;; lib/host/handler.sx — Host handler layer: the bridge from a Dream request to a
;; subsystem call and back to a Dream response. A host handler IS a Dream handler
;; (request -> response); these helpers build the JSON envelope every host
;; endpoint shares: {"ok":true,"data":...} on success, {"ok":false,"error":...}
;; on failure. Plus a status-carrying JSON constructor that Dream's own dream-json
;; (200-only) lacks, and a couple of request-reading conveniences.
;; Depends on lib/dream/types.sx + lib/dream/json.sx.

;; ── responses ──────────────────────────────────────────────────────

;; JSON response at an arbitrary status (dream-json is 200-only).
(define host/json-status
  (fn (status value)
    (dream-response status {:content-type "application/json"}
      (dream-json-encode value))))

;; Success envelope: 200 {"ok":true,"data":<value>}.
(define host/ok
  (fn (value)
    (host/json-status 200 {:ok true :data value})))

;; Success envelope at a chosen status (e.g. 201 for a created resource).
(define host/ok-status
  (fn (status value)
    (host/json-status status {:ok true :data value})))

;; Error envelope: {"ok":false,"error":<message>} at the given status.
(define host/error
  (fn (status message)
    (host/json-status status {:ok false :error message})))

;; ── request reading ────────────────────────────────────────────────

;; Integer query param with a fallback (query params arrive as strings).
;; Absent param -> fallback; present -> parsed number.
(define host/query-int
  (fn (req name fallback)
    (let ((raw (dream-query-param req name)))
      (if raw (string->number raw) fallback))))