/*

   DHTML Snowstorm! OO-style Jascript-based Snow effect

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

   Version 1.4.20091115 (Previous rev: v1.3.20081215)

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

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

  

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

   To customize properties, edit below or override configuration after this script

   has run (but before body.onload), eg. snowStorm.snowStick = false;



*/



var snowStorm = null;



function SnowStorm() {



  // --- PROPERTIES ---



  this.flakesMax = 128;           // Limit total amount of snow made (falling + sticking)

  this.flakesMaxActive = 64;      // Limit amount of snow falling at once (less = lower CPU use)

  this.animationInterval = 33;    // Theoretical "miliseconds per frame" measurement. 20 = fast + smooth, but high CPU use. 50 = more conservative, but slower

  this.flakeBottom = null;        // Integer for Y axis snow limit, 0 or null for "full-screen" snow effect

  this.targetElement = null;      // element which snow will be appended to (document body if null/undefined) - can be an element ID string, or a DOM node reference

  this.followMouse = true;        // Snow will change movement with the user's mouse

  this.snowColor = '#CFCFCF';        // Don't eat (or use?) yellow snow.

  this.snowCharacter = '*';  // • = bullet, · is square on some systems etc.

  this.snowStick = true;          // Whether or not snow should "stick" at the bottom. When off, will never collect.

  this.useMeltEffect = true;      // When recycling fallen snow (or rarely, when falling), have it "melt" and fade out if browser supports it

  this.useTwinkleEffect = false;  // Allow snow to randomly "flicker" in and out of view while falling

  this.usePositionFixed = false;  // true = snow not affected by window scroll. may increase CPU load, disabled by default - if enabled, used only where supported



  // --- less-used bits ---



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

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

  this.flakeWidth = 15;            // max pixel width for snow element

  this.flakeHeight = 15;           // max pixel height for snow element

  this.vMaxX = 5;                 // Maximum X velocity range for snow

  this.vMaxY = 4;                 // Maximum Y velocity range

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



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



  // jslint global declarations

  /*global window, document, navigator, clearInterval, setInterval */



  var addEvent = (typeof(window.attachEvent)=='undefined'?function(o,evtName,evtHandler) {

	return o.addEventListener(evtName,evtHandler,false);

  }:function(o,evtName,evtHandler) {

	return o.attachEvent('on'+evtName,evtHandler);

  });



  var removeEvent = (typeof(window.attachEvent)=='undefined'?function(o,evtName,evtHandler) {

    return o.removeEventListener(evtName,evtHandler,false);

  }:function(o,evtName,evtHandler) {

	return o.detachEvent('on'+evtName,evtHandler);

  });



  function rnd(n,min) {

    if (isNaN(min)) {

	  min = 0;

	}

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

  }



  function plusMinus(n) {

    return (parseInt(rnd(2),10)==1?n*-1:n);

  }



  var s = this;

  var storm = this;

  this.timers = [];

  this.flakes = [];

  this.disabled = false;

  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 noFixed = ((isBackCompatIE || isIE6 || isiPhone)?true:false);

  var screenX = null;

  var screenX2 = null;

  var screenY = null;

  var scrollY = null;

  var vRndX = null;

  var vRndY = null;

  var windOffset = 1;

  var windMultiplier = 2;

  var flakeTypes = 6;

  var fixedForEverything = false;

  var opacitySupported = (function(){

    try {

	  document.createElement('div').style.opacity = '0.5';

    } catch (e) {

	  return false;

    }

    return true;

  })();

  var docFrag = document.createDocumentFragment();

  if (s.flakeLeftOffset === null) {

	s.flakeLeftOffset = 0;

  }

  if (s.flakeRightOffset === null) {

	s.flakeRightOffset = 0;

  }



  this.meltFrameCount = 20;

  this.meltFrames = [];

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

	this.meltFrames.push(1-(i/this.meltFrameCount));

  }



  this.randomizeWind = function() {

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

    vRndY = rnd(s.vMaxY,0.2);

    if (this.flakes) {

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

        if (this.flakes[i].active) {

          this.flakes[i].setVelocities();

		}

      }

    }

  };



  this.scrollHandler = function() {

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

    scrollY = (s.flakeBottom?0:parseInt(window.scrollY||document.documentElement.scrollTop||document.body.scrollTop,10));

    if (isNaN(scrollY)) {

	  scrollY = 0; // Netscape 6 scroll fix

	}

    if (!fixedForEverything && !s.flakeBottom && s.flakes) {

      for (var 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)-s.flakeRightOffset;

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

    } else {

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

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

    }

    screenX2 = parseInt(screenX/2,10);

  };



  this.resizeHandlerAlt = function() {

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

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

    screenX2 = parseInt(screenX/2,10);

  };



  this.freeze = function() {

    // pause animation

    if (!s.disabled) {

      s.disabled = 1;

    } else {

      return false;

    }

    for (var 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();

    } else {

      s.active = !s.active;

      if (s.active) {

        s.show();

        s.resume();

      } else {

        s.stop();

        s.freeze();

      }

    }

  };



  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 (!isOldIE) {

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

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

    }

  };



  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),10);

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

    this.vX = null;

    this.vY = null;

    this.vAmpTypes = [1,1.2,1.4,1.6,1.8]; // "amplification" for vX/vY (based on flake size/type)

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

    this.melting = false;

    this.meltFrameCount = storm.meltFrameCount;

    this.meltFrames = storm.meltFrames;

    this.meltFrame = 0;

    this.twinkleFrame = 0;

    this.active = 1;

    this.fontSize = (18+(this.type/5)*10);

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

    this.o.innerHTML = storm.snowCharacter;

    this.o.style.color = storm.snowColor;

    this.o.style.position = (fixedForEverything?'fixed':'absolute');

