Integrate WorkManager (WIP)

Change-Id: Iedf81220336911ab3ed6ea4ca71b10f07e645bc9

app/build.gradle

@@ -121,8 +121,11 @@ dependencies {
 
     implementation project(':core-ui')
 
+    implementation project(':sync')
+
     androidTestImplementation project(':core-testing')
     androidTestImplementation project(':core-datastore-test')
+    androidTestImplementation project(':core-domain-test')
 
     coreLibraryDesugaring libs.android.desugarJdkLibs
 

app/src/main/java/com/google/samples/apps/nowinandroid/NiAApp.kt

@@ -17,10 +17,17 @@
 package com.google.samples.apps.nowinandroid
 
 import android.app.Application
+import com.google.samples.apps.nowinandroid.sync.initializers.Sync
 import dagger.hilt.android.HiltAndroidApp
 
 /**
  * [Application] class for NiA
  */
 @HiltAndroidApp
-class NiAApp : Application()
+class NiAApp : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        // Initialize Sync; the system responsible for keeping data in the app up to date.
+        Sync.initialize(context = this)
+    }
+}

build.gradle

@@ -68,6 +68,9 @@ subprojects {
             freeCompilerArgs += '-Xopt-in=kotlinx.coroutines.FlowPreview'
             freeCompilerArgs += '-Xopt-in=kotlin.Experimental'
 
+            // Enable experimental kotlinx serialization APIs
+            freeCompilerArgs += '-Xopt-in=kotlinx.serialization.ExperimentalSerializationApi'
+
             // Set JVM target to 1.8
             jvmTarget = "1.8"
         }

core-common/src/main/res/drawable-anydpi-v24/ic_nia_notification.xml

@@ -0,0 +1,15 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="#FFFFFF">
+  <group android:scaleX="0.92"
+      android:scaleY="0.92"
+      android:translateX="0.96"
+      android:translateY="0.96">
+      <path
+          android:pathData="M17.6,11.48 L19.44,8.3a0.63,0.63 0,0 0,-1.09 -0.63l-1.88,3.24a11.43,11.43 0,0 0,-8.94 0L5.65,7.67a0.63,0.63 0,0 0,-1.09 0.63L6.4,11.48A10.81,10.81 0,0 0,1 20L23,20A10.81,10.81 0,0 0,17.6 11.48ZM7,17.25A1.25,1.25 0,1 1,8.25 16,1.25 1.25,0 0,1 7,17.25ZM17,17.25A1.25,1.25 0,1 1,18.25 16,1.25 1.25,0 0,1 17,17.25Z"
+          android:fillColor="#FF000000"/>
+  </group>
+</vector>

core-database/src/main/java/com/google/samples/apps/nowinandroid/core/database/dao/EpisodeDao.kt

@@ -18,6 +18,7 @@ package com.google.samples.apps.nowinandroid.core.database.dao
 
 import androidx.room.Dao
 import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
 import com.google.samples.apps.nowinandroid.core.database.model.EpisodeEntity
 import com.google.samples.apps.nowinandroid.core.database.model.PopulatedEpisode
@@ -32,6 +33,7 @@ interface EpisodeDao {
     @Query(value = "SELECT * FROM episodes")
     fun getEpisodesStream(): Flow<List<PopulatedEpisode>>
 
-    @Insert
+    // TODO: Perform a proper upsert. See: b/226916817
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
     suspend fun saveEpisodeEntities(entities: List<EpisodeEntity>)
 }

core-database/src/main/java/com/google/samples/apps/nowinandroid/core/database/dao/NewsResourceDao.kt

@@ -18,8 +18,10 @@ package com.google.samples.apps.nowinandroid.core.database.dao
 
 import androidx.room.Dao
 import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
 import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceEntity
+import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceTopicCrossRef
 import com.google.samples.apps.nowinandroid.core.database.model.PopulatedNewsResource
 import com.google.samples.apps.nowinandroid.core.model.data.NewsResource
 import kotlinx.coroutines.flow.Flow
@@ -29,17 +31,32 @@ import kotlinx.coroutines.flow.Flow
  */
 @Dao
 interface NewsResourceDao {
-    @Query(value = "SELECT * FROM news_resources")
+    @Query(
+        value = """
+    SELECT * FROM news_resources
+    ORDER BY publish_date
+    """
+    )
     fun getNewsResourcesStream(): Flow<List<PopulatedNewsResource>>
 
     @Query(
         value = """
         SELECT * FROM news_resources
-        WHERE id IN (:filterTopicIds)
+        WHERE id in
+        (
+            SELECT news_resource_id FROM news_resources_topics
+            WHERE topic_id IN (:filterTopicIds)
+        )
+        ORDER BY publish_date
     """
     )
     fun getNewsResourcesStream(filterTopicIds: Set<Int>): Flow<List<PopulatedNewsResource>>
 
-    @Insert
+    // TODO: Perform a proper upsert. See: b/226916817
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
     suspend fun saveNewsResourceEntities(entities: List<NewsResourceEntity>)
+
+    // TODO: Perform a proper upsert. See: b/226916817
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun saveTopicCrossRefEntities(entities: List<NewsResourceTopicCrossRef>)
 }

core-database/src/main/java/com/google/samples/apps/nowinandroid/core/database/dao/TopicDao.kt

@@ -18,6 +18,7 @@ package com.google.samples.apps.nowinandroid.core.database.dao
 
 import androidx.room.Dao
 import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
 import com.google.samples.apps.nowinandroid.core.database.model.TopicEntity
 import kotlinx.coroutines.flow.Flow
@@ -38,6 +39,7 @@ interface TopicDao {
     )
     fun getTopicEntitiesStream(ids: Set<Int>): Flow<List<TopicEntity>>
 
-    @Insert
+    // TODO: Perform a proper upsert. See: b/226916817
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
     suspend fun saveTopics(entities: List<TopicEntity>)
 }

core-database/src/main/java/com/google/samples/apps/nowinandroid/core/database/model/NewsResourceEntity.kt

@@ -66,3 +66,15 @@ fun NewsResourceEntity.asExternalModel() = NewsResource(
     authors = listOf(),
     topics = listOf()
 )
+
+/**
+ * A shell [EpisodeEntity] to fulfill the foreign key constraint when inserting
+ * a [NewsResourceEntity] into the DB
+ */
+fun NewsResourceEntity.episodeEntityShell() = EpisodeEntity(
+    id = episodeId,
+    name = "",
+    publishDate = Instant.fromEpochMilliseconds(0),
+    alternateVideo = null,
+    alternateAudio = null,
+)

core-datastore-test/build.gradle

@@ -39,10 +39,10 @@ android {
 }
 
 dependencies {
-    implementation project(':core-datastore')
+    api project(':core-datastore')
     implementation project(':core-testing')
 
-    implementation libs.androidx.dataStore
+    api libs.androidx.dataStore.core
 
     implementation libs.hilt.android
     kapt libs.hilt.compiler
@@ -54,4 +54,4 @@ dependencies {
             force 'org.objenesis:objenesis:2.6'
         }
     }
-}
+}

core-datastore-test/src/main/java/com/google/samples/apps/nowinandroid/core/datastore/test/TestDataStoreModule.kt

