writeonce/docs/examples/chat/main.wo

-- chat — iteration 24's acceptance workload. Rooms, presence and
-- broadcast over WebSocket: every connection is a reader actor (sole fd
-- reader) plus a writer actor (sole fd writer); rooms and the registry
-- are actors; delivery between them is ownership-moving sends, across
-- shards when placement lands them there. One binary, no broker.
--
--   CHAT_TOKEN is not needed — chat is open; the framework serves it
--   through [deps] exactly like web-app:
--     woc . && ./target/chat 8080
--     ws://127.0.0.1:8080/ws?room=lobby&name=alice
--
-- The actor split exists because an actor takes ONE message at a time:
-- a single per-connection actor blocked in net read could never hear a
-- broadcast. The reader owns the socket's inbound half and the carry
-- buffer; the writer owns the outbound half so frames never interleave.
use env
use net
use time
use framework
use framework/http
use framework/router

-- ---- message types (one per actor) --------------------------------------

-- To a writer: 1 = text frame, 2 = close (frame + fd close), 3 = pong.
class WriterMsg {
  kind: Int
  text: Text
}

-- To a room: 1 = join, 2 = leave, 3 = text, 4 = shutdown (drain).
class RoomMsg {
  kind:   Int
  name:   Text
  text:   Text
  writer: actor WriterMsg
}

-- To the registry: 1 = lookup (a `call` — the reply is the room's
-- address), 2 = shutdown every room (a `send` on SIGTERM).
class Lookup {
  kind: Int
  room: Text
}

-- To a reader: everything the connection's inbound loop needs.
class ReaderMsg {
  fd:     net.Conn
  room:   actor RoomMsg
  writer: actor WriterMsg
  name:   Text
}

-- One connection accepted, one worker: builds its own App and runs the
-- framework's keep-alive loop (the serving-slice pattern).
class Conn {
  fd: net.Conn
}

-- ---- the writer: sole owner of the outbound half -------------------------

class Writer {
  fd:   net.Conn
  dead: Int
  fn receive(msg: WriterMsg) {
    if self.dead == 1 { return; }
    if msg.kind == 1 {
      let ok = try net.write_dl(self.fd, ws_text(msg.text), 2000) catch (e) false;
      if ok == false {
        -- a stalled or gone client: tear the fd; the reader will see EOF
        -- and route the leave through the room
        self.dead = 1;
        net.close(self.fd);
      }
      return;
    }
    if msg.kind == 3 {
      let ok2 = try net.write_dl(self.fd, ws_pong(msg.text), 2000) catch (e) false;
      if ok2 == false {
        self.dead = 1;
        net.close(self.fd);
      }
      return;
    }
    -- close: the drain path (room shutdown or reader-detected close)
    self.dead = 1;
    let ig = try net.write_dl(self.fd, ws_close(), 1000) catch (e) false;
    net.close(self.fd);
  }
}

-- ---- the room: members, presence, fan-out --------------------------------

class Mem {
  w:    actor WriterMsg
  name: Text
}

class Room {
  members: multi Mem
  fn receive(msg: RoomMsg) {
    if msg.kind == 1 {
      push(self.members, Mem { w: msg.writer, name: "${msg.name}" });
      self.say("* ${msg.name} joined");
      return;
    }
    if msg.kind == 2 {
      let keep: multi Mem = [];
      while len(self.members) > 0 {
        let m = shift(self.members);
        if m.name != msg.name { push(keep, m); }
      }
      self.members = keep;
      self.say("* ${msg.name} left");
      return;
    }
    if msg.kind == 3 {
      self.say("${msg.name}: ${msg.text}");
      return;
    }
    -- shutdown: every member gets a close frame; the list empties
    while len(self.members) > 0 {
      let m = shift(self.members);
      let r = try send_close(m.w) catch (e) 0;
    }
  }

  -- fan-out one line; a member whose mailbox is FULL is a slow client —
  -- the fail-fast cap turns it into a drop-from-the-room (the backpressure
  -- policy earning its keep)
  fn say(line: Text) {
    let keep: multi Mem = [];
    while len(self.members) > 0 {
      let m = shift(self.members);
      let ok = try send_text(m.w, "${line}") catch (e) 0;
      if ok == 1 {
        push(keep, m);
      } else {
        let r = try send_close(m.w) catch (e) 0;
      }
    }
    self.members = keep;
  }
}

-- send wrappers: `try` is an expression, so give it Int results
fn send_text(w: actor WriterMsg, line: Text) -> Int {
  send(w, WriterMsg { kind: 1, text: line });
  return 1;
}

fn send_close(w: actor WriterMsg) -> Int {
  send(w, WriterMsg { kind: 2, text: "" });
  return 1;
}

-- ---- the registry: name -> room, spawn on demand --------------------------

class RoomRef {
  r: actor RoomMsg
}

class Registry {
  rooms:    map<Text, RoomRef>
  fallback: actor RoomMsg
  fn receive(msg: Lookup) -> actor RoomMsg {
    if msg.kind == 2 {
      for k, v in self.rooms {
        send(v.r, RoomMsg { kind: 4, name: "", text: "", writer: dummy_writer() });
      }
      return self.fallback;
    }
    if has(self.rooms, msg.room) == 1 {
      let have = self.rooms[msg.room];
      if have != nil {
        return have.r;
      }
    }
    let room: actor RoomMsg = spawn Room { members: [] };
    self.rooms[msg.room] = RoomRef { r: room };
    return room;
  }
}

