events: iCalendar (RFC 5545) export + 21 tests

ical.sx serializes events to VEVENT/VCALENDAR text for import by standard
clients: UTC basic-format stamps, DURATION (PT#H#M), full RRULE
(FREQ/INTERVAL/COUNT/UNTIL/BYDAY incl. monthly ordinals 2TU/-1FR/BYMONTHDAY)
plus EXDATE/RDATE. Line-oriented (ev/event->ical-lines / ev/events->ical-lines)
with ev/ical-render joining CRLF for the wire format. 332/332 green.

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

lib/events/conformance.conf

@@ -19,6 +19,7 @@ PRELOADS=(
   lib/datalog/magic.sx
   lib/events/calendar.sx
   lib/events/timezone.sx
+  lib/events/ical.sx
   lib/events/availability.sx
   lib/persist/event.sx
   lib/persist/backend.sx
@@ -49,6 +50,7 @@ PRELOADS=(
 SUITES=(
   "calendar:lib/events/tests/calendar.sx:(ev-calendar-tests-run!)"
   "timezone:lib/events/tests/timezone.sx:(ev-timezone-tests-run!)"
+  "ical:lib/events/tests/ical.sx:(ev-ical-tests-run!)"
   "availability:lib/events/tests/availability.sx:(ev-availability-tests-run!)"
   "api:lib/events/tests/api.sx:(ev-api-tests-run!)"
   "booking:lib/events/tests/booking.sx:(ev-booking-tests-run!)"

