Fix issue where selected topic in list was not showing as selected. Minor tidy ups.

Change-Id: Icfa79eac6f7327c365f79fd7d15dfa1f8c77184d

app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/interests2pane/Interests2PaneViewModel.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid.ui.interests2pane
+
+import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModel
+import androidx.navigation.toRoute
+import com.google.samples.apps.nowinandroid.feature.interests.navigation.InterestsDestination
+import com.google.samples.apps.nowinandroid.feature.interests.navigation.TOPIC_ID_KEY
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.StateFlow
+import javax.inject.Inject
+
+const val TOPIC_ID_KEY = "selectedTopicId"
+
+@HiltViewModel
+class Interests2PaneViewModel @Inject constructor(
+    private val savedStateHandle: SavedStateHandle,
+) : ViewModel() {
+
+    val destination = savedStateHandle.toRoute<InterestsDestination>()
+    val selectedTopicId: StateFlow<String?> = savedStateHandle.getStateFlow(
+        key = TOPIC_ID_KEY,
+        initialValue = destination.initialTopicId,
+    )
+
+    fun onTopicClick(topicId: String?) {
+        savedStateHandle[TOPIC_ID_KEY] = topicId
+    }
+}

app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/interests2pane/InterestsListDetailScreen.kt

@@ -26,14 +26,13 @@ import androidx.compose.material3.adaptive.navigation.rememberListDetailPaneScaf
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
+import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.navigation.NavGraphBuilder
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.rememberNavController
-import androidx.navigation.toRoute
 import com.google.samples.apps.nowinandroid.feature.interests.InterestsRoute
 import com.google.samples.apps.nowinandroid.feature.interests.navigation.InterestsDestination
 import com.google.samples.apps.nowinandroid.feature.topic.TopicDetailPlaceholder
@@ -46,13 +45,22 @@ import kotlinx.serialization.Serializable
 @Serializable object DetailPaneNavHostDestination
 
 fun NavGraphBuilder.interestsListDetailScreen() {
-    composable<InterestsDestination> { backStackEntry ->
-        val topicIdArgument = backStackEntry.toRoute<InterestsDestination>().topicId
-        var topicId: String? by rememberSaveable { mutableStateOf(topicIdArgument) }
-        InterestsListDetailScreen(selectedTopicId = topicId, onTopicClick = { topicId = it })
+    composable<InterestsDestination> {
+        InterestsListDetailScreen()
     }
 }
 
+@Composable
+internal fun InterestsListDetailScreen(
+    viewModel: Interests2PaneViewModel = hiltViewModel(),
+) {
+    val selectedTopicId by viewModel.selectedTopicId.collectAsStateWithLifecycle()
+    InterestsListDetailScreen(
+        selectedTopicId = selectedTopicId,
+        onTopicClick = viewModel::onTopicClick,
+    )
+}
+
 @OptIn(ExperimentalMaterial3AdaptiveApi::class)
 @Composable
 internal fun InterestsListDetailScreen(
@@ -86,7 +94,7 @@ internal fun InterestsListDetailScreen(
         detailPane = {
             NavHost(
                 navController = nestedNavController,
-                startDestination = TopicPlaceholderDestination::class,
+                startDestination = TopicPlaceholderDestination,
                 route = DetailPaneNavHostDestination::class,
             ) {
                 topicScreen(

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

@@ -35,7 +35,7 @@ fun NavController.navigateToForYou(navOptions: NavOptions) = navigate(route = Fo
 fun NavGraphBuilder.forYouScreen(onTopicClick: (String) -> Unit) {
     composable<ForYouDestination>(
         deepLinks = listOf(
-            navDeepLink { uriPattern = DEEP_LINK_URI_PATTERN },
+            navDeepLink<ForYouDestination>(basePath = DEEP_LINK_URI_PATTERN),
         ),
     ) {
         ForYouRoute(onTopicClick)

feature/interests/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/interests/InterestsScreen.kt

@@ -46,7 +46,10 @@ fun InterestsRoute(
     InterestsScreen(
         uiState = uiState,
         followTopic = viewModel::followTopic,
-        onTopicClick = onTopicClick,
+        onTopicClick = {
+            viewModel.onTopicClick(it)
+            onTopicClick(it)
+        },
         highlightSelectedTopic = highlightSelectedTopic,
         modifier = modifier,
     )

feature/interests/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/interests/InterestsViewModel.kt

