;; 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.

;; 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 is always mounted first; Dream's router returns a JSON-free
;; 404 for unmatched paths, which host endpoints override per-domain as needed.
(define host/make-app
  (fn (groups)
    (dream-router
      (cons host/health-route groups))))