;; lib/host/router.sx — Host application assembly. A host app is a single Dream
;; router built from per-domain route groups, with a built-in health endpoint and
;; a JSON 404 fallback so the native OCaml HTTP server has one entry point:
;; request -> response. Each subsystem contributes a list of Dream routes (see
;; lib/host/feed.sx); host/make-app concatenates them under one router.
;; dr/flatten-routes (Dream) flattens the nested groups, so a group is just a list
;; of routes. Depends on lib/dream/router.sx + lib/host/handler.sx + the host
;; session middleware (lib/host/session.sx) and login routes (lib/host/auth.sx).

;; Liveness probe — GET /health -> 200 {"ok":true,"data":"healthy"}.
(define host/health-route
  (dream-get "/health" (fn (req) (host/ok "healthy"))))

;; Build the host app from a list of route groups (each a list of Dream routes).
;; The health route + login routes are always mounted; Dream's router returns a
;; JSON 404 for unmatched paths, which host endpoints override per-domain as
;; needed. The WHOLE app is wrapped in the signed-session middleware so every
;; request carries a session and any handler can log a principal in/out — this is
;; the front door, so sessions are not optional.
(define host/make-app
  (fn (groups)
    (let ((router (dream-router
                    (cons host/health-route
                      (cons host/auth-routes groups)))))
      ((host/sessions) router))))