Implement LP L discount rule

lib/planet_express.rb

@@ -13,13 +13,14 @@ require 'planet_express/invalid_shipment'
 require 'planet_express/shipment'
 require 'planet_express/shipment_repository'
 require 'planet_express/shipment_reader'
+# require 'planet_express/shipment_formatter'
 
 require 'planet_express/shipping_option'
 require 'planet_express/shipping_option_repository'
 
 require 'planet_express/rule'
 require 'planet_express/s_shipment_discount_rule'
-# require 'planet_express/l_shipment_discount_rule'
+require 'planet_express/l_shipment_discount_rule'
 
 require 'planet_express/shipment_discount_calculator'
 

lib/planet_express/l_shipment_discount_rule.rb

@@ -0,0 +1,39 @@
+module PlanetExpress
+  class LShipmentDiscountRule < Rule
+    protected
+
+    def applicable_to?(shipment)
+      lp_provider_shipment?(shipment) &&
+        third_l_shipment_in_month?(shipment) &&
+        rule_not_applied_in_month_already?(shipment)
+    end
+
+    def discount_for(shipment)
+      Discount.new(discount_amount(shipment), self)
+    end
+
+    private
+
+    def lp_provider_shipment?(shipment)
+      shipment.lp_provider?
+    end
+
+    def third_l_shipment_in_month?(shipment)
+      provider = shipment.provider
+      month = shipment.month
+
+      count = shipment_repository.l_shipment_count_for_provider_and_month(provider,
+                                                                          month)
+      (count % 3) == 2
+    end
+
+    def rule_not_applied_in_month_already?(shipment)
+      !shipment_repository.rule_applied_in_month?(shipment.month, self.class)
+    end
+
+    def discount_amount(shipment)
+      desired_amount = price(shipment)
+      discount_budget(shipment).maximum_possible_discount(desired_amount)
+    end
+  end
+end

lib/planet_express/shipment.rb

@@ -14,6 +14,18 @@ module PlanetExpress
       date.begin_of_month
     end
 
+    def price_with_discounts
+      shipping_option.price_in_cents - total_discount_amount
+    end
+
+    def total_discount_amount
+      discounts.map(&:amount).sum
+    end
+
+    def lp_provider?
+      shipping_option.lp_provider?
+    end
+
     def s_shipment?
       shipping_option.s_shipment?
     end

lib/planet_express/shipping_option.rb

@@ -10,6 +10,10 @@ module PlanetExpress
       package_size == 'L'
     end
 
+    def lp_provider?
+      provider == 'LP'
+    end
+
     def inspect
       "ShippingOption [proivder=#{provider} package_size=#{package_size} price_in_cents=#{price_in_cents}]"
     end

spec/l_shipment_discount_rule_spec.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+RSpec.describe PlanetExpress::LShipmentDiscountRule do
+  let(:budget_repo) { PlanetExpress::DiscountBudgetForMonthRepository.new }
+  let(:shipping_option_repo) { PlanetExpress::ShippingOptionRepository.new }
+  let(:shipment_repo) { PlanetExpress::ShipmentRepository.new(data: []) }
+
+  subject do
+    described_class.new(
+      discount_budget_for_month_repository: budget_repo,
+      shipping_option_repository: shipping_option_repo,
+      shipment_repository: shipment_repo)
+  end
+
+  let(:correct_shipping_option) do
+    shipping_option_repo.find_by_provider_and_package_size('LP', 'L')
+  end
+
+  let(:applicable_shipment) do
+    PlanetExpress::Shipment.new(Date.today, correct_shipping_option)
+  end
+
+  context 'l_shipment' do
+    context 'not the third shipment' do
+      it 'does not apply the discount' do
+        expect do
+          subject.apply_to(applicable_shipment)
+        end.to_not(change { applicable_shipment.discounts })
+      end
+    end
+
+    context 'third shipment for LP' do
+      context 'LP provider' do
+        before(:each) do
+          shipment_repo.add(applicable_shipment)
+          shipment_repo.add(applicable_shipment)
+        end
+
+        it 'does apply the discount' do
+          expect do
+            subject.apply_to(applicable_shipment)
+          end.to(change { applicable_shipment.discounts.length }.by(1))
+
+          discount = applicable_shipment.discounts.last
+          expect(discount.amount).to eq(applicable_shipment.shipping_option.price_in_cents)
+        end
+
+        it 'updates the discount budget' do
+          expected_difference = -applicable_shipment.shipping_option.price_in_cents
+
+          expect do
+            subject.apply_to(applicable_shipment)
+          end.to(change { budget_repo.for_month(applicable_shipment.month).available_budget }.by(expected_difference))
+        end
+      end
+
+      context 'non LP provider' do
+        before(:each) do
+          shipment_repo.add(applicable_shipment)
+          shipment_repo.add(applicable_shipment)
+        end
+        let(:shipping_option) do
+          shipping_option_repo.find_by_provider_and_package_size('MR', 'L')
+        end
+        let(:shipment) do
+          PlanetExpress::Shipment.new(Date.today, shipping_option)
+        end
+
+        it 'does not update the discounts' do
+          expect do
+            subject.apply_to(shipment)
+          end.to_not(change { shipment.discounts })
+        end
+      end
+    end
+  end
+end

spec/shipping_option_spec.rb

@@ -32,4 +32,22 @@ RSpec.describe PlanetExpress::ShippingOption do
       end
     end
   end
+
+  describe '#lp_provider?' do
+    context 'with LP provider' do
+      subject { build(:shipping_option, provider: 'LP') }
+
+      it 'returns true' do
+        expect(subject.lp_provider?).to eq(true)
+      end
+    end
+
+    context 'with non L package size' do
+      subject { build(:shipping_option, provider: 'MP') }
+
+      it 'returns false' do
+        expect(subject.lp_provider?).to eq(false)
+      end
+    end
+  end
 end