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ruby/potter/5/potter.rb

@@ -0,0 +1,33 @@
+class Potter  
+
+  #Constants
+  BPRICE = 8
+  #Main invocation for returning the price
+  def price(books)
+    #Checks for an empty collection
+      return 0 if books.empty?
+      if books.uniq.size == 1
+        BPRICE * books.count
+      else
+        count_collection(books)
+      end
+
+  end
+
+
+  def count_collection(books)
+    collection = books.clone.uniq.size
+    sum = 0    
+    case collection            
+         when 2
+           sum += BPRICE * collection * 0.95
+         when 3
+           sum += BPRICE * collection * 0.90
+         when 4
+           sum += BPRICE * collection * 0.80
+         when 5
+           sum += BPRICE * collection * 0.75
+         end     
+  end
+
+end

ruby/potter/5/potter_test.rb

@@ -0,0 +1,42 @@
+require "minitest/autorun"
+require './potter'
+
+class Test_Potter < Minitest::Test
+  def setup
+    @potter = Potter.new
+  end
+
+  def test_basics
+    assert_equal(0, @potter.price([]))
+    assert_equal(8, @potter.price([0]))
+    assert_equal(8, @potter.price([0]))
+    assert_equal(8, @potter.price([0]))
+    assert_equal(8, @potter.price([0]))
+    assert_equal(8, @potter.price([0]))
+
+    assert_equal(8 * 2, @potter.price([0, 0]))
+    assert_equal(8 * 3, @potter.price([0, 0, 0]))
+  end
+
+  def test_simple_discounts
+    assert_equal(8 * 2 * 0.95, @potter.price([0, 1])) #15.2
+    assert_equal(8 * 3 * 0.90, @potter.price([0, 1, 2])) #21.6
+    assert_equal(8 * 4 * 0.80, @potter.price([0, 1, 2, 3])) #25.6
+    assert_equal(8 * 5 * 0.75, @potter.price([0, 1, 2, 3, 4])) #30.0
+
+  end
+
+  def test_several_discounts
+    assert_equal(8 + (8 * 2 * 0.95), @potter.price([0, 0, 1])) #23.2
+    #assert_equal(2 * (8 * 2 * 0.95), @potter.price({b1: 2, b2: 2, b3: 0, b4: 0, b5: 0})) #30.4
+    #assert_equal((8 * 4 * 0.8) + (8 * 2 * 0.95), @potter.price({b1: 2, b2: 1, b3: 2, b4: 1, b5: 0})) #40.8
+    #assert_equal(8 + (8 * 5 * 0.75), @potter.price({b1: 1, b2: 2, b3: 1, b4: 1, b5: 1})) #38
+  end
+
+  def edge_cases
+    assert_equal(2 * (8 * 4 * 0.80), @potter.price({b1: 2, b2: 2, b3: 2, b4: 1, b5: 1}))
+    assert_equal(3 * (8 * 5 * 0.75) + 2 * (8 * 4 * 0.8),
+    @potter.price({b1: 5, b2: 5, b3: 4, b4: 5, b5: 4}))
+  end
+
+end