Fix Timeline not loading (#2398)

* fix cached timeline

* fix network timeline

* delete unused inc / dec extensions

* fix tests and bug in network timeline

* add db migration

* remove unused import

* commit 31.json

* improve placeholder inserting logic, add comment

* fix tests

* improve tests

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

@@ -30,7 +30,6 @@ import com.keylesspalace.tusky.db.TimelineStatusEntity
 import com.keylesspalace.tusky.db.TimelineStatusWithAccount
 import com.keylesspalace.tusky.entity.Status
 import com.keylesspalace.tusky.network.MastodonApi
-import com.keylesspalace.tusky.util.dec
 import kotlinx.coroutines.rx3.await
 import retrofit2.HttpException
 
@@ -102,9 +101,14 @@ class CachedTimelineRemoteMediator(
             db.withTransaction {
                 val overlappedStatuses = replaceStatusRange(statuses, state)
 
-                if (loadType == LoadType.REFRESH && overlappedStatuses == 0 && statuses.isNotEmpty() && !dbEmpty) {
+                /* In case we loaded a whole page and there was no overlap with existing statuses,
+                   we insert a placeholder because there might be even more unknown statuses */
+                if (loadType == LoadType.REFRESH && overlappedStatuses == 0 && statuses.size == state.config.pageSize && !dbEmpty) {
+                    /* This overrides the last of the newly loaded statuses with a placeholder
+                       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.dec(), loading = false).toEntity(activeAccount.id)
+                        Placeholder(statuses.last().id, loading = false).toEntity(activeAccount.id)
                     )
                 }
             }

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

@@ -41,8 +41,6 @@ import com.keylesspalace.tusky.entity.Poll
 import com.keylesspalace.tusky.network.FilterModel
 import com.keylesspalace.tusky.network.MastodonApi
 import com.keylesspalace.tusky.network.TimelineCases
-import com.keylesspalace.tusky.util.dec
-import com.keylesspalace.tusky.util.inc
 import com.keylesspalace.tusky.viewdata.StatusViewData
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.map
@@ -149,9 +147,11 @@ class CachedTimelineViewModel @Inject constructor(
 
                 timelineDao.insertStatus(Placeholder(placeholderId, loading = true).toEntity(activeAccount.id))
 
-                val nextPlaceholderId = timelineDao.getNextPlaceholderIdAfter(activeAccount.id, placeholderId)
-
-                val response = api.homeTimeline(maxId = placeholderId.inc(), sinceId = nextPlaceholderId, limit = LOAD_AT_ONCE).await()
+                val response = db.withTransaction {
+                    val idAbovePlaceholder = timelineDao.getIdAbove(activeAccount.id, placeholderId)
+                    val nextPlaceholderId = timelineDao.getNextPlaceholderIdAfter(activeAccount.id, placeholderId)
+                    api.homeTimeline(maxId = idAbovePlaceholder, sinceId = nextPlaceholderId, limit = LOAD_AT_ONCE)
+                }.await()
 
                 val statuses = response.body()
                 if (!response.isSuccessful || statuses == null) {
@@ -185,9 +185,14 @@ class CachedTimelineViewModel @Inject constructor(
                         )
                     }
 
-                    if (overlappedStatuses == 0 && statuses.isNotEmpty()) {
+                    /* In case we loaded a whole page and there was no overlap with existing statuses,
+                       we insert a placeholder because there might be even more unknown statuses */
+                    if (overlappedStatuses == 0 && statuses.size == LOAD_AT_ONCE) {
+                        /* This overrides the last of the newly loaded statuses with a placeholder
+                           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.dec(), loading = false).toEntity(activeAccount.id)
+                            Placeholder(statuses.last().id, loading = false).toEntity(activeAccount.id)
                         )
                     }
                 }

