begin
  require 'json'
rescue LoadError
  raise <<-ERR
The json gem must be installed for json output.
To install it:
$ [sudo] gem install json -v"~>1.4.6"
  ERR
end

module Timetrap
  module Formatters
    class Json
      attr_accessor :output

      def initialize entries
        @output = entries.map do |e|
          next unless e.end
          e.values
        end.compact.to_json
      end
    end
  end
end