From: "bcparanj@..." <bcparanj@...>
Date: 2007-03-17T03:50:07+09:00
Subject: Need feedback on improving Ruby code

require 'print_receipt'
require "test/unit"

class TestReceiptBuilder < Test::Unit::TestCase

  def test_create_dynamic_method_list
    r = ReceiptBuilder.new([["1 book at 12.49"], ["1 music cd at
14.99"], ["1 chocolate bar at 0.85"]])
    r.create_dynamic_method_list

    assert_equal r.dynamic_method_list.size, 3

    assert_equal r.dynamic_method_list[0].to_s, "buy(1,' book ') { at
12.49 }"
    assert_equal r.dynamic_method_list[1].to_s, "buy(1,' music cd ')
{ at  14.99 }"
    assert_equal r.dynamic_method_list[2].to_s, "buy(1,' chocolate bar
') { at  0.85 }"

  end

  def test_nearest_five_rounding
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.01),
0.05
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.02),
0.05
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.03),
0.05
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.04),
0.05
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.05),
0.05
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.06),
0.1
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.07),
0.1
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.08),
0.1
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.09),
0.1
     assert_equal ReceiptBuilder.round_to_nearest_five_cents(0.1), 0.1

  end

  def test_exempt_products
    r = ReceiptBuilder.new([])

    exempt_products = ["book", "chocolate bar", "packet of headache
pills", "imported box of chocolates",
                       "box of imported chocolates"]

    exempt_products.each do |product|
      assert r.is_exempt_product?(product)
    end

    non_exempt_products = ["tin tin", "bugs bunny"]
    non_exempt_products.each do |product|
        assert !r.is_exempt_product?(product)
    end

  end

  def test_imported_products
    r = ReceiptBuilder.new([])

    imported_products = ["imported box of chocolates", "imported
bottle of perfume", "box of imported chocolates"]

    imported_products.each do |product|
      assert r.is_imported_product?(product)
    end
  end

  def test_line_item
    r = ReceiptBuilder.new([["1 book at 12.49"], ["1 music cd at
14.99"], ["1 chocolate bar at 0.85"]])
    r.create_dynamic_method_list

    r.generate_output
    r.print_output

    line_item = LineItem.new(1, 'book', 15.99)

    assert_not_nil line_item.nil?

    assert_not_nil line_item.quantity
    assert_equal line_item.quantity, 1

    assert_not_nil line_item.name
    assert_equal line_item.name, 'book'

    assert_not_nil line_item.price
    assert_equal line_item.price, 15.99
    # Check for all combinations of exempt and imported status
    assert_equal line_item.sales_tax_for('imported bottle of perfume',
10, 1), 1.5
    assert_equal line_item.sales_tax_for('chocolate bar', 10,1), 0
    assert_equal line_item.sales_tax_for('bugs bunny', 10,1), 1
    assert_equal line_item.sales_tax_for('imported box of chocolates',
10,1), 0.5

  end

  def test_output_two
    r = ReceiptBuilder.new([["1 imported box of chocolates at 10.00"],
["1 imported bottle of perfume at 47.50"]])
    r.create_dynamic_method_list
    r.generate_output
    r.print_output

    # line_item = LineItem.new(1, 'imported bottle of perfume', 10)
#
#     assert_equal line_item.sales_tax_for('imported box of
chocolates', 47.5,1), 2.375
#
  end

  def test_output_three
    r = ReceiptBuilder.new([["1 imported bottle of perfume at 27.99"],
["1 bottle of perfume at 18.99"], ["1 packet of headache pills at
9.75"],["1 box of imported chocolates at 11.25"]])
    r.create_dynamic_method_list

    r.generate_output
    r.print_output

  end
end

The same inputs and outputs are:

# Input 1:
# 1 book at 12.49
# 1 music CD at 14.99
# 1 chocolate bar at 0.85
#
# Input 2:
# 1 imported box of chocolates at 10.00
# 1 imported bottle of perfume at 47.50
#
# Input 3:
# 1 imported bottle of perfume at 27.99
# 1 bottle of perfume at 18.99
# 1 packet of headache pills at 9.75
# 1 box of imported chocolates at 11.25
#
# OUTPUT
#
# Output 1:
# 1 book : 12.49
# 1 music CD: 16.49
# 1 chocolate bar: 0.85
# Sales Taxes: 1.50
# Total: 29.83
#
# Output 2:
# 1 imported box of chocolates: 10.50
# 1 imported bottle of perfume: 54.65
# Sales Taxes: 7.65
# Total: 65.15
#
# Output 3:
# 1 imported bottle of perfume: 32.19
# 1 bottle of perfume: 20.89
# 1 packet of headache pills: 9.75
# 1 imported box of chocolates: 11.85
# Sales Taxes: 6.70
# Total: 74.68

