Implement change list invalidation in repositories

Change-Id: I75a1d378089a52eaf84f2fa7b01e54144d69107b

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

@@ -25,6 +25,13 @@ import kotlinx.coroutines.flow.firstOrNull
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.retry
 
+data class ChangeListVersions(
+    val topicVersion: Int = -1,
+    val authorVersion: Int = -1,
+    val episodeVersion: Int = -1,
+    val newsResourceVersion: Int = -1,
+)
+
 class NiaPreferences @Inject constructor(
     private val userPreferences: DataStore<UserPreferences>
 ) {
@@ -81,4 +88,42 @@ class NiaPreferences @Inject constructor(
             Log.e("NiaPreferences", "Failed to update user preferences", ioException)
         }
     }
+
+    suspend fun getChangeListVersions() = userPreferences.data
+        .map {
+            ChangeListVersions(
+                topicVersion = it.topicChangeListVersion,
+                authorVersion = it.authorChangeListVersion,
+                episodeVersion = it.episodeChangeListVersion,
+                newsResourceVersion = it.newsResourceChangeListVersion,
+            )
+        }
+        .firstOrNull() ?: ChangeListVersions()
+
+    /**
+     * Update the [ChangeListVersions] using [update].
+     */
+    suspend fun updateChangeListVersion(update: ChangeListVersions.() -> ChangeListVersions) {
+        try {
+            userPreferences.updateData { currentPreferences ->
+                val updatedChangeListVersions = update(
+                    ChangeListVersions(
+                        topicVersion = currentPreferences.topicChangeListVersion,
+                        authorVersion = currentPreferences.authorChangeListVersion,
+                        episodeVersion = currentPreferences.episodeChangeListVersion,
+                        newsResourceVersion = currentPreferences.newsResourceChangeListVersion
+                    )
+                )
+
+                currentPreferences.copy {
+                    topicChangeListVersion = updatedChangeListVersions.topicVersion
+                    authorChangeListVersion = updatedChangeListVersions.authorVersion
+                    episodeChangeListVersion = updatedChangeListVersions.episodeVersion
+                    newsResourceChangeListVersion = updatedChangeListVersions.newsResourceVersion
+                }
+            }
+        } 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

@@ -22,4 +22,8 @@ option java_multiple_files = true;
 message UserPreferences {
     repeated int32 followed_topic_ids = 1;
     bool has_run_first_time_sync = 2;
+    int32 topicChangeListVersion = 3;
+    int32 authorChangeListVersion = 4;
+    int32 episodeChangeListVersion = 5;
+    int32 newsResourceChangeListVersion = 6;
 }

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

@@ -17,6 +17,9 @@
 package com.google.samples.apps.nowinandroid.core.domain
 
 import android.util.Log
+import com.google.samples.apps.nowinandroid.core.datastore.ChangeListVersions
+import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkChangeList
 import kotlin.coroutines.cancellation.CancellationException
 
 /**
@@ -35,3 +38,36 @@ suspend fun <T> suspendRunCatching(block: suspend () -> T): Result<T> = try {
     )
     Result.failure(exception)
 }
+
+/**
+ * Utility function for syncing a repository with the network.
+ * [versionReader] Reads the current version of the model that needs to be synced
+ * [changeListFetcher] Fetches the change list for the model
+ * [versionUpdater] Updates the [ChangeListVersions] after a successful sync
+ * [modelUpdater] Updates the model by consuming the ids of the models that have changed.
+ *
+ * Note that the blocks defined above may be run concurrently due to concurrent calls
+ * to [changeListSync]. It is the caller's responsibility to make [modelUpdater] performs atomic
+ * operations.
+ */
+suspend fun changeListSync(
+    niaPreferences: NiaPreferences,
+    versionReader: (ChangeListVersions) -> Int,
+    changeListFetcher: suspend (Int) -> List<NetworkChangeList>,
+    versionUpdater: ChangeListVersions.(Int) -> ChangeListVersions,
+    modelUpdater: suspend (List<Int>) -> Unit
+) = suspendRunCatching {
+    // Fetch the change list since last sync (akin to a git fetch)
+    val currentVersion = versionReader(niaPreferences.getChangeListVersions())
+    val changeList = changeListFetcher(currentVersion)
+    if (changeList.isEmpty()) return@suspendRunCatching true
+
+    // Using the change list, pull down and save the changes (akin to a git pull)
+    modelUpdater(changeList.map(NetworkChangeList::id))
+
+    // Update the last synced version (akin to updating local git HEAD)
+    val latestVersion = changeList.last().changeListVersion
+    niaPreferences.updateChangeListVersion {
+        versionUpdater(latestVersion)
+    }
+}.isSuccess