lib/events/ical.sx

@@ -0,0 +1,191 @@
+;; lib/events/ical.sx — iCalendar (RFC 5545) export.
+;;
+;; Serializes events to VEVENT / VCALENDAR text so a rose-ash calendar can be
+;; imported by any standard client (Google/Apple/Outlook). Datetimes are UTC
+;; epoch-minutes, emitted as basic-format UTC stamps (YYYYMMDDTHHMM00Z). The
+;; full RRULE / EXDATE / RDATE model maps directly to the standard properties.
+;;
+;; Export is line-oriented: `ev/event->ical-lines` returns the VEVENT as a list
+;; of content lines (no folding/CRLF — easy to assert on); `ev/ical-render`
+;; joins lines with CRLF, the on-the-wire format. Requires calendar.sx.
+
+;; ---- formatting helpers ----
+
+(define ev-ical-pad2 (fn (n) (if (< n 10) (str "0" n) (str n))))
+
+(define
+  ev-ical-pad4
+  (fn
+    (n)
+    (cond
+      ((< n 10) (str "000" n))
+      ((< n 100) (str "00" n))
+      ((< n 1000) (str "0" n))
+      (else (str n)))))
+
+(define
+  ev-ical-nth
+  (fn
+    (xs i)
+    (if
+      (= i 0)
+      (first xs)
+      (ev-ical-nth (rest xs) (- i 1)))))
+
+(define
+  ev-ical-join
+  (fn
+    (parts sep)
+    (if
+      (empty? parts)
+      ""
+      (reduce (fn (acc p) (str acc sep p)) (first parts) (rest parts)))))
+
+;; A UTC epoch-minute as an iCal basic-format UTC stamp.
+(define
+  ev-ical-dt
+  (fn
+    (t)
+    (let
+      ((civ (ev-dt->civil t)) (tod (ev-dt-tod t)))
+      (str
+        (ev-ical-pad4 (ev-civ-y civ))
+        (ev-ical-pad2 (ev-civ-m civ))
+        (ev-ical-pad2 (ev-civ-d civ))
+        "T"
+        (ev-ical-pad2 (quotient tod 60))
+        (ev-ical-pad2 (modulo tod 60))
+        "00Z"))))
+
+;; A duration in minutes as an iCal DURATION value (PT#H#M).
+(define
+  ev-ical-duration
+  (fn
+    (mins)
+    (let
+      ((h (quotient mins 60)) (m (modulo mins 60)))
+      (cond
+        ((and (> h 0) (> m 0)) (str "PT" h "H" m "M"))
+        ((> h 0) (str "PT" h "H"))
+        (else (str "PT" m "M"))))))
+
+(define
+  ev-ical-wd
+  (fn (w) (ev-ical-nth (list "MO" "TU" "WE" "TH" "FR" "SA" "SU") w)))
+
+(define
+  ev-ical-freq
+  (fn
+    (f)
+    (cond
+      ((= f :daily) "DAILY")
+      ((= f :weekly) "WEEKLY")
+      ((= f :monthly) "MONTHLY")
+      (else "DAILY"))))
+
+;; One BYDAY token: a weekly weekday number -> "MO"; a monthly ordinal weekday
+;; {:ord :wd} -> "2TU" / "-1FR".
+(define
+  ev-ical-byday-token
+  (fn
+    (e)
+    (if
+      (dict? e)
+      (str (get e :ord) (ev-ical-wd (get e :wd)))
+      (ev-ical-wd e))))
+
+;; ---- RRULE ----
+(define
+  ev-ical-rrule
+  (fn
+    (rrule)
+    (let
+      ((parts (list (str "FREQ=" (ev-ical-freq (get rrule :freq))))))
+      (begin
+        (when
+          (and
+            (not (nil? (get rrule :interval)))
+            (> (get rrule :interval) 1))
+          (append! parts (str "INTERVAL=" (get rrule :interval))))
+        (when
+          (not (nil? (get rrule :count)))
+          (append! parts (str "COUNT=" (get rrule :count))))
+        (when
+          (not (nil? (get rrule :until)))
+          (append! parts (str "UNTIL=" (ev-ical-dt (get rrule :until)))))
+        (when
+          (not (nil? (get rrule :byday)))
+          (append!
+            parts
+            (str
+              "BYDAY="
+              (ev-ical-join (map ev-ical-byday-token (get rrule :byday)) ","))))
+        (when
+          (not (nil? (get rrule :bymonthday)))
+          (append!
+            parts
+            (str
+              "BYMONTHDAY="
+              (ev-ical-join
+                (map (fn (d) (str d)) (get rrule :bymonthday))
+                ","))))
+        (str "RRULE:" (ev-ical-join parts ";"))))))
+
+;; ---- VEVENT / VCALENDAR ----
+
+;; The VEVENT content lines for an event (list of strings).
+(define
+  ev/event->ical-lines
+  (fn
+    (event)
+    (let
+      ((lines (list "BEGIN:VEVENT")))
+      (begin
+        (append! lines (str "UID:" (get event :id)))
+        (append! lines (str "SUMMARY:" (get event :id)))
+        (append! lines (str "DTSTART:" (ev-ical-dt (get event :dtstart))))
+        (append!
+          lines
+          (str "DURATION:" (ev-ical-duration (get event :duration))))
+        (when
+          (not (nil? (get event :rrule)))
+          (append! lines (ev-ical-rrule (get event :rrule))))
+        (when
+          (and
+            (not (nil? (get event :exdate)))
+            (> (len (get event :exdate)) 0))
+          (append!
+            lines
+            (str
+              "EXDATE:"
+              (ev-ical-join (map ev-ical-dt (get event :exdate)) ","))))
+        (when
+          (and
+            (not (nil? (get event :rdate)))
+            (> (len (get event :rdate)) 0))
+          (append!
+            lines
+            (str
+              "RDATE:"
+              (ev-ical-join (map ev-ical-dt (get event :rdate)) ","))))
+        (append! lines "END:VEVENT")
+        lines))))
+
+;; A full VCALENDAR (list of content lines) wrapping every event.
+(define
+  ev/events->ical-lines
+  (fn
+    (events)
+    (let
+      ((lines (list "BEGIN:VCALENDAR" "VERSION:2.0" "PRODID:-//rose-ash//events-on-sx//EN")))
+      (begin
+        (for-each
+          (fn
+            (ev)
+            (for-each (fn (l) (append! lines l)) (ev/event->ical-lines ev)))
+          events)
+        (append! lines "END:VCALENDAR")
+        lines))))
+
+;; Render content lines to the on-the-wire iCalendar text (CRLF-separated).
+(define ev/ical-render (fn (lines) (ev-ical-join lines "\r\n")))

lib/events/scoreboard.json

@@ -1,11 +1,12 @@
 {
   "lang": "events",
-  "total_passed": 311,
+  "total_passed": 332,
   "total_failed": 0,
-  "total": 311,
+  "total": 332,
   "suites": [
     {"name":"calendar","passed":51,"failed":0,"total":51},
     {"name":"timezone","passed":17,"failed":0,"total":17},
+    {"name":"ical","passed":21,"failed":0,"total":21},
     {"name":"availability","passed":22,"failed":0,"total":22},
     {"name":"api","passed":32,"failed":0,"total":32},
     {"name":"booking","passed":82,"failed":0,"total":82},
@@ -16,5 +17,5 @@
     {"name":"federation","passed":29,"failed":0,"total":29},
     {"name":"integration","passed":8,"failed":0,"total":8}
   ],
-  "generated": "2026-06-07T13:59:09+00:00"
+  "generated": "2026-06-07T14:40:54+00:00"
 }

