SVG.easing = {
  '-': function(pos){return pos}
, '<>':function(pos){return -Math.cos(pos * Math.PI) / 2 + 0.5}
, '>': function(pos){return  Math.sin(pos * Math.PI / 2)}
, '<': function(pos){return -Math.cos(pos * Math.PI / 2) + 1}
}

SVG.morph = function(pos){
  return function(from, to) {
    return new SVG.MorphObj(from, to).at(pos)
  }
}

SVG.Situation = SVG.invent({

  create: function(o){
    this.init = false
    this.reversed = false
    this.reversing = false

    this.duration = new SVG.Number(o.duration).valueOf()
    this.delay = new SVG.Number(o.delay).valueOf()

    this.start = +new Date() + this.delay
    this.finish = this.start + this.duration
    this.ease = o.ease

    // this.loop is incremented from 0 to this.loops
    // it is also incremented when in an infinite loop (when this.loops is true)
    this.loop = 0
    this.loops = false

    this.animations = {
      // functionToCall: [list of morphable objects]
      // e.g. move: [SVG.Number, SVG.Number]
    }

    this.attrs = {
      // holds all attributes which are not represented from a function svg.js provides
      // e.g. someAttr: SVG.Number
    }

    this.styles = {
      // holds all styles which should be animated
      // e.g. fill-color: SVG.Color
    }

    this.transforms = [
      // holds all transformations as transformation objects
      // e.g. [SVG.Rotate, SVG.Translate, SVG.Matrix]
    ]

    this.once = {
      // functions to fire at a specific position
      // e.g. "0.5": function foo(){}
    }

  }

})


SVG.FX = SVG.invent({

  create: function(element) {
    this._target = element
    this.situations = []
    this.active = false
    this.situation = null
    this.paused = false
    this.lastPos = 0
    this.pos = 0
    // The absolute position of an animation is its position in the context of its complete duration (including delay and loops)
    // When performing a delay, absPos is below 0 and when performing a loop, its value is above 1
    this.absPos = 0
    this._speed = 1
  }

, extend: {

    /**
     * sets or returns the target of this animation
     * @param o object || number In case of Object it holds all parameters. In case of number its the duration of the animation
     * @param ease function || string Function which should be used for easing or easing keyword
     * @param delay Number indicating the delay before the animation starts
     * @return target || this
     */
    animate: function(o, ease, delay){

      if(typeof o == 'object'){
        ease = o.ease
        delay = o.delay
        o = o.duration
      }

      var situation = new SVG.Situation({
        duration: o || 1000,
        delay: delay || 0,
        ease: SVG.easing[ease || '-'] || ease
      })

      this.queue(situation)

      return this
    }

    /**
     * sets a delay before the next element of the queue is called
     * @param delay Duration of delay in milliseconds
     * @return this.target()
     */
  , delay: function(delay){
      // The delay is performed by an empty situation with its duration
      // attribute set to the duration of the delay
      var situation = new SVG.Situation({
        duration: delay,
        delay: 0,
        ease: SVG.easing['-']
      })

      return this.queue(situation)
    }

    /**
     * sets or returns the target of this animation
     * @param null || target SVG.Element which should be set as new target
     * @return target || this
     */
  , target: function(target){
      if(target && target instanceof SVG.Element){
        this._target = target
        return this
      }

      return this._target
    }

    // returns the absolute position at a given time
  , timeToAbsPos: function(timestamp){
      return (timestamp - this.situation.start) / (this.situation.duration/this._speed)
    }

    // returns the timestamp from a given absolute positon
  , absPosToTime: function(absPos){
      return this.situation.duration/this._speed * absPos + this.situation.start
    }

    // starts the animationloop
  , startAnimFrame: function(){
      this.stopAnimFrame()
      this.animationFrame = requestAnimationFrame(function(){ this.step() }.bind(this))
    }

    // cancels the animationframe
  , stopAnimFrame: function(){
      cancelAnimationFrame(this.animationFrame)
    }

    // kicks off the animation - only does something when the queue is currently not active and at least one situation is set
  , start: function(){
      // dont start if already started
      if(!this.active && this.situation){
        this.active = true
        this.startCurrent()
      }

      return this
    }

    // start the current situation
  , startCurrent: function(){
      this.situation.start = +new Date + this.situation.delay/this._speed
      this.situation.finish = this.situation.start + this.situation.duration/this._speed
      return this.initAnimations().step()
    }