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

@@ -22,7 +22,6 @@ import androidx.paging.RemoteMediator
 import com.keylesspalace.tusky.components.timeline.util.ifExpected
 import com.keylesspalace.tusky.db.AccountManager
 import com.keylesspalace.tusky.util.HttpHeaderLink
-import com.keylesspalace.tusky.util.dec
 import com.keylesspalace.tusky.util.toViewData
 import com.keylesspalace.tusky.viewdata.StatusViewData
 import retrofit2.HttpException
@@ -93,7 +92,7 @@ class NetworkTimelineRemoteMediator(
                 viewModel.statusData.addAll(0, data)
 
                 if (insertPlaceholder) {
-                    viewModel.statusData.add(statuses.size, StatusViewData.Placeholder(statuses.last().id.dec(), false))
+                    viewModel.statusData[statuses.size - 1] = StatusViewData.Placeholder(statuses.last().id, false)
                 }
             } else {
                 val linkHeader = statusResponse.headers()["Link"]

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

@@ -35,9 +35,7 @@ import com.keylesspalace.tusky.entity.Status
 import com.keylesspalace.tusky.network.FilterModel
 import com.keylesspalace.tusky.network.MastodonApi
 import com.keylesspalace.tusky.network.TimelineCases
-import com.keylesspalace.tusky.util.dec
 import com.keylesspalace.tusky.util.getDomain
-import com.keylesspalace.tusky.util.inc
 import com.keylesspalace.tusky.util.isLessThan
 import com.keylesspalace.tusky.util.isLessThanOrEqual
 import com.keylesspalace.tusky.util.toViewData
@@ -142,8 +140,10 @@ class NetworkTimelineViewModel @Inject constructor(
                     statusData.indexOfFirst { it is StatusViewData.Placeholder && it.id == placeholderId }
                 statusData[placeholderIndex] = StatusViewData.Placeholder(placeholderId, isLoading = true)
 
+                val idAbovePlaceholder = statusData.getOrNull(placeholderIndex - 1)?.id
+
                 val statusResponse = fetchStatusesForKind(
-                    fromId = placeholderId.inc(),
+                    fromId = idAbovePlaceholder,
                     uptoId = null,
                     limit = 20
                 )
@@ -157,7 +157,7 @@ class NetworkTimelineViewModel @Inject constructor(
                 statusData.removeAt(placeholderIndex)
 
                 val activeAccount = accountManager.activeAccount!!
-                val data = statuses.map { status ->
+                val data: MutableList<StatusViewData> = statuses.map { status ->
                     status.toViewData(
                         isShowingContent = activeAccount.alwaysShowSensitiveMedia || !status.actionableStatus.sensitive,
                         isExpanded = activeAccount.alwaysOpenSpoiler,
@@ -175,7 +175,7 @@ class NetworkTimelineViewModel @Inject constructor(
                         data.mapIndexed { i, status -> i to statusData.firstOrNull { it.asStatusOrNull()?.id == status.id }?.asStatusOrNull() }
                             .filter { (_, oldStatus) -> oldStatus != null }
                             .forEach { (i, oldStatus) ->
-                                data[i] = data[i]
+                                data[i] = data[i].asStatusOrNull()!!
                                     .copy(
                                         isShowingContent = oldStatus!!.isShowingContent,
                                         isExpanded = oldStatus.isExpanded,
@@ -190,7 +190,7 @@ class NetworkTimelineViewModel @Inject constructor(
                             }
                         }
                     } else {
-                        statusData.add(overlappedFrom, StatusViewData.Placeholder(statuses.last().id.dec(), isLoading = false))
+                        data[data.size - 1] = StatusViewData.Placeholder(statuses.last().id, isLoading = false)
                     }
                 }
 
@@ -240,7 +240,7 @@ class NetworkTimelineViewModel @Inject constructor(
     }
 
     override fun fullReload() {
-        nextKey = statusData.firstOrNull { it is StatusViewData.Concrete }?.asStatusOrNull()?.id?.inc()
+        nextKey = statusData.firstOrNull { it is StatusViewData.Concrete }?.asStatusOrNull()?.id
         statusData.clear()
         currentSource?.invalidate()
     }