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

@@ -19,8 +19,10 @@ package com.google.samples.apps.nowinandroid.core.domain.repository
 import com.google.samples.apps.nowinandroid.core.database.dao.AuthorDao
 import com.google.samples.apps.nowinandroid.core.database.model.AuthorEntity
 import com.google.samples.apps.nowinandroid.core.database.model.asExternalModel
+import com.google.samples.apps.nowinandroid.core.datastore.ChangeListVersions
+import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
+import com.google.samples.apps.nowinandroid.core.domain.changeListSync
 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.Author
 import com.google.samples.apps.nowinandroid.core.network.NiANetwork
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkAuthor
@@ -34,17 +36,27 @@ import kotlinx.coroutines.flow.map
 class LocalAuthorsRepository @Inject constructor(
     private val authorDao: AuthorDao,
     private val network: NiANetwork,
+    private val niaPreferences: NiaPreferences,
 ) : AuthorsRepository {
 
     override fun getAuthorsStream(): Flow<List<Author>> =
         authorDao.getAuthorEntitiesStream()
             .map { it.map(AuthorEntity::asExternalModel) }
 
-    // TODO: Pass change list for incremental sync. See b/227206738
-    override suspend fun sync(): Boolean = suspendRunCatching {
-        val networkAuthors = network.getAuthors()
-        authorDao.upsertAuthors(
-            entities = networkAuthors.map(NetworkAuthor::asEntity)
-        )
-    }.isSuccess
+    override suspend fun sync(): Boolean = changeListSync(
+        niaPreferences = niaPreferences,
+        versionReader = ChangeListVersions::authorVersion,
+        changeListFetcher = { currentVersion ->
+            network.getAuthorChangeList(after = currentVersion)
+        },
+        versionUpdater = { latestVersion ->
+            copy(authorVersion = latestVersion)
+        },
+        modelUpdater = { changedIds ->
+            val networkAuthors = network.getAuthors(ids = changedIds)
+            authorDao.upsertAuthors(
+                entities = networkAuthors.map(NetworkAuthor::asEntity)
+            )
+        }
+    )
 }

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

@@ -25,13 +25,15 @@ import com.google.samples.apps.nowinandroid.core.database.model.EpisodeEntity
 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.database.model.asExternalModel
+import com.google.samples.apps.nowinandroid.core.datastore.ChangeListVersions
+import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
+import com.google.samples.apps.nowinandroid.core.domain.changeListSync
 import com.google.samples.apps.nowinandroid.core.domain.model.asEntity
 import com.google.samples.apps.nowinandroid.core.domain.model.authorCrossReferences
 import com.google.samples.apps.nowinandroid.core.domain.model.authorEntityShells
 import com.google.samples.apps.nowinandroid.core.domain.model.episodeEntityShell
 import com.google.samples.apps.nowinandroid.core.domain.model.topicCrossReferences
 import com.google.samples.apps.nowinandroid.core.domain.model.topicEntityShells
-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
@@ -48,6 +50,7 @@ class LocalNewsRepository @Inject constructor(
     private val authorDao: AuthorDao,
     private val topicDao: TopicDao,
     private val network: NiANetwork,
+    private val niaPreferences: NiaPreferences,
 ) : NewsRepository {
 
     override fun getNewsResourcesStream(): Flow<List<NewsResource>> =
@@ -58,44 +61,53 @@ class LocalNewsRepository @Inject constructor(
         newsResourceDao.getNewsResourcesStream(filterTopicIds = filterTopicIds)
             .map { it.map(PopulatedNewsResource::asExternalModel) }
 
-    // TODO: Pass change list for incremental sync. See b/227206738
-    override suspend fun sync() = suspendRunCatching {
-        val networkNewsResources = network.getNewsResources()
+    override suspend fun sync() = changeListSync(
+        niaPreferences = niaPreferences,
+        versionReader = ChangeListVersions::newsResourceVersion,
+        changeListFetcher = { currentVersion ->
+            network.getNewsResourceChangeList(after = currentVersion)
+        },
+        versionUpdater = { latestVersion ->
+            copy(newsResourceVersion = latestVersion)
+        },
+        modelUpdater = { changedIds ->
+            val networkNewsResources = network.getNewsResources(ids = changedIds)
 
-        // Order of invocation matters to satisfy id and foreign key constraints!
+            // Order of invocation matters to satisfy id and foreign key constraints!
 
