Post List: Fix excessive media requests

WordPress/src/main/java/org/wordpress/android/ui/posts/PostListEventListener.kt

@@ -174,8 +174,8 @@ class PostListEventListener(
     @Suppress("unused", "SpreadOperator")
     @Subscribe(threadMode = BACKGROUND)
     fun onMediaChanged(event: OnMediaChanged) {
+        featuredMediaChanged(*event.mediaList.map { it.mediaId }.toLongArray())
         if (!event.isError) {
-            featuredMediaChanged(*event.mediaList.map { it.mediaId }.toLongArray())
             uploadStatusChanged(*event.mediaList.map { it.localPostId }.toIntArray())
         }
     }

WordPress/src/main/java/org/wordpress/android/ui/posts/PostListFeaturedImageTracker.kt

@@ -1,6 +1,7 @@
 package org.wordpress.android.ui.posts
 
 import android.annotation.SuppressLint
+import androidx.annotation.VisibleForTesting
 import org.wordpress.android.fluxc.Dispatcher
 import org.wordpress.android.fluxc.generated.MediaActionBuilder
 import org.wordpress.android.fluxc.model.MediaModel
@@ -22,21 +23,39 @@ class PostListFeaturedImageTracker(private val dispatcher: Dispatcher, private v
     https://github.com/wordpress-mobile/WordPress-Android/issues/11487
      */
     @SuppressLint("UseSparseArrays")
-    private val featuredImageMap = HashMap<Long, String>()
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    internal val featuredImageMap = HashMap<Long, String>()
+
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    internal val ongoingRequests = HashSet<Long>()
 
     fun getFeaturedImageUrl(site: SiteModel, featuredImageId: Long): String? {
         if (featuredImageId == 0L) {
             return null
         }
-        featuredImageMap[featuredImageId]?.let { return it }
+
+        featuredImageMap[featuredImageId]?.let {
+            return it
+        }
+
+        // Check if a request for this image is already ongoing
+        if (ongoingRequests.contains(featuredImageId)) {
+            // If the request is ongoing, just return. The callback will be invoked upon completion.
+            return null
+        }
+
         mediaStore.getSiteMediaWithId(site, featuredImageId)?.let { media ->
             // This should be a pretty rare case, but some media seems to be missing url
             return if (media.url.isNotBlank()) {
                 featuredImageMap[featuredImageId] = media.url
                 media.url
             } else null
         }
+
         // Media is not in the Store, we need to download it
+        // Mark the request as ongoing
+        ongoingRequests.add(featuredImageId)
+
         val mediaToDownload = MediaModel(
             site.id,
             featuredImageId
@@ -47,6 +66,9 @@ class PostListFeaturedImageTracker(private val dispatcher: Dispatcher, private v
     }
 
     fun invalidateFeaturedMedia(featuredImageIds: List<Long>) {
-        featuredImageIds.forEach { featuredImageMap.remove(it) }
+        featuredImageIds.forEach {
+            featuredImageMap.remove(it)
+            ongoingRequests.remove(it)
+        }
     }
 }

WordPress/src/test/java/org/wordpress/android/ui/posts/PostListFeaturedImageTrackerTest.kt

@@ -0,0 +1,111 @@
+package org.wordpress.android.ui.posts
+
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Before
+import org.mockito.kotlin.any
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.never
+import org.mockito.kotlin.verify
+import org.mockito.kotlin.whenever
+import org.wordpress.android.BaseUnitTest
+import org.wordpress.android.fluxc.Dispatcher
+import org.wordpress.android.fluxc.model.MediaModel
+import org.wordpress.android.fluxc.model.SiteModel
+import org.wordpress.android.fluxc.store.MediaStore
+import kotlin.test.Test
+
+@Suppress("UNCHECKED_CAST")
+@ExperimentalCoroutinesApi
+class PostListFeaturedImageTrackerTest : BaseUnitTest() {
+    private val dispatcher: Dispatcher = mock()
+    private val mediaStore: MediaStore = mock()
+
+    private lateinit var tracker: PostListFeaturedImageTracker
+
+    private val site = SiteModel().apply { id = 123 }
+
+    @Before
+    fun setup() {
+        tracker = PostListFeaturedImageTracker(dispatcher, mediaStore)
+    }
+
+    @Test
+    fun `given id exists in map, when getFeaturedImageUrl invoked, then return url`() {
+        val imageId = 123L
+        val imageUrl = "https://example.com/image.jpg"
+        tracker.featuredImageMap[imageId] = imageUrl
+
+        val result = tracker.getFeaturedImageUrl(site, imageId)
+
+        assertEquals(imageUrl, result)
+    }
+
+    @Test
+    fun `given id is 0, when getFeaturedImageUrl invoked, then return null`() {
+        val result = tracker.getFeaturedImageUrl(site, 0L)
+
+        assertNull(result)
+    }
+
+    @Test
+    fun `given id not in map and exists in store, when invoked, then return url from media store`() {
+        val imageId = 456L
+        val imageUrl = "https://example.com/image.jpg"
+        val mediaModel = MediaModel(site.id, imageId).apply {
+            url = imageUrl
+        }
+
+        whenever(mediaStore.getSiteMediaWithId(site, imageId)).thenReturn(mediaModel)
+
+        val result = tracker.getFeaturedImageUrl(site, imageId)
+
+        assertEquals(imageUrl, result)
+        assertEquals(imageUrl, tracker.featuredImageMap[imageId])
+    }
+
+    @Test
+    fun `given id not in map or store, when invoked, then return null and dispatch fetch request`() {
+        val imageId = 123L
+
+        whenever(mediaStore.getSiteMediaWithId(site, imageId)).thenReturn(null)
+
+        val result = tracker.getFeaturedImageUrl(site, imageId)
+
+        assertNull(result)
+        verify(dispatcher).dispatch(any())
+        assert(tracker.ongoingRequests.contains(imageId))
+    }
+
+    @Test
+    fun `given request ongoing for id, when invoked, should return null`() {
+        val imageId = 123L
+
+        tracker.ongoingRequests.add(imageId)
+
+        val result = tracker.getFeaturedImageUrl(site, imageId)
+
+        assertNull(result)
+        verify(mediaStore, never()).getSiteMediaWithId(site, imageId)
+        verify(dispatcher, never()).dispatch(any())
+    }
+
+    @Test
+    fun `given id in map and ongoingRequests, when invalidate, then remove id from map and ongoingRequests`() {
+        val imageId1 = 123L
+        val imageId2 = 456L
+
+        tracker.featuredImageMap[imageId1] = "https://example.com/image1.jpg"
+        tracker.featuredImageMap[imageId2] = "https://example.com/image2.jpg"
+        tracker.ongoingRequests.add(imageId1)
+        tracker.ongoingRequests.add(imageId2)
+
+        tracker.invalidateFeaturedMedia(listOf(imageId1, imageId2))
+
+        assertNull(tracker.featuredImageMap[imageId1])
+        assertNull(tracker.featuredImageMap[imageId2])
+        assert(!tracker.ongoingRequests.contains(imageId1))
+        assert(!tracker.ongoingRequests.contains(imageId2))
+    }
+}