//application/x-www-form-urlencoded
function QueryString(query) {
    var qs = {};
    
    this.set = function(n, v) {
        qs[n.toLowerCase()] = v.toString();
        return this;
    };
    
    this.get = function(n) {
        return qs[n.toLowerCase()];
    };

    this.fromString = function(s) {
        var nvps = s.split('&');
        for (i = 0; i < nvps.length; i++) {
            var nvp = nvps[i].split('=');
            if (!nvp[0]) continue;
            this.set(nvp[0], (nvp.length > 1) ? unescape(nvp[1].replace('+', ' ')) : '');
        }
        return this;
    };
 
    this.toObject = function() {
        return qs;
    };
 
    this.toString = function(opt) {
        opt = opt || {};
        var s = '';
        for (q in qs)
            s += (
                (opt.toCase == "upper" ? q.toUpperCase() : q)
                + '='
                + escape(qs[q].replace(' ', '+'))
                + '&'
            );
        return s.slice(0, -1);
    };
    
    this.toUpperCaseString = function() {
        return this.toString({ toCase: "upper" });
    };
    
    this.applyTo = function(s, opt) {
        return s.split('?')[0] + '?' + this.toString(opt);
    };
    
    this.applyUpperCaseTo = function(s) {
        return this.applyTo(s, { toCase: "upper" });
    };
    
    //Parse passed querystring parameter if present.
    if (!query) return;
    if (query.constructor === Object)
        for (q in query)
            this.set(query, query[q]);
    else
        if (query.constructor === String)
            this.fromString((query.indexOf('?') > -1) ? query.split('?')[1] : query);
        else
            throw new Error("Unsupported querystring type.");
};