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/*
 * Milyn - Copyright (C) 2006 - 2011
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License (version 2.1) as published by the Free Software
 * Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * See the GNU Lesser General Public License for more details:
 * http://www.gnu.org/licenses/lgpl.txt
 */
package org.milyn.edi.utils;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.xerces.impl.XMLEntityManager;
import org.apache.xerces.xni.XMLResourceIdentifier;
import org.apache.xerces.xni.XNIException;
import org.apache.xerces.xni.parser.XMLEntityResolver;
import org.apache.xerces.xni.parser.XMLInputSource;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.filter.ElementFilter;
import org.jdom2.input.SAXBuilder;
import org.milyn.util.ClassUtil;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * Extension of Xerces {@link XMLEntityManager} that implements
 * {@link XMLEntityResolver} which additinally able to resolve Smooks XML
 * Schemas
 *
 * @author zubairov
 */
public class EDISchemaEntityManager extends XMLEntityManager {

    private final Map catalog;

    private static final Log log = LogFactory.getLog(EDISchemaEntityManager.class);

    /**
     * Factory method to create a new instance
     *
     * @return
     * @throws IOException
     */
    public static EDISchemaEntityManager createInstance() throws IOException {
        List urnFiles = ClassUtil.getResources("/fragment.xml",
                EDISchemaEntityManager.class);
        Map catalog = new HashMap();
        log.debug("Loading XML schemas information from " + urnFiles);
        for (URL url : urnFiles) {
            InputStream in = url.openStream();
            try {
                if (in != null) {
                    SAXBuilder builder = new SAXBuilder();
                    Document document = builder.build(in);
                    @SuppressWarnings("unchecked")
                    Iterator it = document
                            .getDescendants(new ElementFilter("uri"));
                    while (it.hasNext()) {
                        Element next = it.next();
                        String uri = next.getAttributeValue("uri");
                        String name = next.getAttributeValue("name");
                        // URI is now something like platform:/fragment/org.milyn.edi.unedifact.d99a-mapping/path/path/file.xsd
                        // we need only /path/path/file.xsd
                        // cut platform:/fragment/
                        uri = uri.substring(19);
                        // cut after first '/'
                        uri = uri.substring(uri.indexOf('/'));
                        catalog.put(name, uri);
                    }
                }
            } catch (JDOMException e) {
                e.printStackTrace();
            } finally {
                if (in != null) {
                    in.close();
                }
            }
        }
        // One resource we have to add manually
        catalog.put("urn:org.milyn.edi.unedifact.v41",
                "/META-INF/schema/v41-segments.xsd");
        log.debug("Loaded " + catalog.size() + " entries");
        return new EDISchemaEntityManager(catalog);
    }

    /**
     * Constructor called from {@link #createInstance()} with Map NamespaceURI
     * --> ResourceLocation
     *
     * @param catalog
     */
    protected EDISchemaEntityManager(Map catalog) {
        super();
        this.catalog = catalog;
    }

    @Override
    public XMLInputSource resolveEntity(XMLResourceIdentifier resourceIdentifier)
            throws IOException, XNIException {
        XMLInputSource result = super.resolveEntity(resourceIdentifier);
        if (result.getPublicId() == null && result.getSystemId() == null
                && result.getCharacterStream() == null
                && result.getByteStream() == null) {
            String ns = resourceIdentifier.getNamespace();
            if (ns != null) {
                log.debug("Resolving schema to namespace: " + ns);
                if (catalog.containsKey(ns)) {
                    result = new XMLInputSource(resourceIdentifier);
                    String location = catalog.get(ns);
                    InputStream stream = EDISchemaEntityManager.class
                            .getResourceAsStream(location);
                    if (stream == null) {
                        throw new XNIException(
                                "Smooks Entity Manager was unable to find resource "
                                        + "with location: " + location);
                    }
                    result.setByteStream(stream);
                } else {
                    throw new XNIException("Can't find schema with NS: " + ns);
                }
            }
        }
        return result;
    }

}