Make the update scheduling more readable (hopefully)

build.gradle

@@ -33,6 +33,7 @@ test {
 def jvmTargetVersion = "11"
 compileKotlin {
     kotlinOptions.jvmTarget = jvmTargetVersion
+    kotlinOptions.freeCompilerArgs += "-Xopt-in=kotlin.RequiresOptIn"
 }
 compileJava {
     targetCompatibility = jvmTargetVersion

src/main/kotlin/org/mosad/thecitadelofricks/controller/CacheController.kt

@@ -38,6 +38,8 @@ import kotlin.collections.ArrayList
 import kotlin.collections.HashMap
 import kotlin.collections.HashSet
 import kotlin.concurrent.scheduleAtFixedRate
+import kotlin.time.Duration
+import kotlin.time.ExperimentalTime
 
 class CacheController {
 
@@ -247,30 +249,39 @@ class CacheController {
          * update the CourseList every 24h, the Timetables every 3h and the Mensa Menu every hour
          * doesn't account the change between winter and summer time!
          */
+        @OptIn(ExperimentalTime::class)
         private fun scheduledUpdates() {
             val currentTime = System.currentTimeMillis()
-            val initDelay24h = (86400000 - ((currentTime + 3600000) % 86400000)) + 60000
-            val initDelay3h = (10800000 - ((currentTime + 3600000) % 10800000)) + 60000
-            val initDelay1h = (3600000 - ((currentTime + 3600000) % 3600000)) + 60000
+
+            val duration24h = Duration.hours(24).inWholeMilliseconds
+            val duration3h = Duration.hours(3).inWholeMilliseconds
+            val duration1h = Duration.hours(1).inWholeMilliseconds
+            val duration1m = Duration.minutes(1).inWholeMilliseconds
+
+            // Calculate the initial delay to make the update time independent of the start time
+            fun calcInitDelay(period: Long) = (period - ((currentTime + duration1h) % period)) + duration1m
+            val initDelay24h = calcInitDelay(duration24h)
+            val initDelay3h = calcInitDelay(duration3h)
+            val initDelay1h = calcInitDelay(duration1h)
 
             // update courseList every 24 hours (time in ms)
-            Timer().scheduleAtFixedRate(initDelay24h, 86400000) {
+            Timer().scheduleAtFixedRate(initDelay24h, duration24h) {
                 asyncUpdateCourseList()
             }
 
             // update all already existing timetables every 3 hours (time in ms)
-            Timer().scheduleAtFixedRate(initDelay3h, 10800000) {
+            Timer().scheduleAtFixedRate(initDelay3h, duration3h) {
                 asyncUpdateTimetables()
             }
 
             // update courses every hour (time in ms)
-            Timer().scheduleAtFixedRate(initDelay1h, 3600000) {
+            Timer().scheduleAtFixedRate(initDelay1h, duration1h) {
                 asyncUpdateMensa()
             }
 
             // post to status.mosad.xyz every hour, if an API key is present
             if (StartupController.cachetAPIKey != "0") {
-                Timer().scheduleAtFixedRate(initDelay1h, 3600000) {
+                Timer().scheduleAtFixedRate(initDelay1h, duration1h) {
                     CachetAPIController.postTotalRequests()
                 }
             }