/*
Copyright (c) 2006, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
Version: 0.11.3
*/

/**
* The Connection Manager provides a simplified interface to the XMLHttpRequest
* object.  It handles cross-browser instantiantion of XMLHttpRequest, negotiates the
* interactive states and server response, returning the results to a pre-defined
* callback you create.
* @ class
*/
YAHOO.util.Connect =
{
    /**
    * Array of MSFT ActiveX ids for XMLHttpRequest.
    * @private
    * @type array
    */
    _msxml_progid: [
		'MSXML2.XMLHTTP.3.0',
		'MSXML2.XMLHTTP',
		'Microsoft.XMLHTTP'
		],

    /**
    * Object literal of HTTP header(s)
    * @private
    * @type object
    */
    _http_header: {},

    /**
    * Determines if HTTP headers are set.
    * @private
    * @type boolean
    */
    _has_http_headers: false,

    /**
    * Determines if a default header of
    * Content-Type of 'application/x-www-form-urlencoded'
    * will be added to any client HTTP headers sent for POST
    * transactions.
    * @private
    * @type boolean
    */
    _use_default_post_header: true,

    /**
    * Determines if a default header of
    * Content-Type of 'application/x-www-form-urlencoded'
    * will be added to any client HTTP headers sent for POST
    * transactions.
    * @private
    * @type boolean
    */
    _default_post_header: 'application/x-www-form-urlencoded',

    /**
    * Property modified by setForm() to determine if the data
    * should be submitted as an HTML form.
    * @private
    * @type boolean
    */
    _isFormSubmit: false,

    /**
    * Property modified by setForm() to determine if a file(s)
    * upload is expected.
    * @private
    * @type boolean
    */
    _isFileUpload: false,

    /**
    * Property modified by setForm() to set a reference to the HTML
    * form node if the desired action is file upload.
    * @private
    * @type object
    */
    _formNode: null,

    /**
    * Property modified by setForm() to set the HTML form data
    * for each transaction.
    * @private
    * @type string
    */
    _sFormData: null,

    /**
    * Collection of polling references to the polling mechanism in handleReadyState.
    * @private
    * @type object
    */
    _poll: {},

    /**
    * Queue of timeout values for each transaction callback with a defined timeout value.
    * @private
    * @type object
    */
    _timeOut: {},

    /**
    * The polling frequency, in milliseconds, for HandleReadyState.
    * when attempting to determine a transaction's XHR readyState.
    * The default is 50 milliseconds.
    * @private
    * @type int
    */
    _polling_interval: 50,

    /**
    * A transaction counter that increments the transaction id for each transaction.
    * @private
    * @type int
    */
    _transaction_id: 0,

    /**
    * Member to add an ActiveX id to the existing xml_progid array.
    * In the event(unlikely) a new ActiveX id is introduced, it can be added
    * without internal code modifications.
    * @public
    * @param string id The ActiveX id to be added to initialize the XHR object.
    * @return void
    */
    setProgId: function(id) {
        this._msxml_progid.unshift(id);
    },

    /**
    * Member to enable or disable the default POST header.
    * @public
    * @param boolean b Set and use default header - true or false .
    * @return void
    */
    setDefaultPostHeader: function(b) {
        this._use_default_post_header = b;
    },

    /**
    * Member to modify the default polling interval.
    * @public
    * @param {int} i The polling interval in milliseconds.
    * @return void
    */
    setPollingInterval: function(i) {
        if (typeof i == 'number' && isFinite(i)) {
            this._polling_interval = i;
        }
    },

    /**
    * Instantiates a XMLHttpRequest object and returns an object with two properties:
    * the XMLHttpRequest instance and the transaction id.
    * @private
    * @param {int} transactionId Property containing the transaction id for this transaction.
    * @return connection object
    */
    createXhrObject: function(transactionId) {
        var obj, http;
        try {
            // Instantiates XMLHttpRequest in non-IE browsers and assigns to http.
            http = new XMLHttpRequest();
            //  Object literal with http and tId properties
            obj = { conn: http, tId: transactionId };
        }
        catch (e) {
            for (var i = 0; i < this._msxml_progid.length; ++i) {
                try {
                    // Instantiates XMLHttpRequest for IE and assign to http.
                    http = new ActiveXObject(this._msxml_progid[i]);
                    //  Object literal with http and tId properties
                    obj = { conn: http, tId: transactionId };
                    break;
                }
                catch (e) { }
            }
        }
        finally {
            return obj;
        }
    },

