/*
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 */

package net.wotonomy.foundation.internal;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

/**
 * This implementation of URL Resource Reader assumes 2 types of base urls. A
 * base url that ends with / is considered a resource folder, whereas a resource
 * that does not end with / is considered a zip/jar resource folder.
 *
 * If the resource folder happens is a zip/jar archive, the entries are always
 * cached. For non-zip base urls, one could specify whether or not it should be
 * cached.
 *
 * @author Harish Prabandham
 */
public class URLResourceReader {
	private Hashtable<String, Object> resourceCache = new Hashtable<>();
	private boolean iszip = true;
	private URL url = null;
	private boolean cache = true;

	/**
	 * Creates a new URLResourceReader object. You can either give the URL of the
	 * zip/jar file or a base url where to look for additional resources. If the url
	 * ends with "/" then it is assumed to be a Base URL.
	 * 
	 * @param The base url to look for the resources.
	 * @param If  the base url is not a zip/jar, then true indicates that entries
	 *            should be cached, false otherwise.
	 */
	public URLResourceReader(URL baseurl, boolean cache) throws IOException {
		this.url = baseurl;
		this.cache = cache;
		this.iszip = !url.getFile().endsWith("/");
		if (this.iszip)
			this.cache = true;
		initialize();
	}

	/**
	 * equivalent to URLResourceReader(baseurl, false)
	 */
	public URLResourceReader(URL baseurl) throws IOException {
		this(baseurl, false);
	}

	/**
	 * Creates a new URLResourceReader object with the given input stream. The
	 * stream is assumed to be a zip/jar stream.
	 */
	public URLResourceReader(InputStream is) throws IOException {
		init(is);
	}

	private void initialize() throws IOException {
		if (iszip) {
			InputStream is = url.openStream();
			init(is);
			is.close();
		}
	}

	private byte[] readFully(InputStream is) throws IOException {
		byte[] buf = new byte[1024];
		int num = 0;
		ByteArrayOutputStream bout = new ByteArrayOutputStream();

		while ((num = is.read(buf)) != -1) {
			bout.write(buf, 0, num);
		}

		return bout.toByteArray();
	}

	private void init(InputStream is) throws IOException {
		ZipInputStream zstream = new ZipInputStream(is);
		ZipEntry entry;

		while ((entry = zstream.getNextEntry()) != null) {
			byte[] entryData = readFully(zstream);
			if (cache)
				resourceCache.put(entry.getName(), entryData);
			zstream.closeEntry();
		}

		zstream.close();
	}

	/**
	 * Returns an Enumeration of all "known" resource names.
	 */
	public Enumeration<String> getResourceNames() {
		return resourceCache.keys();
	}

	/**
	 * Returns an array of bytes read for this resource if the resource exists. This
	 * method blocks until the resource has been fully read. If the resource does
	 * not exist, this method returns null.
	 */
	public byte[] getResource(String resource) {
		// lookup the data in the cache...
		byte[] data = (byte[]) resourceCache.get(resource);
		if (data != null) {
			return data;
		}

		// if the data was to come from a zip file that we
		// already read fully & cached , then it is probably
		// not there.
		if (iszip) {
			return null;
		}

		// Now the only choice left is to make a url connection.
		try {
			URL realURL = new URL(url.getProtocol(), url.getHost(), url.getFile() + resource);
			data = readFully(realURL.openStream());
			// add it to cache if needed...
			if (cache)
				resourceCache.put(resource, data);
			return data;
		} catch (Exception e) {
			return null;
		}
	}

	public void close() {
		resourceCache.clear();
		resourceCache = null;
	}

	@Override
	public String toString() {
		return url.toString();
	}
}