@@ -40,11 +40,14 @@ object TestDataStoreModule {
     fun providesUserPreferencesDataStore(
         userPreferencesSerializer: UserPreferencesSerializer,
         tmpFolder: TemporaryFolder
-    ): DataStore<UserPreferences> {
-        return DataStoreFactory.create(
-            serializer = userPreferencesSerializer,
-        ) {
-            tmpFolder.newFile("user_preferences_test.pb")
-        }
-    }
+    ): DataStore<UserPreferences> =
+        tmpFolder.testUserPreferencesDataStore(userPreferencesSerializer)
+}
+
+fun TemporaryFolder.testUserPreferencesDataStore(
+    userPreferencesSerializer: UserPreferencesSerializer = UserPreferencesSerializer()
+) = DataStoreFactory.create(
+    serializer = userPreferencesSerializer,
+) {
+    newFile("user_preferences_test.pb")
 }

core-datastore/build.gradle

@@ -63,7 +63,7 @@ dependencies {
 
     implementation libs.kotlinx.coroutines.android
 
-    implementation libs.androidx.dataStore
+    implementation libs.androidx.dataStore.core
     implementation(libs.protobuf.kotlin.lite) {
         // TODO: https://github.com/protocolbuffers/protobuf/issues/9517
         exclude group: "org.jetbrains.kotlin", module: "kotlin-test"
@@ -72,4 +72,4 @@ dependencies {
     implementation libs.hilt.android
     kapt libs.hilt.compiler
     kaptAndroidTest libs.hilt.compiler
-}
+}

core-datastore/src/main/java/com/google/samples/apps/nowinandroid/core/datastore/NiaPreferences.kt

@@ -21,6 +21,7 @@ import androidx.datastore.core.DataStore
 import java.io.IOException
 import javax.inject.Inject
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.firstOrNull
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.retry
 
@@ -65,4 +66,19 @@ class NiaPreferences @Inject constructor(
             true
         }
         .map { it.followedTopicIdsList.toSet() }
+
+    suspend fun hasRunFirstTimeSync() = userPreferences.data
+        .map { it.hasRunFirstTimeSync }.firstOrNull() ?: false
+
+    suspend fun markFirstTimeSyncDone() {
+        try {
+            userPreferences.updateData {
+                it.copy {
+                    hasRunFirstTimeSync = true
+                }
+            }
+        } catch (ioException: IOException) {
+            Log.e("NiaPreferences", "Failed to update user preferences", ioException)
+        }
+    }
 }

core-datastore/src/main/proto/com/google/samples/apps/nowinandroid/data/user_preferences.proto

@@ -21,4 +21,5 @@ option java_multiple_files = true;
 
 message UserPreferences {
     repeated int32 followed_topic_ids = 1;
+    bool has_run_first_time_sync = 2;
 }

core-datastore/src/test/java/com/google/samples/apps/nowinandroid/core/datastore/UserPreferencesSerializerTest.kt

@@ -41,6 +41,7 @@ class UserPreferencesSerializerTest {
         val expectedUserPreferences = userPreferences {
             followedTopicIds.add(0)
             followedTopicIds.add(1)
+            hasRunFirstTimeSync = true
         }
 
         val outputStream = ByteArrayOutputStream()

core-domain-test/.gitignore

@@ -0,0 +1 @@
+/build

core-domain-test/build.gradle

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2022 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.
+ */
+plugins {
+    id 'com.android.library'
+    id 'kotlin-android'
+    id 'kotlin-kapt'
+    id 'dagger.hilt.android.plugin'
+}
+
+android {
+    compileSdk buildConfig.compileSdk
+
+    defaultConfig {
+        minSdk buildConfig.minSdk
+        targetSdk buildConfig.targetSdk
+    }
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
+}
+
+dependencies {
+    api project(':core-domain')
+    implementation project(':core-testing')
+
+    implementation libs.hilt.android
+    kapt libs.hilt.compiler
+    kaptAndroidTest libs.hilt.compiler
+
+    configurations.configureEach {
+        resolutionStrategy {
+            // Temporary workaround for https://issuetracker.google.com/174733673
+            force 'org.objenesis:objenesis:2.6'
+        }
+    }
+}

core-domain-test/src/main/AndroidManifest.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.google.samples.apps.nowinandroid.core.domain.test">
+
+</manifest>

core-domain-test/src/main/java/com/google/samples/apps/nowinandroid/core/domain/test/TestDomainModule.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2022 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.core.domain.test
+
+import com.google.samples.apps.nowinandroid.core.domain.di.DomainModule
+import com.google.samples.apps.nowinandroid.core.domain.repository.NewsRepository
+import com.google.samples.apps.nowinandroid.core.domain.repository.TopicsRepository
+import com.google.samples.apps.nowinandroid.core.domain.repository.fake.FakeNewsRepository
+import com.google.samples.apps.nowinandroid.core.domain.repository.fake.FakeTopicsRepository
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.components.SingletonComponent
+import dagger.hilt.testing.TestInstallIn
+
+@Module
+@TestInstallIn(
+    components = [SingletonComponent::class],
+    replaces = [DomainModule::class]
+)
+interface TestDomainModule {
+    @Binds
+    fun bindsTopicRepository(
+        fakeTopicsRepository: FakeTopicsRepository
+    ): TopicsRepository
+
+    @Binds
+    fun bindsNewsResourceRepository(
+        fakeNewsRepository: FakeNewsRepository
+    ): NewsRepository
+}

core-domain/build.gradle

@@ -45,6 +45,7 @@ dependencies {
     implementation project(':core-network')
 
     testImplementation project(':core-testing')
+    testImplementation project(':core-datastore-test')
 
     implementation libs.kotlinx.datetime
     implementation libs.kotlinx.coroutines.android
@@ -52,4 +53,4 @@ dependencies {
 
     implementation libs.hilt.android
     kapt libs.hilt.compiler
-}
+}

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

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2022 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.core.domain
+
+import android.util.Log
+import kotlin.coroutines.cancellation.CancellationException
+
+/**
+ * Attempts [block], returning a successful [Result] if it succeeds, otherwise a [Result.Failure]
+ * taking care not to break structured concurrency
+ */
+suspend fun <T> suspendRunCatching(block: suspend () -> T): Result<T> = try {
+    Result.success(block())
+} catch (cancellationException: CancellationException) {
+    throw cancellationException
+} catch (exception: Exception) {
+    Log.i(
+        "suspendRunCatching",
+        "Failed to evaluate a suspendRunCatchingBlock. Returning failure Result",
+        exception
+    )
+    Result.failure(exception)
+}

core-domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/di/DomainModule.kt

@@ -16,10 +16,10 @@
 
 package com.google.samples.apps.nowinandroid.core.domain.di
 
+import com.google.samples.apps.nowinandroid.core.domain.repository.LocalNewsRepository
+import com.google.samples.apps.nowinandroid.core.domain.repository.LocalTopicsRepository
 import com.google.samples.apps.nowinandroid.core.domain.repository.NewsRepository
 import com.google.samples.apps.nowinandroid.core.domain.repository.TopicsRepository
-import com.google.samples.apps.nowinandroid.core.domain.repository.fake.FakeNewsRepository
-import com.google.samples.apps.nowinandroid.core.domain.repository.fake.FakeTopicsRepository
 import dagger.Binds
 import dagger.Module
 import dagger.hilt.InstallIn
@@ -31,11 +31,11 @@ interface DomainModule {
 
     @Binds
     fun bindsTopicRepository(
-        fakeTopicsRepository: FakeTopicsRepository
+        topicsRepository: LocalTopicsRepository
     ): TopicsRepository
 
     @Binds
     fun bindsNewsResourceRepository(
-        fakeNewsRepository: FakeNewsRepository
+        newsRepository: LocalNewsRepository
     ): NewsRepository
 }

core-domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/model/NewsResource.kt

@@ -17,6 +17,7 @@
 package com.google.samples.apps.nowinandroid.core.domain.model
 
 import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceEntity
+import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceTopicCrossRef
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResourceExpanded
 
@@ -41,3 +42,12 @@ fun NetworkNewsResourceExpanded.asEntity() = NewsResourceEntity(
     publishDate = publishDate,
     type = type,
 )
+
+fun NetworkNewsResource.topicCrossReferences(): List<NewsResourceTopicCrossRef> =
+    topics.map { topicId ->
+        NewsResourceTopicCrossRef(
+            newsResourceId = id,
+            topicId = topicId
+
+        )
+    }

core-domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/repository/LocalNewsRepository.kt

