// ==UserScript==
// @name        ArtInt Navigator
// @namespace   gorn/aiNav
// @description Enables back and forth navigation using the arrow keys on AI book webpage
// @include     http://artint.info/html/ArtInt_*.html
// @version     1
// @grant       none
// ==/UserScript==

var base = "http://artint.info/html/ArtInt_";
var end = ".html"

function getNumber()
{
  var url = document.URL;
  var number = parseInt(url.match("[0-9]+"));
  return number;
}

document.onkeydown = function(evt) {
    evt = evt || window.event;
    switch (evt.keyCode) {
        case 37:
            newUrl = base + (getNumber() - 1) + end;
            document.location.href = newUrl;
            break;
        case 39:
            newUrl = base + (getNumber() + 1) + end;
            document.location.href = newUrl;
            break;
    }
};