// Ajax

var HTTP = {};		// first create our HTTP namespace

// This is a list of XMLHttpRequest creation factory functions to try
HTTP._factories = [
    function() { return new XMLHttpRequest(); },
    function() { return new ActiveXObject("Msxml2.XMLHTTP"); },
    function() { return new ActiveXObject("Microsoft.XMLHTTP"); }
];

// When we find a factory that works, store it here
HTTP._factory = null;

// Create and return a new XMLHttpRequest object.
// 
// The first time we're called, try the list of factory functions until
// we find one that returns a nonnull value and does not throw an
// exception.  Once we find a working factory, remember it for later use.
//
HTTP.newRequest = function() {
    if (HTTP._factory != null) return HTTP._factory();

    for(var i = 0; i < HTTP._factories.length; i++) {
        try {
            var factory = HTTP._factories[i];
            var request = factory();
            if (request != null) {
                HTTP._factory = factory;
									// debugText ("Got response factory", 1);
                return request;
            }
        }
        catch(e) {
            continue;
        }
    }

    // If we get here, none of the factory candidates succeeded,
    // so throw an exception now and for all future calls.
    HTTP._factory = function() {
        throw new Error("XMLHttpRequest not supported");
    }
    HTTP._factory(); // Throw an error
}


/**
 * Use XMLHttpRequest to fetch the contents of the specified URL using
 * an HTTP GET request.  When the response arrives, pass it (as plain
 * text) to the specified callback function.
 * 
 * This function does not block and has no return value.
 -- DH mod: add extra parameters for optional use
 */
HTTP.getText = function(url, callback, param1, param2) {
    var request = HTTP.newRequest();
    request.onreadystatechange = function() {
        if (request.readyState == 4 && request.status == 200)
					if (callback)
            callback(request.responseText, param1, param2);
    }
    request.open("GET", url);
    request.send(null);
};

/**
 * Send an HTTP POST request to the specified URL, using the names and values
 * of the properties of the values object as the body of the request.
 * Parse the server's response according to its content type and pass
 * the resulting value to the callback function.  If an HTTP error occurs,
 * call the specified errorHandler function, or pass null to the callback
 * if no error handler is specified.
 **/
HTTP.post = function(url, values, callback, errorHandler) {
    var request = HTTP.newRequest();
    request.onreadystatechange = function() {
        if (request.readyState == 4) {
            if (request.status == 200) {
                callback(HTTP._getResponse(request));
            }
            else {
                if (errorHandler) errorHandler(request.status,
                                               request.statusText);
                else callback(null);
            }
        }
    }

    request.open("POST", url);
    // This header tells the server how to interpret the body of the request
    request.setRequestHeader("Content-Type",
                             "application/x-www-form-urlencoded");
    // Encode the properties of the values object and send them as
    // the body of the request.
    request.send(HTTP.encodeFormData(values));
};

/**
 * Encode the property name/value pairs of an object as if they were from
 * an HTML form, using application/x-www-form-urlencoded format
 */
HTTP.encodeFormData = function(data) {
    var pairs = [];
    var regexp = /%20/g; // A regular expression to match an encoded space

    for(var name in data) {
        var value = data[name].toString();
														// debugText (name + '=' + value, 1);
        // Create a name/value pair, but encode name and value first
        // The global function encodeURIComponent does almost what we want,
        // but it encodes spaces as %20 instead of as "+". We have to
        // fix that with String.replace()
        var pair = encodeURIComponent(name).replace(regexp,"+") + '=' +
            encodeURIComponent(value).replace(regexp,"+");
        pairs.push(pair);
    }

    // Concatenate all the name/value pairs, separating them with &
    return pairs.join('&');
};

/**
 * Parse an HTTP response based on its Content-Type header
 * and return the parsed object
 */
HTTP._getResponse = function(request) {
    // Check the content type returned by the server
    switch(request.getResponseHeader("Content-Type")) {
    case "text/xml":
        // If it is an XML document, use the parsed Document object
        return request.responseXML;

    case "text/json":
    case "application/json": 
    case "text/javascript":
    case "application/javascript":
    case "application/x-javascript":
        // If the response is JavaScript code, or a JSON-encoded value,
        // call eval() on the text to "parse" it to a JavaScript value.
        // Note: only do this if the JavaScript code is from a trusted server!
        return eval(request.responseText);

    default:
        // Otherwise, treat the response as plain text and return as a string
        return request.responseText;
    }
};

// ----------------------------------------------------------------------------------- Dan's code

HTTP.encodeFormElements = function(f) {
		var els = f.elements;
		var res = '';
		var doit;
		for (var i = 0; i < els.length; i++) {
			e = els[i];
			doit = false;
			if (e.type=="radio" || e.type=="checkbox") {
				if (e.checked)
					doit = true;
			}
			else if (e.type!="button")
				doit = true;
			if (doit && (res > ''))
				res += '&';
			if (doit)
				res += e.name + '=' + e.value;
			res = res.replace(/ /g, "+");
		}
		return res;
};

HTTP.get = function(url, values, callback, errorHandler) {
    var request = HTTP.newRequest();
    request.onreadystatechange = function() {
				// debugText ("readyState: " + request.readyState, 1);
        if (request.readyState == 4) {
            if (request.status == 200) {
								// debugText ("readyState: " + request.readyState + ", status: " + request.status, 1);
							if (callback)
                callback(HTTP._getResponse(request));
            }
            else {
                if (errorHandler) errorHandler(request.status,
                                               request.statusText);
                else alert(request.status + ': ' + request.statusText);
            }
        }
    }

		var target = url;
		if (values)
			target += '?' + values;
    request.open("GET", target);
    // This header tells the server how to interpret the body of the request
    // request.setRequestHeader("Content-Type",
    //                         "application/x-www-form-urlencoded");
    // Encode the properties of the values object and send them as
    // the body of the request.
		// debugText ("sending request", 1);
    // request.send(values);
		request.send(null);
		// debugText ("sent request", 1);
};