/** @license

 * DHTML Snowstorm! JavaScript-based Snow for web pages

 * --------------------------------------------------------

 * Version 1.42.20111120 (Previous rev: 1.41.20101113)

 * Copyright (c) 2007, Scott Schiller. All rights reserved.

 * Code provided under the BSD License:

 * http://schillmania.com/projects/snowstorm/license.txt

 */



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

/*jslint white: false, onevar: true, plusplus: false, undef: true, nomen: true, eqeqeq: true, bitwise: true, regexp: true, newcap: true, immed: true */



var snowStorm = (function(window, document) {



  // --- common properties ---



  this.flakesMax = 256;           // Limit total amount of snow made (falling + sticking)

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

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

  this.excludeMobile = true;      // Snow is likely to be bad news for mobile phones' CPUs (and batteries.) By default, be nice.

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

  this.followMouse = true;        // Snow movement can respond to the user's mouse

  this.snowColor = '#fff';        // 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.targetElement = null;      // element which snow will be appended to (null = document.body) - can be an element ID eg. 'myDiv', or a DOM node reference

  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 does not shift vertically when scrolling. May increase CPU load, disabled by default - if enabled, used only where supported



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



  this.freezeOnBlur = true;       // Only snow when the window is in focus (foreground.) Saves CPU.

  this.flakeLeftOffset = 0;       // Left margin/gutter space on edge of container (eg. browser window.) Bump up these values if seeing horizontal scrollbars.

  this.flakeRightOffset = 0;      // Right margin/gutter space on edge of container

  this.flakeWidth = 8;            // Max pixel width reserved for snow element

  this.flakeHeight = 8;           // Max pixel height reserved for snow element

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

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

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



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



  var s = this, storm = this, i,

  // UA sniffing and backCompat rendering mode checks for fixed position, etc.

  isIE = navigator.userAgent.match(/msie/i),

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

  isWin98 = navigator.appVersion.match(/windows 98/i),

  isMobile = navigator.userAgent.match(/mobile/i),

  isBackCompatIE = (isIE && document.compatMode === 'BackCompat'),

  noFixed = (isMobile || isBackCompatIE || isIE6),

  screenX = null, screenX2 = null, screenY = null, scrollY = null, vRndX = null, vRndY = null,

  windOffset = 1,

  windMultiplier = 2,

  flakeTypes = 6,

  fixedForEverything = false,

  opacitySupported = (function(){

    try {

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

    } catch(e) {

      return false;

    }

    return true;

  }()),

  didInit = false,

  docFrag = document.createDocumentFragment();



  this.timers = [];

  this.flakes = [];

  this.disabled = false;

  this.active = false;

  this.meltFrameCount = 20;

  this.meltFrames = [];



  this.events = (function() {



    var old = (!window.addEventListener && window.attachEvent), slice = Array.prototype.slice,

    evt = {

      add: (old?'attachEvent':'addEventListener'),

      remove: (old?'detachEvent':'removeEventListener')

    };



    function getArgs(oArgs) {

      var args = slice.call(oArgs), len = args.length;

      if (old) {

        args[1] = 'on' + args[1]; // prefix

        if (len > 3) {

          args.pop(); // no capture

        }

      } else if (len === 3) {

        args.push(false);

      }

      return args;

    }



    function apply(args, sType) {

      var element = args.shift(),

          method = [evt[sType]];

      if (old) {

        element[method](args[0], args[1]);

      } else {

        element[method].apply(element, args);

      }

    }



    function addEvent() {

      apply(getArgs(arguments), 'add');

    }



    function removeEvent() {

      apply(getArgs(arguments), 'remove');

    }



    return {

      add: addEvent,

      remove: removeEvent

    };



  }());



  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);

  }



  this.randomizeWind = function() {

    var i;

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

    vRndY = rnd(s.vMaxY,0.2);

    if (this.flakes) {

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

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

          this.flakes[i].setVelocities();

        }

      }

    }

  };



  this.scrollHandler = function() {

    var i;

    // "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 (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?16:16)-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

    var i;

    if (!s.disabled) {

      s.disabled = 1;

    } else {

      return false;

    }

    for (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() {

    var i;

    this.freeze();

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

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

    }

    s.events.remove(window,'scroll',s.scrollHandler);

    s.events.remove(window,'resize',s.resizeHandler);

    if (s.freezeOnBlur) {

      if (isIE) {

        s.events.remove(document,'focusout',s.freeze);

        s.events.remove(document,'focusin',s.resume);

      } else {

        s.events.remove(window,'blur',s.freeze);

        s.events.remove(window,'focus',s.resume);

      }

    }

  };



  this.show = function() {

    var i;

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

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

    }

  };



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

    var s = this, 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 = (10+(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, yDiff;

      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 < -storm.flakeWidth) {

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

      }

      s.refresh();

      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, used = 0, waiting = 0, flake = null, i;

    for (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) {

    var i;

    for (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 = (!isWin98?[setInterval(s.snow,s.animationInterval)]:[setInterval(s.snow,s.animationInterval*3),setInterval(s.snow,s.animationInterval)]);

  };



  this.init = function() {

    var i;

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

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

    }

    s.randomizeWind();

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

    s.events.add(window,'resize',s.resizeHandler);

    s.events.add(window,'scroll',s.scrollHandler);

    if (s.freezeOnBlur) {

      if (isIE) {

        s.events.add(document,'focusout',s.freeze);

        s.events.add(document,'focusin',s.resume);

      } else {

        s.events.add(window,'blur',s.freeze);

        s.events.add(window,'focus',s.resume);

      }

    }

    s.resizeHandler();

    s.scrollHandler();

    if (s.followMouse) {

      s.events.add(isIE?document:window,'mousemove',s.mouseMove);

    }

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

    s.timerInit();

  };



  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 doDelayedStart() {

    window.setTimeout(function() {

      s.start(true);

    }, 20);

    // event cleanup

    s.events.remove(isIE?document:window,'mousemove',doDelayedStart);

  }



  function doStart() {

    if (!s.excludeMobile || !isMobile) {

      if (s.freezeOnBlur) {

        s.events.add(isIE?document:window,'mousemove',doDelayedStart);

      } else {

        doDelayedStart();

      }

    }

    // event cleanup

    s.events.remove(window, 'load', doStart);

  }



  // hooks for starting the snow

  s.events.add(window, 'load', doStart, false);



  return this;



}(window, document));