parsing.rb

namespace :test do
  task :parsing do
    article_text = <<-eos
    ;ljaf dsf
    asflkj asd;lkfj

      sdflkjasf;ajksf
      ;lkadjsf;asdjf

    {{calendar 2015-06-26 2015-06-28}} 

    aqui algo mas de texto

    y despues el otro calendario

    {{calendar 2015-07-04 2015-07-04 2015-07-04}}
    eos

    RE = /\{\{calendar(.*?)\}\}/
    def parse_re(text)
      text.gsub(RE) do |s|
        fechas = $1.split(' ')
        dates = fechas.map{|f| Date.parse(f)}
        dates_by_month = dates.sort.group_by{|date| date.month}
        rtn = ''
        dates_by_month.each do |month, dates|
          rtn << <<-eos
            <div id='calendar_#{month}' class='article_calendar'>
              #{dates.map{|d| "<span>#{d.to_s(:db)}</span>"  }.join}
            </div>
          eos
        end
        rtn
      end
    end

    puts parse_re(article_text)
  end
end