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2022 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.core.domain.repository
+
+import com.google.samples.apps.nowinandroid.core.database.dao.EpisodeDao
+import com.google.samples.apps.nowinandroid.core.database.dao.NewsResourceDao
+import com.google.samples.apps.nowinandroid.core.database.model.EpisodeEntity
+import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceEntity
+import com.google.samples.apps.nowinandroid.core.database.model.PopulatedNewsResource
+import com.google.samples.apps.nowinandroid.core.database.model.asExternalModel
+import com.google.samples.apps.nowinandroid.core.database.model.episodeEntityShell
+import com.google.samples.apps.nowinandroid.core.domain.model.asEntity
+import com.google.samples.apps.nowinandroid.core.domain.model.topicCrossReferences
+import com.google.samples.apps.nowinandroid.core.domain.suspendRunCatching
+import com.google.samples.apps.nowinandroid.core.model.data.NewsResource
+import com.google.samples.apps.nowinandroid.core.network.NiANetwork
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
+import javax.inject.Inject
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
+
+/**
+ * Room database backed implementation of the [NewsRepository].
+ */
+class LocalNewsRepository @Inject constructor(
+    private val newsResourceDao: NewsResourceDao,
+    private val episodeDao: EpisodeDao,
+    private val network: NiANetwork,
+) : NewsRepository {
+
+    override fun getNewsResourcesStream(): Flow<List<NewsResource>> =
+        newsResourceDao.getNewsResourcesStream()
+            .map { it.map(PopulatedNewsResource::asExternalModel) }
+
+    override fun getNewsResourcesStream(filterTopicIds: Set<Int>): Flow<List<NewsResource>> =
+        newsResourceDao.getNewsResourcesStream(filterTopicIds = filterTopicIds)
+            .map { it.map(PopulatedNewsResource::asExternalModel) }
+
+    override suspend fun sync() = suspendRunCatching {
+        val networkNewsResources = network.getNewsResources()
+
+        val newsResourceEntities = networkNewsResources
+            .map(NetworkNewsResource::asEntity)
+
+        val episodeEntityShells = newsResourceEntities
+            .map(NewsResourceEntity::episodeEntityShell)
+            .distinctBy(EpisodeEntity::id)
+
+        val topicCrossReferences = networkNewsResources
+            .map(NetworkNewsResource::topicCrossReferences)
+            .distinct()
+            .flatten()
+
+        // Order of invocation matters to satisfy id and foreign key constraints!
+
+        // TODO: Create a separate method for saving shells with proper conflict resolution
+        //  See: b/226919874
+        episodeDao.saveEpisodeEntities(
+            episodeEntityShells
+        )
+        newsResourceDao.saveNewsResourceEntities(
+            newsResourceEntities
+        )
+        newsResourceDao.saveTopicCrossRefEntities(
+            topicCrossReferences
+        )
+
+        // TODO: Save author as well
+    }.isSuccess
+}

core-domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/repository/LocalTopicsRepository.kt

@@ -21,20 +21,18 @@ import com.google.samples.apps.nowinandroid.core.database.model.TopicEntity
 import com.google.samples.apps.nowinandroid.core.database.model.asExternalModel
 import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
 import com.google.samples.apps.nowinandroid.core.domain.model.asEntity
+import com.google.samples.apps.nowinandroid.core.domain.suspendRunCatching
 import com.google.samples.apps.nowinandroid.core.model.data.Topic
 import com.google.samples.apps.nowinandroid.core.network.NiANetwork
-import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
 import javax.inject.Inject
-import kotlin.coroutines.cancellation.CancellationException
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 
 /**
  * Room database backed implementation of the [TopicsRepository].
  */
-class RoomTopicsRepository @Inject constructor(
-    private val dispatchers: NiaDispatchers,
+class LocalTopicsRepository @Inject constructor(
     private val topicDao: TopicDao,
     private val network: NiANetwork,
     private val niaPreferences: NiaPreferences
@@ -52,15 +50,10 @@ class RoomTopicsRepository @Inject constructor(
 
     override fun getFollowedTopicIdsStream() = niaPreferences.followedTopicIds
 
-    override suspend fun sync(): Boolean = try {
+    override suspend fun sync(): Boolean = suspendRunCatching {
+        val networkTopics = network.getTopics()
         topicDao.saveTopics(
-            network.getTopics()
-                .map(NetworkTopic::asEntity)
+            networkTopics.map(NetworkTopic::asEntity)
         )
-        true
-    } catch (cancellationException: CancellationException) {
-        throw cancellationException
-    } catch (exception: Exception) {
-        false
-    }
+    }.isSuccess
 }

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/repository/LocalNewsRepositoryTest.kt

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2022 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.core.domain.repository
+
+import com.google.samples.apps.nowinandroid.core.database.model.EpisodeEntity
+import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceEntity
+import com.google.samples.apps.nowinandroid.core.database.model.PopulatedEpisode
+import com.google.samples.apps.nowinandroid.core.database.model.PopulatedNewsResource
+import com.google.samples.apps.nowinandroid.core.database.model.asExternalModel
+import com.google.samples.apps.nowinandroid.core.database.model.episodeEntityShell
+import com.google.samples.apps.nowinandroid.core.domain.model.asEntity
+import com.google.samples.apps.nowinandroid.core.domain.model.topicCrossReferences
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.TestEpisodeDao
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.TestNewsResourceDao
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.TestNiaNetwork
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.filteredTopicIds
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.nonPresentTopicIds
+import com.google.samples.apps.nowinandroid.core.model.data.NewsResource
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+
+class LocalNewsRepositoryTest {
+
+    private lateinit var subject: LocalNewsRepository
+
+    private lateinit var newsResourceDao: TestNewsResourceDao
+
+    private lateinit var episodeDao: TestEpisodeDao
+
+    private lateinit var network: TestNiaNetwork
+
+    @Before
+    fun setup() {
+        newsResourceDao = TestNewsResourceDao()
+        episodeDao = TestEpisodeDao()
+        network = TestNiaNetwork()
+
+        subject = LocalNewsRepository(
+            newsResourceDao = newsResourceDao,
+            episodeDao = episodeDao,
+            network = network
+        )
+    }
+
+    @Test
+    fun localNewsRepository_news_resources_stream_is_backed_by_news_resource_dao() =
+        runTest {
+            assertEquals(
+                newsResourceDao.getNewsResourcesStream()
+                    .first()
+                    .map(PopulatedNewsResource::asExternalModel),
+                subject.getNewsResourcesStream()
+                    .first()
+            )
+        }
+
+    @Test
+    fun localNewsRepository_news_resources_filtered_stream_is_backed_by_news_resource_dao() =
+        runTest {
+            assertEquals(
+                newsResourceDao.getNewsResourcesStream(filterTopicIds = filteredTopicIds)
+                    .first()
+                    .map(PopulatedNewsResource::asExternalModel),
+                subject.getNewsResourcesStream(filterTopicIds = filteredTopicIds)
+                    .first()
+            )
+
+            assertEquals(
+                emptyList<NewsResource>(),
+                subject.getNewsResourcesStream(filterTopicIds = nonPresentTopicIds)
+                    .first()
+            )
+        }
+
+    @Test
+    fun localNewsRepository_sync_pulls_from_network() =
+        runTest {
+            subject.sync()
+
+            val newsResourcesFromNetwork = network.getNewsResources()
+                .map(NetworkNewsResource::asEntity)
+                .map(NewsResourceEntity::asExternalModel)
+
+            val newsResourcesFromDb = newsResourceDao.getNewsResourcesStream()
+                .first()
+                .map(PopulatedNewsResource::asExternalModel)
+
+            assertEquals(
+                newsResourcesFromNetwork.map(NewsResource::id),
+                newsResourcesFromDb.map(NewsResource::id)
+            )
+        }
+
+    @Test
+    fun localNewsRepository_sync_saves_shell_episode_entities() =
+        runTest {
+            subject.sync()
+
+            assertEquals(
+                network.getNewsResources()
+                    .map(NetworkNewsResource::asEntity)
+                    .map(NewsResourceEntity::episodeEntityShell)
+                    .distinctBy(EpisodeEntity::id),
+                episodeDao.getEpisodesStream()
+                    .first()
+                    .map(PopulatedEpisode::entity)
+            )
+        }
+
+    @Test
+    fun localNewsRepository_sync_saves_topic_cross_references() =
+        runTest {
+            subject.sync()
+
+            assertEquals(
+                network.getNewsResources()
+                    .map(NetworkNewsResource::topicCrossReferences)
+                    .distinct()
+                    .flatten(),
+                newsResourceDao.topicCrossReferences
+            )
+        }
+}

