/*******************************************************************************
 * Copyright (c) 2013 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Andrew Banks - initial API and implementation and initial documentation
 *******************************************************************************/


// Only expose a single object name in the global namespace.
// Everything must go through this module. Global Messaging module
// only has a single public function, client, which returns
// a Messaging client object given connection details.

/**
 * @namespace Messaging
 * Send and receive messages using web browsers.
 * <p>
 * This programming interface lets a JavaScript client application use the MQTT V3.1 protocol to
 * connect to an MQTT-supporting messaging server.
 *
 * The function supported includes:
 * <ol>
 * <li>Connecting to and disconnecting from a server. The server is identified by its host name and port number.
 * <li>Specifying options that relate to the communications link with the server,
 * for example the frequency of keep-alive heartbeats, and whether SSL/TLS is required.
 * <li>Subscribing to and receiving messages from MQTT Topics.
 * <li>Publishing messages to MQTT Topics.
 * </ol>
 * <p>
 * <h2>The API consists of two main objects:</h2>
 * The <b>Messaging.Client</b> object. This contains methods that provide the functionality of the API,
 * including provision of callbacks that notify the application when a message arrives from or is delivered to the messaging server,
 * or when the status of its connection to the messaging server changes.
 * <p>
 * The <b>Messaging.Message</b> object. This encapsulates the payload of the message along with various attributes
 * associated with its delivery, in particular the destination to which it has been (or is about to be) sent.
 * <p>
 * The programming interface validates parameters passed to it, and will throw an Error containing an error message
 * intended for developer use, if it detects an error with any parameter.
 * <p>
 * Example:
 *
 * <code><pre>
 client = new Messaging.Client(location.hostname, Number(location.port), "clientId");
 client.onConnectionLost = onConnectionLost;
 client.onMessageArrived = onMessageArrived;
 client.connect({onSuccess:onConnect});

 function onConnect() {
  // Once a connection has been made, make a subscription and send a message.
  console.log("onConnect");
  client.subscribe("/World");
  message = new Messaging.Message("Hello");
  message.destinationName = "/World";
  client.send(message);
};
 function onConnectionLost(responseObject) {
  if (responseObject.errorCode !== 0)
    console.log("onConnectionLost:"+responseObject.errorMessage);
};
 function onMessageArrived(message) {
  console.log("onMessageArrived:"+message.payloadString);
  client.disconnect();
};
 * </pre></code>
 * <p>
 * Other programming languages,
 * <a href="/clients/java/doc/javadoc/index.html"><big>Java</big></a>,
 * <a href="/clients/c/doc/html/index.html"><big>C</big></a>.
 */
Messaging = (function (global) {

    // Private variables below, these are only visible inside the function closure
    // which is used to define the module.

    var version = "0.0.0.0";
    var buildLevel = "@BUILDLEVEL@";

    /**
     * Unique message type identifiers, with associated
     * associated integer values.
     * @private
     */
    var MESSAGE_TYPE = {
        CONNECT: 1,
        CONNACK: 2,
        PUBLISH: 3,
        PUBACK: 4,
        PUBREC: 5,
        PUBREL: 6,
        PUBCOMP: 7,
        SUBSCRIBE: 8,
        SUBACK: 9,
        UNSUBSCRIBE: 10,
        UNSUBACK: 11,
        PINGREQ: 12,
        PINGRESP: 13,
        DISCONNECT: 14
    };

    // Collection of utility methods used to simplify module code
    // and promote the DRY pattern.

    /**
     * Validate an object's parameter names to ensure they
     * match a list of expected variables name for this option
     * type. Used to ensure option object passed into the API don't
     * contain erroneous parameters.
     * @param {Object} obj User options object
     * @param {key:type, key2:type, ...} valid keys and types that may exist in obj.
     * @throws {Error} Invalid option parameter found.
     * @private
     */
    var validate = function (obj, keys) {
        for (key in obj) {
            if (obj.hasOwnProperty(key)) {
                if (keys.hasOwnProperty(key)) {
                    if (typeof obj[key] !== keys[key])
                        throw new Error(format(ERROR.INVALID_TYPE, [typeof obj[key], key]));
                } else {
                    var errorStr = "Unknown property, " + key + ". Valid properties are:";
                    for (key in keys)
                        if (keys.hasOwnProperty(key))
                            errorStr = errorStr + " " + key;
                    throw new Error(errorStr);
                }
            }
        }
    };

    /**
     * Return a new function which runs the user function bound
     * to a fixed scope.
     * @param {function} User function
     * @param {object} Function scope
     * @return {function} User function bound to another scope
     * @private
     */
    var scope = function (f, scope) {
        return function () {
            return f.apply(scope, arguments);
        };
    };

    /**
     * Unique message type identifiers, with associated
     * associated integer values.
     * @private
     */
    var ERROR = {
        OK: {code: 0, text: "AMQJSC0000I OK."},
        CONNECT_TIMEOUT: {code: 1, text: "AMQJSC0001E Connect timed out."},
        SUBSCRIBE_TIMEOUT: {code: 2, text: "AMQJS0002E Subscribe timed out."},
        UNSUBSCRIBE_TIMEOUT: {code: 3, text: "AMQJS0003E Unsubscribe timed out."},
        PING_TIMEOUT: {code: 4, text: "AMQJS0004E Ping timed out."},
        INTERNAL_ERROR: {code: 5, text: "AMQJS0005E Internal error."},
        CONNACK_RETURNCODE: {code: 6, text: "AMQJS0006E Bad Connack return code:{0} {1}."},
        SOCKET_ERROR: {code: 7, text: "AMQJS0007E Socket error:{0}."},
        SOCKET_CLOSE: {code: 8, text: "AMQJS0008I Socket closed."},
        MALFORMED_UTF: {code: 9, text: "AMQJS0009E Malformed UTF data:{0} {1} {2}."},
        UNSUPPORTED: {code: 10, text: "AMQJS0010E {0} is not supported by this browser."},
        INVALID_STATE: {code: 11, text: "AMQJS0011E Invalid state {0}."},
        INVALID_TYPE: {code: 12, text: "AMQJS0012E Invalid type {0} for {1}."},
        INVALID_ARGUMENT: {code: 13, text: "AMQJS0013E Invalid argument {0} for {1}."},
        UNSUPPORTED_OPERATION: {code: 14, text: "AMQJS0014E Unsupported operation."},
        INVALID_STORED_DATA: {code: 15, text: "AMQJS0015E Invalid data in local storage key={0} value={1}."},
        INVALID_MQTT_MESSAGE_TYPE: {code: 16, text: "AMQJS0016E Invalid MQTT message type {0}."},
        MALFORMED_UNICODE: {code: 17, text: "AMQJS0017E Malformed Unicode string:{0} {1}."},
    };

    /** CONNACK RC Meaning. */
    var CONNACK_RC = {
        0: "Connection Accepted",
        1: "Connection Refused: unacceptable protocol version",
        2: "Connection Refused: identifier rejected",
        3: "Connection Refused: server unavailable",
        4: "Connection Refused: bad user name or password",
        5: "Connection Refused: not authorized"
    };

    /**
     * Format an error message text.
     * @private
     * @param {error} ERROR.KEY value above.
     * @param {substitutions} [array] substituted into the text.
     * @return the text with the substitutions made.
     */
    var format = function (error, substitutions) {
        var text = error.text;
        if (substitutions) {
            for (var i = 0; i < substitutions.length; i++) {
                field = "{" + i + "}";
                start = text.indexOf(field);
                if (start > 0) {
                    var part1 = text.substring(0, start);
                    var part2 = text.substring(start + field.length);
                    text = part1 + substitutions[i] + part2;
                }
            }
        }
        return text;
    };

    //MQTT protocol and version        6    M    Q    I    s    d    p    3
    var MqttProtoIdentifier = [0x00, 0x06, 0x4d, 0x51, 0x49, 0x73, 0x64, 0x70, 0x03];

    /**
     * @ignore
     * Construct an MQTT wire protocol message.
     * @param type MQTT packet type.
     * @param options optional wire message attributes.
     *
     * Optional properties
     *
     * messageIdentifier: message ID in the range [0..65535]
     * payloadMessage:    Application Message - PUBLISH only
     * connectStrings:    array of 0 or more Strings to be put into the CONNECT payload
     * topics:            array of strings (SUBSCRIBE, UNSUBSCRIBE)
     * requestQoS:        array of QoS values [0..2]
     *
     * "Flag" properties
     * cleanSession:    true if present / false if absent (CONNECT)
     * willMessage:    true if present / false if absent (CONNECT)
     * isRetained:        true if present / false if absent (CONNECT)
     * userName:        true if present / false if absent (CONNECT)
     * password:        true if present / false if absent (CONNECT)
     * keepAliveInterval:    integer [0..65535]  (CONNECT)
     *
     * @private
     */
    var WireMessage = function (type, options) {
        this.type = type;
        for (name in options) {
            if (options.hasOwnProperty(name)) {
                this[name] = options[name];
            }
        }
    };

