From 2857150f9e6a7bdda0ab792696d8a15466f0e337 Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Wed, 19 Mar 2025 20:39:18 +0100
Subject: Skew deadlines because of calendar apps

I am too lazy to generalize this, goodbye
---
 icalproxy.go | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/icalproxy.go b/icalproxy.go
index 0a3ea36..152eed6 100644
--- a/icalproxy.go
+++ b/icalproxy.go
@@ -5,6 +5,7 @@ import (
 	"log"
 	"net/http"
 	"net/url"
+	"strings"
 	"time"
 
 	"github.com/emersion/go-ical"
@@ -15,10 +16,16 @@ func main() {
 	cfg := loadConfig()
 	printConfig(&cfg)
 
+	amsTz, err := time.LoadLocation("Europe/Amsterdam")
+	if err != nil {
+		log.Fatalln("Failed to load time zone", err)
+	}
+
 	handler := handler{
 		calURL: url.URL(cfg.CalendarURL.v),
 		ignore: cfg.Ignore,
 		tokens: cfg.UserTokens,
+		amsTz:  amsTz,
 	}
 
 	mux := http.ServeMux{}
@@ -40,6 +47,7 @@ type handler struct {
 	ignore ignoreRules
 	tokens map[string]userToken
 	calURL url.URL
+	amsTz  *time.Location
 }
 
 func (h handler) makeTokenURL(token string) string {
@@ -72,6 +80,7 @@ func (h handler) handle(w http.ResponseWriter, r *http.Request) {
 	}
 
 	filter(h.ignore, cal.Component)
+	skewMidnightDeadlines(h.amsTz, cal.Component)
 
 	if err = ical.NewEncoder(w).Encode(cal); err != nil {
 		log.Println("Error writing calendar:", err)
@@ -108,6 +117,51 @@ func filter(ignore ignoreRules, c *ical.Component) {
 	c.Children = c.Children[:j]
 }
 
+// We often see events which are scheduled for exactly 'end of day', i.e.
+// 23:59:59, with no difference between the start/end time. Unfortunately,
+// these are not shown properly in two open-source Android calendar apps, so we
+// monkey-hack the event to start at 23:30 and add a note to the description :)
+func skewMidnightDeadlines(ams *time.Location, c *ical.Component) {
+	for _, child := range c.Children {
+		if child.Name == ical.CompEvent {
+			if summary := child.Props.Get(ical.PropSummary); summary != nil &&
+				strings.HasSuffix(summary.Value, " - Due") {
+
+				// Modify the start time of the event
+				startTime, stErr := c.Props.DateTime(ical.PropDateTimeStart, ams)
+				endTime, etErr := c.Props.DateTime(ical.PropDateTimeEnd, ams)
+				if stErr != nil || etErr != nil || startTime.IsZero() ||
+					endTime.IsZero() || !startTime.Equal(endTime) ||
+					startTime.Hour() != 23 || startTime.Minute() != 59 ||
+					startTime.Second() != 59 {
+					continue
+				}
+				newStartTime := time.Date(startTime.Year(), startTime.Month(),
+					startTime.Day(), 23, 30, 0, 0, ams)
+				child.Props.SetDateTime(ical.PropDateTimeStart, newStartTime)
+
+				// Update the event description to notify about the change
+				descProp := child.Props.Get(ical.PropDescription)
+				if descProp == nil {
+					descProp = ical.NewProp(ical.PropDescription)
+				}
+
+				curText, err := descProp.Text()
+				if err != nil {
+					// forget about editing the text, at least we 'fixed' the
+					// event time :)
+					continue
+				}
+				curText = "+++ ICALPROXY: DEADLINE MOVED FROM 23:59:59 TO" +
+					"23:30:00 (Europe/Amsterdam) +++\n\n" + curText
+				descProp.SetText(curText)
+
+				child.Props.Set(descProp)
+			}
+		}
+	}
+}
+
 func userOK(tokens map[string]userToken, id string, token []byte) bool {
 	info, ok := tokens[id]
 	if !ok {
-- 
cgit v1.2.3