _c14nizedBytes           */
    private byte[] _c14nizedBytes = null;

    private Element c14nMethod;
    private Element signatureMethod;

    /**
     * Overwrites {@link Manifest#addDocument} because it creates another 
     * Element.
     *
     * @param doc the {@link Document} in which <code>XMLsignature</code> will 
     *    be placed
     * @throws XMLSecurityException
     */
    public SignedInfo(Document doc) throws XMLSecurityException {
        this(doc, XMLSignature.ALGO_ID_SIGNATURE_DSA, 
	     Canonicalizer.ALGO_ID_C14N_OMIT_COMMENTS);
    }

    /**
     * Constructs {@link SignedInfo} using given Canonicalization algorithm and 
     * Signature algorithm.
     *
     * @param doc <code>SignedInfo</code> is placed in this document
     * @param signatureMethodURI URI representation of the Digest and 
     *    Signature algorithm
     * @param canonicalizationMethodURI URI representation of the 
     *    Canonicalization method
     * @throws XMLSecurityException
     */
    public SignedInfo(Document doc, String signatureMethodURI, 
	String canonicalizationMethodURI) throws XMLSecurityException {
        this(doc, signatureMethodURI, 0, canonicalizationMethodURI);
    }

    /**
     * Constructor SignedInfo
     *
     * @param doc <code>SignedInfo</code> is placed in this document
     * @param signatureMethodURI URI representation of the Digest and 
     *    Signature algorithm
     * @param hMACOutputLength
     * @param canonicalizationMethodURI URI representation of the 
     *    Canonicalization method
     * @throws XMLSecurityException
     */
    public SignedInfo(Document doc, String signatureMethodURI, 
	int hMACOutputLength, String canonicalizationMethodURI)
              throws XMLSecurityException {

        super(doc);

        c14nMethod = XMLUtils.createElementInSignatureSpace(this._doc,
                                Constants._TAG_CANONICALIZATIONMETHOD);

        c14nMethod.setAttributeNS(null, Constants._ATT_ALGORITHM,
                                  canonicalizationMethodURI);
        this._constructionElement.appendChild(c14nMethod);
        XMLUtils.addReturnToElement(this._constructionElement);

        if (hMACOutputLength > 0) {
            this._signatureAlgorithm = new SignatureAlgorithm(this._doc,
                    signatureMethodURI, hMACOutputLength);
        } else {
            this._signatureAlgorithm = new SignatureAlgorithm(this._doc,
                    signatureMethodURI);
        }

        signatureMethod = this._signatureAlgorithm.getElement();
        this._constructionElement.appendChild(signatureMethod);
        XMLUtils.addReturnToElement(this._constructionElement);
    }
   
    /**
     * @param doc
     * @param signatureMethodElem
     * @param canonicalizationMethodElem
     * @throws XMLSecurityException
     */
    public SignedInfo(Document doc, Element signatureMethodElem, 
	Element canonicalizationMethodElem) throws XMLSecurityException {

        super(doc);
        // Check this?
        this.c14nMethod = canonicalizationMethodElem;
        this._constructionElement.appendChild(c14nMethod);
        XMLUtils.addReturnToElement(this._constructionElement);
   
        this._signatureAlgorithm = 
	    new SignatureAlgorithm(signatureMethodElem, null);

        signatureMethod = this._signatureAlgorithm.getElement();
        this._constructionElement.appendChild(signatureMethod);
      
        XMLUtils.addReturnToElement(this._constructionElement);
    }

    /**
     * Build a {@link SignedInfo} from an {@link Element}
     *
     * @param element <code>SignedInfo</code>
     * @param baseURI the URI of the resource where the XML instance was stored
     * @throws XMLSecurityException
     * @see <A HREF="http://lists.w3.org/Archives/Public/w3c-ietf-xmldsig/2001OctDec/0033.html">Question</A>
     * @see <A HREF="http://lists.w3.org/Archives/Public/w3c-ietf-xmldsig/2001OctDec/0054.html">Answer</A>
     */
    public SignedInfo(Element element, String baseURI)
           throws XMLSecurityException {