-        topicDao.insertOrIgnoreTopics(
-            topicEntities = networkNewsResources
-                .map(NetworkNewsResource::topicEntityShells)
-                .flatten()
-                .distinctBy(TopicEntity::id)
-        )
-        authorDao.insertOrIgnoreAuthors(
-            authorEntities = networkNewsResources
-                .map(NetworkNewsResource::authorEntityShells)
-                .flatten()
-                .distinctBy(AuthorEntity::id)
-        )
-        episodeDao.insertOrIgnoreEpisodes(
-            episodeEntities = networkNewsResources
-                .map(NetworkNewsResource::episodeEntityShell)
-                .distinctBy(EpisodeEntity::id)
-        )
-        newsResourceDao.upsertNewsResources(
-            newsResourceEntities = networkNewsResources
-                .map(NetworkNewsResource::asEntity)
-        )
-        newsResourceDao.insertOrIgnoreTopicCrossRefEntities(
-            newsResourceTopicCrossReferences = networkNewsResources
-                .map(NetworkNewsResource::topicCrossReferences)
-                .distinct()
-                .flatten()
-        )
-        newsResourceDao.insertOrIgnoreAuthorCrossRefEntities(
-            newsResourceAuthorCrossReferences = networkNewsResources
-                .map(NetworkNewsResource::authorCrossReferences)
-                .distinct()
-                .flatten()
-        )
-    }.isSuccess
+            topicDao.insertOrIgnoreTopics(
+                topicEntities = networkNewsResources
+                    .map(NetworkNewsResource::topicEntityShells)
+                    .flatten()
+                    .distinctBy(TopicEntity::id)
+            )
+            authorDao.insertOrIgnoreAuthors(
+                authorEntities = networkNewsResources
+                    .map(NetworkNewsResource::authorEntityShells)
+                    .flatten()
+                    .distinctBy(AuthorEntity::id)
+            )
+            episodeDao.insertOrIgnoreEpisodes(
+                episodeEntities = networkNewsResources
+                    .map(NetworkNewsResource::episodeEntityShell)
+                    .distinctBy(EpisodeEntity::id)
+            )
+            newsResourceDao.upsertNewsResources(
+                newsResourceEntities = networkNewsResources
+                    .map(NetworkNewsResource::asEntity)
+            )
+            newsResourceDao.insertOrIgnoreTopicCrossRefEntities(
+                newsResourceTopicCrossReferences = networkNewsResources
+                    .map(NetworkNewsResource::topicCrossReferences)
+                    .distinct()
+                    .flatten()
+            )
+            newsResourceDao.insertOrIgnoreAuthorCrossRefEntities(
+                newsResourceAuthorCrossReferences = networkNewsResources
+                    .map(NetworkNewsResource::authorCrossReferences)
+                    .distinct()
+                    .flatten()
+            )
+        }
+    )
 }

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

@@ -19,9 +19,10 @@ 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.ChangeListVersions
 import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
+import com.google.samples.apps.nowinandroid.core.domain.changeListSync
 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.model.NetworkTopic
@@ -35,7 +36,7 @@ import kotlinx.coroutines.flow.map
 class LocalTopicsRepository @Inject constructor(
     private val topicDao: TopicDao,
     private val network: NiANetwork,
-    private val niaPreferences: NiaPreferences
+    private val niaPreferences: NiaPreferences,
 ) : TopicsRepository {
 
     override fun getTopicsStream(): Flow<List<Topic>> =
@@ -53,11 +54,20 @@ class LocalTopicsRepository @Inject constructor(
 
     override fun getFollowedTopicIdsStream() = niaPreferences.followedTopicIds
 
-    // TODO: Pass change list for incremental sync. See b/227206738
-    override suspend fun sync(): Boolean = suspendRunCatching {
-        val networkTopics = network.getTopics()
-        topicDao.upsertTopics(
-            entities = networkTopics.map(NetworkTopic::asEntity)
-        )
-    }.isSuccess
+    override suspend fun sync(): Boolean = changeListSync(
+        niaPreferences = niaPreferences,
+        versionReader = ChangeListVersions::topicVersion,
+        changeListFetcher = { currentVersion ->
+            network.getTopicChangeList(after = currentVersion)
+        },
+        versionUpdater = { latestVersion ->
+            copy(topicVersion = latestVersion)
+        },
+        modelUpdater = { changedIds ->
+            val networkTopics = network.getTopics(ids = changedIds)
+            topicDao.upsertTopics(
+                entities = networkTopics.map(NetworkTopic::asEntity)
+            )
+        }
+    )
 }

