Transform a text query to a Sequel filter

to_filter.rb

def to_filter(query)
  query.split(/ +/).map { |chunk|
    case chunk
      when /^by:(.+)/
        {:author => $~[1]}
      when /^is:(.+)/
        {:status => $~[1]}
      else
        :title.like("%#{chunk}%")
    end
  }.inject(:ctime) {|f,e| e & f }
end