# File lib/rbot/maskdb.rb, line 149
    def find(iu)
      debug "find(#{iu.fullform})"
      iud = iu.downcased
      matches = @tree.find(iud.host, iud.user, iud.nick).uniq.map do |val|
        m = metric(iu, *val)
        m ? [val[0], m] : nil
      end.compact.sort { |a, b| a[1] <=> a[1] }
      debug "matches: " + (matches.map do |m|
        "#{m[0].username}: [#{m[1]}]"
      end.join(', '))
      return matches.empty? ? nil : matches[0][0]
    end