    WireMessage.prototype.encode = function () {
        // Compute the first byte of the fixed header
        var first = ((this.type & 0x0f) << 4);

        /*
         * Now calculate the length of the variable header + payload by adding up the lengths
         * of all the component parts
         */

        remLength = 0;
        topicStrLength = new Array();

        // if the message contains a messageIdentifier then we need two bytes for that
        if (this.messageIdentifier != undefined)
            remLength += 2;

        switch (this.type) {
            // If this a Connect then we need to include 12 bytes for its header
            case MESSAGE_TYPE.CONNECT:
                remLength += MqttProtoIdentifier.length + 3;
                remLength += UTF8Length(this.clientId) + 2;
                if (this.willMessage != undefined) {
                    remLength += UTF8Length(this.willMessage.destinationName) + 2;
                    // Will message is always a string, sent as UTF-8 characters with a preceding length.
                    var willMessagePayloadBytes = this.willMessage.payloadBytes;
                    if (!(willMessagePayloadBytes instanceof Uint8Array))
                        willMessagePayloadBytes = new Uint8Array(payloadBytes);
                    remLength += willMessagePayloadBytes.byteLength + 2;
                }
                if (this.userName != undefined)
                    remLength += UTF8Length(this.userName) + 2;
                if (this.password != undefined)
                    remLength += UTF8Length(this.password) + 2;
                break;

            // Subscribe, Unsubscribe can both contain topic strings
            case MESSAGE_TYPE.SUBSCRIBE:
                first |= 0x02; // Qos = 1;
                for (var i = 0; i < this.topics.length; i++) {
                    topicStrLength[i] = UTF8Length(this.topics[i]);
                    remLength += topicStrLength[i] + 2;
                }
                remLength += this.requestedQos.length; // 1 byte for each topic's Qos
                // QoS on Subscribe only
                break;

            case MESSAGE_TYPE.UNSUBSCRIBE:
                first |= 0x02; // Qos = 1;
                for (var i = 0; i < this.topics.length; i++) {
                    topicStrLength[i] = UTF8Length(this.topics[i]);
                    remLength += topicStrLength[i] + 2;
                }
                break;

            case MESSAGE_TYPE.PUBLISH:
                if (this.payloadMessage.duplicate) first |= 0x08;
                first = first |= (this.payloadMessage.qos << 1);
                if (this.payloadMessage.retained) first |= 0x01;
                destinationNameLength = UTF8Length(this.payloadMessage.destinationName);
                remLength += destinationNameLength + 2;
                var payloadBytes = this.payloadMessage.payloadBytes;
                remLength += payloadBytes.byteLength;
                if (payloadBytes instanceof ArrayBuffer)
                    payloadBytes = new Uint8Array(payloadBytes);
                else if (!(payloadBytes instanceof Uint8Array))
                    payloadBytes = new Uint8Array(payloadBytes.buffer);
                break;

            case MESSAGE_TYPE.DISCONNECT:
                break;

            default:
                ;
        }

        // Now we can allocate a buffer for the message

        var mbi = encodeMBI(remLength);  // Convert the length to MQTT MBI format
        var pos = mbi.length + 1;        // Offset of start of variable header
        var buffer = new ArrayBuffer(remLength + pos);
        var byteStream = new Uint8Array(buffer);    // view it as a sequence of bytes

        //Write the fixed header into the buffer
        byteStream[0] = first;
        byteStream.set(mbi, 1);

        // If this is a PUBLISH then the variable header starts with a topic
        if (this.type == MESSAGE_TYPE.PUBLISH)
            pos = writeString(this.payloadMessage.destinationName, destinationNameLength, byteStream, pos);
        // If this is a CONNECT then the variable header contains the protocol name/version, flags and keepalive time

        else if (this.type == MESSAGE_TYPE.CONNECT) {
            byteStream.set(MqttProtoIdentifier, pos);
            pos += MqttProtoIdentifier.length;
            var connectFlags = 0;
            if (this.cleanSession)
                connectFlags = 0x02;
            if (this.willMessage != undefined) {
                connectFlags |= 0x04;
                connectFlags |= (this.willMessage.qos << 3);
                if (this.willMessage.retained) {
                    connectFlags |= 0x20;
                }
            }
            if (this.userName != undefined)
                connectFlags |= 0x80;
            if (this.password != undefined)
                connectFlags |= 0x40;
            byteStream[pos++] = connectFlags;
            pos = writeUint16(this.keepAliveInterval, byteStream, pos);
        }

        // Output the messageIdentifier - if there is one
        if (this.messageIdentifier != undefined)
            pos = writeUint16(this.messageIdentifier, byteStream, pos);

        switch (this.type) {
            case MESSAGE_TYPE.CONNECT:
                pos = writeString(this.clientId, UTF8Length(this.clientId), byteStream, pos);
                if (this.willMessage != undefined) {
                    pos = writeString(this.willMessage.destinationName, UTF8Length(this.willMessage.destinationName), byteStream, pos);
                    pos = writeUint16(willMessagePayloadBytes.byteLength, byteStream, pos);
                    byteStream.set(willMessagePayloadBytes, pos);
                    pos += willMessagePayloadBytes.byteLength;

                }
                if (this.userName != undefined)
                    pos = writeString(this.userName, UTF8Length(this.userName), byteStream, pos);
                if (this.password != undefined)
                    pos = writeString(this.password, UTF8Length(this.password), byteStream, pos);
                break;

            case MESSAGE_TYPE.PUBLISH:
                // PUBLISH has a text or binary payload, if text do not add a 2 byte length field, just the UTF characters.
                byteStream.set(payloadBytes, pos);

                break;

//    	    case MESSAGE_TYPE.PUBREC:
//    	    case MESSAGE_TYPE.PUBREL:
//    	    case MESSAGE_TYPE.PUBCOMP:
//    	    	break;

            case MESSAGE_TYPE.SUBSCRIBE:
                // SUBSCRIBE has a list of topic strings and request QoS
                for (var i = 0; i < this.topics.length; i++) {
                    pos = writeString(this.topics[i], topicStrLength[i], byteStream, pos);
                    byteStream[pos++] = this.requestedQos[i];
                }
                break;

            case MESSAGE_TYPE.UNSUBSCRIBE:
                // UNSUBSCRIBE has a list of topic strings
                for (var i = 0; i < this.topics.length; i++)
                    pos = writeString(this.topics[i], topicStrLength[i], byteStream, pos);
                break;

            default:
            // Do nothing.
        }

        return buffer;
    }

    function decodeMessage(input) {
        //var msg = new Object();  // message to be constructed
        var first = input[0];
        var type = first >> 4;
        var messageInfo = first &= 0x0f;
        var pos = 1;


        // Decode the remaining length (MBI format)

        var digit;
        var remLength = 0;
        var multiplier = 1;
        do {
            digit = input[pos++];
            remLength += ((digit & 0x7F) * multiplier);
            multiplier *= 128;
        } while ((digit & 0x80) != 0);

        var wireMessage = new WireMessage(type);
        switch (type) {
            case MESSAGE_TYPE.CONNACK:
                wireMessage.topicNameCompressionResponse = input[pos++];
                wireMessage.returnCode = input[pos++];
                break;

            case MESSAGE_TYPE.PUBLISH:
                var qos = (messageInfo >> 1) & 0x03;

                var len = readUint16(input, pos);
                pos += 2;
                var topicName = parseUTF8(input, pos, len);
                pos += len;
                // If QoS 1 or 2 there will be a messageIdentifier
                if (qos > 0) {
                    wireMessage.messageIdentifier = readUint16(input, pos);
                    pos += 2;
                }

                var message = new Messaging.Message(input.subarray(pos));
                if ((messageInfo & 0x01) == 0x01)
                    message.retained = true;
                if ((messageInfo & 0x08) == 0x08)
                    message.duplicate = true;
                message.qos = qos;
                message.destinationName = topicName;
                wireMessage.payloadMessage = message;
                break;

            case  MESSAGE_TYPE.PUBACK:
            case  MESSAGE_TYPE.PUBREC:
            case  MESSAGE_TYPE.PUBREL:
            case  MESSAGE_TYPE.PUBCOMP:
            case  MESSAGE_TYPE.UNSUBACK:
                wireMessage.messageIdentifier = readUint16(input, pos);
                break;

            case  MESSAGE_TYPE.SUBACK:
                wireMessage.messageIdentifier = readUint16(input, pos);
                pos += 2;
                wireMessage.grantedQos = input.subarray(pos);
                break;

            default:
                ;
        }

        return wireMessage;
    }

    function writeUint16(input, buffer, offset) {
        buffer[offset++] = input >> 8;      //MSB
        buffer[offset++] = input % 256;     //LSB
        return offset;
    }

    function writeString(input, utf8Length, buffer, offset) {
        offset = writeUint16(utf8Length, buffer, offset);
        stringToUTF8(input, buffer, offset);
        return offset + utf8Length;
    }

    function readUint16(buffer, offset) {
        return 256 * buffer[offset] + buffer[offset + 1];
    }