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

@@ -19,16 +19,19 @@ package com.google.samples.apps.nowinandroid.core.domain.repository
 import com.google.samples.apps.nowinandroid.core.database.dao.AuthorDao
 import com.google.samples.apps.nowinandroid.core.database.model.AuthorEntity
 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.TestAuthorDao
 import com.google.samples.apps.nowinandroid.core.domain.testdoubles.TestNiaNetwork
-import com.google.samples.apps.nowinandroid.core.network.NiANetwork
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkAuthor
 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 LocalAuthorsRepositoryTest {
 
@@ -36,16 +39,25 @@ class LocalAuthorsRepositoryTest {
 
     private lateinit var authorDao: AuthorDao
 
-    private lateinit var network: NiANetwork
+    private lateinit var network: TestNiaNetwork
+
+    private lateinit var niaPreferences: NiaPreferences
+
+    @get:Rule
+    val tmpFolder: TemporaryFolder = TemporaryFolder.builder().assureDeletion().build()
 
     @Before
     fun setup() {
         authorDao = TestAuthorDao()
         network = TestNiaNetwork()
+        niaPreferences = NiaPreferences(
+            tmpFolder.testUserPreferencesDataStore()
+        )
 
         subject = LocalAuthorsRepository(
             authorDao = authorDao,
             network = network,
+            niaPreferences = niaPreferences,
         )
     }
 
@@ -76,5 +88,41 @@ class LocalAuthorsRepositoryTest {
                 network.map(AuthorEntity::id),
                 db.map(AuthorEntity::id)
             )
+
+            // After sync version should be updated
+            Assert.assertEquals(
+                network.lastIndex,
+                niaPreferences.getChangeListVersions().authorVersion
+            )
+        }
+
+    @Test
+    fun localAuthorsRepository_incremental_sync_pulls_from_network() =
+        runTest {
+            // Set author version to 5
+            niaPreferences.updateChangeListVersion {
+                copy(authorVersion = 5)
+            }
+
+            subject.sync()
+
+            val network = network.getAuthors()
+                .map(NetworkAuthor::asEntity)
+                // Drop 5 to simulate the first 5 items being unchanged
+                .drop(5)
+
+            val db = authorDao.getAuthorEntitiesStream()
+                .first()
+
+            Assert.assertEquals(
+                network.map(AuthorEntity::id),
+                db.map(AuthorEntity::id)
+            )
+
+            // After sync version should be updated
+            Assert.assertEquals(
+                network.lastIndex + 5,
+                niaPreferences.getChangeListVersions().authorVersion
+            )
         }
 }

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

@@ -23,6 +23,8 @@ 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.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.model.authorCrossReferences
 import com.google.samples.apps.nowinandroid.core.domain.model.authorEntityShells
@@ -42,7 +44,9 @@ import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.test.runTest
 import org.junit.Assert.assertEquals
 import org.junit.Before
+import org.junit.Rule
 import org.junit.Test
+import org.junit.rules.TemporaryFolder
 
 class LocalNewsRepositoryTest {
 
@@ -58,6 +62,11 @@ class LocalNewsRepositoryTest {
 
     private lateinit var network: TestNiaNetwork
 
+    private lateinit var niaPreferences: NiaPreferences
+
+    @get:Rule
+    val tmpFolder: TemporaryFolder = TemporaryFolder.builder().assureDeletion().build()
+
     @Before
     fun setup() {
         newsResourceDao = TestNewsResourceDao()
@@ -65,6 +74,9 @@ class LocalNewsRepositoryTest {
         authorDao = TestAuthorDao()
         topicDao = TestTopicDao()
         network = TestNiaNetwork()
+        niaPreferences = NiaPreferences(
+            tmpFolder.testUserPreferencesDataStore()
+        )
 
         subject = LocalNewsRepository(
             newsResourceDao = newsResourceDao,
@@ -72,6 +84,7 @@ class LocalNewsRepositoryTest {
             authorDao = authorDao,
             topicDao = topicDao,
             network = network,
+            niaPreferences = niaPreferences,
         )
     }
 
