user_import.rb

class UserEmitter
  include Enumerable

  def initialize(path)
    @table = CSV.table(path, skip_blanks: true)
    @enumerator = Fiber.new do
      @table.each do |row|
        Fiber.yield UserImporter.import(merchant, row)
      end
    end
  end

  attr_reader :table

  def length
    @table.length
  end

  def next
    @enumerator.resume
  end

  def each
    loop do
      yield self.next
    end
  rescue StopIteration
    return self
  end
end

class UserImporter
  def self.import(row)
    new(row).to_user
  end

  def initialize(merchant, row)
    @row = row
  end

  attr_reader :row

  def to_user
    Customer.new do |user|
      user.first_name = row[:first_name] || row[:last_name]
      user.last_name = row[:last_name] || row[:first_name]
      user.email = row[:email_address]
      user.phone_number = temporary_phone_number
      user.password = temporary_password
    end
  end

  def temporary_password
    SecureRandom.urlsafe_base64(12)
  end

  def temporary_phone_number
    '555-111-1111'
  end
end