Mercurial > urweb

datatype log = End | Line of string * source log

fun render log =
    case log of
        End => <xml/>
      | Line (line, logS) => <xml>{[line]}<br/><dyn signal={renderS logS}/></xml>

and renderS logS =
    log <- signal logS;
    return (render log)

structure Room = Broadcast(struct
                               type t = string
                           end)

sequence s
table t : { Id : int, Title : string, Room : Room.topic }

fun chat id =
    r <- oneRow (SELECT t.Title, t.Room FROM t WHERE t.Id = {[id]});
    ch <- Room.subscribe r.T.Room;

    newLine <- source "";
    logHead <- source End;
    logTail <- source logHead;

    let
        fun onload () =
            let
                fun listener () =
                    s <- recv ch;
                    oldTail <- get logTail;
                    newTail <- source End;
                    set oldTail (Line (s, newTail));
                    set logTail newTail;
                    listener ()
            in
                listener ()
            end

        fun getRoom () =
            r <- oneRow (SELECT t.Room FROM t WHERE t.Id = {[id]});
            return r.T.Room

        fun speak line =
            room <- getRoom ();
            Room.send room line

        fun doSpeak () =
            line <- get newLine;
            set newLine "";
            speak line
    in
        return <xml><body onload={onload ()}>
          <h1>{[r.T.Title]}</h1>

          <button value="Send:" onclick={doSpeak ()}/> <ctextbox source={newLine}/>

          <h2>Messages</h2>

          <dyn signal={renderS logHead}/>

        </body></xml>
    end

fun list () =
    queryX (SELECT * FROM t)
    (fn r => <xml><tr>
      <td>{[r.T.Id]}</td> <td><a link={chat r.T.Id}>{[r.T.Title]}</a></td>
      <td><a link={delete r.T.Id}>[delete]</a></td>
    </tr></xml>)

and delete id =
    dml (DELETE FROM t WHERE Id = {[id]});
    main ()

and main () : transaction page =
    let
        fun create r =
            id <- nextval s;
            room <- Room.create;
            dml (INSERT INTO t (Id, Title, Room) VALUES ({[id]}, {[r.Title]}, {[room]}));
            main ()
    in
        ls <- list ();
        return <xml><body>
          <table>
            <tr> <th>ID</th> <th>Title</th> </tr>
            {ls}
          </table>

          <h1>New Channel</h1>

          <form>
            Title: <textbox{#Title}/><br/>
            <submit action={create}/>
          </form>
        </body></xml>
    end
author	Edward Z. Yang <ezyang@mit.edu>
date	Wed, 02 May 2012 17:17:57 -0400
parents	01b6f2ee2ef0
children