@@ -122,6 +135,44 @@ class LocalNewsRepositoryTest {
                 newsResourcesFromNetwork.map(NewsResource::id),
                 newsResourcesFromDb.map(NewsResource::id)
             )
+
+            // After sync version should be updated
+            assertEquals(
+                newsResourcesFromNetwork.lastIndex,
+                niaPreferences.getChangeListVersions().newsResourceVersion
+            )
+        }
+
+    @Test
+    fun localNewsRepository_incremental_sync_pulls_from_network() =
+        runTest {
+            // Set news version to 7
+            niaPreferences.updateChangeListVersion {
+                copy(newsResourceVersion = 7)
+            }
+
+            subject.sync()
+
+            val newsResourcesFromNetwork = network.getNewsResources()
+                .map(NetworkNewsResource::asEntity)
+                .map(NewsResourceEntity::asExternalModel)
+                // Drop 7 to simulate the first 7 items being unchanged
+                .drop(7)
+
+            val newsResourcesFromDb = newsResourceDao.getNewsResourcesStream()
+                .first()
+                .map(PopulatedNewsResource::asExternalModel)
+
+            assertEquals(
+                newsResourcesFromNetwork.map(NewsResource::id),
+                newsResourcesFromDb.map(NewsResource::id)
+            )
+
+            // After sync version should be updated
+            assertEquals(
+                newsResourcesFromNetwork.lastIndex + 7,
+                niaPreferences.getChangeListVersions().newsResourceVersion
+            )
         }
 
     @Test

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

@@ -100,6 +100,42 @@ class LocalTopicsRepositoryTest {
                 network.map(TopicEntity::id),
                 db.map(TopicEntity::id)
             )
+
+            // After sync version should be updated
+            Assert.assertEquals(
+                network.lastIndex,
+                niaPreferences.getChangeListVersions().topicVersion
+            )
+        }
+
+    @Test
+    fun localTopicsRepository_incremental_sync_pulls_from_network() =
+        runTest {
+            // Set topics version to 10
+            niaPreferences.updateChangeListVersion {
+                copy(topicVersion = 10)
+            }
+
+            subject.sync()
+
+            val network = network.getTopics()
+                .map(NetworkTopic::asEntity)
+                // Drop 10 to simulate the first 10 items being unchanged
+                .drop(10)
+
+            val db = topicDao.getTopicEntitiesStream()
+                .first()
+
+            Assert.assertEquals(
+                network.map(TopicEntity::id),
+                db.map(TopicEntity::id)
+            )
+
+            // After sync version should be updated
+            Assert.assertEquals(
+                network.lastIndex + 10,
+                niaPreferences.getChangeListVersions().topicVersion
+            )
         }
 
     @Test

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

@@ -19,6 +19,7 @@ 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.NetworkAuthor
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkChangeList
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
 import kotlinx.serialization.decodeFromString
@@ -31,12 +32,68 @@ class TestNiaNetwork : NiANetwork {
 
     private val networkJson = Json
 
-    override suspend fun getTopics(itemsPerPage: Int): List<NetworkTopic> =
-        networkJson.decodeFromString(FakeDataSource.topicsData)
+    override suspend fun getTopics(ids: List<Int>?): List<NetworkTopic> =
+        networkJson.decodeFromString<List<NetworkTopic>>(FakeDataSource.topicsData)
+            .matchIds(
+                ids = ids,
+                idGetter = NetworkTopic::id
+            )
 
-    override suspend fun getAuthors(itemsPerPage: Int): List<NetworkAuthor> =
-        networkJson.decodeFromString(FakeDataSource.authors)
+    override suspend fun getAuthors(ids: List<Int>?): List<NetworkAuthor> =
+        networkJson.decodeFromString<List<NetworkAuthor>>(FakeDataSource.authors)
+            .matchIds(
+                ids = ids,
+                idGetter = NetworkAuthor::id
+            )
 