lib/events/scoreboard.md

@@ -1,11 +1,12 @@
 # events scoreboard
 
-**311 / 311 passing** (0 failure(s)).
+**332 / 332 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
 | calendar | 51 | 51 | ok |
 | timezone | 17 | 17 | ok |
+| ical | 21 | 21 | ok |
 | availability | 22 | 22 | ok |
 | api | 32 | 32 | ok |
 | booking | 82 | 82 | ok |

lib/events/tests/ical.sx

@@ -0,0 +1,192 @@
+;; lib/events/tests/ical.sx — iCalendar (RFC 5545) export.
+
+(define ev-ic-pass 0)
+(define ev-ic-fail 0)
+(define ev-ic-failures (list))
+
+(define
+  ev-ic-check!
+  (fn
+    (name got expected)
+    (if
+      (= got expected)
+      (set! ev-ic-pass (+ ev-ic-pass 1))
+      (do
+        (set! ev-ic-fail (+ ev-ic-fail 1))
+        (append!
+          ev-ic-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+;; Find the value of a "KEY:value" line in a VEVENT line list (or nil).
+(define
+  ev-ic-line
+  (fn
+    (lines key)
+    (cond
+      ((empty? lines) nil)
+      ((ev-ic-prefix? (first lines) (str key ":")) (first lines))
+      (else (ev-ic-line (rest lines) key)))))
+
+(define
+  ev-ic-prefix?
+  (fn
+    (s p)
+    (and (>= (len s) (len p)) (= (substring s 0 (len p)) p))))
+
+(define
+  ev-ic-run-all!
+  (fn
+    ()
+    (do
+      (let
+        ((lines (ev/event->ical-lines (ev-event (quote one) (ev-dt 2026 6 10 14 0) 60 nil 1))))
+        (do
+          (ev-ic-check! "VEVENT opens" (first lines) "BEGIN:VEVENT")
+          (ev-ic-check! "VEVENT closes" (ev-ic-line lines "END") "END:VEVENT")
+          (ev-ic-check!
+            "UID is the event id"
+            (ev-ic-line lines "UID")
+            "UID:one")
+          (ev-ic-check!
+            "DTSTART is a UTC basic-format stamp"
+            (ev-ic-line lines "DTSTART")
+            "DTSTART:20260610T140000Z")
+          (ev-ic-check!
+            "DURATION of 60m is PT1H"
+            (ev-ic-line lines "DURATION")
+            "DURATION:PT1H")
+          (ev-ic-check!
+            "a one-off event has no RRULE"
+            (ev-ic-line lines "RRULE")
+            nil)))
+      (ev-ic-check!
+        "30m duration is PT30M"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote e)
+              (ev-dt 2026 1 1 9 0)
+              30
+              nil
+              1))
+          "DURATION")
+        "DURATION:PT30M")
+      (ev-ic-check!
+        "90m duration is PT1H30M"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote e)
+              (ev-dt 2026 1 1 9 0)
+              90
+              nil
+              1))
+          "DURATION")
+        "DURATION:PT1H30M")
+      (let
+        ((lines (ev/event->ical-lines (ev-event-full (quote yoga) (ev-dt 2026 6 1 18 0) 90 {:interval 2 :freq :weekly :until (ev-dt 2026 6 30 23 0) :byday (list 0 2)} 20 (list (ev-dt 2026 6 8 18 0)) (list (ev-dt 2026 6 20 18 0))))))
+        (do
+          (ev-ic-check!
+            "weekly RRULE serializes interval/until/byday in order"
+            (ev-ic-line lines "RRULE")
+            "RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=20260630T230000Z;BYDAY=MO,WE")
+          (ev-ic-check!
+            "EXDATE line"
+            (ev-ic-line lines "EXDATE")
+            "EXDATE:20260608T180000Z")
+          (ev-ic-check!
+            "RDATE line"
+            (ev-ic-line lines "RDATE")
+            "RDATE:20260620T180000Z")))
+      (ev-ic-check!
+        "daily COUNT RRULE"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote d)
+              (ev-dt 2026 6 1 9 0)
+              30
+              {:freq :daily :count 5}
+              1))
+          "RRULE")
+        "RRULE:FREQ=DAILY;COUNT=5")
+      (ev-ic-check!
+        "monthly nth-weekday BYDAY (2nd Tuesday)"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote b)
+              (ev-dt 2026 1 13 9 0)
+              60
+              {:freq :monthly :byday (list {:ord 2 :wd 1})}
+              5))
+          "RRULE")
+        "RRULE:FREQ=MONTHLY;BYDAY=2TU")
+      (ev-ic-check!
+        "monthly last-Friday BYDAY"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote b)
+              (ev-dt 2026 1 30 9 0)
+              60
+              {:freq :monthly :byday (list {:ord -1 :wd 4})}
+              5))
+          "RRULE")
+        "RRULE:FREQ=MONTHLY;BYDAY=-1FR")
+      (ev-ic-check!
+        "monthly BYMONTHDAY (incl. negative)"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote b)
+              (ev-dt 2026 1 15 9 0)
+              60
+              {:bymonthday (list 15 -1) :freq :monthly}
+              5))
+          "RRULE")
+        "RRULE:FREQ=MONTHLY;BYMONTHDAY=15,-1")
+      (ev-ic-check!
+        "all seven weekday tokens map correctly"
+        (ev-ic-line
+          (ev/event->ical-lines
+            (ev-event
+              (quote w)
+              (ev-dt 2026 6 1 9 0)
+              30
+              {:freq :weekly :byday (list 0 1 2 3 4 5 6)}
+              1))
+          "RRULE")
+        "RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR,SA,SU")
+      (let
+        ((cal (ev/events->ical-lines (list (ev-event (quote a) (ev-dt 2026 6 1 9 0) 30 nil 1) (ev-event (quote b) (ev-dt 2026 6 2 9 0) 30 nil 1)))))
+        (do
+          (ev-ic-check! "VCALENDAR opens" (first cal) "BEGIN:VCALENDAR")
+          (ev-ic-check!
+            "VCALENDAR declares VERSION"
+            (ev-ic-line cal "VERSION")
+            "VERSION:2.0")
+          (ev-ic-check!
+            "two events -> two VEVENT blocks"
+            (len (filter (fn (l) (= l "BEGIN:VEVENT")) cal))
+            2)
+          (ev-ic-check!
+            "VCALENDAR has exactly one closing line"
+            (len (filter (fn (l) (= l "END:VCALENDAR")) cal))
+            1)))
+      (ev-ic-check!
+        "render joins lines with CRLF"
+        (ev/ical-render
+          (list "BEGIN:VCALENDAR" "VERSION:2.0" "END:VCALENDAR"))
+        "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nEND:VCALENDAR"))))
+
+(define
+  ev-ical-tests-run!
+  (fn
+    ()
+    (do
+      (set! ev-ic-pass 0)
+      (set! ev-ic-fail 0)
+      (set! ev-ic-failures (list))
+      (ev-ic-run-all!)
+      {:failures ev-ic-failures :total (+ ev-ic-pass ev-ic-fail) :passed ev-ic-pass :failed ev-ic-fail})))