        // Parse the Reference children and Id attribute in the Manifest
        super(reparseSignedInfoElem(element), baseURI);

        c14nMethod = XMLUtils.getNextElement(element.getFirstChild());
        signatureMethod = XMLUtils.getNextElement(c14nMethod.getNextSibling());
        this._signatureAlgorithm =
            new SignatureAlgorithm(signatureMethod, this.getBaseURI());
    }

    private static Element reparseSignedInfoElem(Element element)
        throws XMLSecurityException {

        /* 
         * If a custom canonicalizationMethod is used, canonicalize 
         * ds:SignedInfo, reparse it into a new document
         * and replace the original not-canonicalized ds:SignedInfo by
         * the re-parsed canonicalized one.
         */
        Element c14nMethod = XMLUtils.getNextElement(element.getFirstChild());
        String c14nMethodURI = 
            c14nMethod.getAttributeNS(null, Constants._ATT_ALGORITHM);    
        if (!(c14nMethodURI.equals(Canonicalizer.ALGO_ID_C14N_OMIT_COMMENTS) ||
            c14nMethodURI.equals(Canonicalizer.ALGO_ID_C14N_WITH_COMMENTS) ||
	    c14nMethodURI.equals(Canonicalizer.ALGO_ID_C14N_EXCL_OMIT_COMMENTS) ||
	    c14nMethodURI.equals(Canonicalizer.ALGO_ID_C14N_EXCL_WITH_COMMENTS) ||
	    c14nMethodURI.equals(Canonicalizer.ALGO_ID_C14N11_OMIT_COMMENTS) ||
	    c14nMethodURI.equals(Canonicalizer.ALGO_ID_C14N11_WITH_COMMENTS))) {
      	    // the c14n is not a secure one and can rewrite the URIs or like 
	    // so reparse the SignedInfo to be sure    
            try {
                Canonicalizer c14nizer =
                    Canonicalizer.getInstance(c14nMethodURI);

                byte[] c14nizedBytes = c14nizer.canonicalizeSubtree(element);
                javax.xml.parsers.DocumentBuilderFactory dbf =
                    javax.xml.parsers.DocumentBuilderFactory.newInstance();
                dbf.setNamespaceAware(true);
                javax.xml.parsers.DocumentBuilder db = dbf.newDocumentBuilder();        
                Document newdoc =
                    db.parse(new ByteArrayInputStream(c14nizedBytes));
                Node imported = element.getOwnerDocument().importNode
                    (newdoc.getDocumentElement(), true);

                element.getParentNode().replaceChild(imported, element);

                return (Element) imported;
            } catch (ParserConfigurationException ex) {
                throw new XMLSecurityException("empty", ex);
            } catch (IOException ex) {
                throw new XMLSecurityException("empty", ex);
            } catch (SAXException ex) {
                throw new XMLSecurityException("empty", ex);
            }
        }
	return element;
    }

    /**
     * Tests core validation process
     *
     * @return true if verification was successful
     * @throws MissingResourceFailureException
     * @throws XMLSecurityException
     */
    public boolean verify()
           throws MissingResourceFailureException, XMLSecurityException {
        return super.verifyReferences(false);
    }

    /**
     * Tests core validation process
     *
     * @param followManifests defines whether the verification process has to verify referenced <CODE>ds:Manifest</CODE>s, too
     * @return true if verification was successful
     * @throws MissingResourceFailureException
     * @throws XMLSecurityException
     */
    public boolean verify(boolean followManifests)
           throws MissingResourceFailureException, XMLSecurityException {
        return super.verifyReferences(followManifests);
    }