-    override suspend fun getNewsResources(itemsPerPage: Int): List<NetworkNewsResource> =
-        networkJson.decodeFromString(FakeDataSource.data)
+    override suspend fun getNewsResources(ids: List<Int>?): List<NetworkNewsResource> =
+        networkJson.decodeFromString<List<NetworkNewsResource>>(FakeDataSource.data)
+            .matchIds(
+                ids = ids,
+                idGetter = NetworkNewsResource::id
+            )
+
+    override suspend fun getTopicChangeList(after: Int?): List<NetworkChangeList> =
+        getTopics(ids = null).mapToChangeList(
+            after = after,
+            idGetter = NetworkTopic::id
+        )
+
+    override suspend fun getAuthorChangeList(after: Int?): List<NetworkChangeList> =
+        getAuthors(ids = null).mapToChangeList(
+            after = after,
+            idGetter = NetworkAuthor::id
+        )
+
+    override suspend fun getNewsResourceChangeList(after: Int?): List<NetworkChangeList> =
+        getNewsResources(ids = null).mapToChangeList(
+            after = after,
+            idGetter = NetworkNewsResource::id
+        )
+}
+
+/**
+ * Return items from [this] whose id defined by [idGetter] is in [ids] if [ids] is not null
+ */
+private fun <T> List<T>.matchIds(
+    ids: List<Int>?,
+    idGetter: (T) -> Int
+) = when (ids) {
+    null -> this
+    else -> ids.toSet().let { idSet -> this.filter { idSet.contains(idGetter(it)) } }
 }
+
+/**
+ * Maps items to a change list where the change list version is denoted by the index of each item.
+ * [after] simulates which models have changed by excluding items before it
+ */
+private fun <T> List<T>.mapToChangeList(
+    after: Int?,
+    idGetter: (T) -> Int
+) = mapIndexed { index, item ->
+    NetworkChangeList(
+        id = idGetter(item),
+        changeListVersion = index,
+        isDelete = false,
+    )
+}.drop(after ?: 0)

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

@@ -17,6 +17,7 @@
 package com.google.samples.apps.nowinandroid.core.network
 
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkAuthor
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkChangeList
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
 
@@ -24,9 +25,15 @@ import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
  * Interface representing network calls to the NIA backend
  */
 interface NiANetwork {
-    suspend fun getTopics(itemsPerPage: Int = 200): List<NetworkTopic>
+    suspend fun getTopics(ids: List<Int>? = null): List<NetworkTopic>
 
-    suspend fun getAuthors(itemsPerPage: Int = 200): List<NetworkAuthor>
+    suspend fun getAuthors(ids: List<Int>? = null): List<NetworkAuthor>
 
-    suspend fun getNewsResources(itemsPerPage: Int = 200): List<NetworkNewsResource>
+    suspend fun getNewsResources(ids: List<Int>? = null): List<NetworkNewsResource>
+
+    suspend fun getTopicChangeList(after: Int? = null): List<NetworkChangeList>
+
+    suspend fun getAuthorChangeList(after: Int? = null): List<NetworkChangeList>
+
+    suspend fun getNewsResourceChangeList(after: Int? = null): List<NetworkChangeList>
 }

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

@@ -20,6 +20,7 @@ import com.google.samples.apps.nowinandroid.core.network.Dispatcher
 import com.google.samples.apps.nowinandroid.core.network.NiANetwork
 import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkAuthor
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkChangeList
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
 import javax.inject.Inject
@@ -35,18 +36,41 @@ class FakeNiANetwork @Inject constructor(
     @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
     private val networkJson: Json
 ) : NiANetwork {
-    override suspend fun getTopics(itemsPerPage: Int): List<NetworkTopic> =
+    override suspend fun getTopics(ids: List<Int>?): List<NetworkTopic> =
         withContext(ioDispatcher) {
             networkJson.decodeFromString(FakeDataSource.topicsData)
         }
 
-    override suspend fun getNewsResources(itemsPerPage: Int): List<NetworkNewsResource> =
+    override suspend fun getNewsResources(ids: List<Int>?): List<NetworkNewsResource> =
         withContext(ioDispatcher) {
             networkJson.decodeFromString(FakeDataSource.data)
         }
 
