Extension for Date & DateTime classes

date.rb

=begin

 Author: Vigram K
 Date: 27th August 2014
 Title: Extension for Date & DateTime classes
 
 Adds following methods for date object,

 first_monday_of_month, first_tuesday_of_month .. first_sunday_of_month
 last_monday_of_month, last_tuesday_of_month .. last_sunday_of_month
 monday_of_week, tuesday_of_week .. sunday_of_week

Usages:

 date = Date.today            #=> Wed, 27 Aug 2014
 date.first_monday_of_month   #=> Mon, 04 Aug 2014
 date.last_friday_of_month    #=> Fri, 29 Aug 2014
 date.tuesday_of_week         #=> Tue, 26 Aug 2014

=end

module InstanceMethods
  def self.included(base)
    base.class_eval do

      def last_date_of_month
        @last_date_of_month ||= self.class.new(year, month, -1)
      end

      def first_date_of_month
        @first_date_of_month ||= self.class.new(year, month, 1)
      end

      # Dynamic Proxy
      def method_missing(method, *args, &block)
        case
          when method.match(/^(first|last)_(.+)_of_month$/)
            if $1 == "last"
              send("#{$1}_date_of_month").downto(0).find {|day| day.send("#{$2}?") }
            else
              send("#{$1}_date_of_month").upto(10000000).find {|day| day.send("#{$2}?") }
            end
          when method.match(/^(monday|tuesday|wednesday|thursday|friday)_of_week$/)
            (beginning_of_week .. end_of_week).find{|day| day.send("#{$1}?")}
          else
            super
        end
      end

    end

  end

end

class Date
  include InstanceMethods
end

class DateTime
  include InstanceMethods
end