    /**
     * Encodes an MQTT Multi-Byte Integer
     * @private
     */
    function encodeMBI(number) {
        var output = new Array(1);
        var numBytes = 0;

        do {
            var digit = number % 128;
            number = number >> 7;
            if (number > 0) {
                digit |= 0x80;
            }
            output[numBytes++] = digit;
        } while ((number > 0) && (numBytes < 4));

        return output;
    }

    /**
     * Takes a String and calculates its length in bytes when encoded in UTF8.
     * @private
     */
    function UTF8Length(input) {
        var output = 0;
        for (var i = 0; i < input.length; i++) {
            var charCode = input.charCodeAt(i);
            if (charCode > 0x7FF) {
                // Surrogate pair means its a 4 byte character
                if (0xD800 <= charCode && charCode <= 0xDBFF) {
                    i++;
                    output++;
                }
                output += 3;
            }
            else if (charCode > 0x7F)
                output += 2;
            else
                output++;
        }
        return output;
    }

    /**
     * Takes a String and writes it into an array as UTF8 encoded bytes.
     * @private
     */
    function stringToUTF8(input, output, start) {
        var pos = start;
        for (var i = 0; i < input.length; i++) {
            var charCode = input.charCodeAt(i);

            // Check for a surrogate pair.
            if (0xD800 <= charCode && charCode <= 0xDBFF) {
                lowCharCode = input.charCodeAt(++i);
                if (isNaN(lowCharCode)) {
                    throw new Error(format(ERROR.MALFORMED_UNICODE, [charCode, lowCharCode]));
                }
                charCode = ((charCode - 0xD800) << 10) + (lowCharCode - 0xDC00) + 0x10000;

            }

            if (charCode <= 0x7F) {
                output[pos++] = charCode;
            } else if (charCode <= 0x7FF) {
                output[pos++] = charCode >> 6 & 0x1F | 0xC0;
                output[pos++] = charCode & 0x3F | 0x80;
            } else if (charCode <= 0xFFFF) {
                output[pos++] = charCode >> 12 & 0x0F | 0xE0;
                output[pos++] = charCode >> 6 & 0x3F | 0x80;
                output[pos++] = charCode & 0x3F | 0x80;
            } else {
                output[pos++] = charCode >> 18 & 0x07 | 0xF0;
                output[pos++] = charCode >> 12 & 0x3F | 0x80;
                output[pos++] = charCode >> 6 & 0x3F | 0x80;
                output[pos++] = charCode & 0x3F | 0x80;
            }
            ;
        }
        return output;
    }

    function parseUTF8(input, offset, length) {
        var output = "";
        var utf16;
        var pos = offset;

        while (pos < offset + length) {
            var byte1 = input[pos++];
            if (byte1 < 128)
                utf16 = byte1;
            else {
                var byte2 = input[pos++] - 128;
                if (byte2 < 0)
                    throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), ""]));
                if (byte1 < 0xE0)             // 2 byte character
                    utf16 = 64 * (byte1 - 0xC0) + byte2;
                else {
                    var byte3 = input[pos++] - 128;
                    if (byte3 < 0)
                        throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), byte3.toString(16)]));
                    if (byte1 < 0xF0)        // 3 byte character
                        utf16 = 4096 * (byte1 - 0xE0) + 64 * byte2 + byte3;
                    else {
                        var byte4 = input[pos++] - 128;
                        if (byte4 < 0)
                            throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), byte3.toString(16), byte4.toString(16)]));
                        if (byte1 < 0xF8)        // 4 byte character
                            utf16 = 262144 * (byte1 - 0xF0) + 4096 * byte2 + 64 * byte3 + byte4;
                        else                     // longer encodings are not supported
                            throw new Error(format(ERROR.MALFORMED_UTF, [byte1.toString(16), byte2.toString(16), byte3.toString(16), byte4.toString(16)]));
                    }
                }
            }

            if (utf16 > 0xFFFF)   // 4 byte character - express as a surrogate pair
            {
                utf16 -= 0x10000;
                output += String.fromCharCode(0xD800 + (utf16 >> 10)); // lead character
                utf16 = 0xDC00 + (utf16 & 0x3FF);  // trail character
            }
            output += String.fromCharCode(utf16);
        }
        return output;
    }

    /** @ignore Repeat keepalive requests, monitor responses.*/
    var Pinger = function (client, window, keepAliveInterval) {
        this._client = client;
        this._window = window;
        this._keepAliveInterval = keepAliveInterval * 1000;
        this.isReset = false;

        var pingReq = new WireMessage(MESSAGE_TYPE.PINGREQ).encode();

        var doTimeout = function (pinger) {
            return function () {
                return doPing.apply(pinger);
            };
        };

        /** @ignore */
        var doPing = function () {
            if (!this.isReset) {
                this._client._trace("Pinger.doPing", "Timed out");
                this._client._disconnected(ERROR.PING_TIMEOUT.code, format(ERROR.PING_TIMEOUT));
            } else {
                this.isReset = false;
                this._client._trace("Pinger.doPing", "send PINGREQ");
                this._client.socket.send(pingReq);
                this.timeout = this._window.setTimeout(doTimeout(this), this._keepAliveInterval);
            }
        }

        this.reset = function () {
            this.isReset = true;
            this._window.clearTimeout(this.timeout);
            if (this._keepAliveInterval > 0)
                this.timeout = setTimeout(doTimeout(this), this._keepAliveInterval);
        }

        this.cancel = function () {
            this._window.clearTimeout(this.timeout);
        }
    };

    /** @ignore Monitor request completion. */
    var Timeout = function (client, window, timeoutSeconds, action, args) {
        this._window = window;
        if (!timeoutSeconds)
            timeoutSeconds = 30;

        var doTimeout = function (action, client, args) {
            return function () {
                return action.apply(client, args);
            };
        };
        this.timeout = setTimeout(doTimeout(action, client, args), timeoutSeconds * 1000);

        this.cancel = function () {
            this._window.clearTimeout(this.timeout);
        }
    };

    /*
     * Internal implementation of the Websockets MQTT V3.1 client.
     *
     * @name Messaging.ClientImpl @constructor
     * @param {String} host the DNS nameof the webSocket host.
     * @param {Number} port the port number for that host.
     * @param {String} clientId the MQ client identifier.
     */
    var ClientImpl = function (host, port, clientId, webSocket) {
        if ( webSocket === undefined ) {
            // Check dependencies are satisfied in this browser.
            if (!("WebSocket" in global && global["WebSocket"] !== null)) {
                throw new Error(format(ERROR.UNSUPPORTED, ["WebSocket"]));
            }
            this._webSocket = (wsurl, protocols) => new WebSocket(wsurl, protocols);
        } else {
            if ( typeof webSocket !== 'function' ) {
                throw new Error(format(ERROR.INVALID_ARGUMENT, [webSocket, "webSocket"]));
            }
            this._webSocket = webSocket;
        }
        if (!("localStorage" in global && global["localStorage"] !== null)) {
            throw new Error(format(ERROR.UNSUPPORTED, ["localStorage"]));
        }
        if (!("ArrayBuffer" in global && global["ArrayBuffer"] !== null)) {
            throw new Error(format(ERROR.UNSUPPORTED, ["ArrayBuffer"]));
        }

        this._trace("Messaging.Client", host, port, clientId);

        this.host = host;
        this.port = port;
        this.clientId = clientId;

        // Local storagekeys are qualified with the following string.
        this._localKey = host + ":" + port + ":" + clientId + ":";

        // Create private instance-only message queue
        // Internal queue of messages to be sent, in sending order.
        this._msg_queue = [];

        // Messages we have sent and are expecting a response for, indexed by their respective message ids.
        this._sentMessages = {};

        // Messages we have received and acknowleged and are expecting a confirm message for
        // indexed by their respective message ids.
        this._receivedMessages = {};

        // Internal list of callbacks to be executed when messages
        // have been successfully sent over web socket, e.g. disconnect
        // when it doesn't have to wait for ACK, just message is dispatched.
        this._notify_msg_sent = {};

        // Unique identifier for SEND messages, incrementing
        // counter as messages are sent.
        this._message_identifier = 1;

        // Used to determine the transmission sequence of stored sent messages.
        this._sequence = 0;


        // Load the local state, if any, from the saved version, only restore state relevant to this client.
        for (key in localStorage)
            if (key.indexOf("Sent:" + this._localKey) == 0
                || key.indexOf("Received:" + this._localKey) == 0)
                this.restore(key);
    };

    // Messaging Client public instance members.
    ClientImpl.prototype.host;
    ClientImpl.prototype.port;
    ClientImpl.prototype.clientId;

