Prefer generic calculator handler

core/app/models/spree/calculator/distributed_amount.rb

@@ -11,14 +11,20 @@ class Calculator::DistributedAmount < Calculator
     preference :currency, :string, default: -> { Spree::Config[:currency] }
 
     def compute_line_item(line_item)
-      if line_item && preferred_currency.casecmp(line_item.currency).zero?
-        Spree::DistributedAmountsHandler.new(
-          line_item,
-          calculable.promotion,
-          preferred_amount
-        ).amount
-      else
-        0
+      return 0 unless line_item
+      return 0 unless preferred_currency.casecmp(line_item.currency).zero?
+      return 0 unless calculable.promotion.line_item_actionable?(line_item.order, line_item)
+      Spree::DistributedAmountsHandler.new(
+        actionable_line_items(line_item.order),
+        preferred_amount
+      ).amount(line_item)
+    end
+
+    private
+
+    def actionable_line_items(order)
+      order.line_items.select do |line_item|
+        calculable.promotion.line_item_actionable?(order, line_item)
       end
     end
   end

core/app/models/spree/distributed_amounts_handler.rb

@@ -1,17 +1,16 @@
 module Spree
   class DistributedAmountsHandler
-    attr_reader :line_item, :order, :promotion, :total_amount
+    attr_reader :line_items, :total_amount
 
-    def initialize(line_item, promotion, total_amount)
-      @line_item = line_item
-      @order = line_item.order
-      @promotion = promotion
+    def initialize(line_items, total_amount)
+      @line_items = line_items
       @total_amount = total_amount
     end
 
-    # @return [BigDecimal] the weighted adjustment for the initialized line item
-    def amount
-      distributed_amounts[@line_item.id].to_d
+    # @param [LineItem] one of the line_items distributed over
+    # @return [BigDecimal] the weighted adjustment for this line_item
+    def amount(line_item)
+      distributed_amounts[line_item.id].to_d
     end
 
     private
@@ -24,14 +23,11 @@ def distributed_amounts
     end
 
     def line_item_ids
-      @order.line_items.map(&:id)
+      line_items.map(&:id)
     end
 
     def elligible_amounts
-      @order.line_items.map do |line_item|
-        elligible = promotion.line_item_actionable?(line_item.order, line_item)
-        elligible ? line_item.amount : 0
-      end
+      line_items.map(&:amount)
     end
 
     def subtotal
@@ -43,7 +39,7 @@ def weights
     end
 
     def allocated_amounts
-      @total_amount.to_money.allocate(weights).map(&:to_money)
+      total_amount.to_money.allocate(weights).map(&:to_money)
     end
   end
 end

core/spec/models/spree/distributed_amounts_handler_spec.rb

@@ -7,19 +7,20 @@
       line_items_attributes: line_items_attributes
     )
   end
-  let(:promotion) { FactoryBot.build(:promotion) }
+
+  let(:handler) {
+    described_class.new(order.line_items, total_amount)
+  }
 
   describe "#amount" do
     let(:total_amount) { 15 }
 
-    subject { described_class.new(line_item, promotion, total_amount).amount }
-
     context "when there is only one line item" do
       let(:line_items_attributes) { [{ price: 100 }] }
       let(:line_item) { order.line_items.first }
 
       it "applies the entire amount to the line item" do
-        expect(subject).to eq(15)
+        expect(handler.amount(line_item)).to eq(15)
       end
     end
 
@@ -32,9 +33,9 @@
         it "evenly distributes the total amount" do
           expect(
             [
-              described_class.new(order.line_items[0], promotion, total_amount).amount,
-              described_class.new(order.line_items[1], promotion, total_amount).amount,
-              described_class.new(order.line_items[2], promotion, total_amount).amount
+              handler.amount(order.line_items[0]),
+              handler.amount(order.line_items[1]),
+              handler.amount(order.line_items[2])
             ]
           ).to eq(
             [5, 5, 5]
@@ -47,9 +48,9 @@
           it "applies the remainder of the total amount to the last item" do
             expect(
               [
-                described_class.new(order.line_items[0], promotion, total_amount).amount,
-                described_class.new(order.line_items[1], promotion, total_amount).amount,
-                described_class.new(order.line_items[2], promotion, total_amount).amount
+                handler.amount(order.line_items[0]),
+                handler.amount(order.line_items[1]),
+                handler.amount(order.line_items[2])
               ]
             ).to match_array(
               [3.33, 3.33, 3.34]
@@ -66,9 +67,9 @@
         it "distributes the total amount relative to the item's price" do
           expect(
             [
-              described_class.new(order.line_items[0], promotion, total_amount).amount,
-              described_class.new(order.line_items[1], promotion, total_amount).amount,
-              described_class.new(order.line_items[2], promotion, total_amount).amount
+              handler.amount(order.line_items[0]),
+              handler.amount(order.line_items[1]),
+              handler.amount(order.line_items[2])
             ]
           ).to eq(
             [7.5, 2.5, 5]