package com.ora.rmibook.chapter22.tunneler;


import java.io.*;
import java.net.*;
import java.util.*;
import java.rmi.registry.*;
import java.rmi.*;
import java.rmi.server.*;

import javax.servlet.http.*;
import javax.servlet.*;
import sun.rmi.server.MarshalInputStream;


public class ServletForwardCommand {
    public static void execute(HttpServletRequest request, HttpServletResponse response, String stringifiedPort)
        throws ServletClientException, ServletServerException, IOException {
        int port = convertStringToPort(stringifiedPort);
        Socket connectionToLocalServer = null;

        try {
            connectionToLocalServer = connectToLocalServer(port);
            forwardRequest(request, connectionToLocalServer);
            forwardResponse(response, connectionToLocalServer);
        } finally {
            if (null != connectionToLocalServer) {
                connectionToLocalServer.close();
            }
        }
    }

    private static int convertStringToPort(String stringfiedPort) throws ServletClientException {
        int returnValue;

        try {
            returnValue = Integer.parseInt(stringfiedPort);
        } catch (NumberFormatException e) {
            throw new ServletClientException("invalid port number: " + stringfiedPort);
        }
        if (returnValue <= 0 || returnValue > 0xFFFF) {
            throw new ServletClientException("invalid port: " + returnValue);
        }
        if (returnValue < 1024) {
            throw new ServletClientException("permission denied for port: " + returnValue);
        }
        return returnValue;
    }

    private static Socket connectToLocalServer(int port) throws ServletServerException {
        Socket returnValue;

        try {
            returnValue = new Socket(InetAddress.getLocalHost(), port);
        } catch (IOException e) {
            throw new ServletServerException("could not connect to " + "local port");
        }
        return returnValue;
    }

    private static void forwardRequest(HttpServletRequest request, Socket connectionToLocalServer)
        throws IOException, ServletClientException, ServletServerException {
        byte buffer[];
        DataInputStream clientIn = new DataInputStream(request.getInputStream());

        buffer = new byte[request.getContentLength()];
        try {
            clientIn.readFully(buffer);
        } catch (EOFException e) {
            throw new ServletClientException("unexpected EOF " + "reading request body");
        } catch (IOException e) {
            throw new ServletClientException("error reading request" + " body");
        }

        DataOutputStream socketOut = null;

        // send to local server in HTTP
        try {
            socketOut = new DataOutputStream(connectionToLocalServer.getOutputStream());
            socketOut.writeBytes("POST / HTTP/1.0\r\n");
            socketOut.writeBytes("Content-length: " + request.getContentLength() + "\r\n\r\n");
            socketOut.write(buffer);
            socketOut.flush();
        } catch (IOException e) {
            throw new ServletServerException("error writing to server");
        }
    }

    private static void forwardResponse(HttpServletResponse response, Socket connectionToLocalServer)
        throws IOException, ServletClientException, ServletServerException {
        byte[] buffer;
        DataInputStream socketIn;

        try {
            socketIn = new DataInputStream(connectionToLocalServer.getInputStream());
        } catch (IOException e) {
            throw new ServletServerException("error reading from " + "server");
        }
        String key = "Content-length:".toLowerCase();
        boolean contentLengthFound = false;
        String line;
        int responseContentLength = -1;

        do {
            try {
                line = socketIn.readLine();
            } catch (IOException e) {
                throw new ServletServerException("error reading from server");
            }
            if (line == null) {
                throw new ServletServerException("unexpected EOF reading server response");
            }
            if (line.toLowerCase().startsWith(key)) {
                responseContentLength = Integer.parseInt(line.substring(key.length()).trim());
                contentLengthFound = true;
            }
        }
        while ((line.length() != 0) &&
            (line.charAt(0) != '\r') && (line.charAt(0) != '\n'));

        if (!contentLengthFound || responseContentLength < 0)
            throw new ServletServerException("missing or invalid content length in server response");
        buffer = new byte[responseContentLength];
        try {
            socketIn.readFully(buffer);
        } catch (EOFException e) {
            throw new ServletServerException("unexpected EOF reading server response");
        } catch (IOException e) {
            throw new ServletServerException("error reading from server");
        }

        response.setStatus(HttpServletResponse.SC_OK);
        response.setContentType("application/octet-stream");
        response.setContentLength(buffer.length);

        try {
            OutputStream out = response.getOutputStream();

            out.write(buffer);
            out.flush();
        } catch (IOException e) {
            throw new ServletServerException("error writing response");
        }
    }
}