Fix filters in timelines in a simple way, fix #2546 (#2566)

Loading of statuses and loading of filters is an "intended" race:
we want to display statuses first, especially if they are cached.
Unfortunately we do not cache filters themselves so when we load cached
statuses we do not apply filters.

One part of the solution is to re-filter the statuses once we fetch the
filters. This commit implements it. Caching of filters is not included
yet.

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/CachedTimelineViewModel.kt

@@ -21,6 +21,7 @@ import androidx.lifecycle.viewModelScope
 import androidx.paging.ExperimentalPagingApi
 import androidx.paging.Pager
 import androidx.paging.PagingConfig
+import androidx.paging.PagingSource
 import androidx.paging.cachedIn
 import androidx.paging.filter
 import androidx.paging.map
@@ -37,6 +38,7 @@ import com.keylesspalace.tusky.components.timeline.toViewData
 import com.keylesspalace.tusky.components.timeline.util.ifExpected
 import com.keylesspalace.tusky.db.AccountManager
 import com.keylesspalace.tusky.db.AppDatabase
+import com.keylesspalace.tusky.db.TimelineStatusWithAccount
 import com.keylesspalace.tusky.entity.Poll
 import com.keylesspalace.tusky.network.FilterModel
 import com.keylesspalace.tusky.network.MastodonApi
@@ -66,7 +68,16 @@ class CachedTimelineViewModel @Inject constructor(
     filterModel: FilterModel,
     private val db: AppDatabase,
     private val gson: Gson
-) : TimelineViewModel(timelineCases, api, eventHub, accountManager, sharedPreferences, filterModel) {
+) : TimelineViewModel(
+    timelineCases,
+    api,
+    eventHub,
+    accountManager,
+    sharedPreferences,
+    filterModel
+) {
+
+    private var currentPagingSource: PagingSource<Int, TimelineStatusWithAccount>? = null
 
     @OptIn(ExperimentalPagingApi::class)
     override val statuses = Pager(
@@ -78,6 +89,8 @@ class CachedTimelineViewModel @Inject constructor(
                 EmptyTimelinePagingSource()
             } else {
                 db.timelineDao().getStatuses(activeAccount.id)
+            }.also { newPagingSource ->
+                this.currentPagingSource = newPagingSource
             }
         }
     ).flow
@@ -113,13 +126,15 @@ class CachedTimelineViewModel @Inject constructor(
 
     override fun changeContentShowing(isShowing: Boolean, status: StatusViewData.Concrete) {
         viewModelScope.launch {
-            db.timelineDao().setContentShowing(accountManager.activeAccount!!.id, status.id, isShowing)
+            db.timelineDao()
+                .setContentShowing(accountManager.activeAccount!!.id, status.id, isShowing)
         }
     }
 
     override fun changeContentCollapsed(isCollapsed: Boolean, status: StatusViewData.Concrete) {
         viewModelScope.launch {
-            db.timelineDao().setContentCollapsed(accountManager.activeAccount!!.id, status.id, isCollapsed)
+            db.timelineDao()
+                .setContentCollapsed(accountManager.activeAccount!!.id, status.id, isCollapsed)
         }
     }
 
@@ -146,12 +161,21 @@ class CachedTimelineViewModel @Inject constructor(
 
                 val activeAccount = accountManager.activeAccount!!
 
-                timelineDao.insertStatus(Placeholder(placeholderId, loading = true).toEntity(activeAccount.id))
+                timelineDao.insertStatus(
+                    Placeholder(placeholderId, loading = true).toEntity(
+                        activeAccount.id
+                    )
+                )
 
                 val response = db.withTransaction {
                     val idAbovePlaceholder = timelineDao.getIdAbove(activeAccount.id, placeholderId)
-                    val nextPlaceholderId = timelineDao.getNextPlaceholderIdAfter(activeAccount.id, placeholderId)
+                    val nextPlaceholderId =
-                    api.homeTimeline(maxId = idAbovePlaceholder, sinceId = nextPlaceholderId, limit = LOAD_AT_ONCE)
+                        timelineDao.getNextPlaceholderIdAfter(activeAccount.id, placeholderId)
+                    api.homeTimeline(
+                        maxId = idAbovePlaceholder,
+                        sinceId = nextPlaceholderId,
+                        limit = LOAD_AT_ONCE
+                    )
                 }.await()
 
