Add collection count flow to invalidate pagers by recreation

Signed-off-by: Sunik Kupfer <kupfer@bitfire.at>

app/src/main/kotlin/at/bitfire/davdroid/db/CollectionDao.kt

@@ -69,6 +69,12 @@ interface CollectionDao {
     @Query("SELECT * FROM collection WHERE serviceId=:serviceId AND url=:url")
     fun getByServiceAndUrl(serviceId: Long, url: String): Collection?
 
+    /**
+     * Returns the amount of collections currently stored in database
+     */
+    @Query("SELECT COUNT(*) FROM collection")
+    fun getCountFlow(): Flow<Int>
+
     @Query("SELECT * FROM collection WHERE serviceId=:serviceId AND type='${Collection.TYPE_CALENDAR}' AND supportsVEVENT AND sync ORDER BY displayName COLLATE NOCASE, url COLLATE NOCASE")
     fun getSyncCalendars(serviceId: Long): List<Collection>
 

app/src/main/kotlin/at/bitfire/davdroid/repository/DavCollectionRepository.kt

@@ -27,6 +27,7 @@ import at.bitfire.davdroid.servicedetection.RefreshCollectionsWorker
 import at.bitfire.davdroid.util.DavUtils
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.runInterruptible
 import net.fortuna.ical4j.model.Calendar
 import net.fortuna.ical4j.model.Component
@@ -196,6 +197,8 @@ class DavCollectionRepository @Inject constructor(
 
     fun getByServiceAndSync(serviceId: Long) = dao.getByServiceAndSync(serviceId)
 
+    fun getCollectionCountFlow(): Flow<Int> = dao.getCountFlow()
+
     fun getSyncCalendars(serviceId: Long) = dao.getSyncCalendars(serviceId)
 
     fun getSyncJtxCollections(serviceId: Long) = dao.getSyncJtxCollections(serviceId)

app/src/main/kotlin/at/bitfire/davdroid/ui/account/GetServiceCollectionPagerUseCase.kt

@@ -23,7 +23,8 @@ import kotlinx.coroutines.flow.map
 import javax.inject.Inject
 
 /**
- * Gets a list of collections for a service and type, optionally filtered by "show only personal" setting.
+ * Gets PagingData flow of collections for a service and type, optionally filtered by "show only personal" setting and
+ * recreates (invalidates) pagers when collection count changes.
  *
  * Takes the "force read-only address books" setting into account: if set, all address books will have "forceReadOnly" set.
  */
@@ -32,12 +33,9 @@ class GetServiceCollectionPagerUseCase @Inject constructor(
     val settings: SettingsManager
 ) {
 
-    companion object {
-        const val PAGER_SIZE = 20
-    }
-
     val forceReadOnlyAddressBooksFlow = settings.getBooleanFlow(Settings.FORCE_READ_ONLY_ADDRESSBOOKS, false)
 
+    val collectionsCount = collectionRepository.getCollectionCountFlow()
 
     @OptIn(ExperimentalCoroutinesApi::class)
     operator fun invoke(
@@ -45,7 +43,12 @@ class GetServiceCollectionPagerUseCase @Inject constructor(
         @CollectionType collectionType: String,
         showOnlyPersonalFlow: Flow<Boolean>
     ): Flow<PagingData<Collection>> =
-        combine(serviceFlow, showOnlyPersonalFlow, forceReadOnlyAddressBooksFlow) { service, onlyPersonal, forceReadOnlyAddressBooks ->
+        combine(
+            serviceFlow,
+            showOnlyPersonalFlow,
+            forceReadOnlyAddressBooksFlow,
+            collectionsCount // triggers pager recreation when collection amount changes in DB
+        ) { service, onlyPersonal, forceReadOnlyAddressBooks, _ ->
             service?.let { service ->
                 val dataFlow = Pager(
                     config = PagingConfig(PAGER_SIZE),
@@ -69,4 +72,8 @@ class GetServiceCollectionPagerUseCase @Inject constructor(
             } ?: flowOf(PagingData.empty())
         }.flatMapLatest { it }
 
+    companion object {
+        const val PAGER_SIZE = 20
+    }
+
 }