;; lib/host/ta.sx — TA: the fed-sx TRANSPORT ADAPTER (plans/business-logic-fed-flows.md). A seam
;; transport {:emit :deliver} (behavior.sx) over a directional WIRE, so an activity emitted on one
;; instance reaches another instance's engine and fires ITS behaviors — federation.
;;
;; The transport is the SERIALIZATION boundary: activities cross the wire as SX-source strings
;; (string-keyed for persist/wire safety, reconstructed on arrival). The wire is dumb string
;; transport {:send :recv}; the REAL wire is next/ delivery (outbox→peers / inbox), DEFERRED to
;; TA-live (same persistent-kernel prerequisite as RA-live); a mem-wire drives the tests.
;;
;; DIRECTIONAL: :emit → an OUT wire (this instance's outbox → followers); :deliver → an IN wire
;; (its inbox ← those it follows). Separate channels, so processing a delivered activity (which the
;; seam re-emits to log it) goes to THIS instance's outbox, NOT back into the inbox — no loop.

;; canonical activity (keyword-keyed) <-> the flat string-keyed WIRE form (persist/serialise-safe).
(define host/ta--activity->wire
  (fn (a)
    {"verb" (get a :verb) "actor" (get a :actor) "object" (get a :object)
     "type" (get a :object-type) "slug" (get a :slug) "category" (get a :category)
     "relation" (get a :relation) "target" (get a :target)
     "delta" (get a :delta) "id" (get a :id)}))
(define host/ta--wire->activity
  (fn (w)
    {:verb (get w "verb") :actor (get w "actor") :object (get w "object")
     :object-type (get w "type") :slug (get w "slug") :category (get w "category")
     :relation (get w "relation") :target (get w "target")
     :delta (get w "delta") :id (get w "id")}))
(define host/ta--serialize   (fn (a) (serialize (host/ta--activity->wire a))))
(define host/ta--deserialize (fn (s) (host/ta--wire->activity (parse-safe s))))

;; the transport: emit serialises to the OUT wire; deliver deserialises from the IN wire.
(define host/ta--make-transport
  (fn (out-wire in-wire)
    {:emit (fn (a) ((get out-wire :send) (host/ta--serialize a)))
     :deliver (fn () (map host/ta--deserialize ((get in-wire :recv))))}))

;; an in-memory directional wire {:send :recv} (a captured mutable queue) — the test substrate.
(define host/ta--make-mem-wire
  (fn ()
    (let ((q (list)))
      {:send (fn (s) (set! q (concat q (list s))))
       :recv (fn () (let ((batch q)) (begin (set! q (list)) batch)))})))