Move new UseCase and tests into separate files

Change-Id: I4c337473ca0a60a5fccbb8aa640735cf7d616e71

core/domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/GetUserNewsResourcesUseCase.kt

@@ -24,11 +24,7 @@ import com.google.samples.apps.nowinandroid.core.model.data.NewsResource
 import com.google.samples.apps.nowinandroid.core.model.data.UserData
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.filterNot
-import kotlinx.coroutines.flow.flatMapLatest
-import kotlinx.coroutines.flow.flowOf
-import kotlinx.coroutines.flow.map
 import javax.inject.Inject
 
 /**
@@ -55,56 +51,6 @@ class GetUserNewsResourcesUseCase @Inject constructor(
         }.mapToUserNewsResources(userDataRepository.userData)
 }
 
-class GetFollowedUserNewsResourcesUseCase @Inject constructor(
-    private val userDataRepository: UserDataRepository,
-    val getUserNewsResources: GetUserNewsResourcesUseCase,
-) {
-    /**
-     * Returns a list of UserNewsResources for topics which the user is following
-     */
-    operator fun invoke(): Flow<List<UserNewsResource>> =
-        /**
-         * This sequence of flow transformation functions does the following:
-         *
-         * - map: maps the user data into a set of followed topic IDs or null if we should return
-         * an empty list
-         * - distinctUntilChanged: will only emit a set of followed topic IDs if it's changed. This
-         * avoids calling potentially expensive operations (like setting up a new flow) when nothing
-         * has changed.
-         * - flatMapLatest: getUserNewsResources returns a flow, so we have a flow inside a
-         * flow. flatMapLatest moves the inner flow (the one we want to return) to the outer flow
-         * and cancels any previous flows created by getUserNewsResources.
-         */
-        userDataRepository.userData
-            .map { userData ->
-                if (shouldShowEmptyFeed(userData)) {
-                    null
-                } else {
-                    userData.followedTopics
-                }
-            }
-            .distinctUntilChanged()
-            .flatMapLatest { followedTopics ->
-                if (followedTopics == null) {
-                    flowOf(emptyList())
-                } else {
-                    getUserNewsResources(filterTopicIds = followedTopics)
-                }
-            }
-
-    /**
-     * If the user hasn't completed the onboarding and hasn't selected any interests
-     * show an empty news list to clearly demonstrate that their selections affect the
-     * news articles they will see.
-     *
-     * Note: It should not be possible for the user to get into a state where the onboarding
-     * is not displayed AND they haven't followed any topics, however, this method is to safeguard
-     * against that scenario in future.
-     */
-    private fun shouldShowEmptyFeed(userData: UserData) =
-        !userData.shouldHideOnboarding && userData.followedTopics.isEmpty()
-}
-
 private fun Flow<List<NewsResource>>.mapToUserNewsResources(
     userDataStream: Flow<UserData>,
 ): Flow<List<UserNewsResource>> =

core/domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/GetUserNewsResourcesUseCaseTest.kt

@@ -83,55 +83,6 @@ class GetUserNewsResourcesUseCaseTest {
     }
 }
 
-class GetFollowedUserNewsResourcesUseCaseTest {
-
-    @get:Rule
-    val mainDispatcherRule = MainDispatcherRule()
-
-    private val newsRepository = TestNewsRepository()
-    private val userDataRepository = TestUserDataRepository()
-    private val getUserNewsResourcesUseCase =
-        GetUserNewsResourcesUseCase(newsRepository, userDataRepository)
-
-    val useCase =
-        GetFollowedUserNewsResourcesUseCase(userDataRepository, getUserNewsResourcesUseCase)
-
-    @Test
-    fun whenOnboardingShownAndNoTopicsFollowed_emptyListIsReturned() = runTest {
-        val followedNewsResources = useCase()
-
-        // Send some news resources and empty user data
-        newsRepository.sendNewsResources(sampleNewsResources)
-        userDataRepository.setUserData(emptyUserData)
-
-        // Check that an empty list is returned
-        assertEquals(
-            emptyList(),
-            followedNewsResources.first(),
-        )
-    }
-
-    @Test
-    fun whenTopicsAreFollowed_correctNewsResourcesAreReturned() = runTest {
-        val followedNewsResources = useCase()
-
-        // Send some news resources and user data with a followed topic
-        newsRepository.sendNewsResources(sampleNewsResources)
-
-        val userData = emptyUserData.copy(
-            followedTopics = setOf(sampleTopic1.id),
-        )
-        userDataRepository.setUserData(userData)
-
-        assertEquals(
-            sampleNewsResources
-                .filter { it.topics.contains(sampleTopic1) }
-                .mapToUserNewsResources(userData),
-            followedNewsResources.first(),
-        )
-    }
-}
-
 private val sampleTopic1 = Topic(
     id = "Topic1",
     name = "Headlines",

feature/foryou/src/main/java/com/google/samples/apps/nowinandroid/feature/foryou/ForYouViewModel.kt

