discount manager specs

Rakefile

@@ -19,16 +19,16 @@ task :run do
   item1 = Product.new('001', 'Very Cheap Chair', 9.25)
   item2 = Product.new('002', 'Little Table', 45.00)
   item3 = Product.new('003', 'Funky Light', 19.95)
-  item4 = Product.new('001', 'Very Cheap Chair', 9.25)
 
-  puts "first run"
+
+  puts "first basket"
 
   co = Checkout.new(promo_rules)
   puts "scanning"
   co.scan(item1)
   co.scan(item2)
   co.scan(item3)
-  co.scan(item4)
+
 
   puts co.total
 end

lib/checkout.rb

@@ -1,8 +1,10 @@
 class Checkout
   attr_reader :promo_rules
+  attr_reader :discount_manager
   attr_accessor :basket
 
   def initialize(promo_rules = [])
+    @dicount_manager = DiscountManager.new(promo_rules)
     @promo_rules = promo_rules
     @basket = []
   end
@@ -12,16 +14,12 @@ def scan(item)
   end
 
   def total
-    multi_discount_price = 0
+    price = 0
     puts basket
     basket.each do |product|
-      promo_rules.each do |promo_rule|
-        if promo_rule.type == PromoRule::TYPE[:multi_discount]
-          multi_discount_price = promo_rule.apply(product.code, quantity_in_basket(product.code))
-        end
-      end
+      price += product.price
     end
-    multi_discount_price
+    price.round(2)
   end
 
   def quantity_in_basket(code)

lib/discount_manager.rb

@@ -0,0 +1,28 @@
+class DiscountManager
+
+  attr_reader :promo_rules
+
+  def initialize(promo_rules = [])
+    @promo_rules = promo_rules
+  end
+
+  def discount_price_for(product, quantity)
+    discount_price = 0
+
+    promo_rules.each do |promo_rule|
+      if promo_rule.type == PromoRule::TYPE[:multibuy_discount] #multi_discount
+        discount_price = promo_rule.apply(product.code, quantity)
+      end
+    end
+    discount_price == 0 ? product.price : discount_price
+  end
+
+  def discount_total(total)
+    promo_rules.each do |promo_rule|
+      if promo_rule.type == PromoRule::TYPE[:discount] # discount
+        total = promo_rule.apply(total)
+      end
+    end
+    total
+  end
+end

spec/checkout_spec.rb

@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe Checkout do
+  ProductStub = Struct.new(:code, :name, :price)
+  subject { Checkout.new }
+
+  describe "on setup" do
+    it 'should start with an empty basket' do
+      expect(subject.basket.count).to eq(0)
+    end
+    it 'should start with zero price' do
+      expect(subject.total).to eq(0)
+    end
+  end
+
+  context 'with no promo_rules' do
+    describe 'scan items' do
+      let(:product1) { ProductStub.new('001', 'name', 10) }
+      let(:product2) { ProductStub.new('002', 'here', 10) }
+
+      it 'should calculate total as the product price' do
+        subject.scan(product1)
+        subject.scan(product2)
+        expect(subject.total).to eq(20)
+      end
+
+      it 'should round total to two decimal places' do
+        product = ProductStub.new('001', 'name', 25.4552)
+        subject.scan(product)
+        expect(subject.total).to eq(25.46)
+      end
+    end
+  end
+
+  context 'with promo_rules' do
+    let(:product1) { ProductStub.new('001', 'name', 10) }
+    let(:product2) { ProductStub.new('002', 'here', 10) }
+  end
+
+end

spec/discount_manager_spec.rb

@@ -0,0 +1,61 @@
+require 'spec_helper'
+
+describe DiscountManager do
+  let(:promo_rule) {double('promo_rule')}
+  let(:product) { Struct.new(:code, :name, :price).new('001', 'foobar', 10.97) }
+  subject { DiscountManager.new([promo_rule]) }
+
+  describe '#discount_price_for' do
+    before do
+      allow(promo_rule).to receive(:type) { PromoRule::TYPE[:multibuy_discount] }
+      allow(promo_rule).to receive(:apply) { 60 }
+    end
+
+    it 'should pass the calculation to the promo_rule with params' do
+      expect(promo_rule).to receive(:type) { PromoRule::TYPE[:multibuy_discount] }
+      expect(promo_rule).to receive(:apply).with(product.code, 2)
+
+      subject.discount_price_for(product, 2)
+    end
+
+    it 'should return the discounted price when rule applied' do
+      price = subject.discount_price_for(product, 1)
+      expect(price).to eq(60)
+    end
+
+    it 'should return the original price if no rule applied' do
+      discount_manager = DiscountManager.new
+
+      price = discount_manager.discount_price_for(product, 1)
+      expect(price).to eq(product.price)
+    end
+
+  end
+
+  describe '#discount_total' do
+    before do
+      allow(promo_rule).to receive(:type) { PromoRule::TYPE[:discount] }
+      allow(promo_rule).to receive(:apply) { 100 }
+    end
+
+    it 'should pass the calculation to the rule with subtotal' do
+      expect(promo_rule).to receive(:type) { PromoRule::TYPE[:discount] }
+      expect(promo_rule).to receive(:apply).with(10)
+
+      subject.discount_total(10)
+    end
+
+    it 'should return the calculated total when rule applied' do
+      total = subject.discount_total(10)
+      expect(total).to eq(100)
+    end
+
+    it 'should return original subtotal if no rule match' do
+      discount_manager = DiscountManager.new
+
+      total = discount_manager.discount_total(10)
+      expect(total).to eq(10)
+    end
+
+  end
+end