MediaViewer: add error case in the UI.

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerDataSource.kt

@@ -28,6 +28,7 @@ import io.element.android.libraries.mediaviewer.impl.gallery.mediaInfo
 import io.element.android.libraries.mediaviewer.impl.gallery.mediaSource
 import io.element.android.libraries.mediaviewer.impl.gallery.thumbnailSource
 import kotlinx.collections.immutable.PersistentList
+import kotlinx.collections.immutable.persistentListOf
 import kotlinx.collections.immutable.toPersistentList
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
@@ -68,9 +69,15 @@ class MediaViewerDataSource(
     fun dataFlow(): Flow<PersistentList<MediaViewerPageData>> {
         return galleryDataSource.groupedMediaItemsFlow()
             .map { groupedItems ->
-                val mediaItems = groupedItems.dataOrNull()?.getItems(galleryMode).orEmpty()
+                if (groupedItems is AsyncData.Failure) {
-                withContext(dispatcher) {
+                    persistentListOf(
-                    buildMediaViewerPageList(mediaItems)
+                        MediaViewerPageData.Failure(groupedItems.error),
+                    )
+                } else {
+                    val mediaItems = groupedItems.dataOrNull()?.getItems(galleryMode).orEmpty()
+                    withContext(dispatcher) {
+                        buildMediaViewerPageList(mediaItems)
+                    }
                 }
             }
     }

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerState.kt

@@ -28,6 +28,10 @@ data class MediaViewerState(
 )
 
 sealed interface MediaViewerPageData {
+    data class Failure(
+        val throwable: Throwable,
+    ) : MediaViewerPageData
+
     data class Loading(
         val direction: Timeline.PaginationDirection,
     ) : MediaViewerPageData

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerStateProvider.kt

@@ -154,6 +154,11 @@ open class MediaViewerStateProvider : PreviewParameterProvider<MediaViewerState>
                     MediaViewerPageData.Loading(Timeline.PaginationDirection.BACKWARDS)
                 ),
             ),
+            aMediaViewerState(
+                listOf(
+                    MediaViewerPageData.Failure(Exception("error"))
+                ),
+            ),
         )
 }
 

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerView.kt

@@ -55,6 +55,7 @@ import io.element.android.compound.tokens.generated.CompoundIcons
 import io.element.android.libraries.architecture.AsyncData
 import io.element.android.libraries.core.mimetype.MimeTypes
 import io.element.android.libraries.core.mimetype.MimeTypes.isMimeTypeVideo
+import io.element.android.libraries.designsystem.components.async.AsyncFailure
 import io.element.android.libraries.designsystem.components.async.AsyncLoading
 import io.element.android.libraries.designsystem.components.button.BackButton
 import io.element.android.libraries.designsystem.components.dialogs.RetryDialog
@@ -123,6 +124,14 @@ fun MediaViewerView(
             beyondViewportPageCount = 1,
         ) { page ->
             when (val dataForPage = state.listData[page]) {
+                is MediaViewerPageData.Failure -> {
+                    MediaViewerErrorPage(
+                        throwable = dataForPage.throwable,
+                        onDismiss = {
+                            onBackClick()
+                        },
+                    )
+                }
                 is MediaViewerPageData.Loading -> {
                     LaunchedEffect(Unit) {
                         state.eventSink(MediaViewerEvents.LoadMore(dataForPage.direction))
@@ -200,11 +209,13 @@ fun MediaViewerView(
                     else -> {
                         TopAppBar(
                             title = {
-                                Text(
+                                if (currentData is MediaViewerPageData.Loading) {
-                                    text = stringResource(id = CommonStrings.common_loading_more),
+                                    Text(
-                                    style = ElementTheme.typography.fontBodyMdMedium,
+                                        text = stringResource(id = CommonStrings.common_loading_more),
-                                    color = ElementTheme.colors.textPrimary,
+                                        style = ElementTheme.typography.fontBodyMdMedium,
-                                )
+                                        color = ElementTheme.colors.textPrimary,
+                                    )
+                                }
                             },
                             colors = TopAppBarDefaults.topAppBarColors(
                                 containerColor = Color.Transparent.copy(0.6f),
@@ -386,6 +397,41 @@ private fun MediaViewerLoadingPage(
     }
 }
 
+@Composable
+private fun MediaViewerErrorPage(
+    throwable: Throwable,
+    onDismiss: () -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val flickState = rememberFlickToDismissState(dismissThresholdRatio = 0.1f, rotateOnDrag = false)
+
+    DismissFlickEffects(
+        flickState = flickState,
+        onDismissing = { animationDuration ->
+            delay(animationDuration / 3)
+            onDismiss()
+        },
+        onDragging = {},
+    )
+
+    FlickToDismiss(
+        state = flickState,
+        modifier = modifier.background(backgroundColorFor(flickState))
+    ) {
+        Box(
+            modifier = Modifier
+                .fillMaxSize()
+                .navigationBarsPadding(),
+            contentAlignment = Alignment.Center
+        ) {
+            AsyncFailure(
+                throwable = throwable,
+                onRetry = null
+            )
+        }
+    }
+}
+
 @Composable
 private fun DismissFlickEffects(
     flickState: FlickToDismissState,

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerDataSourceTest.kt

@@ -69,8 +69,7 @@ class MediaViewerDataSourceTest {
             galleryDataSource.emitGroupedMediaItems(AsyncData.Loading())
             assertThat(awaitItem().first()).isInstanceOf(MediaViewerPageData.Loading::class.java)
             galleryDataSource.emitGroupedMediaItems(AsyncData.Failure(AN_EXCEPTION))
-            // TODO Add an error screen in the ui
+            assertThat(awaitItem().first()).isEqualTo(MediaViewerPageData.Failure(AN_EXCEPTION))
-            assertThat(awaitItem().first()).isInstanceOf(MediaViewerPageData.Loading::class.java)
         }
     }