-    override suspend fun getAuthors(itemsPerPage: Int): List<NetworkAuthor> =
+    override suspend fun getAuthors(ids: List<Int>?): List<NetworkAuthor> =
         withContext(ioDispatcher) {
             networkJson.decodeFromString(FakeDataSource.authors)
         }
+
+    override suspend fun getTopicChangeList(after: Int?): List<NetworkChangeList> =
+        getTopics().mapToChangeList(NetworkTopic::id)
+
+    override suspend fun getAuthorChangeList(after: Int?): List<NetworkChangeList> =
+        getAuthors().mapToChangeList(NetworkAuthor::id)
+
+    override suspend fun getNewsResourceChangeList(after: Int?): List<NetworkChangeList> =
+        getNewsResources().mapToChangeList(NetworkNewsResource::id)
+}
+
+/**
+ * Converts a list of [T] to change list of all the items in it where [idGetter] defines the
+ * [NetworkChangeList.id]
+ */
+private fun <T> List<T>.mapToChangeList(
+    idGetter: (T) -> Int
+) = mapIndexed { index, item ->
+    NetworkChangeList(
+        id = idGetter(item),
+        changeListVersion = index,
+        isDelete = false,
+    )
 }

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

@@ -0,0 +1,29 @@
+/*
+ * 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.network.model
+
+import kotlinx.serialization.Serializable
+
+/**
+ * Network representation of a change list for a model
+ */
+@Serializable
+data class NetworkChangeList(
+    val id: Int,
+    val changeListVersion: Int,
+    val isDelete: Boolean,
+)

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

@@ -18,6 +18,7 @@ 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.NetworkAuthor
+import com.google.samples.apps.nowinandroid.core.network.model.NetworkChangeList
 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
@@ -38,18 +39,33 @@ import retrofit2.http.Query
 private interface RetrofitNiANetworkApi {
     @GET(value = "topics")
     suspend fun getTopics(
-        @Query("pageSize") itemsPerPage: Int,
+        @Query("id") ids: List<Int>?,
     ): NetworkResponse<List<NetworkTopic>>
 
     @GET(value = "authors")
     suspend fun getAuthors(
-        @Query("pageSize") itemsPerPage: Int,
+        @Query("id") ids: List<Int>?,
     ): NetworkResponse<List<NetworkAuthor>>
 
     @GET(value = "newsresources")
     suspend fun getNewsResources(
-        @Query("pageSize") itemsPerPage: Int,
+        @Query("id") ids: List<Int>?,
     ): NetworkResponse<List<NetworkNewsResource>>
+
+    @GET(value = "changelists/topics")
+    suspend fun getTopicChangeList(
+        @Query("after") after: Int?,
+    ): List<NetworkChangeList>
+
+    @GET(value = "changelists/authors")
+    suspend fun getAuthorsChangeList(
+        @Query("after") after: Int?,
+    ): List<NetworkChangeList>
+
+    @GET(value = "changelists/newsresources")
+    suspend fun getNewsResourcesChangeList(
+        @Query("after") after: Int?,
+    ): List<NetworkChangeList>
 }
 
 private const val NiABaseUrl = "https://staging-url.com/"
@@ -86,12 +102,21 @@ class RetrofitNiANetwork @Inject constructor(
         .build()
         .create(RetrofitNiANetworkApi::class.java)
 
-    override suspend fun getTopics(itemsPerPage: Int): List<NetworkTopic> =
-        networkApi.getTopics(itemsPerPage = itemsPerPage).data
+    override suspend fun getTopics(ids: List<Int>?): List<NetworkTopic> =
+        networkApi.getTopics(ids = ids).data
+
+    override suspend fun getAuthors(ids: List<Int>?): List<NetworkAuthor> =
+        networkApi.getAuthors(ids = ids).data
+
+    override suspend fun getNewsResources(ids: List<Int>?): List<NetworkNewsResource> =
+        networkApi.getNewsResources(ids = ids).data
+
+    override suspend fun getTopicChangeList(after: Int?): List<NetworkChangeList> =
+        networkApi.getTopicChangeList(after = after)
 
-    override suspend fun getAuthors(itemsPerPage: Int): List<NetworkAuthor> =
-        networkApi.getAuthors(itemsPerPage = itemsPerPage).data
+    override suspend fun getAuthorChangeList(after: Int?): List<NetworkChangeList> =
+        networkApi.getAuthorsChangeList(after = after)
 
-    override suspend fun getNewsResources(itemsPerPage: Int): List<NetworkNewsResource> =
-        networkApi.getNewsResources(itemsPerPage = itemsPerPage).data
+    override suspend fun getNewsResourceChangeList(after: Int?): List<NetworkChangeList> =
+        networkApi.getNewsResourcesChangeList(after = after)
 }