From a99972f6b8b13e21a54df418eea1b39e0d582342 Mon Sep 17 00:00:00 2001
From: Bnyro <bnyro@tutanota.com>
Date: Sat, 21 Sep 2024 19:36:09 +0200
Subject: [PATCH] fix: alarm rings at wrong time on summer/winter time change

---
 .../java/com/bnyro/clock/util/AlarmHelper.kt  | 16 ++++++++
 .../java/com/bnyro/clock/SummerTimeTest.kt    | 37 +++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 app/src/test/java/com/bnyro/clock/SummerTimeTest.kt

diff --git a/app/src/main/java/com/bnyro/clock/util/AlarmHelper.kt b/app/src/main/java/com/bnyro/clock/util/AlarmHelper.kt
index f7b762a5..a8b980c7 100644
--- a/app/src/main/java/com/bnyro/clock/util/AlarmHelper.kt
+++ b/app/src/main/java/com/bnyro/clock/util/AlarmHelper.kt
@@ -17,6 +17,7 @@ import java.util.GregorianCalendar
 
 object AlarmHelper {
     const val EXTRA_ID = "alarm_id"
+    private const val HOUR_IN_MILLIS = 60 * 60 * 1000
 
     @SuppressLint("ScheduleExactAlarm")
     fun enqueue(context: Context, alarm: Alarm) {
@@ -79,9 +80,24 @@ object AlarmHelper {
         calendar.add(Calendar.MILLISECOND, alarm.time.toInt())
 
         calendar.add(Calendar.DATE, getPostponeDays(alarm, calendar))
+
+        fixDaylightTime(calendar)
+
         return calendar.timeInMillis
     }
 
+    fun fixDaylightTime(calendar: GregorianCalendar) {
+        val now = TimeHelper.currentTime
+
+        if (calendar.timeZone.useDaylightTime()) {
+            if (calendar.timeZone.inDaylightTime(now) && !calendar.timeZone.inDaylightTime(calendar.time)) {
+                calendar.timeInMillis += HOUR_IN_MILLIS
+            } else if (!calendar.timeZone.inDaylightTime(now) && calendar.timeZone.inDaylightTime(calendar.time)) {
+                calendar.timeInMillis -= HOUR_IN_MILLIS
+            }
+        }
+    }
+
     private fun getPostponeDays(alarm: Alarm, calendar: GregorianCalendar): Int {
         if (alarm.days.isEmpty() && alarm.repeat) return 0
 
diff --git a/app/src/test/java/com/bnyro/clock/SummerTimeTest.kt b/app/src/test/java/com/bnyro/clock/SummerTimeTest.kt
new file mode 100644
index 00000000..9cadb4a2
--- /dev/null
+++ b/app/src/test/java/com/bnyro/clock/SummerTimeTest.kt
@@ -0,0 +1,37 @@
+package com.bnyro.clock
+
+import com.bnyro.clock.util.AlarmHelper
+import org.junit.Test
+import java.util.Date
+import java.util.GregorianCalendar
+import java.util.TimeZone
+
+class SummerTimeTest {
+    @Test
+    fun scheduleWithSummerTime() {
+        TimeZone.setDefault(TimeZone.getTimeZone("Europe/Berlin"))
+        val date = Date(Date.UTC(2024, 10, 30, 15, 0, 0))
+        val calendar = GregorianCalendar()
+        calendar.time = date
+        val millis = calendar.timeInMillis
+        AlarmHelper.fixDaylightTime(calendar)
+
+        if (calendar.timeZone.inDaylightTime(calendar.time)) {
+            assert(millis == calendar.timeInMillis + 60 * 60 * 1000L)
+        } else {
+            assert(millis == calendar.timeInMillis - 60 * 60 * 1000L)
+        }
+    }
+
+    @Test
+    fun scheduleWithoutDaylightDiff() {
+        TimeZone.setDefault(TimeZone.getTimeZone("Europe/Berlin"))
+        val date = Date()
+        val calendar = GregorianCalendar()
+        calendar.time = date
+        val millis = calendar.timeInMillis
+        AlarmHelper.fixDaylightTime(calendar)
+
+        assert(millis == calendar.timeInMillis)
+    }
+}
\ No newline at end of file