Only notify on actual changes

Author: gpunto

stream-feeds-android-client/src/main/kotlin/io/getstream/feeds/android/client/internal/repository/FeedsCapabilityRepository.kt

@@ -44,18 +44,15 @@ internal class FeedsCapabilityRepository(
         batcher.onBatch { ids, _, _ -> processBatch(ids) }
     }
 
-    /** Caches the provided [capabilities], replacing existing entries for the same feed IDs. */
+    /** Caches the provided [capabilities] and notify listeners in case of changes. */
     fun cache(capabilities: Map<FeedId, Set<FeedOwnCapability>>) {
+        val before = cache.toMap()
         cache.putAll(capabilities)
-        // TODO [G.] do we really want to fire an event? The implication is that we'll notify all
-        //  listeners even if they don't care about these feeds. The alternative is to  avoid
-        //  notifying and let `ActivityAdded` handlers/states pull capabilities on demand. Maybe
-        //  that's more error-prone though? We'd have to suspend on an hypothetical `getOrRequest`
-        //  -> is that fine or would it be prone to race conditions?
-        //  Another alternative is to debounce notifications. That should be relatively simple to do
-        //  by launching a coroutine that delays and then notifies, and cancelling the previous job
-        //  each time.
-        subscriptionManager.onEvent(FeedCapabilitiesUpdated(cache.toMap()))
+        val after = cache.toMap()
+
+        if (after != before) {
+            subscriptionManager.onEvent(FeedCapabilitiesUpdated(cache.toMap()))
+        }
     }
 
     fun getOrRequest(id: FeedId): Set<FeedOwnCapability>? {

stream-feeds-android-client/src/test/kotlin/io/getstream/feeds/android/client/internal/repository/FeedsCapabilityRepositoryTest.kt

@@ -57,18 +57,20 @@ internal class FeedsCapabilityRepositoryTest {
         )
 
     @Test
-    fun `cache when given capabilities, store them in cache and notify`() {
-        val feedId1 = FeedId("user:1")
-        val feedId2 = FeedId("user:2")
-        val capabilities =
-            mapOf(
-                feedId1 to setOf(FeedOwnCapability.ReadFeed, FeedOwnCapability.AddActivity),
-                feedId2 to setOf(FeedOwnCapability.ReadFeed),
-            )
+    fun `cache when given same capabilities, notify only on changes`() {
+        val capabilities1 = mapOf(FeedId("user:1") to setOf(FeedOwnCapability.ReadFeed))
+        val capabilities2 = mapOf(FeedId("user:2") to setOf(FeedOwnCapability.AddActivity))
+
+        repository.cache(capabilities1)
+        verify(exactly = 1) { stateEventListener.onEvent(FeedCapabilitiesUpdated(capabilities1)) }
 
-        repository.cache(capabilities)
+        repository.cache(capabilities1)
+        verify(exactly = 1) { stateEventListener.onEvent(any()) }
 
-        verify { stateEventListener.onEvent(FeedCapabilitiesUpdated(capabilities)) }
+        repository.cache(capabilities2)
+        val allCapabilities = capabilities1 + capabilities2
+        verify(exactly = 1) { stateEventListener.onEvent(FeedCapabilitiesUpdated(allCapabilities)) }
+        verify(exactly = 2) { stateEventListener.onEvent(any()) }
     }
 
     @Test