/*

   DHTML PNG Snowstorm! OO-style Jascript-based Snow effect

   --------------------------------------------------------

   Version 1.3.20081215 (Previous rev: v1.2.20041121a)

   Dependencies: GIF/PNG images (0 through 4.gif/png)

   Code by Scott Schiller - http://schillmania.com

   --------------------------------------------------------

   Description:

  

   Initializes after body onload() by default (via addEventHandler() call at bottom.)

  

   Properties:

  

   usePNG

   ---------------

   Enables PNG images if supported ("false" falls back to GIF)

  

   flakeTypes

   ---------------

   Sets the range of flake images to use (eg. a value of 5

   will use images ranging from 0.png to 4.png.)

  

   flakesMax

   ---------------

   Sets the maximum number of snowflakes that can exist on

   the screen at any given time.

   

   flakesMaxActive

   ---------------

   Sets the limit of "falling" snowflakes (ie. moving, thus

   considered to be "active".)

  

   vMax

   ---------------

   Defines the maximum X and Y velocities for the storm.

   A range up to this value is selected at random.

  

   flakeWidth

   ---------------

   The width (in pixels) of each snowflake image.

  

   flakeHeight

   ---------------

   Height (pixels) of each snowflake image.

   

   flakeBottom

   ---------------

   Limits the "bottom" coordinate of the snow.



   snowStick

   ---------------

   Allows the snow to "stick" to the bottom of the window.

   When off, snow will never sit at the bottom.

  

   snowCollect

   ---------------

   Enables snow to pile up (slowly) at bottom of window.

   Can be very CPU/resource-intensive over time.

   Also requires snowStick = true.



   followMouse

   ---------------

   Allow the mouse to affect the "wind", left-to-right.



*/



var snowStorm = null;



function SnowStorm() {



  // PROPERTIES

  // ------------------



  var imagePath = 'snowstorm/image/snow/'; // relative path to snow images (including trailing slash)

  var flakesMax = 128;

  var flakesMaxActive = 64;

  var vMaxX = 3;

  var vMaxY = 2;

  var usePNG = true;

  var flakeBottom = null;        // Integer for fixed bottom, 0 or null for "full-screen" snow effect

  var snowStick = true;

  var snowCollect = false;

  var targetElement = null;      // element which snow will be appended to (document body if undefined)

  var followMouse = true;

  var flakeTypes = 6;

  var flakeWidth = 5;

  var flakeHeight = 5;



  // ------------------



  var zIndex = 0; // CSS stacking order applied to each snowflake

  var flakeLeftOffset = 0; // amount to subtract from edges of container

  var flakeRightOffset = 0; // amount to subtract from edges of container



  // --- End of user section ---



  var addEvent = function(o,evtName,evtHandler) {

    typeof(attachEvent)=='undefined'?o.addEventListener(evtName,evtHandler,false):o.attachEvent('on'+evtName,evtHandler);

  }



  var removeEvent = function(o,evtName,evtHandler) {

    typeof(attachEvent)=='undefined'?o.removeEventListener(evtName,evtHandler,false):o.detachEvent('on'+evtName,evtHandler);

  }



  var classContains = function(o,cStr) {

    return (typeof(o.className)!='undefined'?o.className.indexOf(cStr)+1:false);

  }



  var s = this;

  var storm = this;

  this.timers = [];

  this.flakes = [];

  this.disabled = false;

  this.terrain = [];

  this.active = false;



  var isIE = navigator.userAgent.match(/msie/i);

  var isIE6 = navigator.userAgent.match(/msie 6/i);

  var isOldIE = (isIE && (isIE6 || navigator.userAgent.match(/msie 5/i)));

  var isWin9X = navigator.appVersion.match(/windows 98/i);

  var isiPhone = navigator.userAgent.match(/iphone/i);

  var isBackCompatIE = (isIE && document.compatMode == 'BackCompat');

  var isOpera = navigator.userAgent.match(/opera/i);

  if (isOpera) isIE = false; // Opera (which may be sneaky, pretending to be IE by default)

  var noFixed = (isBackCompatIE || isIE6 || isiPhone);

  var screenX = null;

  var screenX2 = null;

  var screenY = null;

  var scrollY = null;

  var vRndX = null;

  var vRndY = null;

  var windOffset = 1;

  var windMultiplier = 1;

  var pngSupported = (!isIE || (isIE && !isIE6 && !isOldIE)); // IE <7 doesn't do PNG nicely without crap filters

  var docFrag = document.createDocumentFragment();

  this.oControl = null; // toggle element

  if (flakeLeftOffset == null) flakeLeftOffset = 0;

  if (flakeRightOffset == null) flakeRightOffset = 0;



  function rnd(n,min) {

    if (isNaN(min)) min = 0;

    return (Math.random()*n)+min;

  }



  this.randomizeWind = function() {

    vRndX = plusMinus(rnd(vMaxX,0.2));

    vRndY = rnd(vMaxY,0.2);

    if (this.flakes) {

      for (var i=0; i<this.flakes.length; i++) {

        if (this.flakes[i].active) this.flakes[i].setVelocities();

