{interpolateRects, interpolatePoints} = require './geom'
{interpolateColors} = require './color'


class Tween
  
  # * f(0) gets executed in the constructor
  # * f(1) gets executed at the end
  constructor: (@duration, @transition, @f) ->
    @start = new Date().getTime()
    @f 0
    setTimeout (=>@step()), 0
  
  step: () ->
    t = (new Date().getTime() - @start) / @duration
    if t > 1
      t = 1
    @f @transition(t)
    if t < 1
      setTimeout (=>@step()), 0


class Morph
  
  constructor: (elements, info) ->
    {
      duration, transition, oncomplete
      opacity, rect, pos, background
    } = info
    
    if not (elements instanceof Array)
      elements = [elements]
    
    numFrames = 0
    
    new Tween duration, transition, (t) ->
      numFrames++
      for element in elements
        
        if opacity
          element.setOpacity(opacity[0] + (opacity[1] - opacity[0]) * t)
        
        if rect
          element.setRect interpolateRects rect[0], rect[1], t
        
        if pos
          element.setPos interpolatePoints pos[0], pos[1], t
        
        if background
          element._.style.background = interpolateColors(background[0], background[1], t)
      
      if t == 1 and oncomplete
        oncomplete {
          numFrames: numFrames
          info: info
        }


linear    = (t) -> t
#easeIn    = (t) -> 
#easeOut   = (t) -> 
#easeInOut = (t) -> 


module.exports =
  Tween: Tween
  Morph: Morph
  linear: linear