Add TopicScreen as a sub destination in the ForYou section. Fixes #1463

app/src/main/kotlin/com/google/samples/apps/nowinandroid/navigation/NiaNavHost.kt

@@ -20,10 +20,12 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.navigation.compose.NavHost
 import com.google.samples.apps.nowinandroid.feature.bookmarks.navigation.bookmarksScreen
-import com.google.samples.apps.nowinandroid.feature.foryou.navigation.ForYouRoute
-import com.google.samples.apps.nowinandroid.feature.foryou.navigation.forYouScreen
+import com.google.samples.apps.nowinandroid.feature.foryou.navigation.ForYouBaseRoute
+import com.google.samples.apps.nowinandroid.feature.foryou.navigation.forYouSection
 import com.google.samples.apps.nowinandroid.feature.interests.navigation.navigateToInterests
 import com.google.samples.apps.nowinandroid.feature.search.navigation.searchScreen
+import com.google.samples.apps.nowinandroid.feature.topic.navigation.navigateToTopic
+import com.google.samples.apps.nowinandroid.feature.topic.navigation.topicScreen
 import com.google.samples.apps.nowinandroid.navigation.TopLevelDestination.INTERESTS
 import com.google.samples.apps.nowinandroid.ui.NiaAppState
 import com.google.samples.apps.nowinandroid.ui.interests2pane.interestsListDetailScreen
@@ -44,10 +46,18 @@ fun NiaNavHost(
     val navController = appState.navController
     NavHost(
         navController = navController,
-        startDestination = ForYouRoute,
+        startDestination = ForYouBaseRoute,
         modifier = modifier,
     ) {
-        forYouScreen(onTopicClick = navController::navigateToInterests)
+        forYouSection(
+            onTopicClick = navController::navigateToTopic
+        ) {
+            topicScreen(
+                showBackButton = true,
+                onBackClick = navController::popBackStack,
+                onTopicClick = navController::navigateToTopic
+            )
+        }
         bookmarksScreen(
             onTopicClick = navController::navigateToInterests,
             onShowSnackbar = onShowSnackbar,

app/src/main/kotlin/com/google/samples/apps/nowinandroid/navigation/TopLevelDestination.kt

@@ -21,7 +21,7 @@ import androidx.compose.ui.graphics.vector.ImageVector
 import com.google.samples.apps.nowinandroid.R
 import com.google.samples.apps.nowinandroid.core.designsystem.icon.NiaIcons
 import com.google.samples.apps.nowinandroid.feature.bookmarks.navigation.BookmarksRoute
-import com.google.samples.apps.nowinandroid.feature.foryou.navigation.ForYouRoute
+import com.google.samples.apps.nowinandroid.feature.foryou.navigation.ForYouBaseRoute
 import com.google.samples.apps.nowinandroid.feature.interests.navigation.InterestsRoute
 import kotlin.reflect.KClass
 import com.google.samples.apps.nowinandroid.feature.bookmarks.R as bookmarksR
@@ -45,7 +45,7 @@ enum class TopLevelDestination(
         unselectedIcon = NiaIcons.UpcomingBorder,
         iconTextId = forYouR.string.feature_foryou_title,
         titleTextId = R.string.app_name,
-        route = ForYouRoute::class,
+        route = ForYouBaseRoute::class,
     ),
     BOOKMARKS(
         selectedIcon = NiaIcons.Bookmarks,

feature/foryou/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/foryou/navigation/ForYouNavigation.kt

@@ -20,30 +20,45 @@ import androidx.navigation.NavController
 import androidx.navigation.NavGraphBuilder
 import androidx.navigation.NavOptions
 import androidx.navigation.compose.composable
+import androidx.navigation.compose.navigation
 import androidx.navigation.navDeepLink
 import com.google.samples.apps.nowinandroid.core.notifications.DEEP_LINK_URI_PATTERN
 import com.google.samples.apps.nowinandroid.feature.foryou.ForYouScreen
 import kotlinx.serialization.Serializable
 
-@Serializable data object ForYouRoute
+@Serializable data object ForYouRoute // route to ForYou screen
+@Serializable data object ForYouBaseRoute // route to base navigation graph
 
 fun NavController.navigateToForYou(navOptions: NavOptions) = navigate(route = ForYouRoute, navOptions)
 
-fun NavGraphBuilder.forYouScreen(onTopicClick: (String) -> Unit) {
-    composable<ForYouRoute>(
-        deepLinks = listOf(
-            navDeepLink {
-                /**
-                 * This destination has a deep link that enables a specific news resource to be
-                 * opened from a notification (@see SystemTrayNotifier for more). The news resource
-                 * ID is sent in the URI rather than being modelled in the route type because it's
-                 * transient data (stored in SavedStateHandle) that is cleared after the user has
-                 * opened the news resource.
-                 */
-                uriPattern = DEEP_LINK_URI_PATTERN
-            },
-        ),
-    ) {
-        ForYouScreen(onTopicClick)
+/**
+ *  The ForYou section of the app. It can also display information about topics.
+ *  This should be supplied from a separate module.
+ *
+ *  @param onTopicClick - Called when a topic is clicked, contains the ID of the topic
+ *  @param topicDestination - Destination for topic content
+ */
+fun NavGraphBuilder.forYouSection(
+    onTopicClick: (String) -> Unit,
+    topicDestination: NavGraphBuilder.() -> Unit
+) {
+    navigation<ForYouBaseRoute>(startDestination = ForYouRoute) {
+        composable<ForYouRoute>(
+            deepLinks = listOf(
+                navDeepLink {
+                    /**
+                     * This destination has a deep link that enables a specific news resource to be
+                     * opened from a notification (@see SystemTrayNotifier for more). The news resource
+                     * ID is sent in the URI rather than being modelled in the route type because it's
+                     * transient data (stored in SavedStateHandle) that is cleared after the user has
+                     * opened the news resource.
+                     */
+                    uriPattern = DEEP_LINK_URI_PATTERN
+                },
+            ),
+        ) {
+            ForYouScreen(onTopicClick)
+        }
+        topicDestination()
     }
 }

feature/topic/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/topic/TopicScreen.kt

@@ -71,7 +71,7 @@ import com.google.samples.apps.nowinandroid.core.ui.userNewsResourceCardItems
 import com.google.samples.apps.nowinandroid.feature.topic.R.string
 
 @Composable
-internal fun TopicScreen(
+fun TopicScreen(
     showBackButton: Boolean,
     onBackClick: () -> Unit,
     onTopicClick: (String) -> Unit,