    /**
    * This method is called by asyncRequest to create a
    * valid connection object for the transaction.  It also passes a
    * transaction id and increments the transaction id counter.
    * @private
    * @return object
    */
    getConnectionObject: function() {
        var o;
        var tId = this._transaction_id;

        try {
            o = this.createXhrObject(tId);
            if (o) {
                this._transaction_id++;
            }
        }
        catch (e) { }
        finally {
            return o;
        }
    },

    /**
    * Method for initiating an asynchronous request via the XHR object.
    * @public
    * @param {string} method HTTP transaction method
    * @param {string} uri Fully qualified path of resource
    * @param callback User-defined callback function or object
    * @param {string} postData POST body
    * @return {object} Returns the connection object
    */
    asyncRequest: function(method, uri, callback, postData) {
        var o = this.getConnectionObject();

        if (!o) {
            return null;
        }
        else {
            if (this._isFormSubmit) {
                if (this._isFileUpload) {
                    this.uploadFile(o.tId, callback, uri);
                    this.releaseObject(o);
                    return;
                }

                //If the specified HTTP method is GET, setForm() will return an
                //encoded string that is concatenated to the uri to
                //create a querystring.
                if (method == 'GET') {
                    uri += "?" + this._sFormData;
                }
                else if (method == 'POST') {
                    //If POST data exists in addition to the HTML form data,
                    //it will be concatenated to the form data.
                    postData = (postData ? this._sFormData + "&" + postData : this._sFormData);
                }
                this._sFormData = '';
            }

            o.conn.open(method, uri, true);

            if (this._isFormSubmit || (postData && this._use_default_post_header)) {
                this.initHeader('Content-Type', this._default_post_header);
                if (this._isFormSubmit) {
                    this._isFormSubmit = false;
                }
            }

            if (this._has_http_headers) {
                this.setHeader(o);
            }

            this.handleReadyState(o, callback);
            o.conn.send(postData ? postData : null);

            return o;
        }
    },

    /**
    * This method serves as a timer that polls the XHR object's readyState
    * property during a transaction, instead of binding a callback to the
    * onreadystatechange event.  Upon readyState 4, handleTransactionResponse
    * will process the response, and the timer will be cleared.
    *
    * @private
    * @param {object} o The connection object
    * @param callback User-defined callback object
    * @return void
    */
    handleReadyState: function(o, callback) {

        var oConn = this;

        if (callback && callback.timeout) {
            this._timeOut[o.tId] = window.setTimeout(function() { oConn.abort(o, callback, true); }, callback.timeout);
        }

        this._poll[o.tId] = window.setInterval(
			function() {
			    if (o.conn && o.conn.readyState == 4) {
			        window.clearInterval(oConn._poll[o.tId]);
			        delete oConn._poll[o.tId];

			        if (callback && callback.timeout) {
			            delete oConn._timeOut[o.tId];
			        }

			        oConn.handleTransactionResponse(o, callback);
			    }
			}
		, this._polling_interval);
    },

    /**
    * This method attempts to interpret the server response and
    * determine whether the transaction was successful, or if an error or
    * exception was encountered.
    *
    * @private
    * @param {object} o The connection object
    * @param {object} callback - User-defined callback object
    * @param {boolean} determines if the transaction was aborted.
    * @return void
    */
    handleTransactionResponse: function(o, callback, isAbort) {
        // If no valid callback is provided, then do not process any callback handling.
        if (!callback) {
            this.releaseObject(o);
            return;
        }

        var httpStatus, responseObject;

        try {
            if (o.conn.status !== undefined && o.conn.status != 0) {
                httpStatus = o.conn.status;
            }
            else {
                httpStatus = 13030;
            }
        }
        catch (e) {
            // 13030 is the custom code to indicate the condition -- in Mozilla/FF --
            // when the o object's status and statusText properties are
            // unavailable, and a query attempt throws an exception.
            httpStatus = 13030;
        }