    /**
     * adds a function / Situation to the animation queue
     * @param fn function / situation to add
     * @return this
     */
  , queue: function(fn){
      if(typeof fn == 'function' || fn instanceof SVG.Situation)
        this.situations.push(fn)

      if(!this.situation) this.situation = this.situations.shift()

      return this
    }

    /**
     * pulls next element from the queue and execute it
     * @return this
     */
  , dequeue: function(){
      // stop current animation
      this.situation && this.situation.stop && this.situation.stop()

      // get next animation from queue
      this.situation = this.situations.shift()

      if(this.situation){
        if(this.situation instanceof SVG.Situation) {
          this.startCurrent()
        } else {
          // If it is not a SVG.Situation, then it is a function, we execute it
          this.situation.call(this)
        }
      }

      return this
    }

    // updates all animations to the current state of the element
    // this is important when one property could be changed from another property
  , initAnimations: function() {
      var i
      var s = this.situation

      if(s.init) return this

      for(i in s.animations){

        if(i == 'viewbox'){
          s.animations[i] = this.target().viewbox().morph(s.animations[i])
        }else{

          // TODO: this is not a clean clone of the array. We may have some unchecked references
          s.animations[i].value = (i == 'plot' ? this.target().array().value : this.target()[i]())

          // sometimes we get back an object and not the real value, fix this
          if(s.animations[i].value.value){
            s.animations[i].value = s.animations[i].value.value
          }

          if(s.animations[i].relative)
            s.animations[i].destination.value = s.animations[i].destination.value + s.animations[i].value

        }

      }

      for(i in s.attrs){
        if(s.attrs[i] instanceof SVG.Color){
          var color = new SVG.Color(this.target().attr(i))
          s.attrs[i].r = color.r
          s.attrs[i].g = color.g
          s.attrs[i].b = color.b
        }else{
          s.attrs[i].value = this.target().attr(i)// + s.attrs[i].value
        }
      }

      for(i in s.styles){
        s.styles[i].value = this.target().style(i)
      }

      s.initialTransformation = this.target().matrixify()

      s.init = true
      return this
    }
  , clearQueue: function(){
      this.situations = []
      return this
    }
  , clearCurrent: function(){
      this.situation = null
      return this
    }
    /** stops the animation immediately
     * @param jumpToEnd A Boolean indicating whether to complete the current animation immediately.
     * @param clearQueue A Boolean indicating whether to remove queued animation as well.
     * @return this
     */
  , stop: function(jumpToEnd, clearQueue){
      if(!this.active) this.start()

      if(clearQueue){
        this.clearQueue()
      }

      this.active = false

      if(jumpToEnd && this.situation){
        this.atEnd()
      }

      this.stopAnimFrame()

      return this.clearCurrent()
    }

    /** resets the element to the state where the current element has started
     * @return this
     */
  , reset: function(){
      if(this.situation){
        var temp = this.situation
        this.stop()
        this.situation = temp
        this.atStart()
      }
      return this
    }

    // Stop the currently-running animation, remove all queued animations, and complete all animations for the element.
  , finish: function(){

      this.stop(true, false)

      while(this.dequeue().situation && this.stop(true, false));

      this.clearQueue().clearCurrent()

      return this
    }

    // set the internal animation pointer at the start position, before any loops, and updates the visualisation
  , atStart: function() {
    return this.at(0, true)
  }

    // set the internal animation pointer at the end position, after all the loops, and updates the visualisation
  , atEnd: function() {
    if (this.situation.loops === true) {
      // If in a infinite loop, we end the current iteration
      return this.at(this.situation.loop+1, true)
    } else if(typeof this.situation.loops == 'number') {
      // If performing a finite number of loops, we go after all the loops
      return this.at(this.situation.loops, true)
    } else {
      // If no loops, we just go at the end
      return this.at(1, true)
    }
  }

    // set the internal animation pointer to the specified position and updates the visualisation
    // if isAbsPos is true, pos is treated as an absolute position
  , at: function(pos, isAbsPos){
      var durDivSpd = this.situation.duration/this._speed

      this.absPos = pos
      // If pos is not an absolute position, we convert it into one
      if (!isAbsPos) {
        if (this.situation.reversed) this.absPos = 1 - this.absPos
        this.absPos += this.situation.loop
      }

      this.situation.start = +new Date - this.absPos * durDivSpd
      this.situation.finish = this.situation.start + durDivSpd

      return this.step(true)
    }

    /**
     * sets or returns the speed of the animations
     * @param speed null || Number The new speed of the animations
     * @return Number || this
     */
  , speed: function(speed){
      if (speed === 0) return this.pause()

      if (speed) {
        this._speed = speed
        // We use an absolute position here so that speed can affect the delay before the animation
        return this.at(this.absPos, true)
      } else return this._speed
    }

