Share mock db. Add discounts.

Author: John Ollier

Lib/basket.rb

@@ -1,11 +1,12 @@
 class Basket
   attr_reader :purchases
 
-  def initialize(catalogue)
+  def initialize(catalogue, discount_rules)
     # the class is called basket, lets think of a different descriptive name
     @purchases = Hash.new
     @catalogue = catalogue
     @catalogue.products_by_code.each_key { |p_code| @purchases[p_code] = 0 }
+    @discount_rules = discount_rules
   end
 
   def show
@@ -18,7 +19,16 @@ def show
         message_lines << checkout_line(product.name, quantity, price)
       end
     end
-    message_lines << total_line(total)
+    subtotal = total
+    message_lines << total_line(subtotal)
+    @discount_rules.each do |discount_rule|
+      discount = discount_rule.calculate_discount(@catalogue, @purchases)
+      if discount > 0
+        subtotal = subtotal - discount
+        message_lines << discount_rule.discount_line( format_price( discount ) )
+      end
+    end
+    message_lines << total_line(subtotal)
     message_lines
   end
 

Lib/main.rb

@@ -1,5 +1,7 @@
 require './basket'
 require './catalogue'
+require './multiple_purchase_free_discount'
+require './multiple_purchase_reduced_price_discount'
 
 def print_message(lines)
   lines.each { |line| puts line }
@@ -13,7 +15,10 @@ def print_message(lines)
   finish = false
 
   catalogue = Catalogue.new(db)
-  basket = Basket.new(catalogue)
+  buy_fruit_tea_offer = MultiplePurchaseFreeDiscount.new(2, 'FR1')
+  reduced_price_strawbs_offer = MultiplePurchaseReducedPriceDiscount.new(3, 'SR1', 450)
+  discount_rules = [buy_fruit_tea_offer, reduced_price_strawbs_offer]
+  basket = Basket.new(catalogue, discount_rules)
 
   while !finish
     puts "Please enter command from: add [product code], remove [product_code], checkout"

Lib/multiple_purchase_free_discount.rb

@@ -0,0 +1,21 @@
+class MultiplePurchaseFreeDiscount
+
+  def initialize(multiple, product_code)
+    @multiple = multiple
+    @product_code = product_code
+  end
+
+  def product_code
+    @product_code
+  end
+
+  def calculate_discount(catalogue, purchases)
+    product_price = catalogue.products_by_code[@product_code].price
+    product_price * (purchases[@product_code] / 2)
+  end
+
+  def discount_line( discount )
+    "Buy #{@multiple} get one free discount £#{discount}"
+  end
+
+end

Lib/multiple_purchase_reduced_price_discount.rb

@@ -0,0 +1,27 @@
+class MultiplePurchaseReducedPriceDiscount
+
+  def initialize(multiple, product_code, reduced_price)
+    @multiple = multiple
+    @product_code = product_code
+    @reduced_price = reduced_price
+  end
+
+  def product_code
+    @product_code
+  end
+
+  def calculate_discount(catalogue, purchases)
+    product_price = catalogue.products_by_code[@product_code].price
+    if purchases[@product_code] >= @multiple
+      (product_price - @reduced_price) * purchases[@product_code]
+    else
+      0
+    end
+
+  end
+
+  def discount_line(discount)
+    "Buy #{@multiple} get reduced price discount £#{discount}"
+  end
+
+end

Spec/basket_spec.rb

@@ -1,24 +1,14 @@
 require 'basket'
 require 'catalogue'
+require 'mock_db'
 
-# here's a simple mock class, but for anything more complex use a mocking framework
-class MockDB
-  def execute(s)
-    # do nothing
-  end
-
-  def get_first_value(s)
-    nil
-  end
-end
-
-db = MockDB.new
+db = MockDb.new
 