@@ -25,27 +25,33 @@ import com.google.samples.apps.nowinandroid.core.domain.GetFollowableTopicsUseCa
 import com.google.samples.apps.nowinandroid.core.domain.TopicSortField
 import com.google.samples.apps.nowinandroid.core.model.data.FollowableTopic
 import com.google.samples.apps.nowinandroid.feature.interests.navigation.InterestsDestination
+import com.google.samples.apps.nowinandroid.feature.interests.navigation.TOPIC_ID_KEY
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
-import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import javax.inject.Inject
 
 @HiltViewModel
 class InterestsViewModel @Inject constructor(
-    savedStateHandle: SavedStateHandle,
+    private val savedStateHandle: SavedStateHandle,
     val userDataRepository: UserDataRepository,
     getFollowableTopics: GetFollowableTopicsUseCase,
 ) : ViewModel() {
 
     private val interestsDestination: InterestsDestination = savedStateHandle.toRoute()
+    private val selectedTopicId = savedStateHandle.getStateFlow(
+        key = TOPIC_ID_KEY,
+        initialValue = interestsDestination.initialTopicId,
+    )
 
-    val uiState: StateFlow<InterestsUiState> =
-        getFollowableTopics(sortBy = TopicSortField.NAME).map { topics ->
-            InterestsUiState.Interests(interestsDestination.topicId, topics)
-        }.stateIn(
+    val uiState: StateFlow<InterestsUiState> = combine(
+        selectedTopicId,
+        getFollowableTopics(sortBy = TopicSortField.NAME),
+        InterestsUiState::Interests,
+    ).stateIn(
         scope = viewModelScope,
         started = SharingStarted.WhileSubscribed(5_000),
         initialValue = InterestsUiState.Loading,
@@ -56,6 +62,10 @@ class InterestsViewModel @Inject constructor(
             userDataRepository.setTopicIdFollowed(followedTopicId, followed)
         }
     }
+
+    fun onTopicClick(topicId: String?) {
+        savedStateHandle[TOPIC_ID_KEY] = topicId
+    }
 }
 
 sealed interface InterestsUiState {

feature/interests/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/interests/navigation/InterestsNavigation.kt

@@ -20,10 +20,16 @@ import androidx.navigation.NavController
 import androidx.navigation.NavOptions
 import kotlinx.serialization.Serializable
 
-const val TOPIC_ID_ARG = "topicId"
+const val TOPIC_ID_KEY = "topicId"
 
-@Serializable data class InterestsDestination(val topicId: String?)
+@Serializable data class InterestsDestination(
+    // The ID of the topic which will be initially selected at this destination
+    val initialTopicId: String?,
+)
 
-fun NavController.navigateToInterests(topicId: String? = null, navOptions: NavOptions? = null) {
-    navigate(route = InterestsDestination(topicId), navOptions)
+fun NavController.navigateToInterests(
+    initialTopicId: String? = null,
+    navOptions: NavOptions? = null,
+) {
+    navigate(route = InterestsDestination(initialTopicId), navOptions)
 }

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

@@ -48,12 +48,10 @@ class TopicViewModel @Inject constructor(
     userNewsResourceRepository: UserNewsResourceRepository,
 ) : ViewModel() {
 
-    private val topicDestination: TopicDestination = savedStateHandle.toRoute()
-
-    val topicId = topicDestination.id
+    val topicId = savedStateHandle.toRoute<TopicDestination>().id
 
     val topicUiState: StateFlow<TopicUiState> = topicUiState(
-        topicId = topicDestination.id,
+        topicId = topicId,
         userDataRepository = userDataRepository,
         topicsRepository = topicsRepository,
     )
@@ -64,7 +62,7 @@ class TopicViewModel @Inject constructor(
         )
 
     val newsUiState: StateFlow<NewsUiState> = newsUiState(
-        topicId = topicDestination.id,
+        topicId = topicId,
         userDataRepository = userDataRepository,
         userNewsResourceRepository = userNewsResourceRepository,
     )
@@ -76,7 +74,7 @@ class TopicViewModel @Inject constructor(
 
     fun followTopicToggle(followed: Boolean) {
         viewModelScope.launch {
-            userDataRepository.setTopicIdFollowed(topicDestination.id, followed)
+            userDataRepository.setTopicIdFollowed(topicId, followed)
         }
     }