Hide the home navigation bar if the user is not a member of any Space.

https://github.com/element-hq/element-meta/issues/2906: `The tab bar with the option to view joined spaces is only shown when the user has at least one space that they have joined (because otherwise they have no clue what to do in here).`

features/home/impl/src/main/kotlin/io/element/android/features/home/impl/HomePresenter.kt

@@ -74,6 +74,12 @@ class HomePresenter(
             }
         }
 
+        LaunchedEffect(homeSpacesState.spaceRooms.isEmpty()) {
+            // If the last space is left, ensure that the Chat view is rendered.
+            if (homeSpacesState.spaceRooms.isEmpty()) {
+                currentHomeNavigationBarItemOrdinal = HomeNavigationBarItem.Chats.ordinal
+            }
+        }
         val snackbarMessage by snackbarDispatcher.collectSnackbarMessageAsState()
         return HomeState(
             matrixUser = matrixUser.value,

features/home/impl/src/main/kotlin/io/element/android/features/home/impl/HomeState.kt

@@ -29,4 +29,5 @@ data class HomeState(
     val eventSink: (HomeEvents) -> Unit,
 ) {
     val displayActions = currentHomeNavigationBarItem == HomeNavigationBarItem.Chats
+    val showNavigationBar = isSpaceFeatureEnabled && homeSpacesState.spaceRooms.isNotEmpty()
 }

features/home/impl/src/main/kotlin/io/element/android/features/home/impl/HomeStateProvider.kt

@@ -36,6 +36,8 @@ open class HomeStateProvider : PreviewParameterProvider<HomeState> {
                         summaries = generateRoomListRoomSummaryList(),
                     )
                 ),
+                // For the bottom nav bar to be visible in the preview, the user must be member of at least one space
+                homeSpacesState = aHomeSpacesState(),
             ),
             aHomeState(
                 isSpaceFeatureEnabled = true,

features/home/impl/src/main/kotlin/io/element/android/features/home/impl/HomeView.kt

@@ -194,7 +194,7 @@ private fun HomeScaffold(
             )
         },
         bottomBar = {
-            if (state.isSpaceFeatureEnabled) {
+            if (state.showNavigationBar) {
                 NavigationBar(
                     containerColor = Color.Transparent,
                     modifier = Modifier

features/home/impl/src/test/kotlin/io/element/android/features/home/impl/HomePresenterTest.kt

@@ -12,9 +12,11 @@ import app.cash.molecule.moleculeFlow
 import app.cash.turbine.test
 import com.google.common.truth.Truth.assertThat
 import io.element.android.features.home.impl.roomlist.aRoomListState
+import io.element.android.features.home.impl.spaces.HomeSpacesState
 import io.element.android.features.home.impl.spaces.aHomeSpacesState
 import io.element.android.features.logout.api.direct.aDirectLogoutState
 import io.element.android.features.rageshake.api.RageshakeFeatureAvailability
+import io.element.android.libraries.architecture.Presenter
 import io.element.android.libraries.designsystem.utils.snackbar.SnackbarDispatcher
 import io.element.android.libraries.featureflag.api.FeatureFlagService
 import io.element.android.libraries.featureflag.api.FeatureFlags
@@ -30,10 +32,10 @@ import io.element.android.libraries.matrix.test.A_USER_ID
 import io.element.android.libraries.matrix.test.A_USER_NAME
 import io.element.android.libraries.matrix.test.FakeMatrixClient
 import io.element.android.libraries.matrix.test.sync.FakeSyncService
+import io.element.android.tests.testutils.MutablePresenter
 import io.element.android.tests.testutils.WarmUpRule
 import io.element.android.tests.testutils.test
 import kotlinx.coroutines.flow.flowOf
-import kotlinx.coroutines.test.TestScope
 import kotlinx.coroutines.test.runTest
 import org.junit.Rule
 import org.junit.Test
@@ -65,6 +67,7 @@ class HomePresenterTest {
             assertThat(withUserState.matrixUser.avatarUrl).isEqualTo(AN_AVATAR_URL)
             assertThat(withUserState.showAvatarIndicator).isFalse()
             assertThat(withUserState.isSpaceFeatureEnabled).isFalse()
+            assertThat(withUserState.showNavigationBar).isFalse()
         }
     }
 
@@ -145,13 +148,42 @@ class HomePresenterTest {
         }
     }
 
-    private fun TestScope.createHomePresenter(
+    @Test
+    fun `present - NavigationBar is hidden when the last space is left`() = runTest {
+        val homeSpacesPresenter = MutablePresenter(aHomeSpacesState())
+        val presenter = createHomePresenter(
+            featureFlagService = FakeFeatureFlagService(
+                initialState = mapOf(FeatureFlags.Space.key to true),
+            ),
+            homeSpacesPresenter = homeSpacesPresenter,
+        )
+        presenter.test {
+            skipItems(1)
+            val initialState = awaitItem()
+            assertThat(initialState.currentHomeNavigationBarItem).isEqualTo(HomeNavigationBarItem.Chats)
+            assertThat(initialState.showNavigationBar).isTrue()
+            // User navigate to Spaces
+            initialState.eventSink(HomeEvents.SelectHomeNavigationBarItem(HomeNavigationBarItem.Spaces))
+            val spaceState = awaitItem()
+            assertThat(spaceState.currentHomeNavigationBarItem).isEqualTo(HomeNavigationBarItem.Spaces)
+            // The last space is left
+            homeSpacesPresenter.updateState(aHomeSpacesState(spaceRooms = emptyList()))
+            skipItems(1)
+            val finalState = awaitItem()
+            // We are back to Chats
+            assertThat(finalState.currentHomeNavigationBarItem).isEqualTo(HomeNavigationBarItem.Chats)
+            assertThat(finalState.showNavigationBar).isFalse()
+        }
+    }
+
+    private fun createHomePresenter(
         client: MatrixClient = FakeMatrixClient(),
         syncService: SyncService = FakeSyncService(),
         snackbarDispatcher: SnackbarDispatcher = SnackbarDispatcher(),
         rageshakeFeatureAvailability: RageshakeFeatureAvailability = RageshakeFeatureAvailability { flowOf(false) },
         indicatorService: IndicatorService = FakeIndicatorService(),
-        featureFlagService: FeatureFlagService = FakeFeatureFlagService()
+        featureFlagService: FeatureFlagService = FakeFeatureFlagService(),
+        homeSpacesPresenter: Presenter<HomeSpacesState> = Presenter { aHomeSpacesState() },
     ) = HomePresenter(
         client = client,
         syncService = syncService,
@@ -159,7 +191,7 @@ class HomePresenterTest {
         indicatorService = indicatorService,
         logoutPresenter = { aDirectLogoutState() },
         roomListPresenter = { aRoomListState() },
-        homeSpacesPresenter = { aHomeSpacesState() },
+        homeSpacesPresenter = homeSpacesPresenter,
         rageshakeFeatureAvailability = rageshakeFeatureAvailability,
         featureFlagService = featureFlagService,
     )