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/repository/LocalTopicsRepositoryTest.kt

@@ -0,0 +1,150 @@
+/*
+ * Copyright 2022 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.core.domain.repository
+
+import com.google.samples.apps.nowinandroid.core.database.dao.TopicDao
+import com.google.samples.apps.nowinandroid.core.database.model.TopicEntity
+import com.google.samples.apps.nowinandroid.core.database.model.asExternalModel
+import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
+import com.google.samples.apps.nowinandroid.core.datastore.test.testUserPreferencesDataStore
+import com.google.samples.apps.nowinandroid.core.domain.model.asEntity
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.TestNiaNetwork
+import com.google.samples.apps.nowinandroid.core.domain.testdoubles.TestTopicDao
+import com.google.samples.apps.nowinandroid.core.network.NiANetwork
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+
+class LocalTopicsRepositoryTest {
+
+    private lateinit var subject: LocalTopicsRepository
+
+    private lateinit var topicDao: TopicDao
+
+    private lateinit var network: NiANetwork
+
+    private lateinit var niaPreferences: NiaPreferences
+
+    @get:Rule
+    val tmpFolder: TemporaryFolder = TemporaryFolder.builder().assureDeletion().build()
+
+    @Before
+    fun setup() {
+        topicDao = TestTopicDao()
+        network = TestNiaNetwork()
+        niaPreferences = NiaPreferences(
+            tmpFolder.testUserPreferencesDataStore()
+        )
+
+        subject = LocalTopicsRepository(
+            topicDao = topicDao,
+            network = network,
+            niaPreferences = niaPreferences,
+        )
+    }
+
+    @Test
+    fun localTopicsRepository_topics_stream_is_backed_by_topics_dao() =
+        runTest {
+            Assert.assertEquals(
+                topicDao.getTopicEntitiesStream()
+                    .first()
+                    .map(TopicEntity::asExternalModel),
+                subject.getTopicsStream()
+                    .first()
+            )
+        }
+
+    @Test
+    fun localTopicsRepository_news_resources_filtered_stream_is_backed_by_news_resource_dao() =
+        runTest {
+            Assert.assertEquals(
+                niaPreferences.followedTopicIds
+                    .first(),
+                subject.getFollowedTopicIdsStream()
+                    .first()
+            )
+        }
+
+    @Test
+    fun localTopicsRepository_sync_pulls_from_network() =
+        runTest {
+            subject.sync()
+
+            val network = network.getTopics()
+                .map(NetworkTopic::asEntity)
+
+            val db = topicDao.getTopicEntitiesStream()
+                .first()
+
+            Assert.assertEquals(
+                network.map(TopicEntity::id),
+                db.map(TopicEntity::id)
+            )
+        }
+
+    @Test
+    fun localTopicsRepository_toggle_followed_topics_logic_delegates_to_nia_preferences() =
+        runTest {
+            subject.toggleFollowedTopicId(followedTopicId = 0, followed = true)
+
+            Assert.assertEquals(
+                setOf(0),
+                subject.getFollowedTopicIdsStream()
+                    .first()
+            )
+
+            subject.toggleFollowedTopicId(followedTopicId = 1, followed = true)
+
+            Assert.assertEquals(
+                setOf(0, 1),
+                subject.getFollowedTopicIdsStream()
+                    .first()
+            )
+
+            Assert.assertEquals(
+                niaPreferences.followedTopicIds
+                    .first(),
+                subject.getFollowedTopicIdsStream()
+                    .first()
+            )
+        }
+
+    @Test
+    fun localTopicsRepository_set_followed_topics_logic_delegates_to_nia_preferences() =
+        runTest {
+            subject.setFollowedTopicIds(followedTopicIds = setOf(1, 2))
+
+            Assert.assertEquals(
+                setOf(1, 2),
+                subject.getFollowedTopicIdsStream()
+                    .first()
+            )
+
+            Assert.assertEquals(
+                niaPreferences.followedTopicIds
+                    .first(),
+                subject.getFollowedTopicIdsStream()
+                    .first()
+            )
+        }
+}

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/testdoubles/TestEpisodeDao.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2022 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.core.domain.testdoubles
+
+import com.google.samples.apps.nowinandroid.core.database.dao.EpisodeDao
+import com.google.samples.apps.nowinandroid.core.database.model.EpisodeEntity
+import com.google.samples.apps.nowinandroid.core.database.model.PopulatedEpisode
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.datetime.Instant
+
+/**
+ * Test double for [EpisodeDao]
+ */
+class TestEpisodeDao : EpisodeDao {
+
+    private var entities = listOf(
+        EpisodeEntity(
+            id = 1,
+            name = "Topic",
+            publishDate = Instant.fromEpochMilliseconds(0),
+            alternateVideo = null,
+            alternateAudio = null,
+        )
+    )
+
+    override fun getEpisodesStream(): Flow<List<PopulatedEpisode>> =
+        flowOf(entities.map(EpisodeEntity::asPopulatedEpisode))
+
+    override suspend fun saveEpisodeEntities(entities: List<EpisodeEntity>) {
+        this.entities = entities
+    }
+}
+
+private fun EpisodeEntity.asPopulatedEpisode() = PopulatedEpisode(
+    entity = this,
+    newsResources = emptyList(),
+    authors = emptyList(),
+)

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/testdoubles/TestNewsResourceDao.kt

