fix(notifications): notification replies re-check encryption at send time and use the right account (#299)

The service worker posts inline notification replies in the clear (it
cannot encrypt). The Reply action was only withheld for rooms that were
encrypted when the notification was shown, so a reply typed hours later
into a room that has since turned on encryption went out unencrypted.
It also posted with the newest session the worker knew, not the
notification's account.

The worker now GETs the room's m.room.encryption state first and only
sends on a definite 404; notifications carry the user id and the worker
uses that account's session (or refuses). "Reply not sent" says why.

Fixes #299

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/swReply.test.ts

@@ -1,6 +1,12 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { buildReplyContent, replySendUrl, sendNotificationReply } from './swReply';
+import {
+  buildReplyContent,
+  pickReplySession,
+  replyFailureText,
+  replySendUrl,
+  sendNotificationReply,
+} from './swReply';
 
 test('thread replies carry the m.thread relation, room replies do not', () => {
   assert.deepEqual(buildReplyContent('hi'), { msgtype: 'm.text', body: 'hi', 'm.mentions': {} });
@@ -19,40 +25,64 @@ test('send URL encodes the room id against the session base URL', () => {
   );
 });
 
-test('sendNotificationReply PUTs with the bearer token and reports ok / failure', async () => {
+test('sendNotificationReply checks encryption, then PUTs with the bearer token (#203, #299)', async () => {
   const calls: { url: string; init: RequestInit }[] = [];
-  const fetchOk = (async (url: string, init: RequestInit) => {
-    calls.push({ url, init });
-    return { ok: true } as Response;
-  }) as unknown as typeof fetch;
-  assert.equal(
-    await sendNotificationReply(
-      { accessToken: 'tok', baseUrl: 'https://hs' },
-      '!r:hs',
-      '$t',
-      'yo',
-      fetchOk,
-    ),
-    true,
-  );
-  assert.equal(calls[0].init.method, 'PUT');
-  assert.equal((calls[0].init.headers as Record<string, string>).Authorization, 'Bearer tok');
+  const fetchFor = (encStatus: number, sendOk = true) =>
+    (async (url: string, init: RequestInit = {}) => {
+      calls.push({ url, init });
+      if (url.includes('/state/m.room.encryption/')) {
+        return { ok: encStatus === 200, status: encStatus } as Response;
+      }
+      return { ok: sendOk, status: sendOk ? 200 : 500 } as Response;
+    }) as unknown as typeof fetch;
+  const session = { accessToken: 'tok', baseUrl: 'https://hs' };
+
+  assert.equal(await sendNotificationReply(session, '!r:hs', '$t', 'yo', fetchFor(404)), 'sent');
+  assert.match(calls[0].url, /\/rooms\/!r%3Ahs\/state\/m\.room\.encryption\/$/);
+  const put = calls[1];
+  assert.equal(put.init.method, 'PUT');
+  assert.equal((put.init.headers as Record<string, string>).Authorization, 'Bearer tok');
   assert.match(
-    calls[0].url,
+    put.url,
     /^https:\/\/hs\/_matrix\/client\/v3\/rooms\/!r%3Ahs\/send\/m\.room\.message\/swreply-/,
   );
-  assert.equal(JSON.parse(calls[0].init.body as string)['m.relates_to'].event_id, '$t');
+  assert.equal(JSON.parse(put.init.body as string)['m.relates_to'].event_id, '$t');
 
-  const fetchFail = (async () => ({ ok: false }) as Response) as unknown as typeof fetch;
+  // Encryption turned on since the notification was shown: nothing is sent.
+  calls.length = 0;
   assert.equal(
-    await sendNotificationReply(
-      { accessToken: 'tok', baseUrl: 'https://hs' },
-      '!r:hs',
-      undefined,
-      'yo',
-      fetchFail,
-    ),
-    false,
+    await sendNotificationReply(session, '!r:hs', undefined, 'yo', fetchFor(200)),
+    'encrypted',
+  );
+  assert.equal(calls.length, 1);
+  // Can't tell (server error): fail safe, nothing is sent.
+  calls.length = 0;
+  assert.equal(
+    await sendNotificationReply(session, '!r:hs', undefined, 'yo', fetchFor(500)),
+    'failed',
+  );
+  assert.equal(calls.length, 1);
+  assert.equal(
+    await sendNotificationReply(session, '!r:hs', undefined, 'yo', fetchFor(404, false)),
+    'failed',
+  );
+  assert.equal(
+    await sendNotificationReply(undefined, '!r:hs', undefined, 'yo', fetchFor(404)),
+    'no-session',
   );
-  assert.equal(await sendNotificationReply(undefined, '!r:hs', undefined, 'yo', fetchOk), false);
+});
+
+test('pickReplySession: the notification account only (#299)', () => {
+  const a = { accessToken: 'a', baseUrl: 'https://hs', userId: '@a:hs' };
+  const b = { accessToken: 'b', baseUrl: 'https://hs', userId: '@b:hs' };
+  assert.equal(pickReplySession([a, b], '@a:hs'), a);
+  assert.equal(pickReplySession([b], '@a:hs'), undefined, 'logged out of @a here');
+  assert.equal(pickReplySession([a], undefined), a, 'old notification, one session');
+  assert.equal(pickReplySession([a, b], undefined), undefined, 'old notification, ambiguous');
+});
+
+test('replyFailureText says why', () => {
+  assert.match(replyFailureText('encrypted', 'hi'), /now encrypted/);
+  assert.match(replyFailureText('no-session', 'hi'), /no longer signed in/);
+  assert.match(replyFailureText('failed', 'hi'), /retry/);
 });