/*mhttp.js*/

/* mhttp.js */
/**
 * http.js: utilities for scripted HTTP requests
 *
 * From the book JavaScript: The Definitive Guide, 5th Edition,
 * by David Flanagan. Copyright 2006 O'Reilly Media, Inc. (ISBN: 0596101996)
 */

// Make sure we haven't already been loaded
var HTTPlite;
if (HTTPlite && (typeof HTTPlite != "object" || HTTPlite.NAME))
{
    throw new Error("Namespace 'HTTPlite' already exists");
}

// Create our namespace, and specify some meta-information
HTTPlite = {};
HTTPlite.NAME = "HTTPlite";    // The name of this namespace
HTTPlite.VERSION = 1.0;    // The version of this namespace

// This is a list of XMLHttpRequest creation factory functions to try
HTTPlite._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
HTTPlite._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.
 */
HTTPlite.newRequest = function() {
    if (HTTPlite._factory != null) {return HTTPlite._factory();}

    for(var i = 0; i < HTTPlite._factories.length; i++) {
        try {
            var factory = HTTPlite._factories[i];
            var request = factory();
            if (request != null) {
                HTTPlite._factory = factory;
                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.
    HTTPlite._factory = function() {
        throw new Error("XMLHttpRequest not supported");
    };
    HTTPlite._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.
 */
HTTPlite.getText = function(url, callback, errorHandler) {
    var request = HTTPlite.newRequest();
    request.onreadystatechange = function() {
        if (request.readyState == 4)
        {
            if (request.status == 200)
            {
                callback(request.responseText);
            }
            else
            {
                if (errorHandler) {errorHandler(request.status, request.statusText);}
                else {callback(null);}
            }
        }
    };
    request.open("GET", url);
    request.send(null);
    return request;
};