Timeline: avoid pagination when timeline is not ready

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/CannotPaginateException.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * 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
+ *
+ *     http://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 io.element.android.libraries.matrix.api.timeline
+
+sealed class TimelineException: Exception() {
+    object CannotPaginate: TimelineException()
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/MatrixTimeline.kt

@@ -24,8 +24,10 @@ interface MatrixTimeline {
 
     data class PaginationState(
         val isBackPaginating: Boolean,
-        val canBackPaginate: Boolean
-    )
+        val hasMoreToLoadBackwards: Boolean
+    ) {
+        val canBackPaginate = !isBackPaginating && hasMoreToLoadBackwards
+    }
 
     val paginationState: StateFlow<PaginationState>
     val timelineItems: Flow<List<MatrixTimelineItem>>