immutable data model in coffee script

gistfile1.coffee

module.exports = (inputData, onChange, historySize = 100) ->
  data = inputData
  undos = []
  redos = []

  class Cursor

    constructor: (@path = []) ->

    cursor: (path = []) ->
      path = [path] unless path instanceof Array
      new Cursor @path.concat path

    get: (path = []) ->
      path = [path] unless path instanceof Array
      target = data
      target = target[key] for key in @path.concat path
      target

    deref: ->
      target = data
      target = target[key] for key in @path
      target

    set: (path, value) ->
      path = [path] unless path instanceof Array

      target = data
      for key in (@path.concat path).slice 0, -1
        updated = {}
        updated[k] = v for k, v of target[key]
        target = target[key] = updated

      target[path.slice -1] = value

      onChange data

    bind: (path, pre) ->
      (v) => @set path, if pre? then pre v else v

  undo: ->
    return unless undos.length > 0
    redos.push data
    redos.shift() if redos.length > historySize
    data = undos.pop()
    onChange data

  redo: ->
    return unless redos.length > 0
    undos.push data
    undos.shift() if undos.length > historySize
    data = redos.pop()
    onChange data

  root: new Cursor []