From d1513c4d506a8628fb6037bc504960c6a4734f29 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Paul=20H=C3=A4nsch?= <paul@plutz.net>
Date: Fri, 2 Feb 2024 19:54:41 +0100
Subject: [PATCH] nth-last-weekday recurrence

---
 datetime.sh     | 25 +++++++++++++++++++++++++
 macros/calendar | 26 +++++++++++++++++++++++---
 2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/datetime.sh b/datetime.sh
index 124ccfb..2b4bba9 100755
--- a/datetime.sh
+++ b/datetime.sh
@@ -74,3 +74,28 @@ istime(){
   printf '%02i:%02i\n' "${h#0}" "${m#0}"
   return 0
 }
+
+numdays(){
+  # return number of days in a month (i.e. 28, 29, 30, or 31)
+  local y="$1" m="${2#0}"
+
+  case $m in
+    1|3|5|7|10|12)
+      printf 31\\n
+      ;;
+    4|6|8|9|11)
+      printf 30\\n
+      ;;
+    2) if  [ "$((y % 400))" -eq 0 ]; then
+        printf 29\\n
+      elif [ "$((y % 100))" -eq 0 ]; then
+        printf 28\\n
+      elif [ "$((y % 4))" -eq 0 ]; then
+        printf 29\\n
+      else
+        printf 28\\n
+      fi
+      ;;
+    *) return 1;;
+  esac
+}
diff --git a/macros/calendar b/macros/calendar
index 3d013f2..5a48675 100755
--- a/macros/calendar
+++ b/macros/calendar
@@ -182,20 +182,40 @@ rrex_weekday() {
 
   nth=$(( ( $(date -ud @$start +%_d) - 1) / 7))
 
-  nend=$(( 0 * 604800 - (dstart - end) % (rrfreq * 604800) + dstart ))
+  nend=$(( 0 * 604800 - (dstart - end) % 604800 + dstart ))
   nstart=$(( start - end + nend))
 
   while [ "$nstart" -lt "$rrend" -a "$nstart" -lt "$dend" ]; do
     [ "$nstart" -ge "$start" -a "$nstart" -ge "$dstart" ] \
     && [ "$(( ( $(date -ud @$nstart +%_d) -1) / 7 ))" -eq "$nth" ] \
     && printf '%i	%i	%s	%s\n' "$nstart" "$nend" "$evtitle" "$evlink"
-    nstart="$((nstart + rrfreq * 7 * 86400))"
+    nstart="$((nstart + 7 * 86400))"
       nend="$((nstart - start + end))"
   done
 }
 
 rrex_lastweekday() {
-:
+  # helper for rrexpand: Nth last weekday of a month (e.g. 2nd last tuesday, etc.)
+  local nstart nend Y m d nth
+
+  read Y m d <<-EOF
+	$(date -ud @$start +"%Y %_m %_d")
+	EOF
+  nth=$(( ( $(numdays $Y $m) - d ) / 7))
+
+  nend=$(( 0 * 604800 - (dstart - end) % 604800 + dstart ))
+  nstart=$(( start - end + nend))
+
+  while [ "$nstart" -lt "$rrend" -a "$nstart" -lt "$dend" ]; do
+    read Y m d <<-EOF
+	$(date -ud @$nstart +"%Y %_m %_d")
+	EOF
+    [ "$nstart" -ge "$start" -a "$nstart" -ge "$dstart" ] \
+    && [ "$(( ( $(numdays $Y $m) - d ) / 7 ))" -eq "$nth" ] \
+    && printf '%i	%i	%s	%s\n' "$nstart" "$nend" "$evtitle" "$evlink"
+    nstart="$((nstart + 7 * 86400))"
+      nend="$((nstart - start + end))"
+  done
 }
 
 events="$(
-- 
2.39.2