 describe Basket do
   catalogue = Catalogue.new(db)
   describe '#initialize' do
     it "is empty initially" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       # when testing methods test the data not a formatted message containing the data
       expect(basket.purchases['FR1']).to eq(0)
       expect(basket.purchases['SR1']).to eq(0)
@@ -27,14 +17,14 @@ def get_first_value(s)
   end
   describe '#add' do
     it "can add a valid item" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       basket.add("FR1")
       expect(basket.purchases['FR1']).to eq(1)
       expect(basket.purchases['SR1']).to eq(0)
       expect(basket.purchases['CF1']).to eq(0)
     end
     it "will not add an invalid item" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       basket.add("ZZZ")
       expect(basket.purchases['FR1']).to eq(0)
       expect(basket.purchases['SR1']).to eq(0)
@@ -43,7 +33,7 @@ def get_first_value(s)
   end
   describe '#remove' do
     it "can remove a valid item if present" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       basket.add("FR1")
       basket.add("FR1")
       basket.remove("FR1")
@@ -52,7 +42,7 @@ def get_first_value(s)
       expect(basket.purchases['CF1']).to eq(0)
     end
     it "will not remove an invalid item" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       basket.remove("ZZZ")
       expect(basket.purchases['FR1']).to eq(0)
       expect(basket.purchases['SR1']).to eq(0)
@@ -61,11 +51,11 @@ def get_first_value(s)
   end
   describe '#total' do
     it "will be zero initially" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       expect(basket.total).to eq(0)
     end
     it "will calculate the running total" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       basket.add("FR1")
       basket.add("FR1")
       basket.add("CF1")
@@ -74,7 +64,7 @@ def get_first_value(s)
   end
   describe '#show' do
     it "will show product names and quantities" do
-      basket = Basket.new(catalogue)
+      basket = Basket.new(catalogue, [])
       basket.add("FR1")
       basket.add("FR1")
       basket.add("CF1")

Spec/catalogue_spec.rb

@@ -1,16 +1,7 @@
 require 'catalogue'
+require 'mock_db'
 
-class MockDB
-  def execute(s)
-    # do nothing
-  end
-
-  def get_first_value(s)
-    return nil
-  end
-end
-
-db = MockDB.new
+db = MockDb.new
 
 describe Catalogue do
   describe '#initialize' do

Spec/mock_db.rb

@@ -0,0 +1,10 @@
+# here's a simple mock class, but for anything more complex use a mocking framework
+class MockDb
+  def execute(s)
+    # do nothing
+  end
+
+  def get_first_value(s)
+    nil
+  end
+end

Spec/multiple_purchase_free_spec.rb

@@ -0,0 +1,34 @@
+require 'mock_db'
+require 'multiple_purchase_free_discount'
+
+db = MockDb.new
+
+describe MultiplePurchaseFreeDiscount do
+  catalogue = Catalogue.new(db)
+  describe '#calculate_discount' do
+    it "is zero under threshold" do
+      rule = MultiplePurchaseFreeDiscount.new(2, 'FR1')
+      purchases = {'FR1' => 1, 'SR1' => 0, 'CF1' => 0}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(0)
+    end
+    it "is same as price on threshold" do
+      rule = MultiplePurchaseFreeDiscount.new(2, 'FR1')
+      purchases = {'FR1' => 2, 'SR1' => 0, 'CF1' => 0}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(311)
+    end
+    it "is same as price just over threshold" do
+      rule = MultiplePurchaseFreeDiscount.new(2, 'FR1')
+      purchases = {'FR1' => 3, 'SR1' => 0, 'CF1' => 0}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(311)
+    end
+    it "is twice price for twice threshold" do
+      rule = MultiplePurchaseFreeDiscount.new(2, 'FR1')
+      purchases = {'FR1' => 4, 'SR1' => 0, 'CF1' => 0}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(622)
+    end
+  end
+end

Spec/multiple_purchase_reduced_price_spec.rb

@@ -0,0 +1,34 @@
+require 'mock_db'
+require 'multiple_purchase_reduced_price_discount'
+
+db = MockDb.new
+
+describe MultiplePurchaseReducedPriceDiscount do
+  catalogue = Catalogue.new(db)
+  describe '#calculate_discount' do
+    it "is zero under threshold" do
+      rule = MultiplePurchaseReducedPriceDiscount.new(3, 'SR1', 450)
+      purchases = {'SR1' => 2, 'FR1' => 0, 'CF1' => 0 }
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(0)
+    end
+    it "is difference between prices on threshold" do
+      rule = MultiplePurchaseReducedPriceDiscount.new(3, 'SR1', 450)
+      purchases = {'SR1' => 3, 'FR1' => 0, 'CF1' => 0}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(150)
+    end
+    it "is difference between prices over threshold" do
+      rule = MultiplePurchaseReducedPriceDiscount.new(3, 'SR1', 450)
+      purchases = {'SR1' => 4, 'FR1' => 0, 'CF1' => 0}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(200)
+    end
+    it "is zero for other product" do
+      rule = MultiplePurchaseReducedPriceDiscount.new(3, 'SR1', 450)
+      purchases = {'SR1' => 0, 'FR1' => 1, 'CF1' => 2}
+      discount = rule.calculate_discount(catalogue, purchases)
+      expect(discount).to eq(0)
+    end
+  end
+end