    // Messaging Client private instance members.
    ClientImpl.prototype.socket;
    /* true once we have received an acknowledgement to a CONNECT packet. */
    ClientImpl.prototype.connected = false;
    /* The largest message identifier allowed, may not be larger than 2**16 but
     * if set smaller reduces the maximum number of outbound messages allowed.
     */
    ClientImpl.prototype.maxMessageIdentifier = 65536;
    ClientImpl.prototype.connectOptions;
    ClientImpl.prototype.hostIndex;
    ClientImpl.prototype.onConnectionLost;
    ClientImpl.prototype.onMessageDelivered;
    ClientImpl.prototype.onMessageArrived;
    ClientImpl.prototype._msg_queue = null;
    ClientImpl.prototype._connectTimeout;
    /* The sendPinger monitors how long we allow before we send data to prove to the server that we are alive. */
    ClientImpl.prototype.sendPinger = null;
    /* The receivePinger monitors how long we allow before we require evidence that the server is alive. */
    ClientImpl.prototype.receivePinger = null;

    ClientImpl.prototype._traceBuffer = null;
    ClientImpl.prototype._MAX_TRACE_ENTRIES = 100;

    ClientImpl.prototype.connect = function (connectOptions) {
        var connectOptionsMasked = this._traceMask(connectOptions, "password");
        this._trace("Client.connect", connectOptionsMasked, this.socket, this.connected);

        if (this.connected)
            throw new Error(format(ERROR.INVALID_STATE, ["already connected"]));
        if (this.socket)
            throw new Error(format(ERROR.INVALID_STATE, ["already connected"]));

        this.connectOptions = connectOptions;

        if (connectOptions.hosts) {
            this.hostIndex = 0;
            this._doConnect(connectOptions.hosts[0], connectOptions.ports[0]);
        } else {
            this._doConnect(this.host, this.port);
        }

    };

    ClientImpl.prototype.subscribe = function (filter, subscribeOptions) {
        this._trace("Client.subscribe", filter, subscribeOptions);

        if (!this.connected)
            throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));

        var wireMessage = new WireMessage(MESSAGE_TYPE.SUBSCRIBE);
        wireMessage.topics = [filter];
        if (subscribeOptions.qos != undefined)
            wireMessage.requestedQos = [subscribeOptions.qos];
        else
            wireMessage.requestedQos = [0];

        if (subscribeOptions.onSuccess) {
            wireMessage.callback = function () {
                subscribeOptions.onSuccess({invocationContext: subscribeOptions.invocationContext});
            };
        }
        if (subscribeOptions.timeout) {
            wireMessage.timeOut = new Timeout(this, window, subscribeOptions.timeout, subscribeOptions.onFailure
                , [
                    {invocationContext: subscribeOptions.invocationContext,
                        errorCode: ERROR.SUBSCRIBE_TIMEOUT.code,
                        errorMessage: format(ERROR.SUBSCRIBE_TIMEOUT)}
                ]);
        }

        // All subscriptions return a SUBACK.
        this._requires_ack(wireMessage);
        this._schedule_message(wireMessage);
    };

    /** @ignore */
    ClientImpl.prototype.unsubscribe = function (filter, unsubscribeOptions) {
        this._trace("Client.unsubscribe", filter, unsubscribeOptions);

        if (!this.connected)
            throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));

        var wireMessage = new WireMessage(MESSAGE_TYPE.UNSUBSCRIBE);
        wireMessage.topics = [filter];

        if (unsubscribeOptions.onSuccess) {
            wireMessage.callback = function () {
                unsubscribeOptions.onSuccess({invocationContext: unsubscribeOptions.invocationContext});
            };
        }
        if (unsubscribeOptions.timeout) {
            wireMessage.timeOut = new Timeout(this, window, unsubscribeOptions.timeout, unsubscribeOptions.onFailure
                , [
                    {invocationContext: unsubscribeOptions.invocationContext,
                        errorCode: ERROR.UNSUBSCRIBE_TIMEOUT.code,
                        errorMessage: format(ERROR.UNSUBSCRIBE_TIMEOUT)}
                ]);
        }

        // All unsubscribes return a SUBACK.
        this._requires_ack(wireMessage);
        this._schedule_message(wireMessage);
    };

    ClientImpl.prototype.send = function (message) {
        this._trace("Client.send", message);

        if (!this.connected)
            throw new Error(format(ERROR.INVALID_STATE, ["not connected"]));

        wireMessage = new WireMessage(MESSAGE_TYPE.PUBLISH);
        wireMessage.payloadMessage = message;

        if (message.qos > 0)
            this._requires_ack(wireMessage);
        else if (this.onMessageDelivered)
            this._notify_msg_sent[wireMessage] = this.onMessageDelivered(wireMessage.payloadMessage);
        this._schedule_message(wireMessage);
    };

    ClientImpl.prototype.disconnect = function () {
        this._trace("Client.disconnect");

        if (!this.socket)
            throw new Error(format(ERROR.INVALID_STATE, ["not connecting or connected"]));

        wireMessage = new WireMessage(MESSAGE_TYPE.DISCONNECT);

        // Run the disconnected call back as soon as the message has been sent,
        // in case of a failure later on in the disconnect processing.
        // as a consequence, the _disconected call back may be run several times.
        this._notify_msg_sent[wireMessage] = scope(this._disconnected, this);

        this._schedule_message(wireMessage);
    };

    ClientImpl.prototype.getTraceLog = function () {
        if (this._traceBuffer !== null) {
            this._trace("Client.getTraceLog", new Date());
            this._trace("Client.getTraceLog in flight messages", this._sentMessages.length);
            for (key in this._sentMessages)
                this._trace("_sentMessages ", key, this._sentMessages[key]);
            for (key in this._receivedMessages)
                this._trace("_receivedMessages ", key, this._receivedMessages[key]);

            return this._traceBuffer;
        }
    };

    ClientImpl.prototype.startTrace = function () {
        if (this._traceBuffer === null) {
            this._traceBuffer = [];
        }
        this._trace("Client.startTrace", new Date(), version);
    };

    ClientImpl.prototype.stopTrace = function () {
        delete this._traceBuffer;
    };

    ClientImpl.prototype._doConnect = function (host, port) {
        // When the socket is open, this client will send the CONNECT WireMessage using the saved parameters.
        if (this.connectOptions.useSSL)
            wsurl = ["wss://", host, ":", port, "/mqtt"].join("");
        else
            wsurl = ["ws://", host, ":", port, "/mqtt"].join("");
        this.connected = false;
        this.socket = this._webSocket(wsurl);
        this.socket.binaryType = 'arraybuffer';
        this.socket.onopen = scope(this._on_socket_open, this);
        this.socket.onmessage = scope(this._on_socket_message, this);
        this.socket.onerror = scope(this._on_socket_error, this);
        this.socket.onclose = scope(this._on_socket_close, this);

        this.sendPinger = new Pinger(this, window, this.connectOptions.keepAliveInterval);
        this.receivePinger = new Pinger(this, window, this.connectOptions.keepAliveInterval);

        this._connectTimeout = new Timeout(this, window, this.connectOptions.timeout, this._disconnected, [ERROR.CONNECT_TIMEOUT.code, format(ERROR.CONNECT_TIMEOUT)]);
    };


    // Schedule a new message to be sent over the WebSockets
    // connection. CONNECT messages cause WebSocket connection
    // to be started. All other messages are queued internally
    // until this has happened. When WS connection starts, process
    // all outstanding messages.
    ClientImpl.prototype._schedule_message = function (message) {
        this._msg_queue.push(message);
        // Process outstanding messages in the queue if we have an  open socket, and have received CONNACK.
        if (this.connected) {
            this._process_queue();
        }
    };

    ClientImpl.prototype.store = function (prefix, wireMessage) {
        storedMessage = {type: wireMessage.type, messageIdentifier: wireMessage.messageIdentifier, version: 1};

        switch (wireMessage.type) {
            case MESSAGE_TYPE.PUBLISH:
                if (wireMessage.pubRecReceived)
                    storedMessage.pubRecReceived = true;

                // Convert the payload to a hex string.
                storedMessage.payloadMessage = {};
                var hex = "";
                var messageBytes = wireMessage.payloadMessage.payloadBytes;
                for (var i = 0; i < messageBytes.length; i++) {
                    if (messageBytes[i] <= 0xF)
                        hex = hex + "0" + messageBytes[i].toString(16);
                    else
                        hex = hex + messageBytes[i].toString(16);
                }
                storedMessage.payloadMessage.payloadHex = hex;

                storedMessage.payloadMessage.qos = wireMessage.payloadMessage.qos;
                storedMessage.payloadMessage.destinationName = wireMessage.payloadMessage.destinationName;
                if (wireMessage.payloadMessage.duplicate)
                    storedMessage.payloadMessage.duplicate = true;
                if (wireMessage.payloadMessage.retained)
                    storedMessage.payloadMessage.retained = true;

                // Add a sequence number to sent messages.
                if (prefix.indexOf("Sent:") == 0) {
                    if (wireMessage.sequence === undefined)
                        wireMessage.sequence = ++this._sequence;
                    storedMessage.sequence = wireMessage.sequence;
                }
                break;

            default:
                throw Error(format(ERROR.INVALID_STORED_DATA, [key, storedMessage]));
        }
        localStorage.setItem(prefix + this._localKey + wireMessage.messageIdentifier, JSON.stringify(storedMessage));
    };

