/* You may not modify, use, reproduce, or distribute this software except in compliance with the terms of the License at:
 http://developer.sun.com/berkeley_license.html
 $Id: GenericService.java,v 1.5 2007/06/04 18:29:15 gmurray71 Exp $ */

package jmaki.service;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

// for MD5
import java.security.MessageDigest;

/**
 * @author Greg Murray
 */
public class GenericService extends HttpServlet {

    private MessageDigest md;
    // Server Side Token to Append to client provide tokens and host name
    private static String SERVER_TOKEN = "JMAKI_SERVICE";

    public GenericService() {
    }

    private String callback = "callback";

    public void init(ServletConfig config) throws ServletException {
        super.init(config);
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (java.security.NoSuchAlgorithmException nsa) {
            throw new ServletException(nsa);
        }
    }

    public void doGet(HttpServletRequest req, HttpServletResponse response)
        throws ServletException, IOException {

        PrintWriter writer = response.getWriter();
        String action = req.getParameter("action");

        if (action != null) {
            // generate an api key
            if ("genkey".equals(action)) {
            	// build up the host name
                String host = req.getScheme() + "://" +  req.getServerName();
                int port = req.getServerPort();
                if (port != 80) host += ":" + port;
                host += req.getContextPath();
                host += req.getServletPath();
                     	
                String url = req.getParameter("url");
                if (!url.endsWith("/")) url += "/";
                if (url != null) {
                	writer.print("{ 'service' : '" + host + "'," +
                                  " 'key' : '" + generateHash(url + SERVER_TOKEN) + "'}");
                }
                else writer.println("url required to generate an api key");
                return;
            }
        } else {
            if (req.getParameter("apikey") != null) {
                boolean valid = testAPIKey(req, req.getParameter("apikey"));
                String lc = req.getParameter("callback");
                String format = req.getParameter("format");
                if (valid) {
                    if ("jsonp".equals(format)) {
                      response.setContentType("text/javascript");
                      if (lc == null) lc = callback;
                      writer.write(lc +
                                    "(" + jsonContent + ");");
                       return;
                    } else if ("json".equals(format)) {
                       response.setContentType("text/json");
                       writer.write(jsonContent);
                       return;
                    } else {
                        response.setContentType("text/xml");
                        writer.write(xmlContent);
                    }
                } else {
                    String referer = req.getHeader("Referer");
                    // check if it's a relative URL and make sure we end with a slash
                    if (!referer.startsWith("http") &&
                       !referer.endsWith("/") ) referer = referer + "/";                	
                    writer.println("alert('Invalid apikey for " + referer + "');");
                    return;
                }
            } else {
                writer.println("Please provide an apikey.");
                return;
            }
        }
    }
    /**
     * Check the Referer against the API key provided
     * 
     * http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
     */
    private boolean testAPIKey(HttpServletRequest req, String apiKey) {
        String referer = req.getHeader("Referer");
        // check if it's a relative URL and make sure we end with a slash
        if (!referer.startsWith("http") &&
            !referer.endsWith("/") ) referer = referer + "/";
        // get the key for the host used by the request
        String refererKey = generateHash(referer + SERVER_TOKEN);
        if (apiKey != null) return refererKey.equals(apiKey);
        else return false;
    }

    private String generateHash(String key) {
    	key += SERVER_TOKEN;
        // start fresh
        md.reset();
        md.update(key.getBytes());
        byte[] bytes = md.digest();
        // buffer to write the md5 hash to
        StringBuffer buff = new StringBuffer();
        for (int l=0;l< bytes.length;l++) {
            String hx = Integer.toHexString(0xFF & bytes[l]);
            // make sure the hex string is correct if 1 character
            if(hx.length() == 1) buff.append("0");
            buff.append(hx);
        }
        return buff.toString().trim();
    }

    private String jsonContent =
        "{\n" +
        " 'columns' :[\n" +
        "  {'title' : 'Company'},\n" +
        "  {'title' : 'Price'},\n" +
        "  {'title' : 'Change'},\n" +
        "  {'title' : '% Change'},\n" +
        "  {'title' : 'Last Updated'}\n" +
        " ],\n" +
        " 'rows' :\n" +
        "  [\n" +
        "    ['A Co',71.72,0.02,0.03,'9/1 12:00am'],\n" +
        "    ['B Inc',29.01,0.42,1.47,'9/1 12:00am'],\n" +
        "    ['C Group Inc',83.81,0.28,0.34,'9/1 12:00am'],\n" +
        "   ['D Company',52.55,0.01,0.02,'9/1 12:00am']\n" +
        "  ]\n" +
        "}\n";

    private String xmlContent =
        "<table>\n" +
        " <columns>\n" +
        "  <column><title>Company</title></column>\n" +
        "  <column><title>Price</title></column>\n" +
        "  <column><title>Company</title></column>\n" +
        "  <column><title>Change</title></column>\n" +
        "  <column><title>% Change</title></column>\n" +
        "  <column><title>Last Updated</title></column>\n" +
        " </columns>\n" +
        " <rows>\n" +
        "  <row>\n" +
        "   <item>A Co</item>\n" +
        "   <item>71.72</item>\n" +
        "   <item>0.02</item>\n" +
        "   <item>0.03</item>\n" +
        "   <item>9/1 12:00am</item>\n" +
        "  </row>\n" +
        "  <row>\n" +
        "   <item>B Inc</item>\n" +
        "   <item>29.01</item>\n" +
        "   <item>0.42</item>\n" +
        "   <item>1.47</item>\n" +
        "   <item>9/1 12:00am</item>\n" +
        "  </row>\n" +
        "  <row>\n" +
        "   <item>B Inc</item>\n" +
        "   <item>29.01</item>\n" +
        "   <item>0.42</item>\n" +
        "   <item>1.47</item>\n" +
        "   <item>9/1 12:00am</item>\n" +
        "  </row>\n" +
        "  <row>\n" +
        "   <item>C Group Inc</item>\n" +
        "   <item>83.81</item>\n" +
        "   <item>0.28</item>\n" +
        "   <item>0.34</item>\n" +
        "   <item>9/1 12:00am</item>\n" +
        "  </row>\n" +
        "  <row>\n" +
        "   <item>D Company</item>\n" +
        "   <item>52.55</item>\n" +
        "   <item>0.01</item>\n" +
        "   <item>0.02</item>\n" +
        "   <item>9/1 12:00am</item>\n" +
        "  </row>\n" +
        " </rows>\n" +
        "</table>";
}