Adding dynamic text to display as placeholder

app/assets/javascripts/admin/controllers/variant_units_controller.js.coffee

@@ -0,0 +1,42 @@
+angular.module("ofn.admin")
+  .controller "VariantUnitsCtrl", ($scope, optionValueNamer) ->
+    $scope.$watchCollection '[variant.unit_value_with_description, product.variant_unit_name, product.variant_unit_with_scale]', ->
+      [variant_unit, variant_unit_scale] = $scope.productUnitProperties()
+      [unit_value, unit_description] = $scope.variantUnitProperties(variant_unit_scale)
+      variant_object = 
+        unit_value: unit_value
+        unit_description: unit_description
+        product:
+          variant_unit_scale: variant_unit_scale
+          variant_unit: variant_unit
+          variant_unit_name: $scope.product.variant_unit_name
+        
+      $scope.variant.options_text = new optionValueNamer(variant_object).name()
+
+    $scope.productUnitProperties = ->
+      # get relevant product properties
+      if $scope.product.variant_unit_with_scale
+        match = $scope.product.variant_unit_with_scale.match(/^([^_]+)_([\d\.]+)$/)
+        if match
+          variant_unit = match[1]
+          variant_unit_scale = parseFloat(match[2])
+        else
+          variant_unit = $scope.product.variant_unit_with_scale
+          variant_unit_scale = null
+      else
+        variant_unit = variant_unit_scale = null
+
+      [variant_unit, variant_unit_scale]
+
+    $scope.variantUnitProperties = (variant_unit_scale)->
+      # get relevant variant properties
+      if $scope.variant.hasOwnProperty("unit_value_with_description")
+        match = $scope.variant.unit_value_with_description.match(/^([\d\.]+(?= |$)|)( |)(.*)$/)
+        if match
+          unit_value  = parseFloat(match[1])
+          unit_value  = null if isNaN(unit_value)
+          unit_value *= variant_unit_scale if unit_value && variant_unit_scale
+          unit_description = match[3]
+      [unit_value, unit_description]
+      
+        

app/assets/javascripts/admin/services/option_value_namer.js.coffee

@@ -0,0 +1,66 @@
+angular.module("ofn.admin").factory "optionValueNamer", ($resource) ->
+  class OptionValueNamer
+    constructor: (@variant) ->
+
+    name: ->
+      [value, unit] = @option_value_value_unit()
+      separator = if @value_scaled() then '' else ' '
+
+      name_fields = []
+      name_fields.push "#{value}#{separator}#{unit}" if value? && unit?
+      name_fields.push @variant.unit_description if @variant.unit_description?
+      name_fields.join ' '
+
+    value_scaled: ->
+      @variant.product.variant_unit_scale?
+
+    option_value_value_unit: ->
+      if @variant.unit_value?
+        if @variant.product.variant_unit in ["weight", "volume"]
+          [value, unit_name] = @option_value_value_unit_scaled()
+    
+        else
+          value = @variant.unit_value
+          unit_name = @variant.product.variant_unit_name
+          # TODO needs to add pluralize to line below
+          # unit_name = unit_name if value > 1
+    
+        value = parseInt(value, 10) if value == parseInt(value, 10)
+    
+      else
+        value = unit_name = null
+    
+      [value, unit_name]
+
+    option_value_value_unit_scaled: ->
+      [unit_scale, unit_name] = @scale_for_unit_value()
+
+      value = @variant.unit_value / unit_scale
+
+      [value, unit_name]
+
+    scale_for_unit_value: ->
+      units = 
+        'weight':
+          1.0: 'g'
+          1000.0: 'kg'
+          1000000.0: 'T'
+        'volume':
+          0.001: 'mL'
+          1.0: 'L'
+          1000000.0: 'ML'
+
+      # Find the largest available unit where unit_value comes to >= 1 when expressed in it.
+      # If there is none available where this is true, use the smallest available unit.
+      unit = ([scale, unit_name] for scale, unit_name of units[@variant.product.variant_unit] when @variant.unit_value / scale >= 1).reduce (unit, [scale, unit_name]) ->
+        if (unit && scale > unit[0]) || !unit?
+          [scale, unit_name]
+        else
+          unit
+      , null
+      if !unit?
+        unit = ([scale, unit_name] for scale, unit_name of units[@variant.product.variant_unit]).reduce (unit, [scale, unit_name]) ->
+          if scale < unit[0] then [scale, unit_name] else unit
+        , [Infinity,""]
+
+      unit

app/views/spree/admin/products/bulk_edit.html.haml

@@ -155,7 +155,7 @@
             %input{ 'ng-model' => 'variant.display_name', :name => 'variant_display_name', 'ofn-track-variant' => 'display_name', :type => 'text', placeholder: "{{ product.name }}" }
           %td.unit_value{ 'ng-show' => 'columns.unit.visible' }
             %input{ 'ng-model' => 'variant.unit_value_with_description', :name => 'variant_unit_value_with_description', 'ofn-track-variant' => 'unit_value_with_description', :type => 'text' }
-          %td.display_as{ 'ng-show' => 'columns.unit.visible' }
+          %td.display_as{ 'ng-show' => 'columns.unit.visible', 'ng-controller' => "VariantUnitsCtrl" }
             %input{ 'ng-model' => 'variant.display_as', :name => 'variant_display_as', 'ofn-track-variant' => 'display_as', :type => 'text', placeholder: "{{ variant.options_text }}" }
           %td{ 'ng-show' => 'columns.price.visible' }
             %input{ 'ng-model' => 'variant.price', 'ofn-decimal' => :true, :name => 'variant_price', 'ofn-track-variant' => 'price', :type => 'text' }