    ClientImpl.prototype.restore = function (key) {
        var value = localStorage.getItem(key);
        var storedMessage = JSON.parse(value);

        var wireMessage = new WireMessage(storedMessage.type, storedMessage);

        switch (storedMessage.type) {
            case MESSAGE_TYPE.PUBLISH:
                // Replace the payload message with a Message object.
                var hex = storedMessage.payloadMessage.payloadHex;
                var buffer = new ArrayBuffer((hex.length) / 2);
                var byteStream = new Uint8Array(buffer);
                var i = 0;
                while (hex.length >= 2) {
                    var x = parseInt(hex.substring(0, 2), 16);
                    hex = hex.substring(2, hex.length);
                    byteStream[i++] = x;
                }
                var payloadMessage = new Messaging.Message(byteStream);

                payloadMessage.qos = storedMessage.payloadMessage.qos;
                payloadMessage.destinationName = storedMessage.payloadMessage.destinationName;
                if (storedMessage.payloadMessage.duplicate)
                    payloadMessage.duplicate = true;
                if (storedMessage.payloadMessage.retained)
                    payloadMessage.retained = true;
                wireMessage.payloadMessage = payloadMessage;

                break;

            default:
                throw Error(format(ERROR.INVALID_STORED_DATA, [key, value]));
        }

        if (key.indexOf("Sent:" + this._localKey) == 0) {
            this._sentMessages[wireMessage.messageIdentifier] = wireMessage;
        } else if (key.indexOf("Received:" + this._localKey) == 0) {
            this._receivedMessages[wireMessage.messageIdentifier] = wireMessage;
        }
    };

    ClientImpl.prototype._process_queue = function () {
        var message = null;
        // Process messages in order they were added
        var fifo = this._msg_queue.reverse();

        // Send all queued messages down socket connection
        while ((message = fifo.pop())) {
            this._socket_send(message);
            // Notify listeners that message was successfully sent
            if (this._notify_msg_sent[message]) {
                this._notify_msg_sent[message]();
                delete this._notify_msg_sent[message];
            }
        }
    };

    /**
     * @ignore
     * Expect an ACK response for this message. Add message to the set of in progress
     * messages and set an unused identifier in this message.
     */
    ClientImpl.prototype._requires_ack = function (wireMessage) {
        var messageCount = Object.keys(this._sentMessages).length;
        if (messageCount > this.maxMessageIdentifier)
            throw Error("Too many messages:" + messageCount);

        while (this._sentMessages[this._message_identifier] !== undefined) {
            this._message_identifier++;
        }
        wireMessage.messageIdentifier = this._message_identifier;
        this._sentMessages[wireMessage.messageIdentifier] = wireMessage;
        if (wireMessage.type === MESSAGE_TYPE.PUBLISH) {
            this.store("Sent:", wireMessage);
        }
        if (this._message_identifier === this.maxMessagIdentifier) {
            this._message_identifier = 1;
        }
    };

    /**
     * @ignore
     * Called when the underlying websocket has been opened.
     */
    ClientImpl.prototype._on_socket_open = function () {
        // Create the CONNECT message object.
        var wireMessage = new WireMessage(MESSAGE_TYPE.CONNECT, this.connectOptions);
        wireMessage.clientId = this.clientId;
        this._socket_send(wireMessage);
    };

    /**
     * @ignore
     * Called when the underlying websocket has received a complete packet.
     */
    ClientImpl.prototype._on_socket_message = function (event) {
        this._trace("Client._on_socket_message", event.data);

        // Reset the receive ping timer, we now have evidence the server is alive.
        this.receivePinger.reset();
        var byteArray = new Uint8Array(event.data);
        try {
            var wireMessage = decodeMessage(byteArray);
        } catch (error) {
            this._disconnected(ERROR.INTERNAL_ERROR.code, format(ERROR.INTERNAL_ERROR, [error.message]));
            return;
        }
        this._trace("Client._on_socket_message", wireMessage);

        switch (wireMessage.type) {
            case MESSAGE_TYPE.CONNACK:
                this._connectTimeout.cancel();

                // If we have started using clean session then clear up the local state.
                if (this.connectOptions.cleanSession) {
                    for (key in this._sentMessages) {
                        var sentMessage = this._sentMessages[key];
                        localStorage.removeItem("Sent:" + this._localKey + sentMessage.messageIdentifier);
                    }
                    this._sentMessages = {};

                    for (key in this._receivedMessages) {
                        var receivedMessage = this._receivedMessages[key];
                        localStorage.removeItem("Received:" + this._localKey + receivedMessage.messageIdentifier);
                    }
                    this._receivedMessages = {};
                }
                // Client connected and ready for business.
                if (wireMessage.returnCode === 0) {
                    this.connected = true;
                    // Jump to the end of the list of hosts and stop looking for a good host.
                    if (this.connectOptions.hosts)
                        this.hostIndex = this.connectOptions.hosts.length;
                } else {
                    this._disconnected(ERROR.CONNACK_RETURNCODE.code, format(ERROR.CONNACK_RETURNCODE, [wireMessage.returnCode, CONNACK_RC[wireMessage.returnCode]]));
                    break;
                }

                // Resend messages.
                var sequencedMessages = new Array();
                for (var msgId in this._sentMessages) {
                    if (this._sentMessages.hasOwnProperty(msgId))
                        sequencedMessages.push(this._sentMessages[msgId]);
                }

                // Sort sentMessages into the original sent order.
                var sequencedMessages = sequencedMessages.sort(function (a, b) {
                    return a.sequence - b.sequence;
                });
                for (var i = 0, len = sequencedMessages.length; i < len; i++) {
                    var sentMessage = sequencedMessages[i];
                    if (sentMessage.type == MESSAGE_TYPE.PUBLISH && sentMessage.pubRecReceived) {
                        var pubRelMessage = new WireMessage(MESSAGE_TYPE.PUBREL, {messageIdentifier: sentMessage.messageIdentifier});
                        this._schedule_message(pubRelMessage);
                    } else {
                        this._schedule_message(sentMessage);
                    }
                    ;
                }

                // Execute the connectOptions.onSuccess callback if there is one.
                if (this.connectOptions.onSuccess) {
                    this.connectOptions.onSuccess({invocationContext: this.connectOptions.invocationContext});
                }

                // Process all queued messages now that the connection is established.
                this._process_queue();
                break;

            case MESSAGE_TYPE.PUBLISH:
                this._receivePublish(wireMessage);
                break;

            case MESSAGE_TYPE.PUBACK:
                var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
                // If this is a re flow of a PUBACK after we have restarted receivedMessage will not exist.
                if (sentMessage) {
                    delete this._sentMessages[wireMessage.messageIdentifier];
                    localStorage.removeItem("Sent:" + this._localKey + wireMessage.messageIdentifier);
                    if (this.onMessageDelivered)
                        this.onMessageDelivered(sentMessage.payloadMessage);
                }
                break;

            case MESSAGE_TYPE.PUBREC:
                var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
                // If this is a re flow of a PUBREC after we have restarted receivedMessage will not exist.
                if (sentMessage) {
                    sentMessage.pubRecReceived = true;
                    var pubRelMessage = new WireMessage(MESSAGE_TYPE.PUBREL, {messageIdentifier: wireMessage.messageIdentifier});
                    this.store("Sent:", sentMessage);
                    this._schedule_message(pubRelMessage);
                }
                break;

            case MESSAGE_TYPE.PUBREL:
                var receivedMessage = this._receivedMessages[wireMessage.messageIdentifier];
                localStorage.removeItem("Received:" + this._localKey + wireMessage.messageIdentifier);
                // If this is a re flow of a PUBREL after we have restarted receivedMessage will not exist.
                if (receivedMessage) {
                    this._receiveMessage(receivedMessage);
                    delete this._receivedMessages[wireMessage.messageIdentifier];
                }
                // Always flow PubComp, we may have previously flowed PubComp but the server lost it and restarted.
                pubCompMessage = new WireMessage(MESSAGE_TYPE.PUBCOMP, {messageIdentifier: wireMessage.messageIdentifier});
                this._schedule_message(pubCompMessage);


                break;

            case MESSAGE_TYPE.PUBCOMP:
                var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
                delete this._sentMessages[wireMessage.messageIdentifier];
                localStorage.removeItem("Sent:" + this._localKey + wireMessage.messageIdentifier);
                if (this.onMessageDelivered)
                    this.onMessageDelivered(sentMessage.payloadMessage);
                break;

            case MESSAGE_TYPE.SUBACK:
                var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
                if (sentMessage) {
                    if (sentMessage.timeOut)
                        sentMessage.timeOut.cancel();
                    if (sentMessage.callback) {
                        sentMessage.callback();
                    }
                    delete this._sentMessages[wireMessage.messageIdentifier];
                }
                break;

            case MESSAGE_TYPE.UNSUBACK:
                var sentMessage = this._sentMessages[wireMessage.messageIdentifier];
                if (sentMessage) {
                    if (sentMessage.timeOut)
                        sentMessage.timeOut.cancel();
                    if (sentMessage.callback) {
                        sentMessage.callback();
                    }
                    delete this._sentMessages[wireMessage.messageIdentifier];
                }

                break;

            case MESSAGE_TYPE.PINGRESP:
                /* The sendPinger or receivePinger may have sent a ping, the receivePinger has already been reset. */
                this.sendPinger.reset();
                break;

            case MESSAGE_TYPE.DISCONNECT:
                // Clients do not expect to receive disconnect packets.
                this._disconnected(ERROR.INVALID_MQTT_MESSAGE_TYPE.code, format(ERROR.INVALID_MQTT_MESSAGE_TYPE, [wireMessage.type]));
                break;

            default:
                this._disconnected(ERROR.INVALID_MQTT_MESSAGE_TYPE.code, format(ERROR.INVALID_MQTT_MESSAGE_TYPE, [wireMessage.type]));
        }
        ;
    };