        if (httpStatus >= 200 && httpStatus < 300) {
            try {
                responseObject = this.createResponseObject(o, callback.argument);
                if (callback.success) {
                    if (!callback.scope) {
                        callback.success(responseObject);
                    }
                    else {
                        // If a scope property is defined, the callback will be fired from
                        // the context of the object.
                        callback.success.apply(callback.scope, [responseObject]);
                    }
                }
            }
            catch (e) { }
        }
        else {
            try {
                switch (httpStatus) {
                    // The following case labels are wininet.dll error codes that may be encountered. 
                    case 12002: // Server timeout
                    case 12029: // 12029 to 12031 correspond to dropped connections.
                    case 12030:
                    case 12031:
                    case 12152: // Connection closed by server.
                    case 13030: // See above comments for variable status.
                        responseObject = this.createExceptionObject(o.tId, callback.argument, (isAbort ? isAbort : false));
                        if (callback.failure) {
                            if (!callback.scope) {
                                callback.failure(responseObject);
                            }
                            else {
                                callback.failure.apply(callback.scope, [responseObject]);
                            }
                        }
                        break;
                    default:
                        responseObject = this.createResponseObject(o, callback.argument);
                        if (callback.failure) {
                            if (!callback.scope) {
                                callback.failure(responseObject);
                            }
                            else {
                                callback.failure.apply(callback.scope, [responseObject]);
                            }
                        }
                }
            }
            catch (e) { }
        }

        this.releaseObject(o);
        responseObject = null;
    },

    /**
    * This method evaluates the server response, creates and returns the results via
    * its properties.  Success and failure cases will differ in the response
    * object's property values.
    * @private
    * @param {object} o The connection object
    * @param {} callbackArg User-defined argument or arguments to be passed to the callback
    * @return object
    */
    createResponseObject: function(o, callbackArg) {
        var obj = {};
        var headerObj = {};

        try {
            var headerStr = o.conn.getAllResponseHeaders();
            var header = headerStr.split('\n');
            for (var i = 0; i < header.length; i++) {
                var delimitPos = header[i].indexOf(':');
                if (delimitPos != -1) {
                    headerObj[header[i].substring(0, delimitPos)] = header[i].substring(delimitPos + 2);
                }
            }
        }
        catch (e) { }

        obj.tId = o.tId;
        obj.status = o.conn.status;
        obj.statusText = o.conn.statusText;
        obj.getResponseHeader = headerObj;
        obj.getAllResponseHeaders = headerStr;
        obj.responseText = o.conn.responseText;
        obj.responseXML = o.conn.responseXML;

        if (typeof callbackArg !== undefined) {
            obj.argument = callbackArg;
        }

        return obj;
    },

    /**
    * If a transaction cannot be completed due to dropped or closed connections,
    * there may be not be enough information to build a full response object.
    * The failure callback will be fired and this specific condition can be identified
    * by a status property value of 0.
    *
    * If an abort was successful, the status property will report a value of -1.
    *
    * @private
    * @param {int} tId Transaction Id
    * @param callbackArg The user-defined arguments
    * @param isAbort Determines if the exception is an abort.
    * @return object
    */
    createExceptionObject: function(tId, callbackArg, isAbort) {
        var COMM_CODE = 0;
        var COMM_ERROR = 'communication failure';
        var ABORT_CODE = -1;
        var ABORT_ERROR = 'transaction aborted';

        var obj = {};

        obj.tId = tId;
        if (isAbort) {
            obj.status = ABORT_CODE;
            obj.statusText = ABORT_ERROR;
        }
        else {
            obj.status = COMM_CODE;
            obj.statusText = COMM_ERROR;
        }

        if (callbackArg) {
            obj.argument = callbackArg;
        }

        return obj;
    },

    /**
    * Public method that stores the custom HTTP headers for each transaction.
    * @public
    * @param {string} label The HTTP header label
    * @param {string} value The HTTP header value
    * @return void
    */
    initHeader: function(label, value) {
        if (this._http_header[label] === undefined) {
            this._http_header[label] = value;
        }
        else {
            // Concatenate multiple values, comma-delimited,
            // for the same header label,
            this._http_header[label] = value + "," + this._http_header[label];
        }

        this._has_http_headers = true;
    },

    /**
    * Accessor that sets the HTTP headers for each transaction.
    * @private
    * @param {object} o The connection object for the transaction.
    * @return void
    */
    setHeader: function(o) {
        for (var prop in this._http_header) {
            if (this._http_header.hasOwnProperty(prop)) {
                o.conn.setRequestHeader(prop, this._http_header[prop]);
            }
        }
        delete this._http_header;