plans/events-on-sx.md

@@ -18,7 +18,7 @@ capacity rules, transactional booking, and a flow-driven notification dispatcher
 
 ## Status (rolling)
 
-`bash lib/events/conformance.sh` → **311/311** (Phases 1-4 + 10 ext: …timezones+DST, e2e delivery pipeline, cross-event conflict-checked booking)
+`bash lib/events/conformance.sh` → **332/332** (Phases 1-4 + 11 ext: …e2e delivery, conflict-checked booking, iCalendar export)
 
 ## Ground rules
 
@@ -88,6 +88,13 @@ lib/events/api.sx ── (events/schedule) (events/book) (events/agenda) ──
 
 ## Progress log
 
+- 2026-06-07 — iCalendar (RFC 5545) export (extension). `ical.sx` serializes
+  events to VEVENT / VCALENDAR text for import by standard clients. UTC
+  basic-format stamps (YYYYMMDDTHHMM00Z), DURATION (PT#H#M), and the full RRULE
+  model (FREQ/INTERVAL/COUNT/UNTIL/BYDAY incl. monthly ordinals "2TU"/"-1FR"/
+  BYMONTHDAY) plus EXDATE/RDATE. Line-oriented: `ev/event->ical-lines` /
+  `ev/events->ical-lines` return content lines; `ev/ical-render` joins with
+  CRLF (wire format). +21 tests, 332/332 green.
 - 2026-06-07 — Cross-event conflict-checked booking (extension). Capacity is
   per-event, but `ev/book-checked!` also prevents an attendee double-booking
   THEMSELVES across different events: it consults the actor's persist-derived