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2022 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.core.domain.testdoubles
+
+import com.google.samples.apps.nowinandroid.core.database.dao.NewsResourceDao
+import com.google.samples.apps.nowinandroid.core.database.model.AuthorEntity
+import com.google.samples.apps.nowinandroid.core.database.model.EpisodeEntity
+import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceEntity
+import com.google.samples.apps.nowinandroid.core.database.model.NewsResourceTopicCrossRef
+import com.google.samples.apps.nowinandroid.core.database.model.PopulatedNewsResource
+import com.google.samples.apps.nowinandroid.core.database.model.TopicEntity
+import com.google.samples.apps.nowinandroid.core.model.data.NewsResourceType.Video
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.map
+import kotlinx.datetime.Instant
+
+val filteredTopicIds = setOf(1)
+val nonPresentTopicIds = setOf(2)
+
+/**
+ * Test double for [NewsResourceDao]
+ */
+class TestNewsResourceDao : NewsResourceDao {
+
+    private var entities = listOf(
+        NewsResourceEntity(
+            id = 1,
+            episodeId = 0,
+            title = "news",
+            content = "Hilt",
+            url = "url",
+            headerImageUrl = "headerImageUrl",
+            type = Video,
+            publishDate = Instant.fromEpochMilliseconds(1),
+        )
+    )
+
+    internal var topicCrossReferences: List<NewsResourceTopicCrossRef> = listOf()
+
+    override fun getNewsResourcesStream(): Flow<List<PopulatedNewsResource>> =
+        flowOf(entities.map(NewsResourceEntity::asPopulatedNewsResource))
+
+    override fun getNewsResourcesStream(
+        filterTopicIds: Set<Int>
+    ): Flow<List<PopulatedNewsResource>> =
+        getNewsResourcesStream()
+            .map { resources ->
+                resources.filter { resource ->
+                    resource.topics.any { it.id in filterTopicIds }
+                }
+            }
+
+    override suspend fun saveNewsResourceEntities(entities: List<NewsResourceEntity>) {
+        this.entities = entities
+    }
+
+    override suspend fun saveTopicCrossRefEntities(entities: List<NewsResourceTopicCrossRef>) {
+        topicCrossReferences = entities
+    }
+}
+
+private fun NewsResourceEntity.asPopulatedNewsResource() = PopulatedNewsResource(
+    entity = this,
+    episode = EpisodeEntity(
+        id = this.episodeId,
+        name = "episode 4",
+        publishDate = Instant.fromEpochMilliseconds(2),
+        alternateAudio = "audio",
+        alternateVideo = "video",
+    ),
+    authors = listOf(
+        AuthorEntity(
+            id = 2,
+            name = "name",
+            imageUrl = "imageUrl"
+        )
+    ),
+    topics = listOf(
+        TopicEntity(
+            id = filteredTopicIds.random(),
+            name = "name",
+            description = "description",
+        )
+    ),
+)

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/testdoubles/TestNiaNetwork.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2022 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.core.domain.testdoubles
+
+import com.google.samples.apps.nowinandroid.core.network.NiANetwork
+import com.google.samples.apps.nowinandroid.core.network.fake.FakeDataSource
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
+import kotlinx.serialization.decodeFromString
+import kotlinx.serialization.json.Json
+
+/**
+ * Test double for [NiANetwork]
+ */
+class TestNiaNetwork : NiANetwork {
+
+    private val networkJson = Json
+
+    override suspend fun getTopics(itemsPerPage: Int): List<NetworkTopic> =
+        networkJson.decodeFromString(FakeDataSource.topicsData)
+
+    override suspend fun getNewsResources(itemsPerPage: Int): List<NetworkNewsResource> =
+        networkJson.decodeFromString(FakeDataSource.data)
+}

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/testdoubles/TestTopicDao.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2022 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.core.domain.testdoubles
+
+import com.google.samples.apps.nowinandroid.core.database.dao.TopicDao
+import com.google.samples.apps.nowinandroid.core.database.model.TopicEntity
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.map
+
+/**
+ * Test double for [TopicDao]
+ */
+class TestTopicDao : TopicDao {
+
+    private var entities = listOf(
+        TopicEntity(
+            id = 1,
+            name = "Topic",
+            description = "A topic",
+        )
+    )
+
+    override fun getTopicEntitiesStream(): Flow<List<TopicEntity>> =
+        flowOf(entities)
+
+    override fun getTopicEntitiesStream(ids: Set<Int>): Flow<List<TopicEntity>> =
+        getTopicEntitiesStream()
+            .map { topics -> topics.filter { it.id in ids } }
+
+    override suspend fun saveTopics(entities: List<TopicEntity>) {
+        this.entities = entities
+    }
+}

core-network/build.gradle

@@ -48,7 +48,8 @@ dependencies {
     implementation libs.kotlinx.datetime
 
     implementation libs.okhttp.logging
-    implementation libs.retrofit
+    implementation libs.retrofit.core
+    implementation libs.retrofit.kotlin.serialization
 
     implementation libs.hilt.android
     kapt libs.hilt.compiler

core-network/src/main/java/com/google/samples/apps/nowinandroid/core/network/NiANetwork.kt

@@ -23,7 +23,7 @@ import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
  * Interface representing network calls to the NIA backend
  */
 interface NiANetwork {
-    suspend fun getTopics(): List<NetworkTopic>
+    suspend fun getTopics(itemsPerPage: Int = 200): List<NetworkTopic>
 
-    suspend fun getNewsResources(): List<NetworkNewsResource>
+    suspend fun getNewsResources(itemsPerPage: Int = 200): List<NetworkNewsResource>
 }

core-network/src/main/java/com/google/samples/apps/nowinandroid/core/network/di/NetworkModule.kt

@@ -17,7 +17,7 @@
 package com.google.samples.apps.nowinandroid.core.network.di
 
 import com.google.samples.apps.nowinandroid.core.network.NiANetwork
-import com.google.samples.apps.nowinandroid.core.network.fake.FakeNiANetwork
+import com.google.samples.apps.nowinandroid.core.network.retrofit.RetrofitNiANetwork
 import dagger.Binds
 import dagger.Module
 import dagger.Provides
@@ -32,7 +32,7 @@ interface NetworkModule {
 
     @Binds
     fun bindsNiANetwork(
-        fakeNiANetwork: FakeNiANetwork
+        niANetwork: RetrofitNiANetwork
     ): NiANetwork
 
     companion object {

core-network/src/main/java/com/google/samples/apps/nowinandroid/core/network/fake/FakeNiANetwork.kt

@@ -34,12 +34,12 @@ class FakeNiANetwork @Inject constructor(
     @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
     private val networkJson: Json
 ) : NiANetwork {
-    override suspend fun getTopics(): List<NetworkTopic> =
+    override suspend fun getTopics(itemsPerPage: Int): List<NetworkTopic> =
         withContext(ioDispatcher) {
             networkJson.decodeFromString(FakeDataSource.topicsData)
         }
 
-    override suspend fun getNewsResources(): List<NetworkNewsResource> =
+    override suspend fun getNewsResources(itemsPerPage: Int): List<NetworkNewsResource> =
         withContext(ioDispatcher) {
             networkJson.decodeFromString(FakeDataSource.data)
         }

core-network/src/main/java/com/google/samples/apps/nowinandroid/core/network/retrofit/RetrofitNiANetwork.kt

@@ -16,14 +16,73 @@
 
 package com.google.samples.apps.nowinandroid.core.network.retrofit
 
+import com.google.samples.apps.nowinandroid.core.network.NiANetwork
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
+import com.jakewharton.retrofit2.converter.kotlinx.serialization.asConverterFactory
+import javax.inject.Inject
+import javax.inject.Singleton
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import okhttp3.MediaType.Companion.toMediaType
+import okhttp3.OkHttpClient
+import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Retrofit
 import retrofit2.http.GET
+import retrofit2.http.Query
 
-interface RetrofitNiANetwork {
-    @GET(value = "/topics")
-    suspend fun getTopics(): List<NetworkTopic>
+/**
+ * Retrofit API declaration for NIA Network API
+ */
+private interface RetrofitNiANetworkApi {
+    @GET(value = "topics")
+    suspend fun getTopics(
+        @Query("pageSize") itemsPerPage: Int,
+    ): NetworkResponse<List<NetworkTopic>>
+
+    @GET(value = "newsresources")
+    suspend fun getNewsResources(
+        @Query("pageSize") itemsPerPage: Int,
+    ): NetworkResponse<List<NetworkNewsResource>>
+}
+
+private const val NiABaseUrl = "https://staging-url.com/"
+
+/**
+ * Wrapper for data provided from the [NiABaseUrl]
+ */
+@Serializable
+private data class NetworkResponse<T>(
+    val data: T
+)
+
+/**
+ * [Retrofit] backed [NiANetwork]
+ */
+@Singleton
+class RetrofitNiANetwork @Inject constructor(
+    networkJson: Json
+) : NiANetwork {
+
+    private val networkApi = Retrofit.Builder()
+        .baseUrl(NiABaseUrl)
+        .client(
+            OkHttpClient.Builder()
+                .addInterceptor(
+                    // TODO: Decide logging logic
+                    HttpLoggingInterceptor().apply {
+                        setLevel(HttpLoggingInterceptor.Level.BODY)
+                    }
+                )
+                .build()
+        )
+        .addConverterFactory(networkJson.asConverterFactory("application/json".toMediaType()))
+        .build()
+        .create(RetrofitNiANetworkApi::class.java)
+
+    override suspend fun getTopics(itemsPerPage: Int): List<NetworkTopic> =
+        networkApi.getTopics(itemsPerPage = itemsPerPage).data
 
