carousel_collection.coffee

class CarouselCollection extends Backbone.Collection
  initialize: ->
    @currentIndex = 0
    @step = 1

  current: (value = null)->
    @changeIndex @indexOf(value) if value
    @at @currentIndex

  changeIndex: (newIndex)->
    @currentIndex = newIndex
    @trigger 'current:changed'
    newIndex

  isFirst: ->
    @current() == @first()

  isLast: ->
    @current() == @last()

  next: ->
    @nextOrFirstIndex()
    @trigger 'current:next'
    @current()  

  prev: ->
    @prevOrLastIndex()
    @trigger 'current:prev'
    @current()

  nextOrFirstIndex: ->
    if @isLast() then @_goToFirst() else @_step()

  prevOrLastIndex: ->
    if @isFirst() then @_goToLast() else @_step -1
  
  _goToLast: ->
    @changeIndex @indexOf(@last())
    @trigger 'current:prev:loop'

  _goToFirst: ->
    @changeIndex 0
    @trigger 'current:next:loop'
    
  _step: (factor = 1)->
    @changeIndex @currentIndex + (@step * factor)

fixed