public class WebServer {

    public static String version = "Java Web Server 0.0";

    public static void main(String[] args) {
        try {
            ServerSocket ss = new ServerSocket(8080);
            System.out.println(version);
            while (ss.isBound()) new Thread(new Client(ss.accept())).start();
        } 
        catch (IOException e) { e.printStackTrace(); }
    }

}


class Client implements Runnable {

    private static final String userdir = System.getProperty("user.dir");
    static final byte[] EOL = {(byte) '\r', (byte) '\n'};
    private Socket accept;
    private InputStream is;
    private PrintStream os;

    private enum Method {

        GET,
        HEAD,
        UNSUPPORTED;
    }

    public Client(Socket accept) {
        this.accept = accept;
    }

    public void run() {
        try {

            // variables
            is = new BufferedInputStream(accept.getInputStream());
            os = new PrintStream(accept.getOutputStream());
            int character;
            String req = "";
            String[] request;
            Method method;
            File file;

            // store first line of request header
            character = is.read();
            while (character != '\n' && character != '\r') {
                req += (char) character;
                character = is.read();
            }
            System.out.println(req);
            request = req.split(" ");

            // store method
            if (request[0].matches("GET")) {
                method = Method.GET;
            } else if (request[0].matches("HEAD")) {
                method = Method.HEAD;
            } else {
                method = Method.UNSUPPORTED;
            }

            // logic!
            request[1] = request[1].replace("/", File.separator);
            file = new File(userdir + File.separator + request[1]);
            if (file.exists() && !file.isHidden()) {
                if (method == Method.GET || method == Method.HEAD) {
                    writeHeader(file, 200);
                    if (method == Method.GET) {
                        if (file.isFile()) {
                            sendFile(file);
                        } else if (file.isDirectory()) {
                            listDir(request[1], file);
                        }
                    }
                } else {
                    writeHeader(file, 501);
                }
            } else {
                writeHeader(file, 404);
            }

        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            try {
                accept.close();
            } catch (IOException ex) {
                System.exit(1);
            }
        }
    }

    private void sendFile(File file) throws FileNotFoundException, IOException {
        int bufferlen = (int) file.length();
        byte buffer[];
        buffer = new byte[bufferlen];
        InputStream fs = new FileInputStream(file);
        int len = fs.read(buffer);
        while (len < bufferlen) {
            len += fs.read(buffer, len, bufferlen - len);
        }
        os.write(buffer);
        os.flush();
    }

    private void listDir(String currentDir, File dir) {
        currentDir = currentDir.replace(File.separator, "/");
        String listing[] = dir.list();
        if (!currentDir.endsWith("/")) {
            currentDir += "/";
        }
        os.println(WebServer.version + "<br>");
        for (String item : listing) {
            os.println("<a href=\"" + currentDir + item + "\">" + item + "</a><br>");
        }
        os.flush();
    }

    private void writeHeader(File f, int code) throws IOException {
        String fname = f.getName();
        os.print("HTTP/1.0 ");

        switch (code) {
            case 200:
                os.print("200 OK");
                break;
            case 400:
                os.print("400 Bad Request");
                break;
            case 404:
                os.print("404 Not Found");
                break;
            case 501:
                os.print("501 Not Implemented");
                break;
        }
        os.write(EOL);

        if (code == 200) {
            os.print("Content-Type: ");
            if (fname.endsWith("html") || fname.endsWith("htm")) {
                os.print("text/html");
            } else if (fname.endsWith("java")) {
                os.print("text/plain");
            } else if (fname.endsWith("jpeg") || fname.endsWith("jpg")) {
                os.print("image/gif");
            } else {
                os.print("text/html");
            }
            os.write(EOL);
        }

        os.write(EOL);
        os.flush();
    }
}