-    @GET(value = "/newsresources")
-    suspend fun getNewsResources(): List<NetworkNewsResource>
+    override suspend fun getNewsResources(itemsPerPage: Int): List<NetworkNewsResource> =
+        networkApi.getNewsResources(itemsPerPage = itemsPerPage).data
 }

gradle/libs.versions.toml

@@ -15,12 +15,15 @@ androidxLifecycle = "2.4.0"
 androidxMacroBenchmark = "1.1.0-beta04"
 androidxNavigation = "2.4.0-rc01"
 androidxProfileinstaller = "1.2.0-alpha02"
+androidxStartup = "1.1.1"
 androidxWindowManager = "1.0.0"
 androidxTest = "1.4.0"
 androidxTestExt = "1.1.2"
 androidxUiAutomator = "2.2.0"
+androidxWork = "2.7.1"
 coil = "2.0.0-rc01"
 hilt = "2.41"
+hiltExt = "1.0.0"
 jacoco = "0.8.7"
 junit4 = "4.13"
 kotlin = "1.6.10"
@@ -36,6 +39,7 @@ okhttp = "4.9.3"
 protobuf = "3.19.1"
 protobufPlugin = "0.8.18"
 retrofit = "2.9.0"
+retrofitKotlinxSerializationJson = "0.8.0"
 room = "2.4.1"
 spotless = "6.0.0"
 turbine = "0.7.0"
@@ -60,11 +64,13 @@ androidx-compose-ui-tooling = { group = "androidx.compose.ui", name = "ui-toolin
 androidx-compose-ui-tooling-preview = { group = "androidx.compose.ui", name = "ui-tooling-preview", version.ref = "androidxCompose" }
 androidx-compose-ui-util = { group = "androidx.compose.ui", name = "ui-util", version.ref = "androidxCompose" }
 androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "androidxCore" }
-androidx-dataStore = { group = "androidx.datastore", name = "datastore", version.ref = "androidxDataStore" }
+androidx-dataStore-core = { group = "androidx.datastore", name = "datastore", version.ref = "androidxDataStore" }
+androidx-dataStore-preferences = { group = "androidx.datastore", name = "datastore-preferences", version.ref = "androidxDataStore" }
 androidx-hilt-navigation-compose = { group = "androidx.hilt", name = "hilt-navigation-compose", version.ref = "androidxHiltNavigationCompose" }
 androidx-lifecycle-viewModelCompose = { group = "androidx.lifecycle", name = "lifecycle-viewmodel-compose", version.ref = "androidxLifecycle" }
 androidx-navigation-compose = { group = "androidx.navigation", name = "navigation-compose", version.ref = "androidxNavigation" }
 androidx-profileinstaller = { group = "androidx.profileinstaller", name = "profileinstaller", version.ref = "androidxProfileinstaller" }
+androidx-startup = { group = "androidx.startup", name = "startup-runtime", version.ref = "androidxStartup" }
 androidx-window-manager = {module = "androidx.window:window", version.ref = "androidxWindowManager"}
 androidx-test-core = { group = "androidx.test", name = "core", version.ref = "androidxTest" }
 androidx-test-ext = { group = "androidx.test.ext", name = "junit-ktx", version.ref = "androidxTestExt" }
@@ -72,9 +78,13 @@ androidx-test-espresso-core = { group = "androidx.test.espresso", name = "espres
 androidx-test-runner = { group = "androidx.test", name = "runner", version.ref = "androidxTest" }
 androidx-test-rules = { group = "androidx.test", name = "rules", version.ref = "androidxTest" }
 androidx-test-uiautomator = { group = "androidx.test.uiautomator", name = "uiautomator", version.ref = "androidxTestExt" }
+androidx-work-ktx = { group = "androidx.work", name = "work-runtime-ktx", version.ref = "androidxWork" }
+androidx-work-testing = { group = "androidx.work", name = "work-testing", version.ref = "androidxWork" }
 coil-kt = { group = "io.coil-kt", name = "coil", version.ref = "coil"}
 coil-kt-compose = { group = "io.coil-kt", name = "coil-compose", version.ref = "coil"}
 hilt-android = { group = "com.google.dagger", name = "hilt-android", version.ref = "hilt" }
+hilt-ext-work = { group = "androidx.hilt", name = "hilt-work", version.ref = "hiltExt" }
+hilt-ext-compiler = { group = "androidx.hilt", name = "hilt-compiler", version.ref = "hiltExt" }
 hilt-compiler = { group = "com.google.dagger", name = "hilt-android-compiler", version.ref = "hilt" }
 hilt-android-testing = { group = "com.google.dagger", name = "hilt-android-testing", version.ref = "hilt" }
 hilt-gradlePlugin = { group = "com.google.dagger", name = "hilt-android-gradle-plugin", version.ref = "hilt" }
@@ -91,7 +101,8 @@ okhttp-logging = { group = "com.squareup.okhttp3", name = "logging-interceptor",
 protobuf-protoc = { group = "com.google.protobuf", name = "protoc", version.ref = "protobuf" }
 protobuf-kotlin-lite = { group = "com.google.protobuf", name = "protobuf-kotlin-lite", version.ref = "protobuf" }
 turbine = { group = "app.cash.turbine", name = "turbine", version.ref = "turbine" }
-retrofit = { group = "com.squareup.retrofit2", name = "retrofit", version.ref = "retrofit" }
+retrofit-core = { group = "com.squareup.retrofit2", name = "retrofit", version.ref = "retrofit" }
+retrofit-kotlin-serialization = { group = "com.jakewharton.retrofit", name = "retrofit2-kotlinx-serialization-converter", version.ref = "retrofitKotlinxSerializationJson" }
 room-runtime = { group = "androidx.room", name = "room-runtime", version.ref = "room" }
 room-ktx = { group = "androidx.room", name = "room-ktx", version.ref = "room" }
 room-compiler = { group = "androidx.room", name = "room-compiler", version.ref = "room" }

settings.gradle

@@ -32,6 +32,7 @@ include ':app'
 include ':benchmark'
 include ':core-common'
 include ':core-domain'
+include ':core-domain-test'
 include ':core-database'
 include ':core-datastore'
 include ':core-datastore-test'
@@ -41,3 +42,4 @@ include ':core-ui'
 include ':core-testing'
 include ':feature-following'
 include ':feature-foryou'
+include ':sync'

sync/.gitignore

@@ -0,0 +1 @@
+/build

sync/build.gradle

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2022 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.
+ */
+plugins {
+    id 'com.android.library'
+    id 'kotlin-android'
+    id 'kotlin-kapt'
+    id 'dagger.hilt.android.plugin'
+}
+
+android {
+    compileSdk buildConfig.compileSdk
+
+    defaultConfig {
+        minSdk buildConfig.minSdk
+        targetSdk buildConfig.targetSdk
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
+}
+
+dependencies {
+    implementation project(':core-model')
+    implementation project(':core-domain')
+    implementation project(':core-datastore')
+
+    implementation libs.kotlinx.coroutines.android
+
+    implementation libs.androidx.startup
+    implementation libs.androidx.work.ktx
+    implementation libs.hilt.ext.work
+
+    testImplementation project(':core-testing')
+    androidTestImplementation project(':core-testing')
+
+    implementation libs.hilt.android
+    kapt libs.hilt.compiler
+    kapt libs.hilt.ext.compiler
+
+    androidTestImplementation libs.androidx.work.testing
+}

