Николай обнови решението на 07.11.2011 12:02 (преди над 12 години)
+require 'bigdecimal'
+require 'bigdecimal/util'
+
+class Product
+ attr_reader :name, :price
+
+ def initialize(name, price)
+ @name, @price = name, price
+ end
+
+ def counted_price( count )
+ count * price
+ end
+end
+
+class NoPromotion
+ attr_reader :product
+
+ def initialize(name, price, *future)
+ @product = Product.new name, price
+ end
+
+ def promoted_price(count)
+ product.counted_price(count) - discount(count)
+ end
+
+ def discount(count)
+ '0'.to_d
+ end
+
+ def message()
+ ''
+ end
+end
+
+class GetOneFreePromotion < NoPromotion
+ def initialize(name, price, nth_item)
+ super
+ @nth_item = nth_item
+ end
+
+ def discount(count)
+ product.price * ( count / @nth_item )
+ end
+
+ def message
+ "(buy #{@nth_item-1}, get 1 free)"
+ end
+end
+
+class PackagePromotion < NoPromotion
+
+ attr_reader :package_size, :package_discount
+
+ def initialize(name, price, package_info)
+ super
+ @package_size = package_info.keys[0]
+ @package_discount = package_info[@package_size]
+ end
+
+ def discount(count)
+ promoted_products_count = (count / package_size) * package_size
+ product.price * promoted_products_count * (package_discount / '100'.to_d)
+ end
+
+ def message
+ "(get #{package_discount}% off for every #{package_size})"
+ end
+end
+
+class TreshholdPromotion < NoPromotion
+ attr_reader :treshhold, :treshhold_percent
+
+ def initialize(name, price, treshhold_info)
+ super
+ @treshhold = treshhold_info.keys.fetch 0
+ @treshhold_percent = treshhold_info[treshhold]
+ end
+
+ def discount(count)
+ return '0'.to_d if treshhold >= count
+ product.price * ( count - treshhold ) * ( treshhold_percent / '100'.to_d )
+ end
+
+ def message
+ "(#{treshhold_percent}% off of every after the #{place})"
+ end
+
+ private
+
+ def place
+ case treshhold
+ when 1 then '1st'
+ when 2 then '2nd'
+ when 3 then '3rd'
+ else "#{treshhold}th"
+ end
+ end
+end
+
+class PercentCoupon
+ attr_reader :name, :percent
+
+ def initialize(name, percent)
+ @name, @percent = name, percent
+ end
+
+ def discount(money_from)
+ money_from * ( percent / '100'.to_d )
+ end
+
+ def message
+ "Coupon #{name} - #{percent}% off"
+ end
+end
+
+class AmountCoupon
+ attr_reader :name, :amount
+
+ def initialize(name, amount)
+ @name, @amount = name, amount.to_d
+ end
+
+ def discount(money_from)
+ return money_from if amount >= money_from
+ amount
+ end
+
+ def message
+ "Coupon #{name} - #{sprintf "%.2f", amount.round(2).to_f} off"
+ end
+end
+
+class Inventory
+ attr_reader :products, :coupons
+
+ def Inventory.item_factory(name, price, promotion)
+ key = promotion.keys[0]
+ case key
+ when :get_one_free then GetOneFreePromotion.new name, price, promotion[key]
+ when :package then PackagePromotion.new name, price, promotion[key]
+ when :threshold then TreshholdPromotion.new name, price, promotion[key]
+ else NoPromotion.new(name, price)
+ end
+ end
+
+ def Inventory.coupon_factory(name, params)
+ key = params.keys[0]
+ case key
+ when :percent then PercentCoupon.new name, params[key]
+ when :amount then AmountCoupon.new name, params[key]
+ else raise "Unknown coupon type!"
