// Exam 4 Question 1 for CMSC 838P
// Charles B. Cranston xxx-yy-zzz <zben@ni.umd.edu>
// April 28, 1997

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

public class hserve extends Thread {
	public static final int DEFAULT_PORT = 1069;
	public static final int BUFF_SIZE = 4096;

	Socket sock;

// New instantiation of hserve object on every client connect attempt

	public hserve(Socket s) {
		sock = s;		// Save client socket
		this.start();		// Start up our thread
	}

// This thread runs on every client connection attempt

	public void run() {
		try {
			StreamTokenizer st = new StreamTokenizer(
				new InputStreamReader(sock.getInputStream()));
			st.resetSyntax();
			st.whitespaceChars(0,32);
			st.wordChars(33,255);
			if ( (StreamTokenizer.TT_WORD!=st.nextToken()) ||
			     !("GET".equals(st.sval)) )
				throw new IllegalArgumentException("Expected GET");
			if ( (StreamTokenizer.TT_WORD!=st.nextToken()) ||
			     !st.sval.startsWith("/") )
				throw new IllegalArgumentException("Expected /filename");
			String filename = st.sval.substring(1);

			FileInputStream fis = new FileInputStream(filename);
			System.err.println("Delivering " + filename);
			OutputStream os = sock.getOutputStream();

//  Note: we do our own buffering here.

			byte buffer[] = new byte[BUFF_SIZE];
			int num;
			while ( -1 != (num=fis.read(buffer)) )
				os.write(buffer,0,num);
			fis.close();
			sock.close();
			System.err.println("Exit");
		} catch (Exception e) {
			die("Exception in server execution:",e);
		}
	}

// Utility

	public static void die(String why, Exception e) {
		System.err.println(why);
		System.err.println(e);
		System.exit(1);
	}

// Main routine.  Note this is static and creates a new instantiation
//  of the hserve object EACH time a client makes a connection.

	public static void main(String[] args) {
		try {
			int port;
			if ( 0 < args.length )
				port = Integer.parseInt(args[0]);
			else
				port = DEFAULT_PORT;
			ServerSocket ss = new ServerSocket(port);
			System.err.println("Listening on port " + port + "...");
			while (true)
				new hserve( ss.accept() );	// Make thread
		} catch (Exception e) {
			die("Exception in server setup:",e);
		}
	}
}