Handle tasks from the past correctly

Should only ever apply to tasks from a few seconds ago. Longer downtimes should not happen.

module-server/src/main/kotlin/de/twomartens/timetable/bahnApi/service/TaskScheduler.kt

@@ -6,36 +6,66 @@ import de.twomartens.timetable.bahnApi.repository.ScheduledFetchTaskRepository
 import de.twomartens.timetable.bahnApi.tasks.DeleteScheduledTask
 import de.twomartens.timetable.bahnApi.tasks.FetchTimetableTask
 import de.twomartens.timetable.bahnApi.tasks.StoreTimetableTask
-import de.twomartens.timetable.property.TimeProperties
 import de.twomartens.timetable.types.HourAtDay
 import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler
 import org.springframework.stereotype.Service
+import java.time.Clock
 import java.time.ZonedDateTime
 
+private const val PAST_TASK_EXECUTION_OFFSET = 1
+
 @Service
 class TaskScheduler(
-        private val timeProperties: TimeProperties,
+        private val clock: Clock,
         private val threadPoolTaskScheduler: ThreadPoolTaskScheduler,
         private val threadPoolTaskExecutor: ThreadPoolTaskExecutor,
         private val bahnApiService: BahnApiService,
         private val bahnDatabaseService: BahnDatabaseService,
         private val scheduledFetchTaskRepository: ScheduledFetchTaskRepository
 ) {
-    fun scheduleFetchTasks(scheduledTasks: List<ScheduledFetchTask>) {
-        scheduledTasks.forEach {
-            val zonedExecutionTime = it.scheduledExecutionDateTime
-                    .atZone(timeProperties.defaultTimeZone)
-            scheduleDeleteTask(it, zonedExecutionTime)
-            scheduleFetchTimetableTask(it, zonedExecutionTime)
-        }
-    }
-
     fun scheduleStoreTask(timetable: BahnTimetable, hourAtDay: HourAtDay) {
         val storeTask = StoreTimetableTask(timetable, hourAtDay, bahnDatabaseService)
         threadPoolTaskExecutor.execute(storeTask)
     }
 
+    fun scheduleFetchTasks(scheduledTasks: List<ScheduledFetchTask>) {
+        val nowPlus1Minute = ZonedDateTime.now(clock).plusMinutes(1)
+        scheduleTasksFromThePast(scheduledTasks, nowPlus1Minute)
+        scheduleTasksFromTheFuture(scheduledTasks, nowPlus1Minute)
+    }
+
+    private fun scheduleTasksFromThePast(
+            scheduledTasks: List<ScheduledFetchTask>,
+            nowPlus1Minute: ZonedDateTime
+    ) {
+        val tasksScheduledForPast = scheduledTasks.filter {
+            val zonedExecutionTime = it.scheduledExecutionDateTime.atZone(clock.zone)
+            nowPlus1Minute.isAfter(zonedExecutionTime)
+        }
+        tasksScheduledForPast.forEach {
+            val zonedExecutionTime = it.scheduledExecutionDateTime.atZone(clock.zone)
+            val adjustedExecutionTime = nowPlus1Minute.withOffsetAndSecondsFrom(zonedExecutionTime)
+            scheduleDeleteTask(it, adjustedExecutionTime)
+            scheduleFetchTimetableTask(it, adjustedExecutionTime)
+        }
+    }
+
+    private fun scheduleTasksFromTheFuture(
+            scheduledTasks: List<ScheduledFetchTask>,
+            nowPlus1Minute: ZonedDateTime
+    ) {
+        val tasksScheduledForFuture = scheduledTasks.filter {
+            val zonedExecutionTime = it.scheduledExecutionDateTime.atZone(clock.zone)
+            nowPlus1Minute.isOnOrBefore(zonedExecutionTime)
+        }
+        tasksScheduledForFuture.forEach {
+            val zonedExecutionTime = it.scheduledExecutionDateTime.atZone(clock.zone)
+            scheduleDeleteTask(it, zonedExecutionTime)
+            scheduleFetchTimetableTask(it, zonedExecutionTime)
+        }
+    }
+
     private fun scheduleDeleteTask(
             scheduledFetchTask: ScheduledFetchTask,
             zonedExecutionTime: ZonedDateTime
@@ -53,4 +83,12 @@ class TaskScheduler(
                 bahnApiService, this)
         threadPoolTaskScheduler.schedule(timetableTask, zonedExecutionTime.toInstant())
     }
+
+    companion object {
+        fun ZonedDateTime.withOffsetAndSecondsFrom(other: ZonedDateTime): ZonedDateTime =
+                this.withSecond(other.second + PAST_TASK_EXECUTION_OFFSET)
+
+        fun ZonedDateTime.isOnOrBefore(other: ZonedDateTime): Boolean =
+                this.isBefore(other) || this.isEqual(other)
+    }
 }