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

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

    this.o.style.fontFamily = 'arial,verdana';

    this.o.style.overflow = 'hidden';

    this.o.style.fontWeight = 'normal';

    this.o.style.zIndex = storm.zIndex;

    docFrag.appendChild(this.o);



    this.refresh = function() {

	  if (isNaN(s.x) || isNaN(s.y)) {

		// safety check

		return false;

	  }

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

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

    };



    this.stick = function() {

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

        s.o.style.top = (screenY+scrollY-storm.flakeHeight)+'px';

      } else if (storm.flakeBottom) {

	    s.o.style.top = storm.flakeBottom+'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 (s.x >= screenX || screenX-s.x < storm.flakeWidth) { // X-axis scroll check

        s.x = 0;

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

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

      }

      s.refresh();

      var yDiff = screenY+scrollY-s.y;

      if (yDiff<storm.flakeHeight) {

        s.active = 0;

	    if (storm.snowStick) {

          s.stick();

	    } else {

	      s.recycle();

	    }

      } else {

	    if (storm.useMeltEffect && s.active && s.type < 3 && !s.melting && Math.random()>0.998) {

	      // ~1/1000 chance of melting mid-air, with each frame

	      s.melting = true;

	      s.melt();

	      // only incrementally melt one frame

	      // s.melting = false;

	    }

	    if (storm.useTwinkleEffect) {

		  if (!s.twinkleFrame) {

			if (Math.random()>0.9) {

		      s.twinkleFrame = parseInt(Math.random()*20,10);

		    }

		  } else {

			s.twinkleFrame--;

			s.o.style.visibility = (s.twinkleFrame && s.twinkleFrame%2===0?'hidden':'visible');

		  }

	    }

      }

    };



    this.animate = function() {

      // main animation loop

      // move, check status, die etc.

      s.move();

    };



    this.setVelocities = function() {

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

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

    };



	this.setOpacity = function(o,opacity) {

	  if (!opacitySupported) {

		return false;

	  }

	  o.style.opacity = opacity;

	};



    this.melt = function() {

	  if (!storm.useMeltEffect || !s.melting) {

		s.recycle();

	  } else {

		if (s.meltFrame < s.meltFrameCount) {

		  s.meltFrame++;

		  s.setOpacity(s.o,s.meltFrames[s.meltFrame]);

		  s.o.style.fontSize = s.fontSize-(s.fontSize*(s.meltFrame/s.meltFrameCount))+'px';

		  s.o.style.lineHeight = storm.flakeHeight+2+(storm.flakeHeight*0.75*(s.meltFrame/s.meltFrameCount))+'px';

		} else {

		  s.recycle();

		}

	  }

    };



    this.recycle = function() {

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

      s.o.style.position = (fixedForEverything?'fixed':'absolute');

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

      s.setVelocities();

      s.vCheck();

	  s.meltFrame = 0;

	  s.melting = false;

	  s.setOpacity(s.o,1);

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

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

	  s.o.style.fontSize = s.fontSize+'px';

	  s.o.style.lineHeight = (storm.flakeHeight+2)+'px';

	  s.o.style.textAlign = 'center';

	  s.o.style.verticalAlign = 'baseline';

      s.x = parseInt(rnd(screenX-storm.flakeWidth-20),10);

      s.y = parseInt(rnd(screenY)*-1,10)-storm.flakeHeight;

      s.refresh();

      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;

    var flake = null;

    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 (s.flakes[i].melting) {

	    s.flakes[i].melt();

	  }

    }

    if (active<s.flakesMaxActive) {

      flake = s.flakes[parseInt(rnd(s.flakes.length),10)];

      if (flake.active === 0) {

        flake.melting = true;

      }

    }

  };



  this.mouseMove = function(e) {

    if (!s.followMouse) {

	  return true;

	}

    var x = parseInt(e.clientX,10);

    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),10));

      if (allowInactive || i>s.flakesMaxActive) {

	    s.flakes[s.flakes.length-1].active = -1;

	  }

    }

    storm.targetElement.appendChild(docFrag);

  };



  this.timerInit = function() {

    s.timers = (!isWin9X?[setInterval(s.snow,s.animationInterval)]:[setInterval(s.snow,s.animationInterval*3),setInterval(s.snow,s.animationInterval)]);

  };



  this.init = function() {

    s.randomizeWind();

    s.createSnow(s.flakesMax); // create initial batch

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

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

    if (!isOldIE) {

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

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

    }

    s.resizeHandler();

    s.scrollHandler();

    if (s.followMouse) {

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

    }

    s.animationInterval = Math.max(20,s.animationInterval);

    s.timerInit();

  };



  var didInit = false;



  this.start = function(bFromOnLoad) {

	if (!didInit) {

	  didInit = true;

	} else if (bFromOnLoad) {

	  // already loaded and running

	  return true;

	}

    if (typeof s.targetElement == 'string') {

	  var targetID = s.targetElement;

      s.targetElement = document.getElementById(targetID);

      if (!s.targetElement) {

	    throw new Error('Snowstorm: Unable to get targetElement "'+targetID+'"');

	  }

    }

	if (!s.targetElement) {

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

	}

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

	  s.resizeHandler = s.resizeHandlerAlt; // re-map handler to get element instead of screen dimensions

	}

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

    s.usePositionFixed = (s.usePositionFixed && !noFixed); // whether or not position:fixed is supported

    fixedForEverything = s.usePositionFixed;

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

      s.init();

      s.active = true;

    }

  };



  function doStart() {

	  s.start(true);

  }



  if (document.addEventListener) {

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

    document.addEventListener('DOMContentLoaded',doStart,false);

    window.addEventListener('load',doStart,false);

  } else {

    addEvent(window,'load',doStart);

  }



}



snowStorm = new SnowStorm();