    /** @ignore */
    ClientImpl.prototype._on_socket_error = function (error) {
        this._disconnected(ERROR.SOCKET_ERROR.code, format(ERROR.SOCKET_ERROR, [error.data]));
    };

    /** @ignore */
    ClientImpl.prototype._on_socket_close = function () {
        this._disconnected(ERROR.SOCKET_CLOSE.code, format(ERROR.SOCKET_CLOSE));
    };

    /** @ignore */
    ClientImpl.prototype._socket_send = function (wireMessage) {
        if (wireMessage.type == 1) {
            var wireMessageMasked = this._traceMask(wireMessage, "password");
            this._trace("Client._socket_send", wireMessageMasked);
        }
        else this._trace("Client._socket_send", wireMessage);

        this.socket.send(wireMessage.encode());
        /* We have proved to the server we are alive. */
        this.sendPinger.reset();
    };

    /** @ignore */
    ClientImpl.prototype._receivePublish = function (wireMessage) {
        switch (wireMessage.payloadMessage.qos) {
            case "undefined":
            case 0:
                this._receiveMessage(wireMessage);
                break;

            case 1:
                var pubAckMessage = new WireMessage(MESSAGE_TYPE.PUBACK, {messageIdentifier: wireMessage.messageIdentifier});
                this._schedule_message(pubAckMessage);
                this._receiveMessage(wireMessage);
                break;

            case 2:
                this._receivedMessages[wireMessage.messageIdentifier] = wireMessage;
                this.store("Received:", wireMessage);
                var pubRecMessage = new WireMessage(MESSAGE_TYPE.PUBREC, {messageIdentifier: wireMessage.messageIdentifier});
                this._schedule_message(pubRecMessage);

                break;

            default:
                throw Error("Invaild qos=" + wireMmessage.payloadMessage.qos);
        }
        ;
    };

    /** @ignore */
    ClientImpl.prototype._receiveMessage = function (wireMessage) {
        if (this.onMessageArrived) {
            this.onMessageArrived(wireMessage.payloadMessage);
        }
    };

    /**
     * @ignore
     * Client has disconnected either at its own request or because the server
     * or network disconnected it. Remove all non-durable state.
     * @param {errorCode} [number] the error number.
     * @param {errorText} [string] the error text.
     */
    ClientImpl.prototype._disconnected = function (errorCode, errorText) {
        this._trace("Client._disconnected", errorCode, errorText);

        this.sendPinger.cancel();
        this.receivePinger.cancel();
        if (this._connectTimeout)
            this._connectTimeout.cancel();
        // Clear message buffers.
        this._msg_queue = [];
        this._notify_msg_sent = {};

        if (this.socket) {
            // Cancel all socket callbacks so that they cannot be driven again by this socket.
            this.socket.onopen = null;
            this.socket.onmessage = null;
            this.socket.onerror = null;
            this.socket.onclose = null;
            if (this.socket.readyState === 1)
                this.socket.close();
            delete this.socket;
        }

        if (this.connectOptions.hosts && this.hostIndex < this.connectOptions.hosts.length - 1) {
            // Try the next host.
            this.hostIndex++;
            this._doConnect(this.connectOptions.hosts[this.hostIndex], this.connectOptions.ports[this.hostIndex]);

        } else {

            if (errorCode === undefined) {
                errorCode = ERROR.OK.code;
                errorText = format(ERROR.OK);
            }

            // Run any application callbacks last as they may attempt to reconnect and hence create a new socket.
            if (this.connected) {
                this.connected = false;
                // Execute the connectionLostCallback if there is one, and we were connected.
                if (this.onConnectionLost)
                    this.onConnectionLost({errorCode: errorCode, errorMessage: errorText});
            } else {
                // Otherwise we never had a connection, so indicate that the connect has failed.
                if (this.connectOptions.onFailure)
                    this.connectOptions.onFailure({invocationContext: this.connectOptions.invocationContext, errorCode: errorCode, errorMessage: errorText});
            }
        }
    };

    /** @ignore */
    ClientImpl.prototype._trace = function () {
        if (this._traceBuffer !== null) {
            for (var i = 0, max = arguments.length; i < max; i++) {
                if (this._traceBuffer.length == this._MAX_TRACE_ENTRIES) {
                    this._traceBuffer.shift();
                }
                if (i === 0) this._traceBuffer.push(arguments[i]);
                else if (typeof arguments[i] === "undefined") this._traceBuffer.push(arguments[i]);
                else this._traceBuffer.push("  " + JSON.stringify(arguments[i]));
            }
            ;
        }
        ;
    };

    /** @ignore */
    ClientImpl.prototype._traceMask = function (traceObject, masked) {
        var traceObjectMasked = {};
        for (var attr in traceObject) {
            if (traceObject.hasOwnProperty(attr)) {
                if (attr == masked)
                    traceObjectMasked[attr] = "******";
                else
                    traceObjectMasked[attr] = traceObject[attr];
            }
        }
        return traceObjectMasked;
    };

    // ------------------------------------------------------------------------
    // Public Programming interface.
    // ------------------------------------------------------------------------

    /**
     * The JavaScript application communicates to the server using a Messaging.Client object.
     * <p>
     * Other programming languages,
     * <a href="/clients/java/doc/javadoc/com/ibm/micro/client/mqttv3/MqttClient.html"><big>Java</big></a>,
     * <a href="/clients/c/doc/html/index.html"><big>C</big></a>.
     * <p>
     * Most applications will create just one Client object and then call its connect() method,
     * however applications can create more than one Client object if they wish.
     * In this case the combination of host, port and clientId attributes must be different for each Client object.
     * <p>
     * The send, subscribe and unsubscribe methods are implemented as asynchronous JavaScript methods
     * (even though the underlying protocol exchange might be synchronous in nature).
     * This means they signal their completion by calling back to the application,
     * via Success or Failure callback functions provided by the application on the method in question.
     * Such callbacks are called at most once per method invocation and do not persist beyond the lifetime
     * of the script that made the invocation.
     * <p>
     * In contrast there are some callback functions <i> most notably onMessageArrived</i>
     * that are defined on the Messaging.Client object.
     * These may get called multiple times, and aren't directly related to specific method invocations made by the client.
     *
     * @name Messaging.Client
     *
     * @constructor
     * Creates a Messaging.Client object that can be used to communicate with a Messaging server.
     *
     * @param {string} host the address of the messaging server, as a DNS name or dotted decimal IP address.
     * @param {number} port the port number in the host to connect to.
     * @param {string} clientId the Messaging client identifier, between 1 and 23 characters in length.
     *
     * @property {string} host <i>read only</i> the server's DNS hostname or dotted decimal IP address.
     * @property {number} port <i>read only</i> the server's port.
     * @property {string} clientId <i>read only</i> used when connecting to the server.
     * @property {function} onConnectionLost called when a connection has been lost,
     * after a connect() method has succeeded.
     * Establish the call back used when a connection has been lost. The connection may be
     * lost because the client initiates a disconnect or because the server or network
     * cause the client to be disconnected. The disconnect call back may be called without
     * the connectionComplete call back being invoked if, for example the client fails to
     * connect.
     * A single response object parameter is passed to the onConnectionLost callback containing the following fields:
     * <ol>
     * <li>errorCode
     * <li>errorMessage
     * </ol>
     * @property {function} onMessageDelivered called when a message has been delivered.
     * All processing that this Client will ever do has been completed. So, for example,
     * in the case of a Qos=2 message sent by this client, the PubComp flow has been received from the server
     * and the message has been removed from persistent storage before this callback is invoked.
     * Parameters passed to the onMessageDelivered callback are:
     * <ol>
     * <li>Messaging.Message that was delivered.
     * </ol>
     * @property {function} onMessageArrived called when a message has arrived in this Messaging.client.
     * Parameters passed to the onMessageArrived callback are:
     * <ol>
     * <li>Messaging.Message that has arrived.
     * </ol>
     */
    var Client = function (host, port, clientId) {
        if (typeof host !== "string")
            throw new Error(format(ERROR.INVALID_TYPE, [typeof host, "host"]));
        if (typeof port !== "number" || port < 0)
            throw new Error(format(ERROR.INVALID_TYPE, [typeof port, "port"]));

