From 59eea64985d3d0b41e0860b13378ad22ecd0158b Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Mon, 6 Oct 2025 22:02:55 +0100
Subject: [PATCH] add tai64 module to anoia

---
 pkgs/anoia/Makefile  |  4 +--
 pkgs/anoia/tai64.fnl | 78 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 2 deletions(-)
 create mode 100644 pkgs/anoia/tai64.fnl

diff --git a/pkgs/anoia/Makefile b/pkgs/anoia/Makefile
index 2d202d6..cce0946 100644
--- a/pkgs/anoia/Makefile
+++ b/pkgs/anoia/Makefile
@@ -1,9 +1,9 @@
 servicedir:=$(shell mktemp -d)
 outputdir:=$(servicedir)/.outputs
 
-default: fs.lua init.lua nl.lua svc.lua process.lua net/constants.lua
+default: fs.lua init.lua nl.lua svc.lua process.lua net/constants.lua tai64.lua
 
-CHECK=fs.fnl init.fnl svc.fnl process.fnl
+CHECK=fs.fnl init.fnl svc.fnl process.fnl tai64.fnl
 
 check:
 	ln -s . anoia
diff --git a/pkgs/anoia/tai64.fnl b/pkgs/anoia/tai64.fnl
new file mode 100644
index 0000000..d19153a
--- /dev/null
+++ b/pkgs/anoia/tai64.fnl
@@ -0,0 +1,78 @@
+(local { : base64 : assoc } (require :anoia))
+(import-macros { : expect= : define-tests } :anoia.assert)
+
+(local
+ leap-seconds-list
+ (let [tbl
+       [
+        ;; https://data.iana.org/time-zones/data/leap-seconds.list
+        ;; comments are the _start_ of the day where the second was
+        ;; added at the end of the previous day
+        [2272060800      10]   ;    1 jan 1972 ; baseline, not a leap second
+        [2287785600      11]   ;    1 jul 1972
+        [2303683200      12]   ;    1 jan 1973
+        [2335219200      13]   ;    1 jan 1974
+        [2366755200      14]   ;    1 Jan 1975
+        [2398291200      15]   ;    1 Jan 1976
+        [2429913600      16]   ;    1 Jan 1977
+        [2461449600      17]   ;    1 Jan 1978
+        [2492985600      18]   ;    1 Jan 1979
+        [2524521600      19]   ;    1 Jan 1980
+        [2571782400      20]   ;    1 Jul 1981
+        [2603318400      21]   ;    1 Jul 1982
+        [2634854400      22]   ;    1 Jul 1983
+        [2698012800      23]   ;    1 Jul 1985
+        [2776982400      24]   ;    1 Jan 1988
+        [2840140800      25]   ;    1 Jan 1990
+        [2871676800      26]   ;    1 Jan 1991
+        [2918937600      27]   ;    1 Jul 1992
+        [2950473600      28]   ;    1 Jul 1993
+        [2982009600      29]   ;    1 Jul 1994
+        [3029443200      30]   ;    1 Jan 1996
+        [3076704000      31]   ;    1 Jul 1997
+        [3124137600      32]   ;    1 Jan 1999
+        [3345062400      33]   ;    1 Jan 2006
+        [3439756800      34]   ;    1 Jan 2009
+        [3550089600      35]   ;    1 Jul 2012
+        [3644697600      36]   ;    1 Jul 2015
+        [3692217600      37]   ;    1 Jan 2017
+        ]]
+   (icollect [_ [ts dtai] (ipairs tbl)]
+     [(+ (- ts 2208988800) dtai) dtai])))
+
+(fn leap-seconds [timestamp]
+  (accumulate [secs 10
+               _ [epoch leap-seconds] (ipairs leap-seconds-list)
+               &until (> epoch timestamp)]
+    leap-seconds))
+
+(define-tests :leap-seconds
+  (expect= (leap-seconds 104694412) 12)
+  (expect= (leap-seconds 23) 10)
+  (expect= (leap-seconds (+ 3692217600 60)) 37)
+  (expect= (leap-seconds (+ 10 773020829)) 29)
+  (expect= (leap-seconds 362793520) 19))
+
+(fn from-timestamp [str]
+  (if (= (string.sub str 1 1) "@")
+      (let [s (tonumber (string.sub str 2 17) 16)
+            two_62 (lshift 1 62)
+            sec (if (>= s two_62)
+                    (- s two_62)
+                    (- two_62 s))
+            nano (tonumber (string.sub str 18 25) 16)]
+        {:s sec :n nano})
+      nil))
+
+(fn to-utc [tai]
+  (+ (- tai.s (leap-seconds tai.s)) (/ tai.n 1e9)))
+
+(define-tests
+  (expect=
+   (from-timestamp "@4000000068e2f0d3257dc09b")
+   {:s 1759703251 :n 628998299})
+
+  (expect= (to-utc (from-timestamp "@4000000068e2f0d3257dc09b"))
+           1759703214.628998299))
+
+{ : from-timestamp : to-utc }