    /**
     * Returns getCanonicalizedOctetStream
     *
     * @return the canonicalization result octet stream of <code>SignedInfo</code> element
     * @throws CanonicalizationException
     * @throws InvalidCanonicalizerException
     * @throws XMLSecurityException
     */
    public byte[] getCanonicalizedOctetStream()
           throws CanonicalizationException, InvalidCanonicalizerException,
                 XMLSecurityException {

        if (this._c14nizedBytes == null) {
            Canonicalizer c14nizer =
                Canonicalizer.getInstance(this.getCanonicalizationMethodURI());

            this._c14nizedBytes =
                c14nizer.canonicalizeSubtree(this._constructionElement);
        }

        // make defensive copy
        return (byte[]) this._c14nizedBytes.clone();
    }
   
    /**
     * Output the C14n stream to the given OutputStream.
     * @param os
     * @throws CanonicalizationException
     * @throws InvalidCanonicalizerException
     * @throws XMLSecurityException
     */
    public void signInOctectStream(OutputStream os)            
        throws CanonicalizationException, InvalidCanonicalizerException,
            XMLSecurityException {

   	if (this._c14nizedBytes == null) {
            Canonicalizer c14nizer =
                Canonicalizer.getInstance(this.getCanonicalizationMethodURI());
            c14nizer.setWriter(os);
            String inclusiveNamespaces = this.getInclusiveNamespaces();

            if (inclusiveNamespaces == null) {
                c14nizer.canonicalizeSubtree(this._constructionElement);
            } else {
                c14nizer.canonicalizeSubtree
                    (this._constructionElement, inclusiveNamespaces);
            }
        } else {
            try {
		os.write(this._c14nizedBytes);
	    } catch (IOException e) {
		throw new RuntimeException(e);
	    }  
        }    
    }

    /**
     * Returns the Canonicalization method URI
     *
     * @return the Canonicalization method URI
     */
    public String getCanonicalizationMethodURI() {
       return c14nMethod.getAttributeNS(null, Constants._ATT_ALGORITHM);    
    }

    /**
     * Returns the Signature method URI
     *
     * @return the Signature method URI
     */
    public String getSignatureMethodURI() {

        Element signatureElement = this.getSignatureMethodElement();

        if (signatureElement != null) {
            return signatureElement.getAttributeNS(null, Constants._ATT_ALGORITHM);
        }

        return null;
    }

    /**
     * Method getSignatureMethodElement
     * @return returns the SignatureMethod Element   
     *
     */
    public Element getSignatureMethodElement() {
        return signatureMethod;
    }

    /**
     * Creates a SecretKey for the appropriate Mac algorithm based on a
     * byte[] array password.
     *
     * @param secretKeyBytes
     * @return the secret key for the SignedInfo element.
     */
    public SecretKey createSecretKey(byte[] secretKeyBytes) {

        return new SecretKeySpec(secretKeyBytes,
                                 this._signatureAlgorithm
                                  .getJCEAlgorithmString());
    }

    protected SignatureAlgorithm getSignatureAlgorithm() {
        return _signatureAlgorithm;
    }

    /**
     * Method getBaseLocalName
     * @inheritDoc
     *
     */
    public String getBaseLocalName() {
        return Constants._TAG_SIGNEDINFO;
    }

    public String getInclusiveNamespaces() {

        String c14nMethodURI = c14nMethod.getAttributeNS(null, Constants._ATT_ALGORITHM);
        if (!(c14nMethodURI.equals("http://www.w3.org/2001/10/xml-exc-c14n#") ||
	    c14nMethodURI.equals("http://www.w3.org/2001/10/xml-exc-c14n#WithComments"))) {
            return null;
        }

        Element inclusiveElement = XMLUtils.getNextElement(
            c14nMethod.getFirstChild());

        if (inclusiveElement != null) {
            try {
                String inclusiveNamespaces = new InclusiveNamespaces
                    (inclusiveElement,
                     InclusiveNamespaces.ExclusiveCanonicalizationNamespace).getInclusiveNamespaces();
                return inclusiveNamespaces;
            } catch (XMLSecurityException e) {
                return null;
            }
        }
        return null;
    }
}