        var clientIdLength = 0;
        for (var i = 0; i < clientId.length; i++) {
            var charCode = clientId.charCodeAt(i);
            if (0xD800 <= charCode && charCode <= 0xDBFF) {
                i++; // Surrogate pair.
            }
            clientIdLength++;
        }
        if (typeof clientId !== "string" || clientIdLength < 1 | clientIdLength > 23)
            throw new Error(format(ERROR.INVALID_ARGUMENT, [clientId, "clientId"]));

        var client = new ClientImpl(host, port, clientId);
        this._getHost = function () {
            return client.host;
        };
        this._setHost = function () {
            throw new Error(format(ERROR.UNSUPPORTED_OPERATION));
        };

        this._getPort = function () {
            return client.port;
        };
        this._setPort = function () {
            throw new Error(format(ERROR.UNSUPPORTED_OPERATION));
        };

        this._getClientId = function () {
            return client.clientId;
        };
        this._setClientId = function () {
            throw new Error(format(ERROR.UNSUPPORTED_OPERATION));
        };

        this._getOnConnectionLost = function () {
            return client.onConnectionLost;
        };
        this._setOnConnectionLost = function (newOnConnectionLost) {
            if (typeof newOnConnectionLost === "function")
                client.onConnectionLost = newOnConnectionLost;
            else
                throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnConnectionLost, "onConnectionLost"]));
        };

        this._getOnMessageDelivered = function () {
            return client.onMessageDelivered;
        };
        this._setOnMessageDelivered = function (newOnMessageDelivered) {
            if (typeof newOnMessageDelivered === "function")
                client.onMessageDelivered = newOnMessageDelivered;
            else
                throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnMessageDelivered, "onMessageDelivered"]));
        };

        this._getOnMessageArrived = function () {
            return client.onMessageArrived;
        };
        this._setOnMessageArrived = function (newOnMessageArrived) {
            if (typeof newOnMessageArrived === "function")
                client.onMessageArrived = newOnMessageArrived;
            else
                throw new Error(format(ERROR.INVALID_TYPE, [typeof newOnMessageArrived, "onMessageArrived"]));
        };

        /**
         * Connect this Messaging client to its server.
         *
         * @name Messaging.Client#connect
         * @function
         * @param {Object} [connectOptions] attributes used with the connection.
         * <p>
         * Properties of the connect options are:
         * @config {number} [timeout] If the connect has not succeeded within this number of seconds, it is deemed to have failed.
         *                            The default is 30 seconds.
         * @config {string} [userName] Authentication username for this connection.
         * @config {string} [password] Authentication password for this connection.
         * @config {Messaging.Message} [willMessage] sent by the server when the client disconnects abnormally.
         * @config {Number} [keepAliveInterval] the server disconnects this client if there is no activity for this
         *                number of seconds. The default value of 60 seconds is assumed if not set.
         * @config {boolean} [cleanSession] if true(default) the client and server persistent state is deleted on successful connect.
         * @config {boolean} [useSSL] if present and true, use an SSL Websocket connection.
         * @config {object} [invocationContext] passed to the onSuccess callback or onFailure callback.
         * @config {function} [onSuccess] called when the connect acknowledgement has been received from the server.
         * A single response object parameter is passed to the onSuccess callback containing the following fields:
         * <ol>
         * <li>invocationContext as passed in to the onSuccess method in the connectOptions.
         * </ol>
         * @config {function} [onFailure] called when the connect request has failed or timed out.
         * A single response object parameter is passed to the onFailure callback containing the following fields:
         * <ol>
         * <li>invocationContext as passed in to the onFailure method in the connectOptions.
         * <li>errorCode a number indicating the nature of the error.
         * <li>errorMessage text describing the error.
         * </ol>
         * @config {Array} [hosts] If present this set of hostnames is tried in order in place
         * of the host and port paramater on the construtor. The hosts and the matching ports are tried one at at time in order until
         * one of then succeeds.
         * @config {Array} [ports] If present this set of ports matching the hosts.
         * @throws {InvalidState} if the client is not in disconnected state. The client must have received connectionLost
         * or disconnected before calling connect for a second or subsequent time.
         */
        this.connect = function (connectOptions) {
            connectOptions = connectOptions || {};
            validate(connectOptions, {timeout: "number",
                userName: "string",
                password: "string",
                willMessage: "object",
                keepAliveInterval: "number",
                cleanSession: "boolean",
                useSSL: "boolean",
                invocationContext: "object",
                onSuccess: "function",
                onFailure: "function",
                hosts: "object",
                ports: "object"});

            // If no keep alive interval is set, assume 60 seconds.
            if (connectOptions.keepAliveInterval === undefined)
                connectOptions.keepAliveInterval = 60;

            if (connectOptions.willMessage) {
                if (!(connectOptions.willMessage instanceof Message))
                    throw new Error(format(ERROR.INVALID_TYPE, [connectOptions.willMessage, "connectOptions.willMessage"]));
                // The will message must have a payload that can be represented as a string.
                // Cause the willMessage to throw an exception if this is not the case.
                connectOptions.willMessage.stringPayload;

                if (typeof connectOptions.willMessage.destinationName === "undefined")
                    throw new Error(format(ERROR.INVALID_TYPE, [typeof connectOptions.willMessage.destinationName, "connectOptions.willMessage.destinationName"]));
            }
            if (typeof connectOptions.cleanSession === "undefined")
                connectOptions.cleanSession = true;
            if (connectOptions.hosts) {
                if (!connectOptions.ports)
                    throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.ports, "connectOptions.ports"]));
                if (!(connectOptions.hosts instanceof Array))
                    throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.hosts, "connectOptions.hosts"]));
                if (!(connectOptions.ports instanceof Array))
                    throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.ports, "connectOptions.ports"]));
                if (connectOptions.hosts.length < 1)
                    throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.hosts, "connectOptions.hosts"]));
                if (connectOptions.hosts.length != connectOptions.ports.length)
                    throw new Error(format(ERROR.INVALID_ARGUMENT, [connectOptions.ports, "connectOptions.ports"]));
                for (var i = 0; i < connectOptions.hosts.length; i++) {
                    if (typeof connectOptions.hosts[i] !== "string")
                        throw new Error(format(ERROR.INVALID_TYPE, [typeof connectOptions.hosts[i], "connectOptions.hosts[" + i + "]"]));
                    if (typeof connectOptions.ports[i] !== "number" || connectOptions.ports[i] < 0)
                        throw new Error(format(ERROR.INVALID_TYPE, [typeof connectOptions.ports[i], "connectOptions.ports[" + i + "]"]));
                }
            }

            client.connect(connectOptions);
        };

        /**
         * Subscribe for messages, request receipt of a copy of messages sent to the destinations described by the filter.
         *
         * @name Messaging.Client#subscribe
         * @function
         * @param {string} filter describing the destinations to receive messages from.
         * <br>
         * @param {object} [subscribeOptions] used to control the subscription, as follows:
         * <p>
         * @config {number} [qos] the maiximum qos of any publications sent as a result of making this subscription.
         * @config {object} [invocationContext] passed to the onSuccess callback or onFailure callback.
         * @config {function} [onSuccess] called when the subscribe acknowledgement has been received from the server.
         * A single response object parameter is passed to the onSuccess callback containing the following fields:
         * <ol>
         * <li>invocationContext if set in the subscribeOptions.
         * </ol>
         * @config {function} [onFailure] called when the subscribe request has failed or timed out.
         * A single response object parameter is passed to the onFailure callback containing the following fields:
         * <ol>
         * <li>invocationContext if set in the subscribeOptions.
         * <li>errorCode a number indicating the nature of the error.
         * <li>errorMessage text describing the error.
         * </ol>
         * @config {number} [timeout] which if present determines the number of seconds after which the onFailure calback is called
         * the presence of a timeout does not prevent the onSuccess callback from being called when the MQTT Suback is eventually received.
         * @throws {InvalidState} if the client is not in connected state.
         */
        this.subscribe = function (filter, subscribeOptions) {
            if (typeof filter !== "string")
                throw new Error("Invalid argument:" + filter);
            subscribeOptions = subscribeOptions || {};
            validate(subscribeOptions, {qos: "number",
                invocationContext: "object",
                onSuccess: "function",
                onFailure: "function",
                timeout: "number"
            });
            if (subscribeOptions.timeout && !subscribeOptions.onFailure)
                throw new Error("subscribeOptions.timeout specified with no onFailure callback.");
            if (typeof subscribeOptions.qos !== "undefined"
                && !(subscribeOptions.qos === 0 || subscribeOptions.qos === 1 || subscribeOptions.qos === 2 ))
                throw new Error(format(ERROR.INVALID_ARGUMENT, [subscribeOptions.qos, "subscribeOptions.qos"]));
            client.subscribe(filter, subscribeOptions);
        };