print_receipt.rb
class ReceiptBuilder

  module SalesTaxPolicy
    BASE_SALES_TAX = 0.1
    IMPORT_DUTY = 0.05

    def is_exempt_product?(product)
      ["book", "chocolate bar", "packet of headache pills", "imported
box of chocolates",
                           "box of imported chocolates"].include?
(product)
    end

    def is_imported_product?(product)
      ["imported box of chocolates", "imported bottle of perfume",
"box of imported chocolates"].include?(product)
    end
  end

  include SalesTaxPolicy

  attr_accessor :dynamic_method_list, :buffer, :line_items_list
  @@header = "Count  Item                           Price\n"

  def initialize(purchase_list)
    @dynamic_method_list = Array::new
    @purchased_items = purchase_list
    @buffer = Array::new
    @line_items_list = Array::new
  end

  def generate_output
    @dynamic_method_list.each do |element|
     eval(element.to_s)
   end
  end

  def create_dynamic_method_list
    @purchased_items.each do |s|

      input_tokens = s.to_s.split(/(\s+)/)

        input_tokens.each_index do |i|
          input_tokens[i] = "') { at " if input_tokens[i] ==
"at"
        end

      input_tokens[0] = input_tokens[0] + ",'"
      input_tokens.unshift "buy("
      input_tokens << " }"

      @dynamic_method_list << input_tokens
    end
  end

  def buy(quantity, item, &block)
    _save_line_item_output(quantity, item, block.call)
  end

  def at(price)
    price
  end

  def self.round_to_nearest_five_cents(price)
    ((20 * (price + 0.04)).floor)*0.05
  end

  def print_output
    puts "_________________________________________________"
    puts @@header
    puts @buffer.to_s

    total = 0
    @line_items_list.each do |item|
      total += item.tax_inclusive_price
    end

    sales_tax_total = 0
    @line_items_list.each do |item|
      sales_tax_total += item.sales_tax_for(item.name, item.price,
item.quantity)
    end

    rounded_sales_tax =
ReceiptBuilder.round_to_nearest_five_cents(sales_tax_total)
    rounded_total = ReceiptBuilder.round_to_nearest_five_cents(total)
    puts "_________________________________________________"
    puts "Sales Taxes :  #{rounded_sales_tax}"
    puts "Total       :  #{rounded_total}"

  end

  private
    def _save_line_item_output(quantity, item, price)
      rounded_amount =
ReceiptBuilder.round_to_nearest_five_cents(price)
      line_item = LineItem.new(quantity, item.strip, rounded_amount)

      @line_items_list << line_item
      @buffer << line_item.to_s + "\n"
    end

end

class LineItem
  include ReceiptBuilder::SalesTaxPolicy

  attr_reader :quantity, :name, :price, :tax_inclusive_price

  def initialize(quantity, name, price)
    @quantity = quantity
    @name = name
    @price = price
    @tax_inclusive_price =
ReceiptBuilder.round_to_nearest_five_cents(sales_tax_for(name, price,
quantity) + price)
  end

  def to_s
     padding_size = 28 - name.size
     extra_space = []
     temp = padding_size.times { extra_space << ' '}
      "#{quantity}      #{name} :" + extra_space.to_s +
"#{tax_inclusive_price}"
  end

   #  Basic sales tax is applicable at a rate of 10% on all goods,
except books,
   #  food, and medical products that are exempt. Import duty is an
additional
   #  sales tax applicable on all imported goods at a rate of 5%, with
no
   #  exemptions.
  def sales_tax_for(name, price, quantity)
    _importe = is_imported_product?(name)
    _exempte = is_exempt_product?(name)

    (_basic_tax(_exempte, price) + _import_tax(_importe,
price))*quantity
  end


    private

    def _basic_tax(exempt, price)
      if exempt
        0
      else
        BASE_SALES_TAX * price
      end
    end

    def _import_tax(importe, price)
      if importe
        IMPORT_DUTY * price
      else
        0
      end
    end

end

I took a test for a company and they have already decided my
background does not fit their requirements. I want to learn from
advanced Ruby developers on how I can improve the solution. This is
just for improving my Ruby skills. TIA.