
define [
  "backbone",
  "common/has_properties",
], (Backbone, HasProperties) ->


  class LinearMapper extends HasProperties
    initialize: (attrs, options) ->
      super(attrs, options)

      @register_property('mapper_state', @_mapper_state, true)
      @add_dependencies('mapper_state', this, ['source_range', 'target_range'])
      @add_dependencies('mapper_state', @get('source_range'), ['start', 'end'])
      @add_dependencies('mapper_state', @get('target_range'), ['start', 'end'])

    map_to_target: (x) ->
      [scale, offset] = @get('mapper_state')
      return scale * x + offset

    v_map_to_target: (xs) ->
      [scale, offset] = @get('mapper_state')
      result = new Float64Array(xs.length)
      for x, idx in xs
        result[idx] = scale * x + offset
      return result

    map_from_target: (xprime) ->
      [scale, offset] = @get('mapper_state')
      return (xprime - offset) / scale

    v_map_from_target: (xprimes) ->
      [scale, offset] = @get('mapper_state')
      result = new Float64Array(xprimes.length)
      for xprime, idx in xprimes
        result[idx] = (xprime - offset) / scale
      return result

    _mapper_state: () ->
      #
      #  (t1 - t0)       (t1 - t0)
      #  --------- * x - --------- * s0 + t0
      #  (s1 - s0)       (s1 - s0)
      #
      # [  scale  ]     [    offset    ]
      #
      source_start = @get('source_range').get('start')
      source_end   = @get('source_range').get('end')
      target_start = @get('target_range').get('start')
      target_end   = @get('target_range').get('end')
      scale = (target_end - target_start)/(source_end - source_start)
      offset = -(scale * source_start) + target_start
      return [scale, offset]

  class LinearMappers extends Backbone.Collection
    model: LinearMapper

  return {
    "Model": LinearMapper,
    "Collection": new LinearMappers()
  }