$(function() {
    $("#title")
        .click(function() {
            getDefinition("pandora");
        });
    $(".menu")
        .click(function() {
            var $this = $(this);
            $(".menu").removeClass("selected");
            $this.addClass("selected");
        })
    var hash = getHash(),
        history = new History(),
        terms = {},
        $back = $("#back"),
        $forward = $("#forward"),
        $definition = $("#definition");
    history.add(hash);
    getDefinition(hash);
    function getDefinition(term) {
        var terms = history.get();
        $back.empty();
        $forward.empty();
        $definition.empty();
        terms.back && $back.append("&lt;&nbsp; <a class=\"back\" href=\"#" + terms.back + "\">" + toTitleCase(terms.back) + "</a>");
        terms.forward && $forward.append("<a class=\"forward\" href=\"#" + terms.forward + "\">" + toTitleCase(terms.forward) + "</a> &nbsp;&gt;");
        $.get("html/" + term + ".html", function(data) {
            $definition.html(data);
            $("#main a").click(function() {
                if($(this).attr("href").substr(0, 4) == 'http')
                  return;
                var term = $(this).attr("href").substr(1);
                if (term == terms.back) {
                    history.back();
                } else if (term == terms.forward) {
                    history.forward();
                } else {
                    history.add(term);
                }
                getDefinition(term);
            });
        });
    }
    function getHash() {
        return window.location.hash.substr(1) || "pandora";
    }
    function toTitleCase(str) {
        return str.substr(0, 1).toUpperCase() + str.substr(1);
    }
    function History() {
        var items = [],
            position = -1;
        return {
            add: function(item) {
                position++;
                items.splice(position, items.length - position, item);
            },
            back: function() {
                position > 0 && position--;
            },
            forward: function() {
                position < items.length - 1 && position++;
            },
            get: function() {
                return {
                    back: items[position - 1] || "",
                    forward: items[position + 1] || ""
                }
            }
        };
    }
    window.onhashchange = function() {
      var hash = getHash();
      //history.add(hash);
      getDefinition(hash);
    }
});