events: wire persist-backed booking into api.sx + 10 tests

Durable booking path alongside in-memory: ev/book-occ!, ev/cancel-occ!,
ev/roster-occ, ev/seats-left-occ (capacity from scheduled event); ev/free-p?,
ev/next-free-p, ev/conflicts-p derive availability by replaying persist
booking streams. Reordered conformance preloads. 120/120 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/events/api.sx

@@ -1,13 +1,19 @@
 ;; lib/events/api.sx — public events surface over calendar + availability.
 ;;
-;; A `store` is an immutable value holding scheduled events and bookings:
+;; A `store` is an immutable value holding scheduled events and (in-memory)
+;; bookings:
 ;;
 ;;   {:events (event ...) :bookings ((actor key) ...)}
 ;;
+;; The in-memory `:bookings` list supports pure, value-level queries. The
+;; DURABLE booking path (ev/*-occ! and ev/*-p) keeps bookings in persist
+;; streams via booking.sx — capacity-safe, cancellable, replayable — and
+;; derives availability from those streams. Use the persist path for real
+;; bookings; the in-memory path for projections and tests.
+;;
 ;; All queries are windowed: agenda/free/next-free expand recurring events into
 ;; concrete occurrences within an explicit (or derived) window before running
-;; the Datalog availability rules. Phase 2 replaces `ev/book` with a capacity-
-;; safe persist append; the rest of this facade stays put.
+;; the Datalog availability rules.
 
 (define ev/store (fn (events bookings) {:bookings bookings :events events}))
 
@@ -31,8 +37,8 @@
     (store id dtstart duration rrule capacity)
     (ev/add-event store (ev-event id dtstart duration rrule capacity))))
 
-;; Record that `actor` holds the occurrence with `key` (ev-occ-key of an
-;; expanded occurrence). Phase 1: append-only, no capacity check.
+;; Record that `actor` holds the occurrence with `key` (in-memory only — see
+;; ev/book-occ! for the durable, capacity-safe path).
 (define
   ev/book
   (fn
@@ -41,6 +47,27 @@
       (ev/events store)
       (cons (list actor key) (ev/bookings store)))))
 
+;; The event with `id`, or nil.
+(define
+  ev/event-by-id
+  (fn
+    (store id)
+    (reduce
+      (fn
+        (found ev)
+        (if (nil? found) (if (= (get ev :id) id) ev found) found))
+      nil
+      (ev/events store))))
+
+;; Capacity of the event an occurrence belongs to (0 if unknown).
+(define
+  ev/capacity-of
+  (fn
+    (store occ)
+    (let
+      ((ev (ev/event-by-id store (get occ :id))))
+      (if (nil? ev) 0 (get ev :capacity)))))
+
 ;; The maximum event duration in the store (0 when empty) — used to widen
 ;; expansion windows so any occurrence overlapping a query is captured.
 (define
@@ -66,7 +93,7 @@
       ((= k (first keys)) true)
       (else (ev-key-member? k (rest keys))))))
 
-;; Occurrence keys `actor` has booked.
+;; Occurrence keys `actor` has booked (in-memory store).
 (define
   ev/actor-keys
   (fn
@@ -78,7 +105,7 @@
       (list)
       (ev/bookings store))))
 
-;; The agenda restricted to occurrences `actor` is booked into, within window.
+;; The agenda restricted to occurrences `actor` is booked into (in-memory).
 (define
   ev/agenda-for
   (fn
@@ -89,7 +116,8 @@
         (fn (o) (ev-key-member? (ev-occ-key o) keys))
         (ev/agenda store ws we)))))
 
-;; Build an availability db over occurrences expanded in [ws, we).
+;; Build an availability db over occurrences expanded in [ws, we) using the
+;; in-memory bookings.
 (define
   ev/avail-window-db
   (fn
@@ -135,3 +163,89 @@
   (fn
     (store actor ws we)
     (> (len (ev/conflicts store actor ws we)) 0)))
+
+;; ---- durable, persist-backed booking path ----
+;; These take a persist backend `b` (persist/open) plus the schedule `store`.
+;; Bookings live in per-occurrence streams (booking.sx); availability is derived
+;; by replaying those streams for the occurrences in the query window.
+
+;; Durably book `actor` into occurrence `occ` (dict {:id :start :end}),
+;; capacity-safe. Returns the booking.sx result (:booked / :full / :already).
+(define
+  ev/book-occ!
+  (fn
+    (b store actor occ)
+    (ev/book! b (ev-occ-key occ) (ev/capacity-of store occ) actor)))
+
+;; Durably cancel `actor`'s seat on `occ`, freeing capacity.
+(define
+  ev/cancel-occ!
+  (fn (b store actor occ) (ev/cancel! b (ev-occ-key occ) actor)))
+
+;; Live roster / seats-left for a specific occurrence from persist.
+(define ev/roster-occ (fn (b occ) (ev/roster b (ev-occ-key occ))))
+
+(define
+  ev/seats-left-occ
+  (fn
+    (b store occ)
+    (ev/seats-left b (ev-occ-key occ) (ev/capacity-of store occ))))
+
+;; Derive (actor key) booking pairs from the persist rosters of `occs`.
+(define
+  ev/persist-bookings
+  (fn
+    (b occs)
+    (reduce
+      (fn
+        (acc occ)
+        (let
+          ((key (ev-occ-key occ)))
+          (append
+            acc
+            (map (fn (actor) (list actor key)) (ev/roster b key)))))
+      (list)
+      occs)))
+
+;; Availability db over [ws, we) with bookings sourced from persist streams.
+(define
+  ev/avail-db-p
+  (fn
+    (b store ws we)
+    (let
+      ((occs (ev/agenda store ws we)))
+      (ev-avail-db occs (ev/persist-bookings b occs)))))
+
+;; Persist-backed availability queries (mirror the in-memory ev/free? etc).
+(define
+  ev/free-p?
+  (fn
+    (b store actor qs qe)
+    (ev-free?
+      (ev/avail-db-p b store (- qs (ev/store-max-duration store)) qe)
+      actor
+      qs
+      qe)))
+
+(define
+  ev/next-free-p
+  (fn
+    (b store actor after duration horizon)
+    (ev-next-free
+      (ev/avail-db-p b store (- after (ev/store-max-duration store)) horizon)
+      actor
+      after
+      duration
+      horizon)))
+
+(define
+  ev/conflicts-p
+  (fn
+    (b store actor ws we)
+    (ev-conflicts (ev/avail-db-p b store ws we) actor)))
+
+(define
+  ev/has-conflict-p?
+  (fn
+    (b store actor ws we)
+    (> (len (ev/conflicts-p b store actor ws we)) 0)))

