Refresh News-Topics cross references according to the data loaded from network

Change-Id: Ic0fa18ccf53828d6333dc8d4d797ad9f2770fb5e

core/data/src/main/java/com/google/samples/apps/nowinandroid/core/data/repository/OfflineFirstNewsRepository.kt

@@ -99,6 +99,9 @@ class OfflineFirstNewsRepository @Inject constructor(
                     niaPreferencesDataSource.setNewsResourcesViewed(changedIds, true)
                 }
 
+                // Fetch all the cross references
+                val allCrossReferences = newsResourceDao.fetchAllCrossReferences()
+
                 // Obtain the news resources which have changed from the network and upsert them locally
                 changedIds.chunked(SYNC_BATCH_SIZE).forEach { chunkedIds ->
                     val networkNewsResources = network.getNewsResources(ids = chunkedIds)
@@ -116,12 +119,22 @@ class OfflineFirstNewsRepository @Inject constructor(
                             NetworkNewsResource::asEntity,
                         ),
                     )
+
+                    val dataDiff = allCrossReferences.subtract(
+                        networkNewsResources.map(NetworkNewsResource::topicCrossReferences)
+                            .distinct()
+                            .flatten()
+                            .toSet()
+                    )
+
                     newsResourceDao.insertOrIgnoreTopicCrossRefEntities(
                         newsResourceTopicCrossReferences = networkNewsResources
                             .map(NetworkNewsResource::topicCrossReferences)
                             .distinct()
                             .flatten(),
                     )
+
+                    newsResourceDao.deleteCrossReferences(dataDiff.toList())
                 }
 
                 if (hasOnboarded) {

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

@@ -17,6 +17,7 @@
 package com.google.samples.apps.nowinandroid.core.database.dao
 
 import androidx.room.Dao
+import androidx.room.Delete
 import androidx.room.Insert
 import androidx.room.OnConflictStrategy
 import androidx.room.Query
@@ -113,6 +114,12 @@ interface NewsResourceDao {
         newsResourceTopicCrossReferences: List<NewsResourceTopicCrossRef>,
     )
 
+    @Query("SELECT * from news_resources_topics")
+    suspend fun fetchAllCrossReferences(): List<NewsResourceTopicCrossRef>
+
+    @Delete
+    suspend fun deleteCrossReferences(list: List<NewsResourceTopicCrossRef>)
+
     /**
      * Deletes rows in the db matching the specified [ids]
      */