Refactored version of receipt printer

receipt_printer.rb

class ReceiptPrinter

  attr_reader :output, :items

  COST = {
    'meat' => 5,
    'milk' => 3,
    'candy' => 1,
  }

  TAX = 0.05

  def initialize(output: $stdout, items:)
    @output = output
    @items = items
  end

  def print
    subtotal = sum_of_items(items)

    items.each do |item|
      item_cost = COST[item]
      output_item(item, item_cost)
    end

    output.puts divider
    output_item("subtotal", subtotal)

    taxes = calculate_taxes(subtotal)
    output_item("tax", taxes)

    output.puts divider
    output_item("total", receipt_total(subtotal, taxes))
  end

  private

  def divider
    '-' * 13
  end

  def output_item(name, value)
    output.puts "#{name}: #{sprintf('$%.2f', value)}"
  end

  def calculate_taxes(amount)
    amount * TAX
  end

  def receipt_total(subtotal, taxes)
    subtotal + taxes
  end

  def sum_of_items(items)
    subtotal = items.reduce(0) do |sum, item|
      item_cost = COST[item]
      sum + item_cost.to_i
    end
  end
end