Supply chain DCI

context.rb

class ManufacturingContext
  def initialize(manufacturer, payor, item, quantity)
    @manufacturer = manufacturer
    @payor = payor
    @item = item
    @quantity = quantity

    @manufacturer.extend Manufacturer
    @payor.extend Payor
  end

  def call
    (1..@quantity).each do |i|
      @payor.debit @item.cost
      @manufacturer.manufacture @item
    end
  end
end

class MarkupContext
  def initialize(owner, item_name, percentage)
    @owner = owner
    @item_name = item_name
    @percentage = percentage
  end

  def call
    @owner.items.each do |item|
      item.price = (item.cost + (item.cost * @percentage)) if item.name = @item_name
    end
  end
end

# A buyer wants to buy all items available from a seller up
# to a max number
class SalesContext
  def initialize(seller, receiver, payor, item_name, quantity)
    @seller = seller
    @receiver = receiver
    @payor = payor
    @item_name = item_name
    @quantity = quantity

    @seller.extend Payee
    @payor.extend Payor
  end

  def call
    (1..@quantity).each do |i|
      item = @seller.take "yoyo"
      begin
        @payor.debit item.price
        @receiver.receive item
      rescue
        @seller.receive item
        raise $!
      end
    end
  end
end

data.rb

class BankAccount
  attr_accessor :balance

  def initialize
    balance = 0
  end
end

class ItemOwner
  attr_accessor :items

  def initialize
    @items = []
  end

  def take(item_name)
    index = @items.index{|item| item.name == item_name}
    raise "No more items named #{item_name}" if index.nil?
    @items.delete_at(index)
  end

  def receive(item)
    @items << item
  end
end

class Person < ItemOwner
  attr_accessor :bank_account

  def initialize
    super
    @bank_account = BankAccount.new
  end

  def to_s
    "Person(items: #{items.size}, cash: #{bank_account.balance})"
  end
end

class Company < ItemOwner
  attr_accessor :bank_account

  def initialize
    super
    @bank_account = BankAccount.new
  end

  def to_s
    "Company(items: #{items.size}, cash: #{bank_account.balance})"
  end
end

class Item
  attr_accessor :name, :cost, :price

  def initialize(name, cost, price=0.0)
    @name = name
    @cost = cost
    @price = price
  end
end

roles.rb

module Manufacturer
  def manufacture(item)
    receive(item.dup)
  end
end

module Payor
  def debit(amount)
    raise "Not enough funds" if @bank_account.balance < amount
    bank_account.balance -= amount
  end
end

module Payee
  def credit(amount)
    bank_account.balance += amount
  end
end

scenario_1.rb

manufacturer = Company.new
manufacturer.bank_account.balance = 1000000

wholeseller = Company.new
wholeseller.bank_account.balance = 500000

retailer = Company.new
retailer.bank_account.balance = 100000

customer = Person.new
customer.bank_account.balance = 20

yoyo = Item.new 'yoyo', 1.0

ManufacturingContext.new(manufacturer, manufacturer, yoyo, 100).call
puts manufacturer.to_s

MarkupContext.new(manufacturer, "yoyo", 0.4).call

SalesContext.new(manufacturer, wholeseller, wholeseller, "yoyo", 20).call
puts manufacturer.to_s
puts wholeseller.to_s

MarkupContext.new(wholeseller, "yoyo", 0.4).call

SalesContext.new(wholeseller, retailer, retailer, "yoyo", 10).call
puts wholeseller.to_s
puts retailer.to_s

MarkupContext.new(retailer, "yoyo", 0.4).call

SalesContext.new(retailer, customer, customer, "yoyo", 1).call
puts retailer.to_s
puts customer.to_s