module Wukong
  module Streamer
    #
    # For each identical line in the map phase output, emit one representative
    # line followed by the count of occrrences (separated by a tab).
    #
    # (This is the functional equivalent of +'uniq -c'+)
    #
    class CountLines < Wukong::Streamer::Base
      def formatted_count item, key_count
        "%s\t%10d" % [item, key_count.to_i]
      end

      #
      # Delegate to +uniq -c+, but put the count last for idempotence.
      #
      def stream
        %x{/usr/bin/uniq -c}.split("\n").each do |line|
          key_count, item = line.chomp.strip.split(/\s+/, 2)
          puts formatted_count(item, key_count)
        end
      end
    end

  end
end