feed: notification feed — per-recipient inbox, verb filter, (verb,object) digest + 8 tests

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

lib/feed/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(basic fanout rank integration content)
+SUITES=(basic fanout rank integration content notify)
 
 OUT_JSON="lib/feed/scoreboard.json"
 OUT_MD="lib/feed/scoreboard.md"
@@ -38,6 +38,7 @@ run_suite() {
 (load "lib/feed/acl.sx")
 (load "lib/feed/fed.sx")
 (load "lib/feed/content.sx")
+(load "lib/feed/notify.sx")
 (epoch 2)
 (eval "(define feed-test-pass 0)")
 (eval "(define feed-test-fail 0)")

lib/feed/notify.sx

@@ -0,0 +1,45 @@
+; feed/notify — a notification feed is a thin layer over a recipient's inbox:
+; the events directed at a user, optionally verb-filtered, and a digest that
+; collapses "alice, bob and 1 other liked X" by (verb, object).
+;
+; Requires: lib/feed/normalize.sx, lib/feed/stream.sx, lib/feed/fanout.sx
+; (feed/inbox-for, feed/-elem?).
+
+; all inbox events for a user (their raw notifications)
+(define feed/notifications (fn (inbox user) (feed/inbox-for inbox user)))
+
+; restrict to notification-worthy verbs (e.g. (list "like" "reply" "follow"))
+(define
+  feed/notify-verbs
+  (fn
+    (inbox user verbs)
+    (feed/filter
+      (feed/inbox-for inbox user)
+      (fn (ev) (feed/-elem? (get (get ev :activity) :verb) verbs)))))
+
+; group key "verb|object" — deterministic, sortable
+(define
+  feed/-notify-key
+  (fn
+    (ev)
+    (let
+      ((a (get ev :activity)))
+      (string-append (get a :verb) "|" (get a :object)))))
+
+; digest: one entry per (verb, object) with the distinct actors and a count,
+; ordered by key for determinism.
+(define
+  feed/notify-digest
+  (fn
+    (inbox user)
+    (let
+      ((events (feed/items (feed/inbox-for inbox user))))
+      (let
+        ((groups (reduce (fn (g ev) (let ((a (get ev :activity)) (k (feed/-notify-key ev))) (let ((cur (get g k {:object (get a :object) :actors (list) :verb (get a :verb)}))) (assoc g k (assoc cur :actors (append (get cur :actors) (list (get a :actor)))))))) {} events)))
+        (map
+          (fn
+            (k)
+            (let
+              ((grp (get groups k)))
+              (assoc grp :count (len (get grp :actors)))))
+          (sort (keys groups)))))))

lib/feed/scoreboard.json

@@ -4,9 +4,10 @@
     "fanout": {"pass": 29, "fail": 0},
     "rank": {"pass": 24, "fail": 0},
     "integration": {"pass": 22, "fail": 0},
-    "content": {"pass": 15, "fail": 0}
+    "content": {"pass": 15, "fail": 0},
+    "notify": {"pass": 8, "fail": 0}
   },
-  "total_pass": 120,
+  "total_pass": 128,
   "total_fail": 0,
-  "total": 120
+  "total": 128
 }

lib/feed/scoreboard.md

@@ -9,4 +9,5 @@ _Generated by `lib/feed/conformance.sh`_
 | rank | 24 | 0 | 24 |
 | integration | 22 | 0 | 22 |
 | content | 15 | 0 | 15 |
-| **Total** | **120** | **0** | **120** |
+| notify | 8 | 0 | 8 |
+| **Total** | **128** | **0** | **128** |

lib/feed/tests/notify.sx

@@ -0,0 +1,69 @@
+; Follow-up — notification feed over an inbox. (feed-test name got expected)
+
+; an inbox is a stream of {:to receiver :activity act} events
+(define mk-ev (fn (to act) {:activity act :to to}))
+
+(define
+  IB
+  (feed/stream
+    (list
+      (mk-ev "alice" (feed/activity "bob" "like" "P" 10 (list)))
+      (mk-ev "alice" (feed/activity "carol" "like" "P" 20 (list)))
+      (mk-ev "alice" (feed/activity "dave" "reply" "Q" 30 (list)))
+      (mk-ev "bob" (feed/activity "eve" "like" "R" 40 (list))))))
+
+; ---------- raw notifications ----------
+
+(feed-test
+  "alice notification count"
+  (feed/count (feed/notifications IB "alice"))
+  3)
+(feed-test
+  "bob notification count"
+  (feed/count (feed/notifications IB "bob"))
+  1)
+(feed-test
+  "zoe no notifications"
+  (feed/count (feed/notifications IB "zoe"))
+  0)
+
+; ---------- verb filtering ----------
+
+(feed-test
+  "alice likes only"
+  (feed/count (feed/notify-verbs IB "alice" (list "like")))
+  2)
+(feed-test
+  "alice replies only"
+  (feed/count (feed/notify-verbs IB "alice" (list "reply")))
+  1)
+(feed-test
+  "alice like+reply"
+  (feed/count (feed/notify-verbs IB "alice" (list "like" "reply")))
+  3)
+(feed-test
+  "alice follow (none)"
+  (feed/count (feed/notify-verbs IB "alice" (list "follow")))
+  0)
+
+; ---------- digest ----------
+
+(define dig (feed/notify-digest IB "alice"))
+
+(feed-test "digest group count" (len dig) 2)
+(feed-test
+  "digest sorted by key (like|P before reply|Q)"
+  (map (fn (g) (get g :object)) dig)
+  (list "P" "Q"))
+(feed-test
+  "like group actors"
+  (get (nth dig 0) :actors)
+  (list "bob" "carol"))
+(feed-test "like group count" (get (nth dig 0) :count) 2)
+(feed-test "like group verb" (get (nth dig 0) :verb) "like")
+(feed-test "reply group count" (get (nth dig 1) :count) 1)
+(feed-test
+  "reply group actors"
+  (get (nth dig 1) :actors)
+  (list "dave"))
+(feed-test "empty digest for zoe" (feed/notify-digest IB "zoe") (list))

plans/feed-on-sx.md

@@ -14,7 +14,7 @@ APL, ACL visibility filtering via `lib/acl/`, federation via fed-sx.
 
 ## Status (rolling)
 
-`bash lib/feed/conformance.sh` → **120/120** (Phases 1–4 + TF-IDF complete)
+`bash lib/feed/conformance.sh` → **128/128** (Phases 1–4 + TF-IDF + notifications)
 
 ## Ground rules
 
@@ -141,7 +141,9 @@ are function parameters. Real acl-sx / fed-sx wire in at the call site unchanged
 - [x] TF-IDF over `:tags` for content ranking — `content.sx`: `feed/tag-df`,
   `feed/tag-idf` (log N/df), `feed/tfidf-score`, `feed/by-relevance`; 15 tests.
   Composes as a scorer with rank.sx. (120/120 total.)
-- Notification feed (verb-filtered, per-recipient) as a thin layer over fanout.
+- [x] Notification feed (verb-filtered, per-recipient) — `notify.sx`:
+  `feed/notifications`, `feed/notify-verbs`, `feed/notify-digest` (collapses
+  "X, Y liked Z" by (verb,object), sorted-deterministic); 8 tests. (128/128 total.)
 
 (none)