/*
 * @(#)ClassServer.java	1.4 01/05/22
 *
 * Copyright 1994-2004 Sun Microsystems, Inc. All Rights Reserved. 
 *
 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following 
 * conditions are met: 
 * 
 * -Redistribution of source code must retain the above copyright 
 * notice, this list of conditions and the following disclaimer.
 * 
 * Redistribution 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. 
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of 
 * contributors may be used to endorse or promote products derived 
 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any 
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND 
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY 
 * EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL 
 * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT 
 * OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS 
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR 
 * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, 
 * SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER 
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF 
 * THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS 
 * BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 
 * 
 * You acknowledge that this software is not designed, licensed or 
 * intended for use in the design, construction, operation or 
 * maintenance of any nuclear facility. 
 */

import java.io.*;
import java.net.*;
import javax.net.*;

/*
 * ClassServer.java -- a simple file server that can serve
 * Http get request in both clear and secure channel
 */

/**
 * Based on ClassServer.java in tutorial/rmi
 */
public abstract class ClassServer implements Runnable {

    private ServerSocket server = null;
    /**
     * Constructs a ClassServer based on <b>ss</b> and
     * obtains a file's bytecodes using the method <b>getBytes</b>.
     *
     */
    protected ClassServer(ServerSocket ss)
    {
	server = ss;
	newListener();
    }

    /**
     * Returns an array of bytes containing the bytes for
     * the file represented by the argument <b>path</b>.
     *
     * @return the bytes for the file
     * @exception FileNotFoundException if the file corresponding
     * to <b>path</b> could not be loaded.
     * @exception IOException if error occurs reading the class
     */
    public abstract byte[] getBytes(String path)
	throws IOException, FileNotFoundException;

    /**
     * The "listen" thread that accepts a connection to the
     * server, parses the header to obtain the file name
     * and sends back the bytes for the file (or error
     * if the file is not found or the response was malformed).
     */
    public void run()
    {
	Socket socket;

	// accept a connection
	try {
	    socket = server.accept();
	} catch (IOException e) {
	    System.out.println("Class Server died: " + e.getMessage());
	    e.printStackTrace();
	    return;
	}

	// create a new thread to accept the next connection
	newListener();

	try {
	    OutputStream rawOut = socket.getOutputStream();

	    PrintWriter out = new PrintWriter(
				new BufferedWriter(
				new OutputStreamWriter(
				rawOut)));
	    try {
		// get path to class file from header
		BufferedReader in =
		    new BufferedReader(
			new InputStreamReader(socket.getInputStream()));
		String path = getPath(in);
		// retrieve bytecodes
		byte[] bytecodes = getBytes(path);
		// send bytecodes in response (assumes HTTP/1.0 or later)
		try {
		    out.print("HTTP/1.0 200 OK\r\n");
		    out.print("Content-Length: " + bytecodes.length +
				   "\r\n");
		    out.print("Content-Type: text/html\r\n\r\n");
		    out.flush();
		    rawOut.write(bytecodes);
		    rawOut.flush();
		} catch (IOException ie) {
		    ie.printStackTrace();
		    return;
		}

	    } catch (Exception e) {
		e.printStackTrace();
		// write out error response
		out.println("HTTP/1.0 400 " + e.getMessage() + "\r\n");
		out.println("Content-Type: text/html\r\n\r\n");
		out.flush();
	    }

	} catch (IOException ex) {
	    // eat exception (could log error to log file, but
	    // write out to stdout for now).
	    System.out.println("error writing response: " + ex.getMessage());
	    ex.printStackTrace();

	} finally {
	    try {
		socket.close();
	    } catch (IOException e) {
	    }
	}
    }

    /**
     * Create a new thread to listen.
     */
    private void newListener()
    {
	(new Thread(this)).start();
    }

    /**
     * Returns the path to the file obtained from
     * parsing the HTML header.
     */
    private static String getPath(BufferedReader in)
	throws IOException
    {
	String line = in.readLine();
	String path = "";
	// extract class from GET line
	if (line.startsWith("GET /")) {
	    line = line.substring(5, line.length()-1).trim();
	    int index = line.indexOf(' ');
	    if (index != -1) {
		path = line.substring(0, index);
	    }
	}

	// eat the rest of header
	do {
	    line = in.readLine();
	} while ((line.length() != 0) &&
		 (line.charAt(0) != '\r') && (line.charAt(0) != '\n'));

	if (path.length() != 0) {
	    return path;
	} else {
	    throw new IOException("Malformed Header");
	}
    }
}