@@ -21,13 +21,18 @@ import androidx.lifecycle.viewModelScope
 import com.google.samples.apps.nowinandroid.core.data.repository.UserDataRepository
 import com.google.samples.apps.nowinandroid.core.data.util.SyncStatusMonitor
 import com.google.samples.apps.nowinandroid.core.domain.GetFollowableTopicsUseCase
-import com.google.samples.apps.nowinandroid.core.domain.GetFollowedUserNewsResourcesUseCase
+import com.google.samples.apps.nowinandroid.core.domain.GetUserNewsResourcesUseCase
+import com.google.samples.apps.nowinandroid.core.domain.model.UserNewsResource
+import com.google.samples.apps.nowinandroid.core.model.data.UserData
 import com.google.samples.apps.nowinandroid.core.ui.NewsFeedUiState
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
@@ -37,7 +42,7 @@ import javax.inject.Inject
 class ForYouViewModel @Inject constructor(
     syncStatusMonitor: SyncStatusMonitor,
     private val userDataRepository: UserDataRepository,
-    getFollowedUserNewsResources: GetFollowedUserNewsResourcesUseCase,
+    private val getUserNewsResources: GetUserNewsResourcesUseCase,
     getFollowableTopics: GetFollowableTopicsUseCase,
 ) : ViewModel() {
 
@@ -51,10 +56,8 @@ class ForYouViewModel @Inject constructor(
             initialValue = false,
         )
 
-    val feedState: StateFlow<NewsFeedUiState> =
+    val feedState: StateFlow<NewsFeedUiState> = getFollowedUserNewsResources()
-        getFollowedUserNewsResources().map {
+        .map(NewsFeedUiState::Success)
-            NewsFeedUiState.Success(it)
-        }
         .stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(5_000),
@@ -95,4 +98,66 @@ class ForYouViewModel @Inject constructor(
             userDataRepository.setShouldHideOnboarding(true)
         }
     }
+
+    /**
+     * This sequence of flow transformation functions does the following:
+     *
+     * - map: maps the user data into a set of followed topic IDs or null if we should return
+     * an empty list
+     * - distinctUntilChanged: will only emit a set of followed topic IDs if it's changed. This
+     * avoids calling potentially expensive operations (like setting up a new flow) when nothing
+     * has changed.
+     * - flatMapLatest: getUserNewsResources returns a flow, so we have a flow inside a
+     * flow. flatMapLatest moves the inner flow (the one we want to return) to the outer flow
+     * and cancels any previous flows created by getUserNewsResources.
+     */
+    private fun getFollowedUserNewsResources(): Flow<List<UserNewsResource>> =
+        userDataRepository.userData
+            .map { userData ->
+                if (userData.shouldShowEmptyFeed()) {
+                    null
+                } else {
+                    userData.followedTopics
+                }
+            }
+            .distinctUntilChanged()
+            .flatMapLatest { followedTopics ->
+                if (followedTopics == null) {
+                    flowOf(emptyList())
+                } else {
+                    getUserNewsResources(filterTopicIds = followedTopics)
+                }
+            }
 }
+
+// Alternative approach (not currently being called)
+private fun Flow<UserData>.getFollowedUserNewsResources(
+    getUserNewsResources: GetUserNewsResourcesUseCase,
+): Flow<List<UserNewsResource>> =
+    map { userData ->
+        if (userData.shouldShowEmptyFeed()) {
+            null
+        } else {
+            userData.followedTopics
+        }
+    }
+    .distinctUntilChanged()
+    .flatMapLatest { followedTopics ->
+        if (followedTopics == null) {
+            flowOf(emptyList())
+        } else {
+            getUserNewsResources(filterTopicIds = followedTopics)
+        }
+    }
+
+/**
+ * If the user hasn't completed the onboarding and hasn't selected any interests
+ * show an empty news list to clearly demonstrate that their selections affect the
+ * news articles they will see.
+ *
+ * Note: It should not be possible for the user to get into a state where the onboarding
+ * is not displayed AND they haven't followed any topics, however, this method is to safeguard
+ * against that scenario in future.
+ */
+private fun UserData.shouldShowEmptyFeed() =
+    !shouldHideOnboarding && followedTopics.isEmpty()

feature/foryou/src/test/java/com/google/samples/apps/nowinandroid/feature/foryou/ForYouViewModelTest.kt

@@ -17,7 +17,6 @@
 package com.google.samples.apps.nowinandroid.feature.foryou
 
 import com.google.samples.apps.nowinandroid.core.domain.GetFollowableTopicsUseCase
-import com.google.samples.apps.nowinandroid.core.domain.GetFollowedUserNewsResourcesUseCase
 import com.google.samples.apps.nowinandroid.core.domain.GetUserNewsResourcesUseCase
 import com.google.samples.apps.nowinandroid.core.domain.model.FollowableTopic
 import com.google.samples.apps.nowinandroid.core.domain.model.UserNewsResource
@@ -61,10 +60,6 @@ class ForYouViewModelTest {
         newsRepository = newsRepository,
         userDataRepository = userDataRepository,
     )
-    private val getFollowedUserNewsResourcesUseCase = GetFollowedUserNewsResourcesUseCase(
-        userDataRepository = userDataRepository,
-        getUserNewsResources = getUserNewsResourcesUseCase,
-    )
 
     private val getFollowableTopicsUseCase = GetFollowableTopicsUseCase(
         topicsRepository = topicsRepository,
@@ -77,7 +72,7 @@ class ForYouViewModelTest {
         viewModel = ForYouViewModel(
             syncStatusMonitor = syncStatusMonitor,
             userDataRepository = userDataRepository,
-            getFollowedUserNewsResources = getFollowedUserNewsResourcesUseCase,
+            getUserNewsResources = getUserNewsResourcesUseCase,
             getFollowableTopics = getFollowableTopicsUseCase,
         )
     }