      }

    }

  }



  function plusMinus(n) {

    return (parseInt(rnd(2))==1?n*-1:n);

  }



  this.scrollHandler = function() {

    // "attach" snowflakes to bottom of window if no absolute bottom value was given

    scrollY = (flakeBottom?0:parseInt(window.scrollY||document.documentElement.scrollTop||document.body.scrollTop));

    if (isNaN(scrollY)) scrollY = 0; // Netscape 6 scroll fix

    if (!flakeBottom && s.flakes) {

      for (var i=0; i<s.flakes.length; i++) {

        if (s.flakes[i].active == 0) s.flakes[i].stick();

      }

    }

  }



  this.resizeHandler = function() {

    if (window.innerWidth || window.innerHeight) {

      screenX = window.innerWidth-(!isIE?16:2)-flakeRightOffset;

      screenY = (flakeBottom?flakeBottom:window.innerHeight);

    } else {

      screenX = (document.documentElement.clientWidth||document.body.clientWidth||document.body.scrollWidth)-(!isIE?8:0)-flakeRightOffset;

      screenY = flakeBottom?flakeBottom:(document.documentElement.clientHeight||document.body.clientHeight||document.body.scrollHeight);

    }

    screenX2 = parseInt(screenX/2);

  }



  this.resizeHandlerAlt = function() {

    screenX = targetElement.offsetLeft+targetElement.offsetWidth-flakeRightOffset;

    screenY = flakeBottom?flakeBottom:targetElement.offsetTop+targetElement.offsetHeight;

    screenX2 = parseInt(screenX/2);

  }



  this.freeze = function() {

    // pause animation

    if (!s.disabled) {

      s.disabled = 1;

    } else {

      return false;

    }
	// if you set i to more than 0 the animation continues, if the value is 0 it pauses the animation while user work in other fields..
    for (var i=0; i<s.timers.length; i++) {

      clearInterval(s.timers[i]);

    }

  }



  this.resume = function() {

    if (s.disabled) {

       s.disabled = 0;

    } else {

      return false;

    }

    s.timerInit();

  }



  this.toggleSnow = function() {

    if (!s.flakes.length) {

      // first run

      s.start();

      s.setControlActive(true);

    } else {

      s.active = !s.active;

      if (s.active) {

        s.show();

        s.resume();

        s.setControlActive(true);

      } else {

        s.stop();

        s.freeze();

        s.setControlActive(false);

      }

    }

  }



  this.stop = function() {

    this.freeze();

    for (var i=this.flakes.length; i--;) {

      this.flakes[i].o.style.display = 'none';

    }

    removeEvent(window,'scroll',s.scrollHandler);

    removeEvent(window,'resize',s.resizeHandler);

    if (!isIE) {

      removeEvent(window,'blur',s.freeze);

      removeEvent(window,'focus',s.resume);

    }

    // removeEventHandler(window,'resize',this.resizeHandler,false);

  }



  this.show = function() {

    for (var i=this.flakes.length; i--;) {

      this.flakes[i].o.style.display = 'block';

    }

  }



  this.SnowFlake = function(parent,type,x,y) {

    var s = this;

    var storm = parent;

    this.type = type;

    this.x = x||parseInt(rnd(screenX-20));

    this.y = (!isNaN(y)?y:-rnd(screenY)-12);

    this.vX = null;

    this.vY = null;

    this.vAmpTypes = [2.0,1.0,1.25,1.0,1.5,1.75]; // "amplification" for vX/vY (based on flake size/type)

    this.vAmp = this.vAmpTypes[this.type];



    this.active = 1;

    this.o = document.createElement('img');

    this.o.style.position = 'absolute';

    this.o.style.width = flakeWidth+'px';

    this.o.style.height = flakeHeight+'px';

    this.o.style.fontSize = '1px'; // so IE keeps proper size

    this.o.style.zIndex = zIndex;

    this.o.src = imagePath+this.type+(pngSupported && usePNG?'.png':'.gif');

    docFrag.appendChild(this.o);



    this.refresh = function() {

      s.o.style.left = s.x+'px';

      s.o.style.top = s.y+'px';

    }



    this.stick = function() {

      if (noFixed || (targetElement != document.documentElement && targetElement != document.body)) {

	s.o.style.top = (screenY+scrollY-flakeHeight-storm.terrain[Math.floor(s.x)])+'px';

      } else {

        s.o.style.display = 'none';

	s.o.style.top = 'auto';

        s.o.style.bottom = '0px';

	s.o.style.position = 'fixed';

        s.o.style.display = 'block';

      }

    }



    this.vCheck = function() {

      if (s.vX>=0 && s.vX<0.2) {

        s.vX = 0.2;

      } else if (s.vX<0 && s.vX>-0.2) {

        s.vX = -0.2;

      }

      if (s.vY>=0 && s.vY<0.2) {

        s.vY = 0.2;

      }

    }



    this.move = function() {

      var vX = s.vX*windOffset;

      s.x += vX;

      s.y += (s.vY*s.vAmp);

      if (vX >= 0 && (s.x >= screenX || screenX-s.x < (flakeWidth+1))) { // X-axis scroll check

        s.x = 0;

