/**
 * 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.
 */
/*
 * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
 */
package org.apache.jcp.xml.dsig.internal.dom;

import java.security.InvalidAlgorithmParameterException;
import java.security.spec.AlgorithmParameterSpec;
import java.util.ArrayList;
import java.util.List;

import javax.xml.crypto.Data;
import javax.xml.crypto.MarshalException;
import javax.xml.crypto.XMLCryptoContext;
import javax.xml.crypto.XMLStructure;
import javax.xml.crypto.dsig.CanonicalizationMethod;
import javax.xml.crypto.dsig.TransformException;
import javax.xml.crypto.dsig.spec.C14NMethodParameterSpec;
import javax.xml.crypto.dsig.spec.ExcC14NParameterSpec;
import javax.xml.crypto.dsig.spec.TransformParameterSpec;

import org.apache.xml.security.c14n.Canonicalizer;
import org.apache.xml.security.c14n.InvalidCanonicalizerException;
import org.w3c.dom.Element;

/**
 * DOM-based implementation of CanonicalizationMethod for Exclusive
 * Canonical XML algorithm (with or without comments).
 * Uses Apache XML-Sec Canonicalizer.
 *
 */
public final class DOMExcC14NMethod extends ApacheCanonicalizer {

    @Override
    public void init(TransformParameterSpec params)
        throws InvalidAlgorithmParameterException
    {
        if (params != null) {
            if (!(params instanceof ExcC14NParameterSpec)) {
                throw new InvalidAlgorithmParameterException
                    ("params must be of type ExcC14NParameterSpec");
            }
            this.params = (C14NMethodParameterSpec)params;
        }
    }

    @Override
    public void init(XMLStructure parent, XMLCryptoContext context)
        throws InvalidAlgorithmParameterException
    {
        super.init(parent, context);
        Element paramsElem = DOMUtils.getFirstChildElement(transformElem);
        if (paramsElem == null) {
            this.params = null;
            this.inclusiveNamespaces = null;
            return;
        }
        unmarshalParams(paramsElem);
    }

    private void unmarshalParams(Element paramsElem) {
        String prefixListAttr = paramsElem.getAttributeNS(null, "PrefixList");
        this.inclusiveNamespaces = prefixListAttr;
        int begin = 0;
        int end = prefixListAttr.indexOf(' ');
        List<String> prefixList = new ArrayList<>();
        while (end != -1) {
            prefixList.add(prefixListAttr.substring(begin, end));
            begin = end + 1;
            end = prefixListAttr.indexOf(' ', begin);
        }
        if (begin <= prefixListAttr.length()) {
            prefixList.add(prefixListAttr.substring(begin));
        }
        this.params = new ExcC14NParameterSpec(prefixList);
    }

    @SuppressWarnings("unchecked")
    public List<String> getParameterSpecPrefixList(ExcC14NParameterSpec paramSpec) {
        return paramSpec.getPrefixList();
    }

    @Override
    public void marshalParams(XMLStructure parent, XMLCryptoContext context)
        throws MarshalException
    {
        super.marshalParams(parent, context);
        AlgorithmParameterSpec spec = getParameterSpec();
        if (spec == null) {
            return;
        }

        String prefix = DOMUtils.getNSPrefix(context,
                                             CanonicalizationMethod.EXCLUSIVE);
        Element eElem = DOMUtils.createElement(ownerDoc,
                                               "InclusiveNamespaces",
                                               CanonicalizationMethod.EXCLUSIVE,
                                               prefix);
        if (prefix == null || prefix.length() == 0) {
            eElem.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns",
                                 CanonicalizationMethod.EXCLUSIVE);
        } else {
            eElem.setAttributeNS("http://www.w3.org/2000/xmlns/",
                                   "xmlns:" + prefix,
                                   CanonicalizationMethod.EXCLUSIVE);
        }

        ExcC14NParameterSpec params = (ExcC14NParameterSpec)spec;
        StringBuilder prefixListAttr = new StringBuilder("");
        List<String> prefixList = getParameterSpecPrefixList(params);
        for (int i = 0, size = prefixList.size(); i < size; i++) {
            prefixListAttr.append(prefixList.get(i));
            if (i < size - 1) {
                prefixListAttr.append(' ');
            }
        }
        DOMUtils.setAttribute(eElem, "PrefixList", prefixListAttr.toString());
        this.inclusiveNamespaces = prefixListAttr.toString();
        transformElem.appendChild(eElem);
    }

    public String getParamsNSURI() {
        return CanonicalizationMethod.EXCLUSIVE;
    }

    @Override
    public Data transform(Data data, XMLCryptoContext xc)
        throws TransformException
    {
        // ignore comments if dereferencing same-document URI that require
        // you to omit comments, even if the Transform says otherwise -
        // this is to be compliant with section 4.3.3.3 of W3C Rec.
        if (data instanceof DOMSubTreeData) {
            DOMSubTreeData subTree = (DOMSubTreeData)data;
            if (subTree.excludeComments()) {
                try {
                    canonicalizer = Canonicalizer.getInstance
                        (CanonicalizationMethod.EXCLUSIVE);
                } catch (InvalidCanonicalizerException ice) {
                    throw new TransformException
                        ("Couldn't find Canonicalizer for: " +
                         CanonicalizationMethod.EXCLUSIVE + ": " +
                         ice.getMessage(), ice);
                }
            }
        }

        return canonicalize(data, xc);
    }
}
