From 0a44f5375982e12954660d55382ce6a5ab197297 Mon Sep 17 00:00:00 2001
From: kolaente <k@knt.li>
Date: Mon, 4 Aug 2025 13:41:28 +0200
Subject: [PATCH] feat(caldav): return proper caldav intervals instead of
 FREQ=SECONDLY (#1230)

---
 pkg/caldav/caldav.go       | 25 ++++++++++++++++++++++-
 pkg/caldav/parsing_test.go |  2 +-
 pkg/caldav/repeat_test.go  | 42 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 pkg/caldav/repeat_test.go

diff --git a/pkg/caldav/caldav.go b/pkg/caldav/caldav.go
index fd32393fe..fd6f98f64 100644
--- a/pkg/caldav/caldav.go
+++ b/pkg/caldav/caldav.go
@@ -104,6 +104,28 @@ func formatDuration(duration time.Duration) string {
 		strconv.FormatFloat(seconds, 'f', 0, 64) + `S`
 }
 
+func getRruleFromInterval(interval int64) (freq string, newInterval int64) {
+	const (
+		minute = 60
+		hour   = minute * 60
+		day    = hour * 24
+		week   = day * 7
+	)
+
+	switch {
+	case interval%week == 0:
+		return "WEEKLY", interval / week
+	case interval%day == 0:
+		return "DAILY", interval / day
+	case interval%hour == 0:
+		return "HOURLY", interval / hour
+	case interval%minute == 0:
+		return "MINUTELY", interval / minute
+	default:
+		return "SECONDLY", interval
+	}
+}
+
 // ParseTodos returns a caldav vcalendar string with todos
 func ParseTodos(config *Config, todos []*Todo) (caldavtodos string) {
 	caldavtodos = `BEGIN:VCALENDAR
@@ -172,8 +194,9 @@ PRIORITY:` + strconv.Itoa(mapPriorityToCaldav(t.Priority))
 				caldavtodos += `
 RRULE:FREQ=MONTHLY;BYMONTHDAY=` + t.DueDate.Format("02") // Day of the month
 			} else {
+				freq, interval := getRruleFromInterval(t.RepeatAfter)
 				caldavtodos += `
-RRULE:FREQ=SECONDLY;INTERVAL=` + strconv.FormatInt(t.RepeatAfter, 10)
+RRULE:FREQ=` + freq + `;INTERVAL=` + strconv.FormatInt(interval, 10)
 			}
 		}
 
diff --git a/pkg/caldav/parsing_test.go b/pkg/caldav/parsing_test.go
index f852f5cab..1f3516ab8 100644
--- a/pkg/caldav/parsing_test.go
+++ b/pkg/caldav/parsing_test.go
@@ -578,7 +578,7 @@ STATUS:COMPLETED
 DUE:20181201T011202Z
 CREATED:20181201T011201Z
 PRIORITY:3
-RRULE:FREQ=SECONDLY;INTERVAL=86400
+RRULE:FREQ=DAILY;INTERVAL=1
 CATEGORIES:label1,label2
 LAST-MODIFIED:20181201T011205Z
 BEGIN:VALARM
diff --git a/pkg/caldav/repeat_test.go b/pkg/caldav/repeat_test.go
new file mode 100644
index 000000000..6f146575e
--- /dev/null
+++ b/pkg/caldav/repeat_test.go
@@ -0,0 +1,42 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package caldav
+
+import "testing"
+
+func Test_getRruleFromInterval(t *testing.T) {
+	tests := []struct {
+		name         string
+		interval     int64
+		wantFreq     string
+		wantInterval int64
+	}{
+		{"seconds", 435, "SECONDLY", 435},
+		{"minutes", 120, "MINUTELY", 2},
+		{"hours", 7200, "HOURLY", 2},
+		{"daily", 86400, "DAILY", 1},
+		{"weekly", 1209600, "WEEKLY", 2},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotFreq, gotInterval := getRruleFromInterval(tt.interval)
+			if gotFreq != tt.wantFreq || gotInterval != tt.wantInterval {
+				t.Errorf("getRruleFromInterval() = %s,%d; want %s,%d", gotFreq, gotInterval, tt.wantFreq, tt.wantInterval)
+			}
+		})
+	}
+}