/*
 * Copyright 2006 SitePoint Pty. Ltd, www.sitepoint.com
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS;
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
*/

function Ajax()
{
    this.req = null;
    this.url = null;
    this.status = null;
    this.statusText = '';
    this.method = 'GET';
    this.async = true;
    this.dataPayload = null;
    this.readyState = null;
    this.responseText = null;
    this.responseXML = null;
    this.handleResp = null;
    this.responseFormat = 'text'; // 'text', 'xml', 'object'
    this.mimeType = null;
    this.headers = [];

    this.init = function() {
        var i = 0;
        var reqTry = [
            function() { return new XMLHttpRequest(); },
            function() { return new ActiveXObject('Msxml2.XMLHTTP') },
            function() { return new ActiveXObject('Microsoft.XMLHTTP' )} ];

        while (!this.req && (i < reqTry.length)) {
            try {
                this.req = reqTry[i++]();
            }
            catch(e) {}
        }
        return true;
    };

    this.doGet = function(url, hand, format) {
        this.url = url;
        this.handleResp = hand;
        this.responseFormat = format || 'text';
        this.doReq();
    };

    this.doPost = function(url, dataPayload, hand, format) {
        this.url = url;
        this.dataPayload = dataPayload;
        this.handleResp = hand;
        this.responseFormat = format || 'text';
        this.method = 'POST';
        this.doReq();
    };

    this.doReq = function()
    {
        var self = null;
        var req = null;

        if (!this.init()) {
            alert('Could not create XMLHttpRequest object.');
            return;
        }

        req = this.req;

        req.open(this.method, this.url, this.async);

        if (this.method == "POST") {
            this.req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
        }

        if (this.method == 'POST') {
            req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
        }

        self = this;

        req.onreadystatechange = function()
        {
            var resp = null;

            self.readyState = req.readyState;

            if (req.readyState == 4)
            {
                self.status = req.status;
                self.statusText = req.statusText;
                self.responseText = req.responseText;
                self.responseXML = req.responseXML;

                switch(self.responseFormat)
                {
                    case 'text':
                    resp = self.responseText;
                        break;
                    case 'xml':
                    resp = self.responseXML;
                        break;
                    case 'object':
                    resp = req;
                        break;
                }

                if (self.status > 199 && self.status < 300)
                {
                    if (!self.handleResp)
                    {
                        alert('No response handler defined ' +
                        'for this XMLHttpRequest object.');
                        return;
                    }
                    else
                    {
                        self.handleResp(resp);
                    }
                }
                else
                {
                    self.handleErr(resp);
                }

            }
            
        }
        req.send(this.dataPayload);
    };

    this.abort = function() {
        if (this.req) {
            this.req.onreadystatechange = function() { };
            this.req.abort();
            this.req = null;
        }
    };

    this.handleErr = function() {
        var errorWin;
        // Create new window and display error
        try {
            errorWin = window.open('', 'errorWin');
            errorWin.document.body.innerHTML = this.responseText;
        }
        // If pop-up gets blocked, inform user
        catch(e) {
            alert('An error occurred, but the error message cannot be' +
            ' displayed because of your browser\'s pop-up blocker.\n' +
            'Please allow pop-ups from this Web site.');
        }
    };

    this.setMimeType = function(mimeType) {
        this.mimeType = mimeType;
    };

    this.setHandlerResp = function(funcRef) {
        this.handleResp = funcRef;
    };

    this.setHandlerErr = function(funcRef) {
        this.handleErr = funcRef;
    };

    this.setHandlerBoth = function(funcRef) {
        this.handleResp = funcRef;
        this.handleErr = funcRef;
    };

    this.setRequestHeader = function(headerName, headerValue) {
        this.headers.push(headerName + ': ' + headerValue);
    };

}