    // Make loopable
  , loop: function(times, reverse) {
      var c = this.last()

      // store total loops
      c.loops = (times != null) ? times : true
      c.loop = 0

      if(reverse) c.reversing = true
      return this
    }

    // pauses the animation
  , pause: function(){
      this.paused = true
      this.stopAnimFrame()

      return this
    }

    // unpause the animation
  , play: function(){
      if(!this.paused) return this
      this.paused = false
      // We use an absolute position here so that the delay before the animation can be paused
      return this.at(this.absPos, true)
    }

    /**
     * toggle or set the direction of the animation
     * true sets direction to backwards while false sets it to forwards
     * @param reversed Boolean indicating whether to reverse the animation or not (default: toggle the reverse status)
     * @return this
     */
  , reverse: function(reversed){
      var c = this.last()

      if(typeof reversed == 'undefined') c.reversed = !c.reversed
      else c.reversed = reversed

      return this
    }


    /**
     * returns a float from 0-1 indicating the progress of the current animation
     * @param eased Boolean indicating whether the returned position should be eased or not
     * @return number
     */
  , progress: function(easeIt){
      return easeIt ? this.situation.ease(this.pos) : this.pos
    }

    /**
     * adds a callback function which is called when the current animation is finished
     * @param fn Function which should be executed as callback
     * @return number
     */
  , after: function(fn){
      var c = this.last()
        , wrapper = function wrapper(e){
            if(e.detail.situation == c){
              fn.call(this, c)
              this.off('finished.fx', wrapper) // prevent memory leak
            }
          }

      this.target().on('finished.fx', wrapper)
      return this
    }

    // adds a callback which is called whenever one animation step is performed
  , during: function(fn){
      var c = this.last()
        , wrapper = function(e){
            if(e.detail.situation == c){
              fn.call(this, e.detail.pos, SVG.morph(e.detail.pos), e.detail.eased, c)
            }
          }

      // see above
      this.target().off('during.fx', wrapper).on('during.fx', wrapper)

      return this.after(function(){
        this.off('during.fx', wrapper)
      })
    }

    // calls after ALL animations in the queue are finished
  , afterAll: function(fn){
      var wrapper = function wrapper(e){
            fn.call(this)
            this.off('allfinished.fx', wrapper)
          }

      // see above
      this.target().off('allfinished.fx', wrapper).on('allfinished.fx', wrapper)
      return this
    }

    // calls on every animation step for all animations
  , duringAll: function(fn){
      var wrapper = function(e){
            fn.call(this, e.detail.pos, SVG.morph(e.detail.pos), e.detail.eased, e.detail.situation)
          }

      this.target().off('during.fx', wrapper).on('during.fx', wrapper)

      return this.afterAll(function(){
        this.off('during.fx', wrapper)
      })
    }

  , last: function(){
      return this.situations.length ? this.situations[this.situations.length-1] : this.situation
    }

    // adds one property to the animations
  , add: function(method, args, type){
      this.last()[type || 'animations'][method] = args
      setTimeout(function(){this.start()}.bind(this), 0)
      return this
    }

    /** perform one step of the animation
     *  @param ignoreTime Boolean indicating whether to ignore time and use position directly or recalculate position based on time
     *  @return this
     */
  , step: function(ignoreTime){

      // convert current time to an absolute position
      if(!ignoreTime) this.absPos = this.timeToAbsPos(+new Date)

      // This part convert an absolute position to a position
      if(this.situation.loops !== false) {
        var absPos, absPosInt, lastLoop

        // If the absolute position is below 0, we just treat it as if it was 0
        absPos = Math.max(this.absPos, 0)
        absPosInt = Math.floor(absPos)

        if(this.situation.loops === true || absPosInt < this.situation.loops) {
          this.pos = absPos - absPosInt
          lastLoop = this.situation.loop
          this.situation.loop = absPosInt
        } else {
          this.absPos = this.situation.loops
          this.pos = 1
          // The -1 here is because we don't want to toggle reversed when all the loops have been completed
          lastLoop = this.situation.loop - 1
          this.situation.loop = this.situation.loops
        }

        if(this.situation.reversing) {
          // Toggle reversed if an odd number of loops as occured since the last call of step
          this.situation.reversed = this.situation.reversed != Boolean((this.situation.loop - lastLoop) % 2)
        }

