New mail in the other signed-in accounts: counts, a dot, and a notification

With more than one account signed in (#49), mail arriving in one that
isn't in front went unseen until someone switched to it (multi-account
spec, MA-8).

- GET /api/auth/accounts/unread answers the Inbox unread count of each
  account not in front, asked through that account's own session (its
  OAuth token renewed first if due), kept a minute per account.
- The web app asks every two minutes while another account is signed
  in. The account menu shows each one's count beside its name, and the
  avatar carries a dot when any of them has unread mail.
- When a count rises while the app is open and desktop notifications
  are on, a notification names the account ("New mail for
  [email protected]"); clicking it switches to that account. An
  account seen for the first time doesn't notify: its mail was already
  there.

Not in this change: notifications with the app closed, which need each
added account's own Web Push subscription.

New strings (3, English only in the other ten catalogs): "New mail for
{name}", "Unread in the Inbox: {count}", "Account: new mail in another
account". Tests: the server answers the other account's count and
nothing when alone; the client keeps the counts, notifies only on a
rise and only with notifications on. Checked in Chrome against the
mock. typecheck, tests (web 1541, server 277) and build pass.

server/src/app.ts

@@ -363,6 +363,30 @@ function liveOthers(c: Context): { cookie: string; session: LiveSession }[] {
   return out;
 }
 
+/** inbuxa MA-8: Inbox unread counts of accounts not in front, briefly kept. */
+const UNREAD_CACHE_MS = 60_000;
+const unreadCache = new Map<string, { unread: number | null; at: number }>();
+
+/** The Inbox's unread count for one session's account, or null when it has none. */
+async function inboxUnread(session: LiveSession): Promise<number | null> {
+  const upstream = await getUpstreamSession(session.id, session.authorization, upstreamFor(session.username));
+  const accountId = upstream.primaryAccounts?.["urn:ietf:params:jmap:mail"];
+  if (!accountId) return null;
+  const res = await fetch(absoluteUpstream(upstream.apiUrl, upstream.baseUrl), {
+    method: "POST",
+    headers: { authorization: session.authorization, "content-type": "application/json", accept: "application/json" },
+    body: JSON.stringify({
+      using: ["urn:ietf:params:jmap:core", "urn:ietf:params:jmap:mail"],
+      methodCalls: [["Mailbox/get", { accountId, ids: null, properties: ["role", "unreadEmails"] }, "0"]],
+    }),
+    signal: AbortSignal.timeout(config.upstreamTimeout),
+  });
+  if (!res.ok) return null;
+  const body = (await res.json()) as { methodResponses?: [string, { list?: { role?: string | null; unreadEmails?: number }[] }, string][] };
+  const inbox = body.methodResponses?.[0]?.[1]?.list?.find((m) => m.role === "inbox");
+  return typeof inbox?.unreadEmails === "number" ? inbox.unreadEmails : null;
+}
+
 /** Whether the account in front may have more beside it, or why not. */
 async function addRefusal(c: Context, front: LiveSession): Promise<string | null> {
   if (1 + liveOthers(c).length >= MAX_ACCOUNTS) return "add_full";
@@ -756,6 +780,32 @@ export function createApp(basePath = config.basePath): Hono<Env> {
     });
   });
 
+  /*
+   * inbuxa MA-8: the Inbox unread count of each account not in front, asked
+   * through that account's own session, so the menu can say where new mail
+   * is. A minute's cache per account: the web app asks every few minutes, and
+   * several tabs may ask at once.
+   */
+  api.get("/auth/accounts/unread", requireSession, async (c) => {
+    const answers = await Promise.all(
+      liveOthers(c).map(async ({ cookie, session }) => {
+        const cached = unreadCache.get(session.id);
+        if (cached && Date.now() - cached.at < UNREAD_CACHE_MS) return { id: session.id, unread: cached.unread };
+        try {
+          let live: LiveSession | null = session;
+          if (live.tokens && needsRefresh(live.tokens)) live = await refreshSession(cookie, live);
+          if (!live) return { id: session.id, unread: null };
+          const unread = await inboxUnread(live);
+          unreadCache.set(session.id, { unread, at: Date.now() });
+          return { id: session.id, unread };
+        } catch {
+          return { id: session.id, unread: null };
+        }
+      }),
+    );
+    return c.json({ accounts: answers });
+  });
+
   /* inbuxa MA-B: bring another signed-in account to the front. */
   api.post("/auth/accounts/:id/front", requireSession, async (c) => {
     const frontCookie = getCookie(c, config.cookieName)!;