        this._http_header = {};
        this._has_http_headers = false;
    },

    /**
    * This method assembles the form label and value pairs and
    * constructs an encoded string.
    * asyncRequest() will automatically initialize the
    * transaction with a HTTP header Content-Type of
    * application/x-www-form-urlencoded.
    * @public
    * @param {string || object} form id or name attribute, or form object.
    * @param {string} optional boolean to indicate SSL environment.
    * @param {string || boolean} optional qualified path of iframe resource for SSL in IE.
    * @return void
    */
    setForm: function(formId, isUpload, secureUri) {
        this._sFormData = '';
        if (typeof formId == 'string') {
            // Determine if the argument is a form id or a form name.
            // Note form name usage is deprecated by supported
            // here for legacy reasons.
            var oForm = (document.getElementById(formId) || document.forms[formId]);
        }
        else if (typeof formId == 'object') {
            // Treat argument as an HTML form object.
            var oForm = formId;
        }
        else {
            return;
        }

        // If the isUpload argument is true, setForm will call createFrame to initialize
        // an iframe as the form target.
        //
        // The argument secureURI is also required by IE in SSL environments
        // where the secureURI string is a fully qualified HTTP path, used to set the source
        // of the iframe, to a stub resource in the same domain.
        if (isUpload) {
            this.createFrame(secureUri ? secureUri : null);
            this._isFormSubmit = true;
            this._isFileUpload = true;
            this._formNode = oForm;

            return;
        }

        var oElement, oName, oValue, oDisabled;
        var hasSubmit = false;

        // Iterate over the form elements collection to construct the
        // label-value pairs.
        for (var i = 0; i < oForm.elements.length; i++) {
            oElement = oForm.elements[i];
            oDisabled = oForm.elements[i].disabled;
            oName = oForm.elements[i].name;
            oValue = oForm.elements[i].value;

            // Do not submit fields that are disabled or
            // do not have a name attribute value.
            if (!oDisabled && oName) {
                switch (oElement.type) {
                    case 'select-one':
                    case 'select-multiple':
                        for (var j = 0; j < oElement.options.length; j++) {
                            if (oElement.options[j].selected) {
                                if (window.ActiveXObject) {
                                    this._sFormData += encodeURIComponent(oName) + '=' + encodeURIComponent(oElement.options[j].attributes['value'].specified ? oElement.options[j].value : oElement.options[j].text) + '&';
                                }
                                else {
                                    this._sFormData += encodeURIComponent(oName) + '=' + encodeURIComponent(oElement.options[j].hasAttribute('value') ? oElement.options[j].value : oElement.options[j].text) + '&';
                                }

                            }
                        }
                        break;
                    case 'radio':
                    case 'checkbox':
                        if (oElement.checked) {
                            this._sFormData += encodeURIComponent(oName) + '=' + encodeURIComponent(oValue) + '&';
                        }
                        break;
                    case 'file':
                        // stub case as XMLHttpRequest will only send the file path as a string.
                    case undefined:
                        // stub case for fieldset element which returns undefined.
                    case 'reset':
                        // stub case for input type reset button.
                    case 'button':
                        // stub case for input type button elements.
                        break;
                    case 'submit':
                        if (hasSubmit == false) {
                            this._sFormData += encodeURIComponent(oName) + '=' + encodeURIComponent(oValue) + '&';
                            hasSubmit = true;
                        }
                        break;
                    default:
                        this._sFormData += encodeURIComponent(oName) + '=' + encodeURIComponent(oValue) + '&';
                        break;
                }
            }
        }

        this._isFormSubmit = true;
        this._sFormData = this._sFormData.substr(0, this._sFormData.length - 1);
    },

    /**
    * Creates an iframe to be used for form file uploads.  It is remove from the
    * document upon completion of the upload transaction.
    *
    * @private
    * @param {string} optional qualified path of iframe resource for SSL in IE.
    * @return void
    */
    createFrame: function(secureUri) {

        // IE does not allow the setting of id and name attributes as object
        // properties via createElement().  A different iframe creation
        // pattern is required for IE.
        var frameId = 'yuiIO' + this._transaction_id;
        if (window.ActiveXObject) {
            var io = document.createElement('<IFRAME id="' + frameId + '" name="' + frameId + '">');