                 val statuses = response.body()
@@ -165,14 +189,19 @@ class CachedTimelineViewModel @Inject constructor(
                     timelineDao.delete(activeAccount.id, placeholderId)
 
                     val overlappedStatuses = if (statuses.isNotEmpty()) {
-                        timelineDao.deleteRange(activeAccount.id, statuses.last().id, statuses.first().id)
+                        timelineDao.deleteRange(
+                            activeAccount.id,
+                            statuses.last().id,
+                            statuses.first().id
+                        )
                     } else {
                         0
                     }
 
                     for (status in statuses) {
                         timelineDao.insertAccount(status.account.toEntity(activeAccount.id, gson))
-                        status.reblog?.account?.toEntity(activeAccount.id, gson)?.let { rebloggedAccount ->
+                        status.reblog?.account?.toEntity(activeAccount.id, gson)
+                            ?.let { rebloggedAccount ->
                                 timelineDao.insertAccount(rebloggedAccount)
                             }
                         timelineDao.insertStatus(
@@ -193,7 +222,10 @@ class CachedTimelineViewModel @Inject constructor(
                            to guarantee the placeholder has an id that exists on the server as not all
                            servers handle client generated ids as expected */
                         timelineDao.insertStatus(
-                            Placeholder(statuses.last().id, loading = false).toEntity(activeAccount.id)
+                            Placeholder(
+                                statuses.last().id,
+                                loading = false
+                            ).toEntity(activeAccount.id)
                         )
                     }
                 }
@@ -208,7 +240,8 @@ class CachedTimelineViewModel @Inject constructor(
     private suspend fun loadMoreFailed(placeholderId: String, e: Exception) {
         Log.w("CachedTimelineVM", "failed loading statuses", e)
         val activeAccount = accountManager.activeAccount!!
-        db.timelineDao().insertStatus(Placeholder(placeholderId, loading = false).toEntity(activeAccount.id))
+        db.timelineDao()
+            .insertStatus(Placeholder(placeholderId, loading = false).toEntity(activeAccount.id))
     }
 
     override fun handleReblogEvent(reblogEvent: ReblogEvent) {
@@ -234,6 +267,10 @@ class CachedTimelineViewModel @Inject constructor(
         }
     }
 
+    override fun invalidate() {
+        currentPagingSource?.invalidate()
+    }
+
     companion object {
         private const val MAX_STATUSES_IN_CACHE = 1000
     }

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/NetworkTimelineViewModel.kt

@@ -249,6 +249,10 @@ class NetworkTimelineViewModel @Inject constructor(
         currentSource?.invalidate()
     }
 
+    override fun invalidate() {
+        currentSource?.invalidate()
+    }
+
     @Throws(IOException::class, HttpException::class)
     suspend fun fetchStatusesForKind(
         fromId: String?,

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/TimelineViewModel.kt

@@ -173,6 +173,9 @@ abstract class TimelineViewModel(
 
     abstract fun fullReload()
 
+    /** Triggered when currently displayed data must be reloaded. */
+    protected abstract fun invalidate()
+
     protected fun shouldFilterStatus(statusViewData: StatusViewData): Boolean {
         val status = statusViewData.asStatusOrNull()?.status ?: return false
         return status.inReplyToId != null && filterRemoveReplies ||
@@ -288,6 +291,9 @@ abstract class TimelineViewModel(
                     filterContextMatchesKind(kind, it.context)
                 }
             )
+            // After the filters are loaded we need to reload displayed content to apply them.
+            // It can happen during the usage or at startup, when we get statuses before filters.
+            invalidate()
         }
     }