      } else if (vX < 0 && s.x-flakeLeftOffset<0-flakeWidth) {

        s.x = screenX-flakeWidth-1; // flakeWidth;

      }

      s.refresh();

      var yDiff = screenY+scrollY-s.y-storm.terrain[Math.floor(s.x)];

      if (yDiff<flakeHeight) {

        s.active = 0;

        if (snowCollect && snowStick) {

          var height = [0.75,1.5,0.75];

          for (var i=0; i<2; i++) {

            storm.terrain[Math.floor(s.x)+i+2] += height[i];

          }

        }

        s.o.style.left = (s.x/screenX*100)+'%'; // set "relative" left (change with resize)

        if (!flakeBottom) {

	  if (snowStick) {

            s.stick();

	  } else {

	    s.recycle();

	  }

        }

      }



    }



    this.animate = function() {

      // main animation loop

      // move, check status, die etc.

      s.move();

    }



    this.setVelocities = function() {

      s.vX = vRndX+rnd(vMaxX*0.12,0.1);

      s.vY = vRndY+rnd(vMaxY*0.12,0.1);

    }



    this.recycle = function() {

      s.o.style.display = 'none';

      s.o.style.position = 'absolute';

      s.o.style.bottom = 'auto';

      s.setVelocities();

      s.vCheck();

      s.x = parseInt(rnd(screenX-flakeWidth-20));

      s.y = parseInt(rnd(screenY)*-1)-flakeHeight;

      s.o.style.left = s.x+'px';

      s.o.style.top = s.y+'px';

      s.o.style.display = 'block';

      s.active = 1;

    }



    this.recycle(); // set up x/y coords etc.

    this.refresh();



  }



  this.snow = function() {

    var active = 0;

    var used = 0;

    var waiting = 0;

    for (var i=s.flakes.length; i--;) {

      if (s.flakes[i].active == 1) {

        s.flakes[i].move();

        active++;

      } else if (s.flakes[i].active == 0) {

        used++;

      } else {

        waiting++;

      }

    }

    if (snowCollect && !waiting) { // !active && !waiting

      // create another batch of snow

      s.createSnow(flakesMaxActive,true);

    }

    if (active<flakesMaxActive) {

      with (s.flakes[parseInt(rnd(s.flakes.length))]) {

        if (!snowCollect && active == 0) {

          recycle();

        } else if (active == -1) {

          active = 1;

        }

      }

    }

  }



  this.mouseMove = function(e) {

    if (!followMouse) return true;

    var x = parseInt(e.clientX);

    if (x<screenX2) {

      windOffset = -windMultiplier+(x/screenX2*windMultiplier);

    } else {

      x -= screenX2;

      windOffset = (x/screenX2)*windMultiplier;

    }

  }



  this.createSnow = function(limit,allowInactive) {

    for (var i=0; i<limit; i++) {

      s.flakes[s.flakes.length] = new s.SnowFlake(s,parseInt(rnd(flakeTypes)));

      if (allowInactive || i>flakesMaxActive) s.flakes[s.flakes.length-1].active = -1;

    }

    targetElement.appendChild(docFrag);

  }



  this.timerInit = function() {

    s.timers = (!isWin9X?[setInterval(s.snow,20)]:[setInterval(s.snow,75),setInterval(s.snow,25)]);

  }



  this.init = function() {

    for (var i=0; i<2048; i++) {

      s.terrain[i] = 0;

    }

    s.randomizeWind();

    s.createSnow(snowCollect?flakesMaxActive:flakesMaxActive*2); // create initial batch

    addEvent(window,'resize',s.resizeHandler);

    addEvent(window,'scroll',s.scrollHandler);

    if (!isIE) {

      addEvent(window,'blur',s.freeze);

      addEvent(window,'focus',s.resume);

    }

    s.resizeHandler();

    s.scrollHandler();

    if (followMouse) {

      addEvent(document,'mousemove',s.mouseMove);

    }

    s.timerInit();

  }



  var didInit = false;



  this.start = function(bFromOnLoad) {

	if (!didInit) {

	  didInit = true;

	} else if (bFromOnLoad) {

	  // already loaded and running

	  return true;

	}

    if (typeof targetElement == 'string') {

      targetElement = document.getElementById(targetElement);

      if (!targetElement) throw new Error('Snowstorm: Unable to get targetElement');

    }

	if (!targetElement) {

	  targetElement = (!isIE?(document.documentElement?document.documentElement:document.body):document.body);

	}

    if (targetElement != document.documentElement && targetElement != document.body) s.resizeHandler = s.resizeHandlerAlt; // re-map handler to get element instead of screen dimensions

    s.resizeHandler(); // get bounding box elements

    if (screenX && screenY && !s.disabled) {

      s.init();

      s.active = true;

    }

  }



  if (document.addEventListener) {

	// safari 3.0.4 doesn't do DOMContentLoaded, maybe others - use a fallback to be safe.

	document.addEventListener('DOMContentLoaded',function(){s.start(true)},false);

    window.addEventListener('load',function(){s.start(true)},false);

  } else {

    addEvent(window,'load',function(){s.start(true)});

  }



}







snowStorm = new SnowStorm();