Close #769 discount maximum cap

app/services/spree_cm_commissioner/discount_cap_calculator.rb

@@ -0,0 +1,15 @@
+module SpreeCmCommissioner
+  class DiscountCapCalculator
+    def initialize(order_amount, percentage_discount, discount_cap)
+      @order_amount = order_amount
+      @percentage_discount = percentage_discount
+      @discount_cap = discount_cap
+    end
+
+    def calculate_discount
+      calculated_discount = (@order_amount * @percentage_discount) / 100
+      final_discount = [calculated_discount, @discount_cap].min
+      final_discount.to_f
+    end
+  end
+end

spec/services/spree_cm_commissioner/discount_cap_calculator_spec.rb

@@ -0,0 +1,26 @@
+require "spec_helper"
+
+RSpec.describe SpreeCmCommissioner::DiscountCapCalculator do
+  let(:order1) { create(:order, total: 100 ) }
+  let(:order2) { create(:order, total: 30 ) }
+  let(:percentage_discount) {50}
+  let(:discount_cap) {20}
+
+  describe '#calculate_discount' do
+    it 'calculates the discount with a cap' do
+      subject = described_class.new(order1.total, percentage_discount, discount_cap)
+
+      final_discount = subject.calculate_discount
+
+      expect(final_discount).to eq(20.0)
+    end
+
+    it 'calculates the discount without a cap' do
+      subject = described_class.new(order2.total, percentage_discount, discount_cap)
+
+      final_discount = subject.calculate_discount
+
+      expect(final_discount).to eq(15.0)
+    end
+  end
+end