first commit

.autotest

@@ -0,0 +1,9 @@
+require 'autotest/restart'
+
+Autotest.add_hook :initialize do |at|
+  at.testlib = ".minitest.rb"
+end
+
+Autotest.add_hook :all_good do |at|
+  system "rake rcov_info"
+end if ENV['RCOV']

.minitest.rb

@@ -0,0 +1,2 @@
+# gem "minitest"
+require "minitest/autorun"

.rvmrc

@@ -0,0 +1 @@
+rvm use 1.9.2@prixfixe

doc/notes.txt

@@ -0,0 +1,12 @@
+Static pricing models
+--------
+list price (price/unit)
+product feature/customer segment - dependent (feature A enabled?)
+volume dependent (list price, but tiered)
+
+Dynamic pricing
+------
+negotiated
+yield management (depends on inventory and/or time of purchase)
+real-time (based on supply and demand)
+auction (competitive bidding)

lib/prixfixe.rb

@@ -0,0 +1,8 @@
+module Prixfixe
+  require 'prixfixe/static_model'
+  require 'prixfixe/list_price'
+  require 'prixfixe/volume_price'
+  require 'prixfixe/conditional_price'
+  require 'prixfixe/minimum_price'
+  require 'prixfixe/unit_price'
+end

lib/prixfixe/conditional_price.rb

@@ -0,0 +1,12 @@
+module Prixfixe
+  class ConditionalPrice < StaticModel
+    def initialize(proc, model)
+      @proc = proc
+      @model = model
+    end
+
+    def calculate(items) 
+      @model.calculate(items.select {|item| @proc.call(item)})
+    end
+  end
+end

lib/prixfixe/list_price.rb

@@ -0,0 +1,15 @@
+module Prixfixe
+  class ListPrice < StaticModel
+    def initialize(unit_price)
+      @unit_price = unit_price
+    end
+
+    def calculate(items)
+      if items.kind_of?(Enumerable)
+        items.size * @unit_price
+      else
+        items * @unit_price
+      end
+    end
+  end
+end

lib/prixfixe/minimum_price.rb

@@ -0,0 +1,13 @@
+module Prixfixe
+  class MinimumPrice < StaticModel
+    def initialize(min, model) 
+      @min = min
+      @model = model
+    end
+
+    def calculate(items)
+      calculated = @model.calculate(items)
+      calculated < @min ? @min : calculated
+    end
+  end
+end

lib/prixfixe/static_model.rb

@@ -0,0 +1,5 @@
+module Prixfixe
+  class StaticModel
+    def calculate(items) 0; end
+  end
+end

lib/prixfixe/unit_price.rb

@@ -0,0 +1,13 @@
+module Prixfixe
+  class UnitPrice < StaticModel
+    def initialize(attr, model)
+      @attr = attr
+      @model = model
+    end
+
+    def calculate(items)
+      total = items.inject(0) {|sum, item| sum + item.send(@attr.to_sym)}
+      @model.calculate(total)
+    end
+  end
+end

lib/prixfixe/volume_price.rb

@@ -0,0 +1,30 @@
+module Prixfixe
+  class VolumePrice < StaticModel
+    def initialize(base_model)
+      @tiers = {0 => base_model}
+    end
+
+    def calculate(items)    
+      sorted_keys.inject(0) do |sum, k| 
+        current_tier = @tiers[k]
+        current_items = items[k..last_index(k)]
+        sum + current_tier.calculate(current_items)
+      end
+    end
+
+    def add_tier(tier, model)
+      @tiers[tier] = model
+      self
+    end
+
+    private
+    def sorted_keys
+      @tiers.keys.sort {|x, y| x <=> y}
+    end
+
+    def last_index(key)
+      min = sorted_keys.select {|k| k > key}.min 
+      min.nil? ? -1 : min - 1
+    end
+  end
+end

test/conditional_price_test.rb

@@ -0,0 +1,17 @@
+require 'test_helper'
+
+class ConditionalPriceTest < MiniTest::Unit::TestCase
+  def setup
+    @items = [
+      OpenStruct.new({:enabled? => true}),
+      OpenStruct.new({:enabled? => false}),
+      OpenStruct.new,
+    ]
+  end
+
+  def test_calculate_with_attribute
+    proc = Proc.new {|item| item.enabled?}
+    model = ConditionalPrice.new(proc, ListPrice.new(25))
+    assert_equal 25, model.calculate(@items)
+  end
+end

test/list_price_test.rb

@@ -0,0 +1,7 @@
+require 'test_helper'
+
+class ListPriceTest < MiniTest::Unit::TestCase
+  def test_calculate
+    assert_equal 100, ListPrice.new(50).calculate([0,1])
+  end
+end

test/minimum_price_test.rb

@@ -0,0 +1,22 @@
+require 'test_helper'
+
+class MinimumPriceTest < MiniTest::Unit::TestCase
+  def setup
+    @items = (0..19).to_a
+  end
+
+  def test_calculate_with_exact_match
+    model = MinimumPrice.new(20, ListPrice.new(1))
+    assert_equal 20, model.calculate(@items)
+  end
+
+  def test_calculate_under_min
+    model = MinimumPrice.new(21, ListPrice.new(1))
+    assert_equal 21, model.calculate(@items)    
+  end
+
+  def test_calculate_over_min
+    model = MinimumPrice.new(10, ListPrice.new(1))
+    assert_equal 20, model.calculate(@items)    
+  end
+end  

test/static_model_test.rb

@@ -0,0 +1,7 @@
+require 'test_helper'
+
+class StaticModelTest < MiniTest::Unit::TestCase
+  def test_calculate
+    assert_equal 0, StaticModel.new.calculate([0,1])
+  end
+end

test/test_helper.rb

@@ -0,0 +1,4 @@
+require 'prixfixe'
+require 'ostruct'
+
+include Prixfixe

test/unit_price_test.rb

@@ -0,0 +1,16 @@
+require 'test_helper'
+
+class UnitPriceTestTest < MiniTest::Unit::TestCase
+  def setup
+    @items = [
+      OpenStruct.new({:recording_length => 10}),
+      OpenStruct.new({:recording_length => 10}),
+      OpenStruct.new({:recording_length => 0}),
+    ]
+  end
+
+  def test_calculate
+    model = UnitPrice.new(:recording_length, ListPrice.new(1))
+    assert_equal 20, model.calculate(@items)
+  end
+end

test/volume_price_test.rb

@@ -0,0 +1,24 @@
+require 'test_helper'
+
+class VolumePriceTest < MiniTest::Unit::TestCase
+  def setup
+    @items = (0..49).to_a
+  end
+
+  def test_calculate_one_tier
+    model = VolumePrice.new(ListPrice.new(2))
+    assert_equal 100, model.calculate(@items)
+  end
+
+  def test_calculate_two_tiers
+    model = VolumePrice.new(ListPrice.new(2)).add_tier(25, ListPrice.new(1))
+    assert_equal 75, model.calculate(@items)
+  end
+
+  def test_calculate_three_tiers
+    model = VolumePrice.new(ListPrice.new(2)).
+      add_tier(20, ListPrice.new(1)).
+      add_tier(40, ListPrice.new(0))
+    assert_equal 60, model.calculate(@items)
+  end
+end