        /**
         * Unsubscribe for messages, stop receiving messages sent to destinations described by the filter.
         *
         * @name Messaging.Client#unsubscribe
         * @function
         * @param {string} filter describing the destinations to receive messages from.
         * @param {object} [unsubscribeOptions] used to control the subscription, as follows:
         * <p>
         * @config {object} [invocationContext] passed to the onSuccess callback or onFailure callback.
         * @config {function} [onSuccess] called when the unsubscribe acknowledgement has been receive dfrom the server.
         * A single response object parameter is passed to the onSuccess callback containing the following fields:
         * <ol>
         * <li>invocationContext if set in the unsubscribeOptions.
         * </ol>
         * @config {function} [onFailure] called when the unsubscribe request has failed or timed out.
         * A single response object parameter is passed to the onFailure callback containing the following fields:
         * <ol>
         * <li>invocationContext if set in the unsubscribeOptions.
         * <li>errorCode a number indicating the nature of the error.
         * <li>errorMessage text describing the error.
         * </ol>
         * @config {number} [timeout] which if present determines the number of seconds after which the onFailure callback is called, the
         * presence of a timeout does not prevent the onSuccess callback from being called when the MQTT UnSuback is eventually received.
         * @throws {InvalidState} if the client is not in connected state.
         */
        this.unsubscribe = function (filter, unsubscribeOptions) {
            if (typeof filter !== "string")
                throw new Error("Invalid argument:" + filter);
            unsubscribeOptions = unsubscribeOptions || {};
            validate(unsubscribeOptions, {invocationContext: "object",
                onSuccess: "function",
                onFailure: "function",
                timeout: "number"
            });
            if (unsubscribeOptions.timeout && !unsubscribeOptions.onFailure)
                throw new Error("unsubscribeOptions.timeout specified with no onFailure callback.");
            client.unsubscribe(filter, unsubscribeOptions);
        };

        /**
         * Send a message to the consumers of the destination in the Message.
         *
         * @name Messaging.Client#send
         * @function
         * @param {Messaging.Message} message to send.

         * @throws {InvalidState} if the client is not in connected state.
         */
        this.send = function (message) {
            if (!(message instanceof Message))
                throw new Error("Invalid argument:" + typeof message);
            if (typeof message.destinationName === "undefined")
                throw new Error("Invalid parameter Message.destinationName:" + message.destinationName);

            client.send(message);
        };

        /**
         * Normal disconnect of this Messaging client from its server.
         *
         * @name Messaging.Client#disconnect
         * @function
         * @throws {InvalidState} if the client is not in connected or connecting state.
         */
        this.disconnect = function () {
            client.disconnect();
        };

        /**
         * Get the contents of the trace log.
         *
         * @name Messaging.Client#getTraceLog
         * @function
         * @return {Object[]} tracebuffer containing the time ordered trace records.
         */
        this.getTraceLog = function () {
            return client.getTraceLog();
        }

        /**
         * Start tracing.
         *
         * @name Messaging.Client#startTrace
         * @function
         */
        this.startTrace = function () {
            client.startTrace();
        };

        /**
         * Stop tracing.
         *
         * @name Messaging.Client#stopTrace
         * @function
         */
        this.stopTrace = function () {
            client.stopTrace();
        };
    };

    Client.prototype = {
        get host() {
            return this._getHost();
        },
        set host(newHost) {
            this._setHost(newHost);
        },

        get port() {
            return this._getPort();
        },
        set port(newPort) {
            this._setPort(newPort);
        },

        get clientId() {
            return this._getClientId();
        },
        set clientId(newClientId) {
            this._setClientId(newClientId);
        },

        get onConnectionLost() {
            return this._getOnConnectionLost();
        },
        set onConnectionLost(newOnConnectionLost) {
            this._setOnConnectionLost(newOnConnectionLost);
        },

        get onMessageDelivered() {
            return this._getOnMessageDelivered();
        },
        set onMessageDelivered(newOnMessageDelivered) {
            this._setOnMessageDelivered(newOnMessageDelivered);
        },

        get onMessageArrived() {
            return this._getOnMessageArrived();
        },
        set onMessageArrived(newOnMessageArrived) {
            this._setOnMessageArrived(newOnMessageArrived);
        }
    };

    /**
     * An application message, sent or received.
     * <p>
     * Other programming languages,
     * <a href="/clients/java/doc/javadoc/com/ibm/micro/client/mqttv3/MqttMessage.html"><big>Java</big></a>,
     * <a href="/clients/c/doc/html/struct_m_q_t_t_client__message.html"><big>C</big></a>.
     * <p>
     * All attributes may be null, which implies the default values.
     *
     * @name Messaging.Message
     * @constructor
     * @param {String|ArrayBuffer} payload The message data to be sent.
     * <p>
     * @property {string} payloadString <i>read only</i> The payload as a string if the payload consists of valid UTF-8 characters.
     * @property {ArrayBuffer} payloadBytes <i>read only</i> The payload as an ArrayBuffer.
     * <p>
     * @property {string} destinationName <b>mandatory</b> The name of the destination to which the message is to be sent
     *                    (for messages about to be sent) or the name of the destination from which the message has been received.
     *                    (for messages received by the onMessage function).
     * <p>
     * @property {number} qos The Quality of Service used to deliver the message.
     * <dl>
     *     <dt>0 Best effort (default).
     *     <dt>1 At least once.
     *     <dt>2 Exactly once.
     * </dl>
     * <p>
     * @property {Boolean} retained If true, the message is to be retained by the server and delivered
     *                     to both current and future subscriptions.
     *                     If false the server only delivers the message to current subscribers, this is the default for new Messages.
     *                     A received message has the retained boolean set to true if the message was published
     *                     with the retained boolean set to true
     *                     and the subscrption was made after the message has been published.
     * <p>
     * @property {Boolean} duplicate <i>read only</i> If true, this message might be a duplicate of one which has already been received.
     *                     This is only set on messages received from the server.
     *
     */
    var Message = function (newPayload) {
        var payload;
        if (typeof newPayload === "string"
            || newPayload instanceof ArrayBuffer
            || newPayload instanceof Int8Array
            || newPayload instanceof Uint8Array
            || newPayload instanceof Int16Array
            || newPayload instanceof Uint16Array
            || newPayload instanceof Int32Array
            || newPayload instanceof Uint32Array
            || newPayload instanceof Float32Array
            || newPayload instanceof Float64Array
            ) {
            payload = newPayload;
        } else {
            throw (format(ERROR.INVALID_ARGUMENT, [newPayload, "newPayload"]));
        }

        this._getPayloadString = function () {
            if (typeof payload === "string")
                return payload;
            else
                return parseUTF8(payload, 0, payload.length);
        };

        this._getPayloadBytes = function () {
            if (typeof payload === "string") {
                var buffer = new ArrayBuffer(UTF8Length(payload));
                var byteStream = new Uint8Array(buffer);
                stringToUTF8(payload, byteStream, 0);

                return byteStream;
            } else {
                return payload;
            }
            ;
        };

        var destinationName = undefined;
        this._getDestinationName = function () {
            return destinationName;
        };
        this._setDestinationName = function (newDestinationName) {
            if (typeof newDestinationName === "string")
                destinationName = newDestinationName;
            else
                throw new Error(format(ERROR.INVALID_ARGUMENT, [newDestinationName, "newDestinationName"]));
        };

        var qos = 0;
        this._getQos = function () {
            return qos;
        };
        this._setQos = function (newQos) {
            if (newQos === 0 || newQos === 1 || newQos === 2)
                qos = newQos;
            else
                throw new Error("Invalid argument:" + newQos);
        };

        var retained = false;
        this._getRetained = function () {
            return retained;
        };
        this._setRetained = function (newRetained) {
            if (typeof newRetained === "boolean")
                retained = newRetained;
            else
                throw new Error(format(ERROR.INVALID_ARGUMENT, [newRetained, "newRetained"]));
        };

        var duplicate = false;
        this._getDuplicate = function () {
            return duplicate;
        };
        this._setDuplicate = function (newDuplicate) {
            duplicate = newDuplicate;
        };
    };

    Message.prototype = {
        get payloadString() {
            return this._getPayloadString();
        },
        get payloadBytes() {
            return this._getPayloadBytes();
        },

        get destinationName() {
            return this._getDestinationName();
        },
        set destinationName(newDestinationName) {
            this._setDestinationName(newDestinationName);
        },

        get qos() {
            return this._getQos();
        },
        set qos(newQos) {
            this._setQos(newQos);
        },

        get retained() {
            return this._getRetained();
        },
        set retained(newRetained) {
            this._setRetained(newRetained);
        },

        get duplicate() {
            return this._getDuplicate();
        },
        set duplicate(newDuplicate) {
            this._setDuplicate(newDuplicate);
        }
    };

    // Module contents.
    return {
        Client: Client,
        Message: Message
    };
})(window);