/**
 * $Id: HttpServer.java,v 1.1 2005/10/20 06:07:00 johnr Exp $
 * 
 * (c) John Reekie 2004
 * (c) The University of Technology, Sydney, 2004
 *
 * This software is written for teaching purposes. As such, you can do
 * anything you want with it, as long as you don't remove this
 * copyright notice, or blame us if it doesn't do what you think
 * it should do.
 */

import java.net.*;
import java.io.*;
import java.util.Map;
import java.util.HashMap;

/** An extremely simple HTTP Server. The goal of this class is to provide
 * the simplest possible implementation of a functioning web server.
 * It gets upset with the slightest provocation, but serves to illustrate
 * how basic HTTP works. It creates a thread for each request, in the
 * same manner as ThreadedServer.
 */
public class HttpServer {

    /** Run the server.
     */
    public void run (int p)
	throws IOException {
	ServerSocket serversocket = new ServerSocket(p);
	System.out.println("Listening on port " + p);

	// Block waiting for input, handle connection, repeat forever
	while (true) {
	    Socket clientsocket = serversocket.accept();
	    ConnectionHandler h = new ConnectionHandler(clientsocket);
	    h.start(); // start a new thread for this connection
	}
    }

    /** The ConnectionHandler class is a subclass of Thread, so that
     * we can run many of them at the same time.
     */
    public class ConnectionHandler extends Thread {

	private Socket _socket;

	/** Construct the ConnectionHandler object with the given
	 * client socket.
	 */
	public ConnectionHandler (Socket s) {
	    _socket = s;
	}
	
	/** Run this thread to handle a connection from a client.
	 */
	public void run () {
	    try {
		InputStream in = _socket.getInputStream();
		OutputStream out = _socket.getOutputStream();
		handleConnection(in, out);
		_socket.close();
	    }
	    catch (Exception e) {
		e.printStackTrace();
	    }
	}
	
	/** Handle the connection. Get the HTTP headers and figure
	 * out what to do.
	 */
	public void handleConnection (InputStream in, OutputStream out)
	    throws IOException {

	    // Read the HTTP request header
	    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
	    String line = reader.readLine();
	    // System.out.println(line); // display received request

	    String[] elements = line.split(" ");
	    String resource = elements[1];

	    // Read the rest of the headers, print, and discard them
	    HashMap headers = new HashMap();
	    while (true) {
		line = reader.readLine();
		if (line.length() == 0) {
		    break; // Blank line, so all headers are read
		}
		if (line == null) {
		    return; // whoops...
		}
		// System.out.println(line); // display received header
	    }
	    // System.out.println("");

	    // Try and find the file... what about directory redirects?
	    String filename = resource.substring(1); // Strip initial '/'
	    if (filename.equals("")) {
		filename = ".";
	    }
	    File file = new File(filename);

	    if (!file.exists()) {
		out.write("HTTP/1.0 404\r\n\r\n".getBytes());
		out.write(("You requested a file that I don't know about: "
			   + resource + "\r\n").getBytes());

	    } else if (file.isDirectory()) {
		if (resource.charAt(resource.length()-1) != '/') {
		    // Redirect with trailing slash
		    out.write("HTTP/1.0 302\r\n".getBytes());
		    out.write(("Location: " + resource + "/\r\n\r\n").getBytes());
		} else {
		    // Generate directory listing
		    out.write("HTTP/1.0 200\r\n\r\n".getBytes());

		    StringBuffer listing = new StringBuffer();
		    listing.append("<a href=\"../\">(Parent directory)</a><br>");
		    String[] files = file.list();
		    for (int j = 0; j < files.length; j++) {
			listing.append("<a href=\"" + files[j] + "\">" + files[j] + "</a><br>");
		    }
		    out.write(listing.toString().getBytes());
		}
	    } else if (false) {
		// Here is where you could check to see if the URL
		// represents something that you would want to do in
		// custom code.
	    } else {
		// Serve a file
		out.write("HTTP/1.0 200\r\n\r\n".getBytes());

		FileInputStream fis = new FileInputStream(file);
		byte[] buffer = new byte[1024];
		while (true) {
		    int readcount = fis.read(buffer);
		    out.write(buffer, 0, readcount);
		    if (readcount < 1024) {
			break;
		    }
		}
	    }
	}
    }

    /** This is the main function to start the server running
     */
    public static void main (String[] argv) {
	if (argv.length != 1) {
	    throw new IllegalArgumentException("Expecting one argument");
	}
	int portnr = Integer.parseInt(argv[0]);

	HttpServer server = new HttpServer();
	try {
	    server.run(portnr);
	}
	catch (Exception e) {
	    System.out.println(e.getStackTrace());
	}
    }
}