Drop reminders when a task loses its last date (#159)

app/src/main/java/de/jeanlucmakiola/agendula/ui/edit/TaskEditViewModel.kt

@@ -316,8 +316,21 @@ class TaskEditViewModel @Inject constructor(
         }
     }
 
-    fun onStartChange(value: Instant?) = update { it.copy(start = value).withDefaultReminders() }
-    fun onDueChange(value: Instant?) = update { it.copy(due = value).withDefaultReminders() }
+    fun onStartChange(value: Instant?) = update {
+        it.copy(start = value).withDefaultReminders().withoutDatelessReminders()
+    }
+    fun onDueChange(value: Instant?) = update {
+        it.copy(due = value).withDefaultReminders().withoutDatelessReminders()
+    }
+
+    /** A task left without dates has nothing for its reminders to count from, so they go with the last one (#159). */
+    private fun TaskEditUiState.withoutDatelessReminders(): TaskEditUiState =
+        if (start != null || due != null || reminders.isEmpty()) {
+            this
+        } else {
+            copy(reminders = emptyList(), remindersChosen = true)
+        }
+
     /**
      * All-day and timed values use different conventions (UTC midnight vs. a real
      * instant in the device zone), so the switch has to move the timestamps too —