Fix for concurrency bug (alamkanak#160)

* fix for concurrency bug

* minimized diff

* used CopyOnWriteArrayList

Co-authored-by: Felix Felten <FPF1993@googlemail.com>

Author: FeFelten

core/src/main/java/com/alamkanak/weekview/EventChipsCache.kt

@@ -2,14 +2,15 @@ package com.alamkanak.weekview
 
 import java.util.Calendar
 import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.CopyOnWriteArrayList
 
 internal class EventChipsCache {
 
     val allEventChips: List<EventChip>
         get() = normalEventChipsByDate.values.flatten() + allDayEventChipsByDate.values.flatten()
 
-    private val normalEventChipsByDate = ConcurrentHashMap<Long, MutableList<EventChip>>()
-    private val allDayEventChipsByDate = ConcurrentHashMap<Long, MutableList<EventChip>>()
+    private val normalEventChipsByDate = ConcurrentHashMap<Long, CopyOnWriteArrayList<EventChip>>()
+    private val allDayEventChipsByDate = ConcurrentHashMap<Long, CopyOnWriteArrayList<EventChip>>()
 
     fun allEventChipsInDateRange(
         dateRange: List<Calendar>
@@ -62,11 +63,11 @@ internal class EventChipsCache {
         normalEventChipsByDate.clear()
     }
 
-    private fun ConcurrentHashMap<Long, MutableList<EventChip>>.addOrReplace(
+    private fun ConcurrentHashMap<Long, CopyOnWriteArrayList<EventChip>>.addOrReplace(
         key: Long,
         eventChip: EventChip
     ) {
-        val results = getOrElse(key) { mutableListOf() }
+        val results = getOrElse(key) { CopyOnWriteArrayList() }
         val indexOfExisting = results.indexOfFirst { it.event.id == eventChip.event.id }
         if (indexOfExisting != -1) {
             // If an event with the same ID already exists, replace it. The new event will likely be
@@ -76,7 +77,6 @@ internal class EventChipsCache {
         } else {
             results.add(eventChip)
         }
-
         this[key] = results
     }
 }