sync/src/androidTest/java/com/google/samples/apps/nowinandroid/sync/workers/SyncWorkerTest.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2022 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.sync.workers
+
+import android.util.Log
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.work.Configuration
+import androidx.work.PeriodicWorkRequestBuilder
+import androidx.work.WorkInfo
+import androidx.work.WorkManager
+import androidx.work.testing.SynchronousExecutor
+import androidx.work.testing.WorkManagerTestInitHelper
+import androidx.work.workDataOf
+import java.util.concurrent.TimeUnit
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+
+class SyncWorkerTest {
+
+    private val context get() = InstrumentationRegistry.getInstrumentation().context
+
+    @Before
+    fun setup() {
+        val config = Configuration.Builder()
+            .setMinimumLoggingLevel(Log.DEBUG)
+            .setExecutor(SynchronousExecutor())
+            .build()
+
+        // Initialize WorkManager for instrumentation tests.
+        WorkManagerTestInitHelper.initializeTestWorkManager(context, config)
+    }
+
+    @Test
+    fun testSyncPeriodicWork() {
+        // Define input data
+        val input = workDataOf()
+
+        // Create request
+        val request = PeriodicWorkRequestBuilder<SyncWorker>(15, TimeUnit.MINUTES)
+            .setInputData(input)
+            .build()
+
+        val workManager = WorkManager.getInstance(context)
+        val testDriver = WorkManagerTestInitHelper.getTestDriver(context)!!
+
+        // Enqueue and wait for result.
+        workManager.enqueue(request).result.get()
+        // Tells the testing framework the period delay is met
+        testDriver.setPeriodDelayMet(request.id)
+        // Get WorkInfo and outputData
+        val workInfo = workManager.getWorkInfoById(request.id).get()
+
+        // Assert
+        assertEquals(workInfo.state, WorkInfo.State.ENQUEUED)
+    }
+}

sync/src/main/AndroidManifest.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    package="com.google.samples.apps.nowinandroid.sync">
+
+    <application>
+        <provider
+            android:name="androidx.startup.InitializationProvider"
+            android:authorities="${applicationId}.androidx-startup"
+            android:exported="false"
+            tools:node="merge">
+            <!--  TODO: b/2173216 Disable auto sync startup till it works well with instrumented tests   -->
+            <meta-data
+                android:name="com.google.samples.apps.nowinandroid.sync.initializers.SyncInitializer"
+                android:value="androidx.startup"
+                tools:node="remove" />
+        </provider>
+
+    </application>
+
+</manifest>

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/SyncRepository.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 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.sync
+
+import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
+import javax.inject.Inject
+
+/**
+ * Source of truth for status of sync.
+ */
+interface SyncRepository {
+    /**
+     * returns whether we should run a first time sync job
+     */
+    suspend fun shouldRunFirstTimeSync(): Boolean
+
+    /**
+     * Notify the repository that first time sync has run successfully
+     */
+    suspend fun notifyFirstTimeSyncRun()
+}
+
+/**
+ * Uses a [NiaPreferences] to manage sync status
+ */
+class LocalSyncRepository @Inject constructor(
+    private val preferences: NiaPreferences
+) : SyncRepository {
+
+    override suspend fun shouldRunFirstTimeSync(): Boolean = !preferences.hasRunFirstTimeSync()
+
+    override suspend fun notifyFirstTimeSyncRun() {
+        preferences.markFirstTimeSyncDone()
+    }
+}

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/di/SyncModule.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2022 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.sync.di
+
+import com.google.samples.apps.nowinandroid.sync.LocalSyncRepository
+import com.google.samples.apps.nowinandroid.sync.SyncRepository
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface SyncModule {
+    @Binds
+    fun bindsSyncStatusRepository(
+        localSyncRepository: LocalSyncRepository
+    ): SyncRepository
+}

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/initializers/SyncInitializer.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2022 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.sync.initializers
+
+import android.content.Context
+import androidx.startup.AppInitializer
+import androidx.startup.Initializer
+import androidx.work.ExistingPeriodicWorkPolicy
+import androidx.work.WorkManager
+import androidx.work.WorkManagerInitializer
+import com.google.samples.apps.nowinandroid.sync.workers.FirstTimeSyncCheckWorker
+import com.google.samples.apps.nowinandroid.sync.workers.SyncWorker
+
+object Sync {
+    // This method is a workaround to manually initialize the sync process instead of relying on
+    // automatic initialization with Androidx Startup. It is called from the app module's
+    // Application.onCreate() and should be only done once.
+    fun initialize(context: Context) {
+        AppInitializer.getInstance(context)
+            .initializeComponent(SyncInitializer::class.java)
+    }
+}
+
+// This name should not be changed otherwise the app may have concurrent sync requests running
+private const val SyncWorkName = "SyncWorkName"
+
+/**
+ * Registers sync to sync the data layer periodically [SyncInterval] on app startup.
+ */
+class SyncInitializer : Initializer<Sync> {
+    override fun create(context: Context): Sync {
+
+        val workManager = WorkManager.getInstance(context)
+
+        workManager.enqueueUniquePeriodicWork(
+            SyncWorkName,
+            ExistingPeriodicWorkPolicy.KEEP,
+            SyncWorker.periodicSyncWork()
+        )
+        workManager.enqueue(FirstTimeSyncCheckWorker.firstTimeSyncCheckWork())
+
+        return Sync
+    }
+
+    override fun dependencies(): List<Class<out Initializer<*>>> =
+        listOf(WorkManagerInitializer::class.java)
+}

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/initializers/SyncWorkHelpers.kt

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2022 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.sync.initializers
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.content.Context
+import android.os.Build
+import androidx.core.app.NotificationCompat
+import androidx.work.Constraints
+import androidx.work.ForegroundInfo
+import androidx.work.NetworkType
+import com.google.samples.apps.nowinandroid.sync.R
+
+private const val SyncNotificationId = 0
+private const val SyncNotificationChannelID = "SyncNotificationChannel"
+
+// All sync work needs an internet connectionS
+val SyncConstraints
+    get() = Constraints.Builder()
+        .setRequiredNetworkType(NetworkType.CONNECTED)
+        .build()
+
+/**
+ * Foreground information for sync on lower API levels when sync workers are being
+ * run with a foreground service
+ */
+fun Context.syncForegroundInfo() = ForegroundInfo(
+    SyncNotificationId,
+    syncWorkNotification()
+)
+
+/**
+ * Notification displayed on lower API levels when sync workers are being
+ * run with a foreground service
+ */
+private fun Context.syncWorkNotification(): Notification {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+        val channel = NotificationChannel(
+            SyncNotificationChannelID,
+            getString(R.string.sync_notification_channel_name),
+            NotificationManager.IMPORTANCE_DEFAULT
+        ).apply {
+            description = getString(R.string.sync_notification_channel_description)
+        }
+        // Register the channel with the system
+        val notificationManager: NotificationManager? =
+            getSystemService(Context.NOTIFICATION_SERVICE) as? NotificationManager
+
+        notificationManager?.createNotificationChannel(channel)
+    }
+
+    return NotificationCompat.Builder(
+        this,
+        SyncNotificationChannelID
+    )
+        .setSmallIcon(R.drawable.ic_nia_notification)
+        .setContentTitle(getString(R.string.sync_notification_title))
+        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+        .build()
+}

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/workers/DelegatingWorker.kt