+ end
+ end
+
+ def initialize()
+ @products, @coupons = {}, {}
+ end
+
+ def has_product?(name)
+ products.has_key? name
+ end
+
+ def register(name, price='0', promotion = {})
+ raise "'#{name}' is in inventory!." if has_product? name
+ raise "Invalid name passed" if name.length > 40
+ raise "Invalid price passed - too low" unless price.to_d.round(2) > 0
+ raise "Invalid price passed - too high" unless price.to_d.round(2) < 1000
+ products[name] = Inventory.item_factory name, price.to_d, promotion
+ end
+
+ def register_coupon(name, params)
+ raise "#{name} coupon is in inventory!" if coupons.has_key? name
+ coupons[name] = Inventory.coupon_factory name, params
+ end
+
+ def new_cart()
+ Cart.new self
+ end
+end
+
+class CartItem
+ attr_reader :inventory_item, :count
+
+ def initialize(inventory_item_paramter)
+ @inventory_item, @count = inventory_item_paramter, 0
+ end
+
+ def add(more)
+ new_count = count + more
+ raise "Too many products!" if new_count > 99
+ raise "Invalid product count!" if new_count <= 0
+ @count = new_count
+ end
+
+ def name
+ inventory_item.product.name
+ end
+
+ def price
+ inventory_item.product.counted_price count
+ end
+
+ def promoted_price
+ inventory_item.promoted_price count
+ end
+
+ def discount
+ -(inventory_item.discount count)
+ end
+
+ def message
+ inventory_item.message
+ end
+end
+
+class Cart
+ attr_reader :inventory, :items, :coupon, :coupon_discount
+
+ def initialize(used_inventory)
+ @inventory, @items = used_inventory, {}
+ end
+
+ def add(name, count = 1)
+ raise "Undefined product!" unless inventory.has_product? name
+ item = items[name] || items[name] = CartItem.new(inventory.products[name])
+ item.add count
+ end
+
+ def use coupon_name
+ raise "A coupon is already used!" if coupon
+ @coupon = inventory.coupons[coupon_name]
+ end
+
+ def products_total
+ items.values.map(&:promoted_price).inject(:+)
+ end
+
+ def total
+ result = products_total
+ result -= coupon.discount(result) if coupon
+ result
+ end
+
+ def invoice
+ Invoice.new(self).to_s
+ end
+
+end
+
+class InvoiceRow
+ attr_reader :cart_item
+
+ def initialize(cart_item_param)
+ @cart_item = cart_item_param
+ end
+
+ def InvoiceRow.generate(name, count, price, message='', discount='')
+ name, count, price = name.ljust(40), count.to_s.rjust(4), price.to_s.rjust(8)
+ product, promotion = "| #{name} #{count} | #{price} |\n", ''
+ if message != ''
+ message, discount = message.to_s.ljust(44), discount.to_s.rjust(8)
+ promotion = "| #{message} | #{discount} |\n"
+ end
+ product + promotion
+ end
+
+ def to_s
+ ci = cart_item
+ price = sprintf("%.2f", ci.price.round(2).to_f)
+ discount = sprintf("%.2f", ci.discount.round(2).to_f)
+ InvoiceRow.generate(ci.name, ci.count, price, ci.message, discount)
+ end
+end
+
+class Invoice
+ attr_reader :cart
+ def initialize(shopping_cart)
+ @cart = shopping_cart
+ end
+
+ def to_s()
+ delimiter + header + delimiter + products + coupon + delimiter + total + delimiter
+ end
+
+ private
+
+ def delimiter
+ "+------------------------------------------------+----------+\n"
+ end
+
+ def header()
+ InvoiceRow.generate('Name', 'qty', 'price')
+ end
+
+ def total()
+ InvoiceRow.generate('TOTAL', '', sprintf("%.2f", cart.total.round(2).to_f))
+ end
+
+ def products
+ cart.items.values.map { |item| InvoiceRow.new(item).to_s }.join ''
+ end
+
+ def coupon
+ return '' unless cart.coupon
+ discount = -(cart.coupon.discount(cart.products_total).round(2).to_f)
+ InvoiceRow.generate(cart.coupon.message, '', sprintf("%.2f", discount))
+ end
+end