      } else {
        // If there are no loop, the absolute position must not be above 1
        this.absPos = Math.min(this.absPos, 1)
        this.pos = this.absPos
      }

      // while the absolute position can be below 0, the position must not be below 0
      if(this.pos < 0) this.pos = 0

      if(this.situation.reversed) this.pos = 1 - this.pos


      // apply easing
      var eased = this.situation.ease(this.pos)

      // call once-callbacks
      for(var i in this.situation.once){
        if(i > this.lastPos && i <= eased){
          this.situation.once[i].call(this.target(), this.pos, eased)
          delete this.situation.once[i]
        }
      }

      // fire during callback with position, eased position and current situation as parameter
      if(this.active) this.target().fire('during', {pos: this.pos, eased: eased, fx: this, situation: this.situation})

      // the user may call stop or finish in the during callback
      // so make sure that we still have a valid situation
      if(!this.situation){
        return this
      }

      // apply the actual animation to every property
      this.eachAt()

      // do final code when situation is finished
      if((this.pos == 1 && !this.situation.reversed) || (this.situation.reversed && this.pos == 0)){

        // stop animation callback
        this.stopAnimFrame()

        // fire finished callback with current situation as parameter
        this.target().fire('finished', {fx:this, situation: this.situation})

        if(!this.situations.length){
          this.target().fire('allfinished')
          this.target().off('.fx') // there shouldnt be any binding left, but to make sure...
          this.active = false
        }

        // start next animation
        if(this.active) this.dequeue()
        else this.clearCurrent()

      }else if(!this.paused && this.active){
        // we continue animating when we are not at the end
        this.startAnimFrame()
      }

      // save last eased position for once callback triggering
      this.lastPos = eased
      return this

    }

    // calculates the step for every property and calls block with it
  , eachAt: function(){
      var i, at, self = this, target = this.target(), s = this.situation

      // apply animations which can be called trough a method
      for(i in s.animations){

        at = [].concat(s.animations[i]).map(function(el){
          return typeof el !== 'string' && el.at ? el.at(s.ease(self.pos), self.pos) : el
        })

        target[i].apply(target, at)

      }

      // apply animation which has to be applied with attr()
      for(i in s.attrs){

        at = [i].concat(s.attrs[i]).map(function(el){
          return typeof el !== 'string' && el.at ? el.at(s.ease(self.pos), self.pos) : el
        })

        target.attr.apply(target, at)

      }

      // apply animation which has to be applied with style()
      for(i in s.styles){

        at = [i].concat(s.styles[i]).map(function(el){
          return typeof el !== 'string' && el.at ? el.at(s.ease(self.pos), self.pos) : el
        })

        target.style.apply(target, at)

      }

      // animate initialTransformation which has to be chained
      if(s.transforms.length){

        // get inital initialTransformation
        at = s.initialTransformation
        for(i in s.transforms){

          // get next transformation in chain
          var a = s.transforms[i]

          // multiply matrix directly
          if(a instanceof SVG.Matrix){

            if(a.relative){
              at = at.multiply(a.at(s.ease(this.pos)))
            }else{
              at = at.morph(a).at(s.ease(this.pos))
            }
            continue
          }

          // when transformation is absolute we have to reset the needed transformation first
          if(!a.relative)
            a.undo(at.extract())

          // and reapply it after
          at = at.multiply(a.at(s.ease(this.pos)))

