/*******************************************************************************
 * Copyright (c) 2003, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 * IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.wst.common.componentcore.internal.impl;

import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;

// TODO: We need to port the strings used in the exceptions.
/**
 * <p>
 * The following class is experimental until fully documented.
 * </p>
 */
public class WTPEntityResolver implements EntityResolver {

	/**
	 * All the dtds that this resolver knows about; import strategies register these at startup
	 */
	protected static Map supportedDtDs;
	
	// static {
	// registerDtD("http://www.w3.org/2001/xml.xsd", "xml.xsd"); //$NON-NLS-1$ //$NON-NLS-2$
	// registerDtD("XMLSchema.dtd", "XMLSchema.dtd"); //$NON-NLS-1$ //$NON-NLS-2$
	// registerDtD("datatypes.dtd", "datatypes.dtd"); //$NON-NLS-1$ //$NON-NLS-2$
	// }
	
	public static WTPEntityResolver INSTANCE = new WTPEntityResolver();

	/**
	 * EjbXmlEntityResolver constructor comment.
	 */
	public WTPEntityResolver() {
		super();
	}

	public static Map getSupportedDtDs() {
		if (supportedDtDs == null)
			supportedDtDs = new HashMap();
		return supportedDtDs;
	}

	/**
	 * Maps the system id for the dtd to a local id to be retrieved loaded from the class path
	 */
	public static void registerDtD(String systemID, String localID) {
		// TODO Removing Registration mechanism until final location is found
		/*
		 * getSupportedDtDs().put(systemID, localID); getSupportedDtDs().put(getShortName(systemID),
		 * localID);
		 */
	}

	/**
	 * for a system id with a URL that begins with "http://java.sun.com/", check to see if that is a
	 * recognized dtd; if so, load the dtd from the class path using the value of the registered
	 * dtd.
	 * 
	 * @return an Input source on a locally resolved dtd, or null of the systemid does not start
	 *         with "http://java.sun.com/"
	 * 
	 * @throws SAXException
	 *             with a nested NotSupportedException if the dtd is not recognized
	 * @throws FileNotFoundException
	 *             if the resolved dtd cannot be loaded from the classpath
	 */
	public org.xml.sax.InputSource resolveEntity(String publicId, String systemId) throws java.io.IOException, org.xml.sax.SAXException {
		String localResourceName = null;
		boolean isJavaSytemId = false;
		if (shouldBeRegistered(systemId)) {
			localResourceName = (String) getSupportedDtDs().get(systemId);
			isJavaSytemId = true;
		} else {
			String shortName = getShortName(systemId);
			localResourceName = (String) getSupportedDtDs().get(shortName);
			if (localResourceName != null)
				systemId = localResourceName;
		}

		if (localResourceName == null) {
			if (isJavaSytemId) {
				String message = "Type is unrecognized or not yet supported: PUBLIC_ID= {0};SYSTEM_ID={1}";
				throw new org.xml.sax.SAXException(message);
			}
			return null;
		}
		ClassLoader loader = getClass().getClassLoader();
		URL url = null;
		if (loader == null) {
			url = ClassLoader.getSystemResource(localResourceName);
		} else {
			url = loader.getResource(localResourceName);
		}


		if (url == null) {
			String message = "Could not parse xml because the resolved resource \"{0}\" could not be found in classpath";
			throw new java.io.FileNotFoundException(message);
		}

		InputSource result = new InputSource(url.toString());
		result.setPublicId(publicId);
		// force the encoding to be UTF8
		result.setEncoding("UTF-8"); //$NON-NLS-1$

		return result;
	}

	protected boolean shouldBeRegistered(String systemId) {
		// TODO Removed Resolver function until file location is known...
		return false;
		/*
		 * return systemId.startsWith(J2EEConstants.JAVA_SUN_COM_URL) ||
		 * systemId.startsWith(J2EEConstants.WWW_W3_ORG_URL) ||
		 * systemId.startsWith(J2EEConstants.WWW_IBM_COM_URL);
		 */
	}

	/**
	 * Returns the filename from the uri, or the segment after the last occurrence of a separator
	 */
	private static String getShortName(String uri) {
		String tempURI = uri.replace('\\', '/');
		while (tempURI.endsWith("/")) //$NON-NLS-1$
			tempURI = tempURI.substring(0, tempURI.length() - 1);
		int lastIndex = tempURI.lastIndexOf('/');
		if (lastIndex == -1)
			return uri;
		return uri.substring(lastIndex + 1, tempURI.length());
	}
}