// ==UserScript==
// @name    TopAndDownButtonsEverywhere
// @description Top and Down buttons everywhere (no Jquery) 
// @version 1.0
// @author  Max Max
// @license MIT
// @include *
// @run-at  document-end
// @grant   none
// ==/UserScript==

// [1] skip all iframe 
if (window.self!=window.top) {return}

// add style
function addStyle(css) {
    var head = document.head || document.getElementsByTagName('head')[0];
    if (head) {
        var style = document.createElement("style");
        style.type = "text/css";
        style.appendChild(document.createTextNode(css));
        head.appendChild(style);
    } // end if
} // end of function

// create element
function ce(n) { return document.createElement(n); } // end of function

// global
var position, 
// scroll element
el, 
// timer
t1, t2,
// speed by
speed_by_click = 500,
speed_by_over = 100;

// move up
function move_up() { 
    position = document.documentElement.scrollTop || document.body.scrollTop;
    window.scrollTo(0, position-35);
    t1 = setTimeout(move_up, speed_by_over);
} // end of function

// move downn
function move_dn() { 
    position = document.documentElement.scrollTop || document.body.scrollTop;
    window.scrollTo(0, position+35);
    t2 = setTimeout(move_dn, speed_by_over);
} // end of function

// document height
function getDocumentHeight() {
    return (document.body.scrollHeight > document.body.offsetHeight)?document.body.scrollHeight:document.body.offsetHeight;
} // end of function

// document scroll
function get_scroll(a) {
   var d = document,
        b = d.body,
        e = d.documentElement,
        c = "client" + a;
        a = "scroll" + a;
    return /CSS/.test(d.compatMode)? (e[c]< e[a]) : (b[c]< b[a])
} // end of function




function scrollTo(element, to, duration) {
    var start = element.scrollTop,
        change = to - start,
        currentTime = 0,
        increment = 20;

    var animateScroll = function(){        
        currentTime += increment;
        var val = Math.easeInOutQuad(currentTime, start, change, duration);                        
        element.scrollTop = val; 
        if(currentTime < duration) {
            setTimeout(animateScroll, increment);
        }
    };
    animateScroll();
} // end of function

//t = current time
//b = start value
//c = change in value
//d = duration
Math.easeInOutQuad = function (t, b, c, d) {
    t /= d/2;
    if (t < 1) return c/2*t*t + b;
    t--;
    return -c/2 * (t*(t-2) - 1) + b;
};

function create_btn_element() { 
    // get scroll
    var up, dn, scrolled,
        h = get_scroll('Height');
    // exit
    if(!h) { 
        dn.style.display = "none";
        return;
    } // end if
    
    // add css
    shareCSS(); 

    if(document.body){ 
        // create DOM element
        up = ce('span');
        dn = ce('span');
        // set attribute
        up.setAttribute('id','play_btn_up');
        dn.setAttribute('id','play_btn_dn');
        // set class
        up.className = "play_btn";
        dn.className = "play_btn";
        
        // append element
        document.body.appendChild(up);
        document.body.appendChild(dn);
        
        // scroll
        scrolled = window.pageYOffset || document.documentElement.scrollTop;
        // if scroll 
        if(scrolled){ 
            up.style.display = "";
        } else {
            up.style.display = "none";
        } // end if
        
        // userAgent 
        if (navigator.userAgent.toLowerCase().indexOf('firefox') > -1) {
           el = document.documentElement; 
        } else {
           el = document.body; 
        } // end if
        
        // add event over
        up.addEventListener('mouseover', move_up, false);
        dn.addEventListener('mouseover', move_dn, false);
        // add event out
        up.addEventListener('mouseout', function(){clearTimeout(t1);},false);
        dn.addEventListener('mouseout', function(){clearTimeout(t2);},false);
        // add event click
        up.addEventListener('click', function(){ scrollTo(el, 0, speed_by_click); }, false);
        dn.addEventListener('click', function(){ scrollTo(el, getDocumentHeight(), speed_by_click); }, false);
        
        // add event scroll
        window.onscroll = function() { 
            var scrolled = window.pageYOffset || document.documentElement.scrollTop;
            // if scroll 
            if(scrolled){
                up.style.display = "";
            } else{
                up.style.display = "none";
            } // end if
        }; // end of function
    } // end if
} // end of function

// add css
function shareCSS(){ 
    // variables
    var s='', img_up, img_dn; 
    
    // img vs button
    img_up = 'data:img/png;base64,iVBORw0KGgoAAAANSUhEUgAAABIAAAAUCAYAAACAl21KAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAB+SURBVDhPY1i1atV/amAGahgCMoNhaIGlS5cKAp19BoRBbLJcj2QILDJINwzoAmMgfoclIkBixkS5DI8hMJcRNgxoSBoOl6CnNZBhaVhdBjWE1MSJahjQkA4KEmYH2GUrV66cSYEhYB+AzKBtFiHkQqKiH6Ro1CDCQTWgYQQAs81DU0G/83sAAAAASUVORK5CYII=';
    img_dn = 'data:img/png;base64,iVBORw0KGgoAAAANSUhEUgAAABIAAAAUCAYAAACAl21KAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAACPSURBVDhPY2DAAlatWvUfH8amB6vYqEGEg2pgw4iQ7cTKM6xcuXImsYpxqQOZAQ4woIIOCgzrQAl1oEFpZBiWhitFgwx7R4SBIDXYDYGZDFRgTMAwkCHGhBMRJMxwGUa8ITCbli5dKgg08AySN8+AxIhyCboiJMPIN4Qsm6miiYioxltawvSDYogohYTUAQC80UNTOht/YwAAAABJRU5ErkJggg==';
    // button id
    s+='#play_btn_up { position:fixed; right:0; bottom:53%;z-index:99; height:36px; width:36px; cursor:pointer; background:url('+img_up+') no-repeat scroll 50% 50% rgba(0, 0, 0, 0.7); border-radius:5px 0 0 5px; margin-top:-24px; }'; 
    s+='#play_btn_dn { position:fixed; right:0; top:53%;   z-index:99; height:36px; width:36px; cursor:pointer; background:url('+img_dn+') no-repeat scroll 50% 50% rgba(0, 0, 0, 0.7); border-radius:5px 0 0 5px; margin-top:-24px; }'; 
    // button class
    s+='.play_btn { -moz-transition-duration:0.2s; opacity:0.65; }'; 
    s+='.play_btn:hover { opacity:1; }'; 
    // append
    addStyle(''+s);
} // end of function

// run it
create_btn_element();