-- RoomMsg requires a writer field on every construction; the shutdown
-- message has no meaningful one, so a throwaway satisfies the shape (it
-- never receives anything — kind 4 reads no fields).
fn dummy_writer() -> actor WriterMsg {
  let w: actor WriterMsg = spawn Writer { fd: 0 - 1, dead: 1 };
  return w;
}

-- ---- the reader: sole owner of the inbound half ---------------------------

class Reader {
  pad: Int
  fn receive(msg: ReaderMsg) {
    let carry = "";
    let alive = true;
    while alive {
      if env.stopping() { alive = false; continue; }
      let got = try net.read_dl(msg.fd, 4096, 30000) catch (e) nil;
      if got == nil {
        -- idle deadline or I/O trap: this client is done
        alive = false;
        continue;
      }
      let bytes = "${got}";
      if len(bytes) == 0 {
        alive = false;
        continue;
      }
      carry = carry .. bytes;
      let more = true;
      while more {
        let f = ws_parse(carry);
        if f.kind == 0 {
          more = false;
          continue;
        }
        carry = f.rest;
        if f.kind == 1 {
          send(msg.room, RoomMsg { kind: 3, name: "${msg.name}", text: f.payload, writer: msg.writer });
          continue;
        }
        if f.kind == 9 {
          send(msg.writer, WriterMsg { kind: 3, text: f.payload });
          continue;
        }
        if f.kind == 10 or f.kind == 2 {
          continue; -- pongs ignored; binary tolerated (echo is not chat)
        }
        -- close frame or protocol error: stop reading
        alive = false;
        more = false;
      }
    }
    -- the tail sends must survive full mailboxes (a leave storm after a
    -- mass close): a trap here would kill the reader and orphan the fd
    let r1 = try send_leave(msg.room, "${msg.name}", msg.writer) catch (e) 0;
    let r2 = try send_close(msg.writer) catch (e) 0;
    if r2 == 0 {
      -- the writer is unreachable (full/dead): close the fd ourselves
      net.close(msg.fd);
    }
  }
}

fn send_leave(room: actor RoomMsg, name: Text, w: actor WriterMsg) -> Int {
  send(room, RoomMsg { kind: 2, name: name, text: "", writer: w });
  return 1;
}

-- ---- HTTP: the upgrade route + usage --------------------------------------

class WsRoute {
  reg: actor Lookup
  fn handle(req: Req) -> Resp {
    if ws_upgrade_valid(req) == false {
      return bad_request("expected a websocket upgrade");
    }
    let rname = req.query["room"];
    if rname == nil { return bad_request("expected ?room=<name>&name=<who>"); }
    let who = req.query["name"];
    if who == nil { return bad_request("expected ?room=<name>&name=<who>"); }
    -- the cross-shard call: this handler runs on the connection worker's
    -- shard, the registry lives wherever placement put it
    let room = call(self.reg, Lookup { kind: 1, room: "${rname}" });
    let fd = ws_accept(req);
    let w: actor WriterMsg = spawn Writer { fd: fd, dead: 0 };
    let rd: actor ReaderMsg = spawn Reader { pad: 0 };
    send(room, RoomMsg { kind: 1, name: "${who}", text: "", writer: w });
    send(rd, ReaderMsg { fd: fd, room: room, writer: w, name: "${who}" });
    return hijacked();
  }
}

class Usage {
  pad: Int
  fn handle(req: Req) -> Resp {
    return ok_json("{\"ws\":\"/ws?room=<name>&name=<who>\"}");
  }
}

fn build_app(reg: actor Lookup) -> App {
  let app = App { middleware: [], routes: [] };
  app.get("/",   Usage { pad: 0 });
  app.get("/ws", WsRoute { reg: reg });
  return app;
}

class ConnWorker {
  reg: actor Lookup
  fn receive(msg: Conn) {
    let app = build_app(self.reg);
    app.handle_conn(msg.fd, 10000, 10000);
  }
}

fn main(args: multi Text) -> Int {
  if len(args) < 1 {
    print_err("usage: chat <port>");
    return 2;
  }
  let port = parse_int(args[0]);
  if port == nil {
    print_err("chat: <port> must be a number");
    return 2;
  }
  let fb: actor RoomMsg = spawn Room { members: [] };
  let reg: actor Lookup = spawn Registry { rooms: {}, fallback: fb };
  let srv = net.listen("127.0.0.1", port);
  print("listening on 127.0.0.1:${port}");
  while true {
    if env.stopping() {
      -- the drain: every room broadcasts a close frame and writers flush.
      -- main must NOT park here (a park after the stop flag unwinds), so
      -- it SPINS — each loop back-edge pays a reduction, and the budget
      -- hands the shard to the draining actors between slices; worker
      -- shards keep adopting their inboxes until the engine stops.
      send(reg, Lookup { kind: 2, room: "" });
      let spin = 0;
      while spin < 20000000 {
        spin = spin + 1;
      }
      net.close(srv);
      return 0;
    }
    let c = net.accept_dl(srv, 250);
    if c != nil {
      let w: actor Conn = spawn ConnWorker { reg: reg };
      send(w, Conn { fd: c });
    }
  }
}