/*******************************************************************************
                             Gentle Anchors v1.1
********************************************************************************
* Author: Kendall Conrad of Angelwatt.com
* Home Page: http://www.angelwatt.com/coding/gentle_anchors.php
* Created: 2008-06-25
* Updated: 2008-06-27
* Description: Gentle Anchors is a page scrolling script for anchor and area
tags on a page.
* License:
  This work is licensed under a Creative Commons Attribution-Share Alike
  3.0 United States License 
  http://creativecommons.org/licenses/by-sa/3.0/us/
*******************************************************************************/
Gentle_Anchors = function() {
  //#### Script preferences ####
  //   Recommended Speed Range: 5 to 40 (fast to slow) default value 15
  var scrollSpeed  = 20;     // Controls speed of scroll:
  var shine        = true;   // Whether to use shine ffect
  var shineColor   = '#dd9'; // Background color for shine
  var shineOutline = '#5f5'; // Outline color for shine; transparent for off
  //#### End script preferences ####
  var timer;      // Timer item
  var elt = null; // the current clicked on element

  // Initialization, grabbing all anchors and adding onclick event
  Init = function() {
    var a = document.getElementsByTagName('a'); // got catch'em all!
    var area = document.getElementsByTagName('area');
    var links = new Array(); // combine NodeLists together
    for (var x=0, y=a.length;    x < y; links.push(a[x]), x++);
    for (var x=0, y=area.length; x < y; links.push(area[x]), x++);
    for (var x=0, l=links.length; x < l; x++) {
      if (links[x].href.match(/#[a-zA-Z0-9:\._-]+/)) {
        links[x].onclick = function() { var s = Setup(this.href); return s; };
      }
    }
  };
  // Set things up for the scrolling effect
  Setup = function(href) {
    var hash = href.match(/#([^\?]+)/)[1]; // get id, but not any query string
    // identify destination element
    if (document.getElementById(hash)) { elt=document.getElementById(hash); }
    else { return true; }
    // Find scroll position to destination
    var dest = elt.offsetTop;
    for (var node=elt; node.offsetParent && node.offsetParent != document.body;
         node = node.offsetParent, dest += node.offsetTop);
    // fix for stupid IE
    if (navigator.appName.indexOf("Microsoft") != -1
        && parseFloat(navigator.appVersion.split("MSIE")[1]) < 8.0)
    { dest = elt.offsetTop; }
    clearTimeout(timer);
    var start = window.pageYOffset
      || document.documentElement.scrollTop
      || document.body.scrollTop;
    // fix for back button
    location.hash = hash;     // jump to destination
    window.scrollTo(0,start); // then quickly jump back to scroll the distance
    var speed = parseInt(Math.abs(start-dest) / scrollSpeed);
    Scroll(speed, dest-10); // minus 10 for padding
    return false;
  };
  Scroll = function(step, desty) {
    was = window.pageYOffset
      || document.documentElement.scrollTop
      || document.body.scrollTop;
    // find out how much to scroll by up/down
    var amt = (was < desty) ? was + step : was - step; 
    window.scrollTo(0, amt);
    now = window.pageYOffset
      || document.documentElement.scrollTop
      || document.body.scrollTop;
    // slow scroll down as approach
    if (Math.abs(now-desty) < 1) { step = 1; }
    else if (Math.abs(now-desty) < step*2) { step *= .6; }
    else if (Math.abs(now-desty) < step*6) { step *= .9; }
    // if we're at the right scroll position
    if (was == now) {
      window.scrollTo(0, desty);
      clearTimeout(timer); // clear interval
      if (shine) { setTimeout(function(){ ShineOn(); }, 400); }
      return;
    }
    timer = setTimeout(function(){ Scroll(step, desty) }, 30);
  };
  ShineOn = function() {
    var c = elt.style.backgroundColor;
    var o = elt.style.outline;
    elt.style.backgroundColor = shineColor;
    elt.style.outline = '1px solid '+shineOutline;
    setTimeout( function() { ShineOff(c,o); }, 1000 );
  };
  ShineOff = function(oldColor, oldOutline) {
    elt.style.backgroundColor = oldColor;
    elt.style.outline = oldOutline;
  };
  // Classic append for onload event to avoid overriding
  function AppendOnLoad(fx) { 
    var old = window.onload;
    if (typeof old != 'function') { window.onload = fx; }
    else { window.onload = function() { old(); fx(); }; }
  }
  AppendOnLoad(Init);
}();