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2022 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.sync.workers
+
+import android.content.Context
+import androidx.hilt.work.HiltWorkerFactory
+import androidx.work.CoroutineWorker
+import androidx.work.Data
+import androidx.work.ForegroundInfo
+import androidx.work.WorkerParameters
+import dagger.hilt.EntryPoint
+import dagger.hilt.InstallIn
+import dagger.hilt.android.EntryPointAccessors
+import dagger.hilt.components.SingletonComponent
+import kotlin.reflect.KClass
+
+/**
+ * An entry point to retrieve the [HiltWorkerFactory] at runtime
+ */
+@EntryPoint
+@InstallIn(SingletonComponent::class)
+interface HiltWorkerFactoryEntryPoint {
+    fun hiltWorkerFactory(): HiltWorkerFactory
+}
+
+private const val WORKER_CLASS_NAME = "RouterWorkerDelegateClassName"
+
+/**
+ * Adds metadata to a WorkRequest to identify what [CoroutineWorker] the [DelegatingWorker] should
+ * delegate to
+ */
+internal fun KClass<out CoroutineWorker>.delegatedData() =
+    Data.Builder()
+        .putString(WORKER_CLASS_NAME, qualifiedName)
+        .build()
+
+/**
+ * A worker that delegates sync to another [CoroutineWorker] constructed with a [HiltWorkerFactory].
+ *
+ * This allows for creating and using [CoroutineWorker] instances with extended arguments
+ * without having to provide a custom WorkManager configuration that the app module needs to utilize.
+ *
+ * In other words, it allows for custom workers in a library module without having to own
+ * configuration of the WorkManager singleton.
+ */
+class DelegatingWorker(
+    appContext: Context,
+    workerParams: WorkerParameters,
+) : CoroutineWorker(appContext, workerParams) {
+
+    private val workerClassName =
+        workerParams.inputData.getString(WORKER_CLASS_NAME) ?: ""
+
+    private val delegateWorker =
+        EntryPointAccessors.fromApplication<HiltWorkerFactoryEntryPoint>(appContext)
+            .hiltWorkerFactory()
+            .createWorker(appContext, workerClassName, workerParams)
+            as? CoroutineWorker
+            ?: throw IllegalArgumentException("Unable to find appropriate worker")
+
+    override suspend fun getForegroundInfo(): ForegroundInfo =
+        delegateWorker.getForegroundInfo()
+
+    override suspend fun doWork(): Result =
+        delegateWorker.doWork()
+}

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/workers/FirstTimeSyncCheckWorker.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2022 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.sync.workers
+
+import android.content.Context
+import androidx.hilt.work.HiltWorker
+import androidx.work.CoroutineWorker
+import androidx.work.ForegroundInfo
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.OutOfQuotaPolicy
+import androidx.work.WorkManager
+import androidx.work.WorkerParameters
+import com.google.samples.apps.nowinandroid.sync.SyncRepository
+import com.google.samples.apps.nowinandroid.sync.initializers.SyncConstraints
+import com.google.samples.apps.nowinandroid.sync.initializers.syncForegroundInfo
+import dagger.assisted.Assisted
+import dagger.assisted.AssistedInject
+
+/**
+ * Checks if the [SyncWorker] has ever run. If it hasn't, it requests one time sync to sync as
+ * quickly as possible, otherwise it does nothing.
+ */
+@HiltWorker
+class FirstTimeSyncCheckWorker @AssistedInject constructor(
+    @Assisted private val appContext: Context,
+    @Assisted workerParams: WorkerParameters,
+    private val syncRepository: SyncRepository,
+) : CoroutineWorker(appContext, workerParams) {
+
+    override suspend fun getForegroundInfo(): ForegroundInfo =
+        appContext.syncForegroundInfo()
+
+    override suspend fun doWork(): Result {
+        if (!syncRepository.shouldRunFirstTimeSync()) return Result.success()
+
+        WorkManager.getInstance(appContext)
+            .enqueue(SyncWorker.firstTimeSyncWork())
+
+        return Result.success()
+    }
+
+    companion object {
+        /**
+         * Work that runs to enqueue an immediate first time sync if the app has yet to sync at all
+         */
+        fun firstTimeSyncCheckWork() = OneTimeWorkRequestBuilder<DelegatingWorker>()
+            .setExpedited(OutOfQuotaPolicy.RUN_AS_NON_EXPEDITED_WORK_REQUEST)
+            .setConstraints(SyncConstraints)
+            .setInputData(FirstTimeSyncCheckWorker::class.delegatedData())
+            .build()
+    }
+}

sync/src/main/java/com/google/samples/apps/nowinandroid/sync/workers/SyncWorker.kt

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2022 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.sync.workers
+
+import android.content.Context
+import androidx.hilt.work.HiltWorker
+import androidx.work.CoroutineWorker
+import androidx.work.ForegroundInfo
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.OutOfQuotaPolicy
+import androidx.work.PeriodicWorkRequestBuilder
+import androidx.work.WorkerParameters
+import com.google.samples.apps.nowinandroid.core.domain.repository.NewsRepository
+import com.google.samples.apps.nowinandroid.core.domain.repository.TopicsRepository
+import com.google.samples.apps.nowinandroid.sync.SyncRepository
+import com.google.samples.apps.nowinandroid.sync.initializers.SyncConstraints
+import com.google.samples.apps.nowinandroid.sync.initializers.syncForegroundInfo
+import dagger.assisted.Assisted
+import dagger.assisted.AssistedInject
+import java.util.concurrent.TimeUnit
+
+/**
+ * Syncs the data layer by delegating to the appropriate repository instances with
+ * sync functionality.
+ */
+@HiltWorker
+class SyncWorker @AssistedInject constructor(
+    @Assisted private val appContext: Context,
+    @Assisted workerParams: WorkerParameters,
+    private val syncRepository: SyncRepository,
+    private val topicRepository: TopicsRepository,
+    private val newsRepository: NewsRepository,
+) : CoroutineWorker(appContext, workerParams) {
+
+    override suspend fun getForegroundInfo(): ForegroundInfo =
+        appContext.syncForegroundInfo()
+
+    override suspend fun doWork(): Result =
+        // First sync the repositories
+        when (topicRepository.sync() && newsRepository.sync()) {
+            // Sync ran successfully, notify the SyncRepository that sync has been run
+            true -> {
+                syncRepository.notifyFirstTimeSyncRun()
+                Result.success()
+            }
+            false -> Result.retry()
+        }
+
+    companion object {
+        private const val SyncInterval = 1L
+        private val SyncIntervalTimeUnit = TimeUnit.DAYS
+
+        /**
+         * Expedited one time work to sync data as quickly as possible because the app has
+         * either launched for the first time, or hasn't had the opportunity to sync at all
+         */
+        fun firstTimeSyncWork() = OneTimeWorkRequestBuilder<DelegatingWorker>()
+            .setExpedited(OutOfQuotaPolicy.RUN_AS_NON_EXPEDITED_WORK_REQUEST)
+            .setConstraints(SyncConstraints)
+            .setInputData(SyncWorker::class.delegatedData())
+            .build()
+
+        /**
+         * Periodic sync work to routinely keep the app up to date
+         */
+        fun periodicSyncWork() = PeriodicWorkRequestBuilder<DelegatingWorker>(
+            SyncInterval,
+            SyncIntervalTimeUnit
+        )
+            .setConstraints(SyncConstraints)
+            .setInputData(SyncWorker::class.delegatedData())
+            .build()
+    }
+}

sync/src/main/res/values/strings.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ Copyright 2022 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.
+  -->
+
+<resources>
+    <string name="sync_notification_title">Now in Android</string>
+    <string name="sync_notification_channel_name">Sync</string>
+    <string name="sync_notification_channel_description">Background tasks for Now in Android</string>
+
+</resources>