yarm6mesq: Refresh expired tokens and revoke on sign-out

src/lib/session-refresh.ts

@@ -0,0 +1,104 @@
+import {
+  deleteSession,
+  getSession,
+  updateSession,
+  type SessionData,
+} from "./session-store";
+import { exchangeFeedToken, refreshProfileTokens, revokeToken } from "./minnect";
+
+// Reusable server-side session logic the route handlers share. The feed route
+// (a later task) calls `ensureFreshSession` before using a token, and
+// `refreshSession` once after a feed call returns 401. Sign-out uses
+// `endSession`. Minnect tokens never leave the server; nothing here is logged.
+
+/** Refresh when a token expires within this window (spec: two minutes). */
+export const REFRESH_WINDOW_MS = 2 * 60 * 1000;
+
+interface RefreshOptions {
+  /** Injectable fetch, for testing. Defaults to the global fetch. */
+  fetchImpl?: typeof fetch;
+  /** Injectable clock for the expiry decision, for testing. Defaults to Date.now(). */
+  now?: number;
+}
+
+/** True when the expiry is known and falls within the refresh window. */
+function expiresSoon(expiresAt: number | null, now: number): boolean {
+  return expiresAt !== null && expiresAt - now <= REFRESH_WINDOW_MS;
+}
+
+/**
+ * Refresh the profile and feed tokens of a session and persist them, keeping the
+ * same session id (and the same person). Uses the stored profile refresh token,
+ * never a password. On any failure the session is deleted and `null` is
+ * returned, so the browser is sent back to the sign-in screen.
+ */
+export async function refreshSession(
+  sessionId: string,
+  options: RefreshOptions = {},
+): Promise<SessionData | null> {
+  const session = getSession(sessionId);
+  if (!session) return null;
+
+  try {
+    const profile = await refreshProfileTokens(
+      session.profileRefreshToken,
+      options,
+    );
+    const feed = await exchangeFeedToken(profile.profileAccessToken, options);
+
+    const updated: SessionData = {
+      ...session,
+      profileAccessToken: profile.profileAccessToken,
+      profileAccessTokenExpiresAt: profile.profileAccessTokenExpiresAt,
+      profileRefreshToken: profile.profileRefreshToken,
+      feedAccessToken: feed.feedAccessToken,
+      feedAccessTokenExpiresAt: feed.feedAccessTokenExpiresAt,
+    };
+    updateSession(sessionId, updated);
+    return updated;
+  } catch {
+    // Refresh failed: drop the session. The caller returns 401 { error: "sign_in" }.
+    deleteSession(sessionId);
+    return null;
+  }
+}
+
+/**
+ * Load a session and, when its profile or feed access token is within the
+ * refresh window, refresh it first. Returns the usable session, or `null` when
+ * there is no session or the refresh failed. Call this before using a token.
+ */
+export async function ensureFreshSession(
+  sessionId: string | undefined,
+  options: RefreshOptions = {},
+): Promise<SessionData | null> {
+  if (!sessionId) return null;
+  const session = getSession(sessionId);
+  if (!session) return null;
+
+  const now = options.now ?? Date.now();
+  if (
+    expiresSoon(session.profileAccessTokenExpiresAt, now) ||
+    expiresSoon(session.feedAccessTokenExpiresAt, now)
+  ) {
+    return refreshSession(sessionId, options);
+  }
+  return session;
+}
+
+/**
+ * Sign-out. Revoke the refresh token (best-effort) and delete the server
+ * session. Always resolves: a revoke error does not stop sign-out. The caller
+ * clears the cookie.
+ */
+export async function endSession(
+  sessionId: string | undefined,
+  options: Pick<RefreshOptions, "fetchImpl"> = {},
+): Promise<void> {
+  if (!sessionId) return;
+  const session = getSession(sessionId);
+  if (session) {
+    await revokeToken(session.profileRefreshToken, options);
+  }
+  deleteSession(sessionId);
+}