month.gemspec

Gem::Specification.new do |s|
  s.name        = 'power-month'
  s.version     = '0.0.4'
  s.platform    = Gem::Platform::RUBY
  s.author      = 'Kevin Melchert'
  s.email       = '[email protected]'
  s.summary     = 'Month of Year.'
  s.description = 'Super simple Month of Year implementation.'
 
  s.files         = ['month.rb']
  s.require_path  = '.'
end

month.rb

require 'date'

class Month
  include Comparable
  
  def self.from(obj)
    if obj.respond_to?(:year) && obj.respond_to?(:month)
      new(obj.year, obj.month)
    else
      raise ArgumentError.new("Argument doesn't respond to 'year' and/or 'month'")
    end
  end

  def self.now
    from Time.now
  end
  
  attr_reader :year, :month
  
  def initialize(year, month)
    @year  = Integer(year)
    @month = Integer(month).clamp(1, 12)
  end
  
  def first_day
    Date.new(year, month, 1)
  end

  def last_day
    Date.new(year, month, -1)
  end

  def length
    last_day.day
  end
  
  def days
    first_day..last_day
  end
  
  def each_day(&block)
    days.each(&block)
  end

  def succ
    self.class.from(last_day + 1)
  end

  def pred
    self.class.from(first_day - 1)
  end
  
  alias_method :next, :succ
  alias_method :prev, :pred

  def hash
    [year, month].hash
  end
  
  def <=>(other)
    (year <=> other.year).nonzero? || month <=> other.month
  end
end