            // IE will throw a security exception in an SSL environment if the
            // iframe source isn't set.
            if (typeof secureUri == 'boolean') {
                io.src = 'javascript:false';
            }
            else {
                io.src = secureUri;
            }
        }
        else {
            var io = document.createElement('IFRAME');
            io.id = frameId;
            io.name = frameId;
        }

        io.style.position = 'absolute';
        io.style.top = '-1000px';
        io.style.left = '-1000px';

        document.body.appendChild(io);
    },

    /**
    * Uploads HTML form, including files/attachments,  targeting the
    * iframe created in createFrame.
    *
    * @private
    * @param {int} id The transaction id.
    * @param {object} callback - User-defined callback object.
    * @param {string} uri Fully qualified path of resource.
    * @return void
    */
    uploadFile: function(id, callback, uri) {

        var frameId = 'yuiIO' + id;
        var io = document.getElementById(frameId);

        // Initialize the HTML form properties in case they are
        // not defined in the HTML form.
        this._formNode.action = uri;
        this._formNode.enctype = 'multipart/form-data';
        this._formNode.method = 'POST';
        this._formNode.target = frameId;
        this._formNode.submit();

        // Reset form status properties.
        this._formNode = null;
        this._isFileUpload = false;
        this._isFormSubmit = false;

        // Create the upload callback handler that fires when the iframe
        // receives the load event.  Subsequently, the event handler is detached
        // and the iframe removed from the document.

        var uploadCallback = function() {
            var obj = {};

            obj.tId = id;
            obj.responseText = io.contentWindow.document.body ? io.contentWindow.document.body.innerHTML : null;
            obj.responseXML = io.contentWindow.document.XMLDocument ? io.contentWindow.document.XMLDocument : io.contentWindow.document;
            obj.argument = callback.argument;

            if (callback.upload) {
                if (!callback.scope) {
                    callback.upload(obj);
                }
                else {
                    callback.upload.apply(callback.scope, [obj]);
                }
            }

            if (YAHOO.util.Event) {
                YAHOO.util.Event.removeListener(io, "load", uploadCallback);
            }
            else if (window.ActiveXObject) {
                io.detachEvent('onload', uploadCallback);
            }
            else {
                io.removeEventListener('load', uploadCallback, false);
            }
            setTimeout(function() { document.body.removeChild(io); }, 100);
        };


        // Bind the onload handler to the iframe to detect the file upload response.
        if (YAHOO.util.Event) {
            YAHOO.util.Event.addListener(io, "load", uploadCallback);
        }
        else if (window.ActiveXObject) {
            io.attachEvent('onload', uploadCallback);
        }
        else {
            io.addEventListener('load', uploadCallback, false);
        }
    },

    /**
    * Public method to terminate a transaction, if it has not reached readyState 4.
    * @public
    * @param {object} o The connection object returned by asyncRequest.
    * @param {object} callback  User-defined callback object.
    * @param {string} isTimeout boolean to indicate if abort was a timeout.
    * @return void
    */
    abort: function(o, callback, isTimeout) {
        if (this.isCallInProgress(o)) {
            o.conn.abort();
            window.clearInterval(this._poll[o.tId]);
            delete this._poll[o.tId];
            if (isTimeout) {
                delete this._timeOut[o.tId];
            }

            this.handleTransactionResponse(o, callback, true);

            return true;
        }
        else {
            return false;
        }
    },

    /**
    * Public method to check if the transaction is still being processed.
    * @public
    * @param {object} o The connection object returned by asyncRequest
    * @return boolean
    */
    isCallInProgress: function(o) {
        // if the XHR object assigned to the transaction has not been dereferenced,
        // then check its readyState status.  Otherwise, return false.
        if (o.conn) {
            return o.conn.readyState != 4 && o.conn.readyState != 0;
        }
        else {
            //The XHR object has been destroyed.
            return false;
        }
    },

    /**
    * Dereference the XHR instance and the connection object after the transaction is completed.
    * @private
    * @param {object} o The connection object
    * @return void
    */
    releaseObject: function(o) {
        //dereference the XHR instance.
        o.conn = null;
        //dereference the connection object.
        o = null;
    }
};