module RedisClient::Config::Common

def build_connection_prelude
  prelude = []
  if protocol == 3
    prelude << if @password
      ["HELLO", "3", "AUTH", @username || DEFAULT_USERNAME, @password]
    else
      ["HELLO", "3"]
    end
  elsif @password
    prelude << if @username && !@username.empty?
      ["AUTH", @username, @password]
    else
      ["AUTH", @password]
    end
  end
  if @db && @db != 0
    prelude << ["SELECT", @db.to_s]
  end
  prelude.freeze
end