Node.js implementation of Tokbox's OpenTokSDK

Node.js OpenTokSDK

/**
 * Node.js implementation of Tokbox's OpenTokSDK 
 *
 * by Brian Stoner
 *
 * var tokbox = require('./tokbox')
 * 
 * var t = new tokbox.OpenTokSDK(API_KEY,API_SECRET)
 * 
 * t.createSession('127.0.0.1', {}, function(session){
 *   var token = t.generateToken(session.sessionId)
 * })
 *
 */


// OpenTok Constants:
var TOKEN_SENTINEL = "T1==",
    SDK_VERSION = "tbpy-0.90.0",
    TOKBOX_HOST = "staging.tokbox.com",
    SESSION_API_ENDPOINT = "/hl/session/create";

var http = require('http'),
    querystring = require('querystring'),
    crypto = require('crypto'),
    httpClient = http.createClient(443, TOKBOX_HOST, true);
    
    
// Session Properties definition:
var SessionProperties = exports.SessionProperties = function(){
    return {
        'echoSuppression.enabled' : null,
        'multiplexer.numOutputStreams' : null,
        'multiplexer.switchType' : null,
        'multiplexer.switchTimeout' : null
    }
}

// Just the session
var OpenTokSession = function(sessionId){
    this.sessionId = sessionId
}

// The SDK
var OpenTokSDK = exports.OpenTokSDK = function(partnerId, partnerSecret){
    this.partnerId = partnerId
    this.partnerSecret = partnerSecret
}

OpenTokSDK.prototype.generateToken = function(sessionId, permissions, expireTime){
    this.sessionId = sessionId || ''
    
    var createTime = OpenTokSDK.prototype._getUTCDate(),
        sig, 
        tokenString,
        tokenParams,
        tokenBuffer,
        dataString, 
        dataParams = {
            session_id:this.sessionId,
            create_time: createTime,
            nonce: Math.floor(Math.random()*999999)
        };

    if(permissions){
        dataParams['permissions'] = permissions
    }

    if(expireTime){
        dataParams['expire_time'] = expireTime
    }
    
    dataString = querystring.stringify(dataParams)
    sig = this._signString(dataString, this.partnerSecret)
    tokenParams = ["partner_id=",this.partnerId,"&sdk_version=",SDK_VERSION,"&sig=",sig,":",dataString].join("")
    tokenBuffer = new Buffer(tokenParams,"utf8");
    return TOKEN_SENTINEL + tokenBuffer.toString('base64');

}

OpenTokSDK.prototype.createSession = function(ipPassthru, properties, callback){
    var sessionId,
        params = {
            partner_id: this.partnerId,
            location_hint: ipPassthru
        }
    
    for(var p in properties){
        params[p] = properties[p]
    }
    
    sessionId = this._doRequest(SESSION_API_ENDPOINT,params, function(sessionId){
        callback(new OpenTokSession(sessionId))
    })

}

OpenTokSDK.prototype._signString = function(string, secret){
    var hmac = crypto.createHmac('sha1',secret)
    hmac.update(string)
    return hmac.digest(encoding='hex')
}

OpenTokSDK.prototype._doRequest = function(url, params, callback){
    var dataString = querystring.stringify(params),
    headers = {
        'host':TOKBOX_HOST,
        'Content-Type': 'application-xml',
        'Content-Length': dataString.length,
        'X-TB-PARTNER-AUTH': this.partnerId + ":" + this.partnerSecret
    }

    req = httpClient.request("POST",url,headers)
    req.write(dataString)
    req.end()
    
    req.on('response', function(res){
        var chunks = ''
        
        res.setEncoding('utf8')
        
        res.on('data', function(chunk){
            chunks += chunk
        })
        
        res.on('end', function(){
            var start = chunks.match('<session_id>'),
                end = chunks.match('</session_id>')
            
            if(start && end){
                var session = chunks.substr(start.index + 12, (end.index - start.index - 12))
                callback(session)
            } else {
                callback('')
            }
        })
    })
}

OpenTokSDK.prototype._getUTCDate = function(){
    var D= new Date();
    return Date.UTC(D.getUTCFullYear(), D.getUTCMonth(), D.getUTCDate(), D.getUTCHours(),
    D.getUTCMinutes(), D.getUTCSeconds()).toString().substr(0,10)
}