/*
url-loading object and a request queue built on top of it
*/

/* namespacing object */
var net = new Object();

net.READY_STATE_UNINITIALIZED	= 0;
net.READY_STATE_LOADING 		= 1;
net.READY_STATE_LOADED 			= 2;
net.READY_STATE_INTERACTIVE 	= 3;
net.READY_STATE_COMPLETE 		= 4;


/*--- content loader object for cross-browser requests ---*/
net.ContentLoader = function(url, onload, onerror, params, method, contentType) {
    this.req = null;
    net.currentLoader = this;
    this.onload = onload;
    this.onerror = (onerror) ? onerror : this.defaultError;
	this.method = (method) ? method : "POST";
    this.loadXMLDoc(url, params, contentType);
}

net.ContentLoader.prototype.loadXMLDoc = function(url, params, contentType) {
    if (!contentType && this.method == "POST") { contentType = 'application/x-www-form-urlencoded'; }
	
	if (window.XMLHttpRequest) {
        this.req = new XMLHttpRequest();
    } else if (window.ActiveXObject) {
		try {
			this.req = new ActiveXObject("MSXML2.XMLHTTP");
		} catch (err) {
			this.req = new ActiveXObject("Microsoft.XMLHTTP");
		}
	}
	
    if (this.req) {
        try {
            var loader = this;
			
			if(typeof(net) != "undefined") {
            	this.req.onreadystatechange = function() { net.ContentLoader.onReadyState.call(loader); }
			}
			
            this.req.open(this.method, url, true);
            if (contentType) { this.req.setRequestHeader('Content-Type', contentType); }
            this.req.send(params);
        } catch (err) {
            this.onerror.call(this);
        }
    }
}


net.ContentLoader.onReadyState = function() {
    var req = this.req;
    var ready = req.readyState;
    if (ready == net.READY_STATE_COMPLETE) {
        var httpStatus = req.status;
        if (httpStatus == 200 || httpStatus == 0) {
            this.onload.call(this);
        } else {
            this.onerror.call(this);
        }
    }
}

net.ContentLoader.prototype.defaultError = function() {
	alert("error fetching data!"
            + "\n\nreadyState:" + this.req.readyState
            + "\nstatus: " + this.req.status
            + "\nheaders: " + this.req.getAllResponseHeaders());
}