calendar

#!/usr/bin/env ruby
require 'active_support/time'

class Calendar
  def build
    header
    body
    out
  end
  private
  def header
    @today = Date.today
    @target = @today.change day: 1
    header = ' SU MO TU WE TH FR SA'
    @out = ['', '']
    [-1, 0, 1].each do |m|
      m3 = @target.advance months: m
      @out[0] << "#{m3.year}-#{m3.month}".center(header.size) << '  '
    end
    3.times do
      @out[1] << header << '  '
    end
  end
  def body
    [-1, 0, 1].each do |m|
      m3 = @target.advance months: m
      line_no = 2
      day = nil
      m3.upto((m3.advance months: 1) - 1) do |d|
        day = d
        @out[line_no] ||= ''
        @out[line_no] << '  ' if m != -1 and (d.day == 1 or d.wday == 0)
        @out[line_no] << '   ' * d.wday if d.day == 1
        if @today == d
          @out[line_no] << ' **'
        else
          @out[line_no] << '%3d' % d.day
        end
        line_no += 1 if d.wday == 6
      end
      @out.last << '   ' * (6 - day.wday)
    end
  end
  def out
    @out.each {|e| puts e }
  end
end

Calendar.new.build if $0 == __FILE__