membership_level.rb

class MembershipLevel

  include Comparable
  include ActiveModel::Validations

  ## Constants

  MONTHLY  = 10
  ANNUAL   = 20
  LIFETIME = 30
  TO_S = {
    MONTHLY  => 'Monthly',
    ANNUAL   => 'Annual',
    LIFETIME => 'Lifetime',
  }
  PRICE = {
    MONTHLY  => BigDecimal.new('50.00'),
    ANNUAL   => BigDecimal.new('500.00'),
    LIFETIME => BigDecimal.new('2000.00'),
  }
  ALL = [MONTHLY, ANNUAL, LIFETIME]

  ## Fields

  attr_accessor :value

  ## Validations

  validates :value, inclusion: { in: ALL, message: "%{value} is not a valid membership level" }

  ## Constructor

  def initialize(value)
    unless value.nil?
      @value = value.to_i
      valid? or raise 'invalid value'
    end
  end

  ## Instance Methods

  def <=>(other)
    value <=> other.value
  end

  def annual?
    value == ANNUAL
  end

  def eql?(other)
    value == other.value
  end

  def hash
    value
  end

  def label
    value.nil? ? nil : TO_S[value]
  end

  def label_full
    value.nil? ? nil : TO_S[value] + " Membership"
  end

  def lifetime?
    value == LIFETIME
  end

  def monthly?
    value == MONTHLY
  end

  def price
    value.nil? ? nil : PRICE[value]
  end

  def to_i
    value
  end

  def to_s
    label
  end

end