var net = {};

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, method, params, contentType) {
    this.req = null;
    this.onload = onload;
    this.onerror = (onerror) ? onerror: this.defaultError;
    this.loadXMLDoc(url, method, params, contentType);
};

net.ContentLoader.prototype = {
loadXMLDoc: function(url, method, params, contentType) {
    if (!method) {
        method = "GET";
    }
    if (!contentType && method == "POST") {
        contentType = 'application/x-www-form-urlencoded';
    }
    if (window.XMLHttpRequest) {
        this.req = new XMLHttpRequest();
    } else if (window.ActiveXObject) {
        this.req = new ActiveXObject("Microsoft.XMLHTTP");
    }
    if (this.req) {
        try {
            var loader = this;
            this.req.onreadystatechange = function() {
                loader.onReadyState.call(loader);
            };
            this.req.open(method, url, true);
            if (contentType) {
                this.req.setRequestHeader('Content-Type', contentType);
            }
            this.req.send(params);
        } catch(err) {
            this.onerror.call(this);
        }
    }
},
    
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);
        }
    }
},
    
defaultError: function() {
    alert("error fetching data!" + "\n\nreadyState:" + this.req.readyState + "\nstatus: " + this.req.status + "\nheaders: " + this.req.getAllResponseHeaders());
}
};



/*--- queue system for efficient transfer of many small commands in a single request ---*/
net.cmdQueues = [];


net.CommandQueue = function(id, url, onUpdate, freq) {
    this.id = id;
    net.cmdQueues[id] = this;
    this.url = url;
    this.queued = [];
    this.sent = [];
    this.onUpdate = onUpdate;
    if (freq) {
        this.repeat(freq);
    }
    this.lastUpdateTime = 0;
};

net.CommandQueue.STATUS_QUEUED = -1;
net.CommandQueue.STATE_UNINITIALIZED = net.READY_STATE_UNINITIALIZED;
net.CommandQueue.STATE_LOADING = net.READY_STATE_LOADING;
net.CommandQueue.STATE_LOADED = net.READY_STATE_LOADED;
net.CommandQueue.STATE_INTERACTIVE = net.READY_STATE_INTERACTIVE;
net.CommandQueue.STATE_COMPLETE = net.READY_STATE_COMPLETE;
net.CommandQueue.STATE_PROCESSED = 5;

net.CommandQueue.PRIORITY_NORMAL = 0;
net.CommandQueue.PRIORITY_IMMEDIATE = 1;


net.CommandQueue.prototype = {
addCommand: function(command) {
    if (this.isCommand(command)) {
        this.queue.append(command, true);
        if (command.priority == net.CommandQueue.PRIORITY_IMMEDIATE) {
            this.fireRequest();
        }
    }
},
    
fireRequest: function() {
    if (!this.onUpdate && this.queued.length === 0) {
        return;
    }
    var data = "lastUpdate=" + this.lastUpdateTime + "&data=";
    for (var i = 0; i < this.queued.length; i++) {
        var cmd = this.queued[i];
        if (this.isCommand(cmd)) {
            data += cmd.toRequestString();
            this.sent[cmd.id] = cmd;
        }
    }
    this.queued = [];
    this.loader = new net.ContentLoader(
                                        this.url,
                                        net.CommandQueue.onload,
                                        net.CommandQueue.onerror,
                                        "POST", data
                                        );
},
    
isCommand: function(obj) {
    return (obj.implementsProp("id") && obj.implementsProp("priority") && obj.implementsFunc("toRequestString") && obj.implementsFunc("parseResponse"));
},
    
repeat: function(freq) {
    this.unrepeat();
    if (freq > 0) {
        this.freq = freq;
        var cmd = "net.cmdQueues[" + this.id + "].fireRequest()";
        this.repeater = setInterval(cmd, freq * 1000);
    }
},
    
unrepeat: function() {
    if (this.repeater) {
        clearInterval(this.repeater);
    }
    this.repeater = null;
}
};

net.CommandQueue.onload = function() {
    var xmlDoc = this.req.responseXML;
    var elDocRoot = xmlDoc.getElementsByTagName("responses")[0];
    var lastUpdate = elDocRoot.attributes.getNamedItem("updateTime");
    if (parseInt(lastUpdate, 10) > this.lastUpdateTime) {
        this.lastUpdateTime = lastUpdate;
    }
    if (elDocRoot) {
        for (i = 0; i < elDocRoot.childNodes.length; i++) {
            elChild = elDocRoot.childNodes[i];
            if (elChild.nodeName == "command") {
                var attrs = elChild.attributes;
                var id = attrs.getNamedItem("id").value;
                var command = net.commandQueue.sent[id];
                if (command) {
                    command.parseResponse(elChild);
                }
            } else if (elChild.nodeName == "update") {
                if (this.implementsFunc("onUpdate")) {
                    this.onUpdate.call(this, elChild);
                }
            }
        }
    }
};

net.CommandQueue.onerror = function() {
    alert("problem sending the data to the server");
};