lib/events/conformance.conf

@@ -19,7 +19,6 @@ PRELOADS=(
   lib/datalog/magic.sx
   lib/events/calendar.sx
   lib/events/availability.sx
-  lib/events/api.sx
   lib/persist/event.sx
   lib/persist/backend.sx
   lib/persist/log.sx
@@ -27,6 +26,7 @@ PRELOADS=(
   lib/persist/concurrency.sx
   lib/persist/api.sx
   lib/events/booking.sx
+  lib/events/api.sx
 )
 
 SUITES=(

lib/events/scoreboard.json

@@ -1,13 +1,13 @@
 {
   "lang": "events",
-  "total_passed": 110,
+  "total_passed": 120,
   "total_failed": 0,
-  "total": 110,
+  "total": 120,
   "suites": [
     {"name":"calendar","passed":37,"failed":0,"total":37},
     {"name":"availability","passed":22,"failed":0,"total":22},
-    {"name":"api","passed":14,"failed":0,"total":14},
+    {"name":"api","passed":24,"failed":0,"total":24},
     {"name":"booking","passed":37,"failed":0,"total":37}
   ],
-  "generated": "2026-06-07T02:09:36+00:00"
+  "generated": "2026-06-07T02:39:08+00:00"
 }

lib/events/scoreboard.md

@@ -1,10 +1,10 @@
 # events scoreboard
 
-**110 / 110 passing** (0 failure(s)).
+**120 / 120 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
 | calendar | 37 | 37 | ok |
 | availability | 22 | 22 | ok |
-| api | 14 | 14 | ok |
+| api | 24 | 24 | ok |
 | booking | 37 | 37 | ok |

lib/events/tests/api.sx

@@ -64,6 +64,14 @@
               "max duration of empty store is zero"
               (ev/store-max-duration (ev/empty))
               0)
+            (ev-api-check!
+              "event-by-id finds the scheduled event"
+              (get (ev/event-by-id s0 (quote yoga)) :capacity)
+              20)
+            (ev-api-check!
+              "event-by-id is nil for unknown id"
+              (ev/event-by-id s0 (quote nope))
+              nil)
             (ev-api-check!
               "agenda-for lists only booked occurrences"
               (map
@@ -162,7 +170,94 @@
                   (quote nia)
                   (ev-date 2026 6 1)
                   (ev-date 2026 7 1))
-                true))))))))
+                true))
+            (let
+              ((b (persist/open)) (occ1 (first occs)))
+              (do
+                (let
+                  ((sp (ev/schedule (ev/empty) (quote clinic) (ev-dt 2026 6 5 9 0) 30 nil 2)))
+                  (let
+                    ((occ (ev-occ (quote clinic) (ev-dt 2026 6 5 9 0) 30)))
+                    (do
+                      (ev-api-check!
+                        "durable book returns booked"
+                        (get (ev/book-occ! b sp (quote a) occ) :status)
+                        :booked)
+                      (ev/book-occ! b sp (quote c) occ)
+                      (ev-api-check!
+                        "durable book past capacity is full"
+                        (get (ev/book-occ! b sp (quote d) occ) :status)
+                        :full)
+                      (ev-api-check!
+                        "durable roster reflects persisted bookings"
+                        (ev/roster-occ b occ)
+                        (list (quote a) (quote c)))
+                      (ev-api-check!
+                        "durable seats-left honours capacity"
+                        (ev/seats-left-occ b sp occ)
+                        0)
+                      (ev-api-check!
+                        "persist free? false during a durable booking"
+                        (ev/free-p?
+                          b
+                          sp
+                          (quote a)
+                          (ev-dt
+                            2026
+                            6
+                            5
+                            9
+                            10)
+                          (ev-dt
+                            2026
+                            6
+                            5
+                            9
+                            20))
+                        false)
+                      (ev-api-check!
+                        "persist free? true in an open window"
+                        (ev/free-p?
+                          b
+                          sp
+                          (quote a)
+                          (ev-dt
+                            2026
+                            6
+                            5
+                            10
+                            0)
+                          (ev-dt
+                            2026
+                            6
+                            5
+                            10
+                            30))
+                        true)
+                      (ev/cancel-occ! b sp (quote a) occ)
+                      (ev-api-check!
+                        "durable cancel frees a seat"
+                        (ev/seats-left-occ b sp occ)
+                        1)
+                      (ev-api-check!
+                        "persist free? true after cancellation"
+                        (ev/free-p?
+                          b
+                          sp
+                          (quote a)
+                          (ev-dt
+                            2026
+                            6
+                            5
+                            9
+                            10)
+                          (ev-dt
+                            2026
+                            6
+                            5
+                            9
+                            20))
+                        true))))))))))))
 
 (define
   ev-api-tests-run!