Auth Flow

An authentication flow with token refresh, constraint ordering, and session management – all driven by Directive’s constraint–resolver pattern.

1. Facts – token, refreshToken, expiresAt, user, status, and a ticking now fact updated every 1s
2. Derivations – isExpiringSoon auto-tracks now and expiresAt, driving the refreshNeeded constraint reactively
3. Constraints – refreshNeeded (priority 90) fires when the token is expiring soon. needsUser (priority 80) uses after: ['refreshNeeded'] to ensure the user profile is fetched with a fresh token
4. Resolvers – login handles authentication, refreshToken retries with exponential backoff, fetchUser loads the user profile
5. Effects – logStatusChange records status transitions to the event timeline for observability

What: An authentication flow with login, automatic token refresh, user profile fetching, and logout – all with configurable failure rates and token lifetimes.

How: A ticking now fact drives isExpiringSoon, which triggers refreshNeeded automatically. The after ordering on needsUser ensures the user profile is always fetched with a valid token.

Why it works: Auth flows are full of timing-dependent, ordered operations. Directive’s constraint ordering (after) and auto-tracked derivations eliminate manual timers and race conditions.