;; lib/host/feed.sx — Feed domain endpoints on the host. The first domain migrated
;; onto the SX host: read the activity timeline (GET /feed) and create activities
;; (POST /feed). Both go straight through the feed subsystem's public API; the
;; write path runs behind the host middleware stack (auth + ACL). Depends on
;; lib/feed/* + lib/host/handler.sx + lib/host/middleware.sx (write routes only).

;; ── read ───────────────────────────────────────────────────────────

;; GET /feed -> recent-first activities as a JSON envelope.
;; Query: ?actor=<id> (filter) ?limit=<n> (cap, applied after filtering).
(define host/feed-timeline
  (fn (req)
    (let ((base (feed/recent (feed/all)))
          (actor (dream-query-param req "actor")))
      (let ((filtered (if actor (feed/by-actor base actor) base))
            (limit (dream-query-param req "limit")))
        (let ((capped
                (if limit (feed/take filtered (string->number limit)) filtered)))
          (host/ok (feed/items capped)))))))

;; Public read route group.
(define host/feed-routes
  (list
    (dream-get "/feed" host/feed-timeline)))

;; ── write ──────────────────────────────────────────────────────────

;; POST /feed -> create an activity from the JSON body. Returns 201 + the created
;; (normalised) activity. Body must be a JSON object; anything else -> 400.
(define host/feed-create
  (fn (req)
    (let ((raw (dream-json-body req)))
      (if (= (type-of raw) "dict")
        (host/ok-status 201 (feed/post raw))
        (host/error 400 "invalid activity")))))

;; Guarded write route group: POST /feed behind auth + ACL ("post" on "feed").
;; resolve : token -> principal | nil (injected auth policy, e.g. token lookup
;; against the identity subsystem). Errors thrown downstream become a JSON 500.
(define host/feed-write-routes
  (fn (resolve)
    (list
      (dream-post "/feed"
        (host/pipeline
          (list
            host/wrap-errors
            (host/require-auth resolve)
            (host/require-permission "post" (fn (req) "feed")))
          host/feed-create)))))