import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.Iterator;
import java.net.*;

public class asyncHTTPServer {

    private ByteBuffer contentBuffer;
    private int port = 80;

    
    public asyncHTTPServer(
					   ByteBuffer data, String encoding, String MIMEType, int port) 
	throws UnsupportedEncodingException {
    
	this.port = port;

	// create header
	String header = "HTTP/1.0 200 OK\r\n"
	    + "Server: OneFile 2.0\r\n"
	    + "Content-length: " + data.limit() + "\r\n"
	    + "Content-type: " + MIMEType + "\r\n\r\n";
	// encode the header using ASCII
	byte[] headerData = header.getBytes("ASCII");
	
	ByteBuffer buffer = ByteBuffer.allocate(data.limit() + headerData.length);

	// add content to buffer
	buffer.put(headerData);
	buffer.put(data);

	// reset buffer to the begining
	buffer.flip();
	this.contentBuffer = buffer;
	
    } // end of asyncHTTPServer

    // The main loop
    public void process_requests() throws IOException {

	// create selector to monitor events
	Selector selector = Selector.open();
  
	// create server channel
	ServerSocketChannel serverChannel = ServerSocketChannel.open();

	// bind the port number of the server socket
	ServerSocket  serverSocket = serverChannel.socket();
	InetSocketAddress localPort = new InetSocketAddress(port);
	serverSocket.bind(localPort);
	serverChannel.configureBlocking(false); // set non-blocking i/o

	// register the accept event of the server channel to monitor
	serverChannel.register(selector, SelectionKey.OP_ACCEPT);
	
	while (true) {
    
	    selector.select(); // check for available events

	    Iterator keys = selector.selectedKeys().iterator();

	    while (keys.hasNext()) {

		SelectionKey key = (SelectionKey) keys.next();
		keys.remove(); // remove first event

		try {
		    if (key.isAcceptable()) {
			// a new connection is ready to be accepted
			ServerSocketChannel server = (ServerSocketChannel) key.channel();

			// create a new socket channel from the accepted connection
			SocketChannel channel = server.accept();

			// make the new connection nonblocking
			channel.configureBlocking(false);

			// register the new connection with READ event
			SelectionKey newKey = channel.register(selector, SelectionKey.OP_READ);
		    } 
		    else if (key.isReadable()) {
			// Don't bother trying to parse the HTTP header since we process just one file
			// Just read something.
			SocketChannel channel = (SocketChannel) key.channel();
			ByteBuffer buffer = ByteBuffer.allocate(4096); 
			channel.read(buffer);

			// switch channel to write-only mode
			key.interestOps(SelectionKey.OP_WRITE);

			// attach the buffer storing the file to be returned
			key.attach(contentBuffer.duplicate());

		    } // end of if (key.isReadable()) {
		    else if (key.isWritable()) {
			SocketChannel channel = (SocketChannel) key.channel();
			ByteBuffer buffer = (ByteBuffer) key.attachment(); 
			if (buffer.hasRemaining()) {
			    channel.write(buffer);   
			}
			else {  // we're done
			    channel.close();   
			}
		    } // end of else if (key.isWritable()) {
		} // end of try
		catch (IOException ex) {
		    key.cancel();
		    try {
			key.channel().close();
		    }
		    catch (IOException cex) {}
		} //end of catch
	    } // end of while (keys.hasNext()) {
	} // end of while (true)
    } // end of run()
  
    // main function
    public static void main(String[] args) {

	if (args.length == 0) {
	    System.out.println(
			       "Usage: java asyncHTTPServer file port encoding"); 
	    return;
	}
      
	try {
	    String contentType = "text/plain";
	    if (args[0].endsWith(".html") || args[0].endsWith(".htm")) {
		contentType = "text/html";
	    }
      
	    // map the file to a byte buffer
	    FileInputStream fin = new FileInputStream(args[0]);
	    FileChannel in = fin.getChannel();
	    ByteBuffer input = in.map(FileChannel.MapMode.READ_ONLY, 0, in.size());
	    
	    // set the port to listen on
	    int port;
	    try {
		port = Integer.parseInt(args[1]);
		if (port < 1 || port > 65535) port = 80;
	    }  
	    catch (Exception ex) {
		port = 80;
	    }  
      
	    String encoding = "ASCII";
	    if (args.length > 2) encoding = args[2]; 
       
	    asyncHTTPServer server
		= new asyncHTTPServer(
						      input, encoding, contentType, port);
	    server.process_requests();         
	    
	} // end of try
	catch (Exception ex) {
	    ex.printStackTrace();
	    System.err.println(ex);
	} // end of catch
  
    } // end of main()

} // end of class