From f2da047720404da59c911d66db1e3b45924c5392 Mon Sep 17 00:00:00 2001
From: Adam Brown <adampsbrown@gmail.com>
Date: Wed, 13 Oct 2021 15:36:37 +0100
Subject: [PATCH] keeping an inmemory cache of the seen ids, fixes delayed sync
 responses causing already dismissed notifications from being shown again -
 uses a simple circular buffer to limit the memory usage

---
 .../notifications/CircularStringCache.kt      | 36 +++++++++++++++++++
 .../NotificationDrawerManager.kt              | 19 ++++++++--
 2 files changed, 52 insertions(+), 3 deletions(-)
 create mode 100644 vector/src/main/java/im/vector/app/features/notifications/CircularStringCache.kt

diff --git a/vector/src/main/java/im/vector/app/features/notifications/CircularStringCache.kt b/vector/src/main/java/im/vector/app/features/notifications/CircularStringCache.kt
new file mode 100644
index 0000000000..97b40daf46
--- /dev/null
+++ b/vector/src/main/java/im/vector/app/features/notifications/CircularStringCache.kt
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.app.features.notifications
+
+/**
+ * A FIFO circular buffer of strings
+ */
+class CircularStringCache(cacheSize: Int) {
+
+    private val cache = Array(cacheSize) { "" }
+    private var writeIndex = 0
+
+    fun contains(key: String): Boolean = cache.contains(key)
+
+    fun put(key: String) {
+        if (writeIndex == cache.size - 1) {
+            writeIndex = 0
+        }
+        cache[writeIndex] = key
+        writeIndex++
+    }
+}
diff --git a/vector/src/main/java/im/vector/app/features/notifications/NotificationDrawerManager.kt b/vector/src/main/java/im/vector/app/features/notifications/NotificationDrawerManager.kt
index ecb1268892..2df093b615 100644
--- a/vector/src/main/java/im/vector/app/features/notifications/NotificationDrawerManager.kt
+++ b/vector/src/main/java/im/vector/app/features/notifications/NotificationDrawerManager.kt
@@ -84,6 +84,13 @@ class NotificationDrawerManager @Inject constructor(private val context: Context
 
     private var useCompleteNotificationFormat = vectorPreferences.useCompleteNotificationFormat()
 
+    /**
+     * An in memory FIFO cache of the seen events.
+     * Acts as a notification debouncer to stop already dismissed push notifications from
+     * displaying again when the /sync response is delayed.
+     */
+    private val seenEventIds = CircularStringCache(cacheSize = 25)
+
     /**
     Should be called as soon as a new event is ready to be displayed.
     The notification corresponding to this event will not be displayed until
@@ -140,8 +147,14 @@ class NotificationDrawerManager @Inject constructor(private val context: Context
                         // Ignore an edit of a not displayed event in the notification drawer
                     }
                 } else {
-                    // Not an edit
-                    eventList.add(notifiableEvent)
+                    if (seenEventIds.contains(notifiableEvent.eventId)) {
+                        // we've already seen the event, lets' skip
+                        Timber.d("onNotifiableEventReceived(): skipping event, already seen}")
+                    } else {
+                        // Not an edit
+                        seenEventIds.put(notifiableEvent.eventId)
+                        eventList.add(notifiableEvent)
+                    }
                 }
             }
         }
@@ -266,7 +279,7 @@ class NotificationDrawerManager @Inject constructor(private val context: Context
                     is InviteNotifiableEvent  -> {
                         if (autoAcceptInvites.hideInvites) {
                             // Forget this event
-                           eventIterator.remove()
+                            eventIterator.remove()
                         } else {
                             invitationEvents.add(event)
                         }