Use existing service to label weight&volume units

We still have the scale stored in two places but in our current system
that's part of a unit's "id".

If the DFC adds that value to its standard then we can use it for lookup
and don't need to repeat it.

* datafoodconsortium/taxonomies#7

app/services/weights_and_measures.rb

@@ -24,16 +24,25 @@ def system
 
   UNITS = {
     'weight' => {
+      0.001 => { 'name' => 'mg', 'system' => 'metric' },
       1.0 => { 'name' => 'g', 'system' => 'metric' },
+      1000.0 => { 'name' => 'kg', 'system' => 'metric' },
+      1_000_000.0 => { 'name' => 'T', 'system' => 'metric' },
+
+      28.349523125 => { 'name' => 'oz', 'system' => 'imperial' },
       28.35 => { 'name' => 'oz', 'system' => 'imperial' },
+      453.59237 => { 'name' => 'lb', 'system' => 'imperial' },
       453.6 => { 'name' => 'lb', 'system' => 'imperial' },
-      1000.0 => { 'name' => 'kg', 'system' => 'metric' },
-      1_000_000.0 => { 'name' => 'T', 'system' => 'metric' }
     },
     'volume' => {
       0.001 => { 'name' => 'mL', 'system' => 'metric' },
+      0.01 => { 'name' => 'cL', 'system' => 'metric' },
+      0.1 => { 'name' => 'dL', 'system' => 'metric' },
       1.0 => { 'name' => 'L', 'system' => 'metric' },
-      1000.0 => { 'name' => 'kL', 'system' => 'metric' }
+      1000.0 => { 'name' => 'kL', 'system' => 'metric' },
+
+      0.25 => { 'name' => 'cu', 'system' => 'imperial' },
+      4.54609 => { 'name' => 'gal', 'system' => 'imperial' },
     }
   }.freeze
 

engines/dfc_provider/app/services/quantitative_value_builder.rb

@@ -31,7 +31,7 @@ def self.apply(quantity, product)
     measure, unit_name, unit_scale = map_unit(quantity.unit)
 
     product.variant_unit = measure
-    product.variant_unit_name = unit_name
+    product.variant_unit_name = unit_name if measure == "items"
     product.variant_unit_scale = unit_scale
     product.unit_value = quantity.value * unit_scale
   end
@@ -69,34 +69,38 @@ def self.apply(quantity, product)
   def self.map_unit(unit) # rubocop:disable Metrics/CyclomaticComplexity, Metrics/MethodLength
     quantity_unit = DfcLoader.connector.MEASURES.UNIT.QUANTITYUNIT
 
+    # The unit name is only set for items. The name is implied for weight and
+    # volume and filled in by `WeightsAndMeasures`.
     case unit
     when quantity_unit.LITRE
-      ["volume", "liter", 1]
+      ["volume", nil, 1]
     when quantity_unit.MILLILITRE
-      ["volume", "ml", 0.001]
+      ["volume", nil, 0.001]
     when quantity_unit.CENTILITRE
-      ["volume", "cl", 0.01]
+      ["volume", nil, 0.01]
     when quantity_unit.DECILITRE
-      ["volume", "dl", 0.1]
+      ["volume", nil, 0.1]
     when quantity_unit.CUP
       # Interpreted as metric cup, not US legal cup.
       # https://github.com/datafoodconsortium/taxonomies/issues/8
-      ["volume", "cu", 0.25]
+      ["volume", nil, 0.25]
     when quantity_unit.GALLON
-      ["volume", "gal", 4.54609]
+      ["volume", nil, 4.54609]
+
     when quantity_unit.MILLIGRAM
-      ["weight", "mg", 0.001]
+      ["weight", nil, 0.001]
     when quantity_unit.GRAM
-      ["weight", "gram", 1]
+      ["weight", nil, 1]
     when quantity_unit.KILOGRAM
-      ["weight", "kg", 1_000]
+      ["weight", nil, 1_000]
     when quantity_unit.TONNE
-      ["weight", "kg", 1_000_000]
+      ["weight", nil, 1_000_000]
     # Not part of the DFC yet:
     # when quantity_unit.OUNCE
-    #   ["weight", "oz", 28.349523125]
+    #   ["weight", nil, 28.349523125]
     when quantity_unit.POUNDMASS
-      ["weight", "lb", 453.59237]
+      ["weight", nil, 453.59237]
+
     when quantity_unit.PAIR
       ["items", "pair", 2]
     when quantity_unit._4PACK

engines/dfc_provider/spec/services/quantitative_value_builder_spec.rb

@@ -71,7 +71,7 @@
       builder.apply(quantity, product)
 
       expect(product.variant_unit).to eq "volume"
-      expect(product.variant_unit_name).to eq "liter"
+      expect(product.variant_unit_name).to eq nil
       expect(product.variant_unit_scale).to eq 1
       expect(product.unit_value).to eq 2
     end
@@ -85,7 +85,7 @@
       builder.apply(quantity, product)
 
       expect(product.variant_unit).to eq "weight"
-      expect(product.variant_unit_name).to eq "kg"
+      expect(product.variant_unit_name).to eq nil
       expect(product.variant_unit_scale).to eq 1_000
       expect(product.unit_value).to eq 4_000
     end
@@ -99,7 +99,7 @@
       builder.apply(quantity, product)
 
       expect(product.variant_unit).to eq "weight"
-      expect(product.variant_unit_name).to eq "mg"
+      expect(product.variant_unit_name).to eq nil
       expect(product.variant_unit_scale).to eq 0.001
       expect(product.unit_value).to eq 0.005
     end
@@ -113,7 +113,7 @@
       builder.apply(quantity, product)
 
       expect(product.variant_unit).to eq "weight"
-      expect(product.variant_unit_name).to eq "lb"
+      expect(product.variant_unit_name).to eq nil
       expect(product.variant_unit_scale).to eq 453.59237
       expect(product.unit_value).to eq 4_535.9237
     end

spec/services/variant_units/option_value_namer_spec.rb

@@ -115,8 +115,8 @@ module VariantUnits
           p = double(:product, variant_unit: 'volume', variant_unit_scale: scale)
           allow(v).to receive(:product) { p }
           allow(p).to receive(:persisted?) { true }
-          allow(v).to receive(:unit_value) { 100 * scale }
-          expect(subject.send(:option_value_value_unit)).to eq [100, unit]
+          allow(v).to receive(:unit_value) { 3 * scale }
+          expect(subject.send(:option_value_value_unit)).to eq [3, unit]
         end
       end