adamc@699: functor Make(M : sig type t end) = struct
adamc@699:     sequence s
adamc@699:     table t : {Id : int, Client : client, Channel : channel M.t}
adamc@709:       PRIMARY KEY (Id, Client)
adamc@699: 
adamc@699:     type topic = int
adamc@699: 
adamc@699:     val inj : sql_injectable topic = _
adamc@699: 
adamc@699:     val create = nextval s
adamc@699: 
adamc@699:     fun subscribe id =
adamc@699:         cli <- self;
adamc@699:         ro <- oneOrNoRows (SELECT t.Channel FROM t WHERE t.Id = {[id]} AND t.Client = {[cli]});
adamc@699:         case ro of
adamc@699:             None =>
adamc@699:             ch <- channel;
adamc@699:             dml (INSERT INTO t (Id, Client, Channel) VALUES ({[id]}, {[cli]}, {[ch]}));
adamc@699:             return ch
adamc@699:           | Some r => return r.T.Channel
adamc@699: 
adamc@699:     fun send id msg =
adamc@699:         queryI (SELECT t.Channel FROM t WHERE t.Id = {[id]})
adamc@699:         (fn r => Basis.send r.T.Channel msg)
adamc@699: 
adamc@699:     fun subscribers id =
adamc@699:         r <- oneRow (SELECT COUNT( * ) AS N FROM t WHERE t.Id = {[id]});
adamc@699:         return r.N
adamc@699: end