        }

        // set new matrix on element
        target.matrix(at)
      }

      return this

    }


    // adds an once-callback which is called at a specific position and never again
  , once: function(pos, fn, isEased){

      if(!isEased)pos = this.situation.ease(pos)

      this.situation.once[pos] = fn

      return this
    }

  }

, parent: SVG.Element

  // Add method to parent elements
, construct: {
    // Get fx module or create a new one, then animate with given duration and ease
    animate: function(o, ease, delay) {
      return (this.fx || (this.fx = new SVG.FX(this))).animate(o, ease, delay)
    }
  , delay: function(delay){
      return (this.fx || (this.fx = new SVG.FX(this))).delay(delay)
    }
  , stop: function(jumpToEnd, clearQueue) {
      if (this.fx)
        this.fx.stop(jumpToEnd, clearQueue)

      return this
    }
  , finish: function() {
      if (this.fx)
        this.fx.finish()

      return this
    }
    // Pause current animation
  , pause: function() {
      if (this.fx)
        this.fx.pause()

      return this
    }
    // Play paused current animation
  , play: function() {
      if (this.fx)
        this.fx.play()

      return this
    }
    // Set/Get the speed of the animations
  , speed: function(speed) {
      if (this.fx)
        if (speed == null)
          return this.fx.speed()
        else
          this.fx.speed(speed)

      return this
    }
  }

})

// MorphObj is used whenever no morphable object is given
SVG.MorphObj = SVG.invent({

  create: function(from, to){
    // prepare color for morphing
    if(SVG.Color.isColor(to)) return new SVG.Color(from).morph(to)
    // prepare number for morphing
    if(SVG.regex.numberAndUnit.test(to)) return new SVG.Number(from).morph(to)

    // prepare for plain morphing
    this.value = 0
    this.destination = to
  }

, extend: {
    at: function(pos, real){
      return real < 1 ? this.value : this.destination
    },

    valueOf: function(){
      return this.value
    }
  }

})

SVG.extend(SVG.FX, {
  // Add animatable attributes
  attr: function(a, v, relative) {
    // apply attributes individually
    if (typeof a == 'object') {
      for (var key in a)
        this.attr(key, a[key])

    } else {
      // the MorphObj takes care about the right function used
      this.add(a, new SVG.MorphObj(null, v), 'attrs')
    }

    return this
  }
  // Add animatable styles
, style: function(s, v) {
    if (typeof s == 'object')
      for (var key in s)
        this.style(key, s[key])

    else
      this.add(s, new SVG.MorphObj(null, v), 'styles')

    return this
  }
  // Animatable x-axis
, x: function(x, relative) {
    if(this.target() instanceof SVG.G){
      this.transform({x:x}, relative)
      return this
    }

    var num = new SVG.Number().morph(x)
    num.relative = relative
    return this.add('x', num)
  }
  // Animatable y-axis
, y: function(y, relative) {
    if(this.target() instanceof SVG.G){
      this.transform({y:y}, relative)
      return this
    }

    var num = new SVG.Number().morph(y)
    num.relative = relative
    return this.add('y', num)
  }
  // Animatable center x-axis
, cx: function(x) {
    return this.add('cx', new SVG.Number().morph(x))
  }
  // Animatable center y-axis
, cy: function(y) {
    return this.add('cy', new SVG.Number().morph(y))
  }
  // Add animatable move
, move: function(x, y) {
    return this.x(x).y(y)
  }
  // Add animatable center
, center: function(x, y) {
    return this.cx(x).cy(y)
  }
  // Add animatable size
, size: function(width, height) {
    if (this.target() instanceof SVG.Text) {
      // animate font size for Text elements
      this.attr('font-size', width)

    } else {
      // animate bbox based size for all other elements
      var box

      if(!width || !height){
        box = this.target().bbox()
      }

      if(!width){
        width = box.width / box.height  * height
      }

      if(!height){
        height = box.height / box.width  * width
      }

      this.add('width' , new SVG.Number().morph(width))
          .add('height', new SVG.Number().morph(height))

    }

    return this
  }
  // Add animatable plot
, plot: function(p) {
    return this.add('plot', this.target().array().morph(p))
  }
  // Add leading method
, leading: function(value) {
    return this.target().leading ?
      this.add('leading', new SVG.Number().morph(value)) :
      this
  }
  // Add animatable viewbox
, viewbox: function(x, y, width, height) {
    if (this.target() instanceof SVG.Container) {
      this.add('viewbox', new SVG.ViewBox(x, y, width, height))
    }

    return this
  }
, update: function(o) {
    if (this.target() instanceof SVG.Stop) {
      if (typeof o == 'number' || o instanceof SVG.Number) {
        return this.update({
          offset:  arguments[0]
        , color:   arguments[1]
        , opacity: arguments[2]
        })
      }

      if (o.opacity != null) this.attr('stop-opacity', o.opacity)
      if (o.color   != null) this.attr('stop-color', o.color)
      if (o.offset  != null) this.attr('offset', o.offset)
    }

    return this
  }
})