Use facets to be more robust against moderator leaving and rejoining

src/secure-chat-client.ts

@@ -4,16 +4,22 @@ import { Assertion, Ref, Turn } from "./actor.js";
 import { attachReadline } from './readline.js';
 
 export default function (t: Turn, ds: Ref) {
-    observe(t, ds, $joinedUser, {
-        assert(t, j0) {
-            const j = asJoin(j0);
-            runSession(t, j.uid, j.handle);
-        }
-    });
+    observe(t, ds, $joinedUser, during((t, j0) => {
+        const j = asJoin(j0);
+        const facet = t.facet(t => runSession(t, j.uid, j.handle));
+        return t => t.stop(facet);
+    }));
 }
 
 function runSession(t: Turn, uid: UserId, session: Ref) {
     let username: string | undefined;
+    let cleanShutdown = false;
+
+    t.activeFacet.onStop(_t => {
+        if (!cleanShutdown) {
+            console.log('Moderator retracted room permission.');
+        }
+    });
 
     function updateUsername(t: Turn, name: string) {
         const q = t.assert(session, fromNickClaim(NickClaim({ uid, name, k: t.ref({
@@ -53,7 +59,10 @@ function runSession(t: Turn, uid: UserId, session: Ref) {
     });
 
     attachReadline(t, {
-        retract(t) { t.stop(); },
+        retract(t) {
+            cleanShutdown = true;
+            t.stopActor();
+        },
         message(t, line: string) {
             if (line.toLowerCase().startsWith('/nick ')) {
                 updateUsername(t, line.slice(5).trimLeft());