import Mixin from '@ember/object/mixin'
import { typeOf } from '@ember/utils'
import { computed, defineProperty } from '@ember/object'

###*
# Provides styleBindings property to bind style
# properties based on object properties.
#
# @class StyleBindingsMixin
# @public
###

StyleBindingsMixin = Mixin.create

  ###*
  # Add `styleBindings` property as a `concatenatedProperties`.
  # @property concatenatedProperties
  # @type array
  ###
  concatenatedProperties: ['styleBindings']

  ###*
  # Apply the `style` attribute to the DOM element.
  # @property attributeBindings
  # @type array
  ####
  attributeBindings: ['style']

  ###*
  # The default unit for numbered value.
  # @property unit
  # @type string
  ###
  unit: 'px'

  ###*
  # Build a style property and its value as a string.
  # @method buildStyleString
  # @param {String} style property name
  # @param {String} property name in the current object that should be resolved as the
  # value of the style property.
  # @private
  ###
  buildStyleString: (styleName, property) ->
    value = @get(property)

    return if value is undefined

    value = value + @get("unit") if typeOf(value) is "number"
    (styleName + ":" + value + ";")

  ###*
  # Apply the style bindings during the view `init` phase.
  #
  # This method assumes that the attribute `styleBindings` is defined as an array of strings where
  # each string is a property name that should be resolved as a style option.
  #
  # @method applyBindings
  # @private
  ###
  applyBindings: (->
    return unless bindings = @get('styleBindings')

    lookup = {}

    bindings.forEach (binding) ->
      propArr = binding.split(":")
      property = propArr[0]
      style = propArr[1]
      lookup[style or property] = property

    styles = Object.keys(lookup)
    properties = styles.map((style) ->
      lookup[style]
    )

    styleComputed = computed(->
      styleTokens = styles.map((style) =>
        @buildStyleString style, lookup[style]
      )
      styleString = styleTokens.join("").htmlSafe()
      styleString  if styleString.length isnt 0
    )

    styleComputed.property.apply styleComputed, properties
    defineProperty @, "style", styleComputed

  ).on('init')

export default StyleBindingsMixin