import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.math.BigInteger;

import java.net.MalformedURLException;

import java.net.URL;

import java.security.InvalidKeyException;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import javax.crypto.Mac;

import javax.crypto.spec.SecretKeySpec;

import org.mortbay.log.Log;

import com.google.appengine.api.urlfetch.HTTPHeader;

import com.google.appengine.api.urlfetch.HTTPMethod;

import com.google.appengine.api.urlfetch.HTTPRequest;

import com.google.appengine.api.urlfetch.HTTPResponse;

import com.google.appengine.api.urlfetch.URLFetchService;

import com.google.appengine.api.urlfetch.URLFetchServiceFactory;

/**

* Static class to send messages to Pusher's REST API.

*

* Please set pusherApplicationId, pusherApplicationKey, pusherApplicationSecret accordingly

* before sending any request.

*

* @author Stephan Scheuermann

* Copyright 2010. Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php

*/

public class Pusher {

/**

* Pusher Host name

*/

private final static String pusherHost = "api.pusherapp.com";

/**

* Pusher Application Identifier

*/

private final static String pusherApplicationId = "";

/**

* Pusher Application Key

*/

private final static String pusherApplicationKey = "";

/**

* Pusher Secret

*/

private final static String pusherApplicationSecret = "";

/**

* Converts a byte array to a string representation

* @param data

* @return

*/

private static String byteArrayToString(byte[] data){

BigInteger bigInteger = new BigInteger(1,data);

String hash = bigInteger.toString(16);

// Zero pad it

while(hash.length() < 32 ){

hash = "0" + hash;

}

return hash;

}

/**

* Returns a md5 representation of the given string

* @param data

* @return

*/

private static String md5Representation(String data) {

try {

//Get MD5 MessageDigest

MessageDigest messageDigest = MessageDigest.getInstance("MD5");

byte[] digest = messageDigest.digest(data.getBytes("US-ASCII"));

return byteArrayToString(digest);

} catch (NoSuchAlgorithmException nsae) {

//We should never come here, because GAE has a MD5 algorithm

throw new RuntimeException("No MD5 algorithm");

} catch (UnsupportedEncodingException e) {

//We should never come here, because UTF-8 should be available

throw new RuntimeException("No UTF-8");

}

}

/**

* Returns a HMAC/SHA256 representation of the given string

* @param data

* @return

*/

private static String hmacsha256Representation(String data) {

try {

// Create the HMAC/SHA256 key from application secret

final SecretKeySpec signingKey = new SecretKeySpec( pusherApplicationSecret.getBytes(), "HmacSHA256");

// Create the message authentication code (MAC)

final Mac mac = Mac.getInstance("HmacSHA256");

mac.init(signingKey);

//Process and return data

byte[] digest = mac.doFinal(data.getBytes("UTF-8"));

digest = mac.doFinal(data.getBytes());

//Convert to string

BigInteger bigInteger = new BigInteger(1,digest);

return String.format("%0" + (digest.length << 1) + "x", bigInteger);

} catch (NoSuchAlgorithmException nsae) {

//We should never come here, because GAE has HMac SHA256

throw new RuntimeException("No HMac SHA256 algorithm");

} catch (UnsupportedEncodingException e) {

//We should never come here, because UTF-8 should be available

throw new RuntimeException("No UTF-8");

} catch (InvalidKeyException e) {

throw new RuntimeException("Invalid key exception while converting to HMac SHA256");

}

}

/**

* Build query string that will be appended to the URI and HMAC/SHA256 encoded

* @param eventName

* @param jsonData

* @return

*/

private static String buildQuery(String eventName, String jsonData, String socketID){

StringBuffer buffer = new StringBuffer();

//Auth_Key

buffer.append("auth_key=");

buffer.append(pusherApplicationKey);

//Timestamp

buffer.append("&auth_timestamp=");

buffer.append(System.currentTimeMillis() / 1000);

//Auth_version

buffer.append("&auth_version=1.0");

//MD5 body

buffer.append("&body_md5=");

buffer.append(md5Representation(jsonData));

//Event Name

buffer.append("&name=");

buffer.append(eventName);

//Append socket id if set

if (!socketID.isEmpty()) {

buffer.append("&socket_id=");

buffer.append(socketID);

}

//Return content of buffer

return buffer.toString();

}

/**

* Build path of the URI that is also required for Authentication

* @return

*/

private static String buildURIPath(String channelName){

StringBuffer buffer = new StringBuffer();

//Application ID

buffer.append("/apps/");

buffer.append(pusherApplicationId);

//Channel name

buffer.append("/channels/");

buffer.append(channelName);

//Event

buffer.append("/events");

//Return content of buffer

return buffer.toString();

}

/**

* Build authentication signature to assure that our event is recognized by Pusher

* @param uriPath

* @param query

* @return

*/

private static String buildAuthenticationSignature(String uriPath, String query){

StringBuffer buffer = new StringBuffer();

//request method

buffer.append("POST\n");

//URI Path

buffer.append(uriPath);

buffer.append("\n");

//Query string

buffer.append(query);

//Encode data

String h = buffer.toString();

return hmacsha256Representation(h);

}

/**

* Build URI where request is send to

* @param uriPath

* @param query

* @param signature

* @return

*/

private static URL buildURI(String uriPath, String query, String signature){

StringBuffer buffer = new StringBuffer();

//Protocol

buffer.append("http://");

//Host

buffer.append(pusherHost);

//URI Path

buffer.append(uriPath);

//Query string

buffer.append("?");

buffer.append(query);

//Authentication signature

buffer.append("&auth_signature=");

buffer.append(signature);

//Build URI

try {

return new url(/sitelet?url=https%3A%2F%2Fgithub.com%2Fmarcbaechinger%2Fgae-java-libpusher%2Fblob%2Fmaster%2Fbuffer.toString%28));

} catch (MalformedURLException e) {

throw new RuntimeException("Malformed URI");

}

}

/**

* Delivers a message to the Pusher API without providing a socket_id

* @param channel

* @param event

* @param jsonData

* @return

*/

public static HTTPResponse triggerPush(String channel, String event, String jsonData){

return triggerPush(channel, event, jsonData, "");

}

/**

* Delivers a message to the Pusher API

* @param channel

* @param event

* @param jsonData

* @param socketId

* @return

*/

public static HTTPResponse triggerPush(String channel, String event, String jsonData, String socketId){

//Build URI path

String uriPath = buildURIPath(channel);

//Build query

String query = buildQuery(event, jsonData, socketId);

//Generate signature

String signature = buildAuthenticationSignature(uriPath, query);

//Build URI

URL url = buildURI(uriPath, query, signature);

//Create Google APP Engine Fetch URL service and request

URLFetchService urlFetchService = URLFetchServiceFactory.getURLFetchService();

HTTPRequest request = new HTTPRequest(url, HTTPMethod.POST);

request.addHeader(new HTTPHeader("Content-Type", "application/json"));

request.setPayload(jsonData.getBytes());

//Start request

try {

return urlFetchService.fetch(request);

} catch (IOException e) {

//Log warning

Log.warn("Pusher request could not be send to the following URI " + url.toString());

return null;

}

}

}