Pinned events : start displaying actions in timeline

libraries/core/src/main/kotlin/io/element/android/libraries/core/coroutine/DerivedStateFlow.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2024 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
+ *
+ *     https://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.core.coroutine
+
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.FlowCollector
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
+
+/**
+ * A [StateFlow] that derives its value from a [Flow].
+ * Useful when you want to apply transformations to a [Flow] and expose it as a [StateFlow].
+ */
+class DerivedStateFlow<T>(
+    private val getValue: () -> T,
+    private val flow: Flow<T>
+) : StateFlow<T> {
+
+    override val replayCache: List<T>
+        get() = listOf(value)
+
+    override val value: T
+        get() = getValue()
+
+    override suspend fun collect(collector: FlowCollector<T>): Nothing {
+        coroutineScope { flow.distinctUntilChanged().stateIn(this).collect(collector) }
+    }
+}
+
+/**
+ * Maps the value of a [StateFlow] to a new value and returns a new [StateFlow] with the mapped value.
+ */
+fun <T1, R> StateFlow<T1>.mapState(transform: (a: T1) -> R): StateFlow<R> {
+    return DerivedStateFlow(
+        getValue = { transform(this.value) },
+        flow = this.map { a -> transform(a) }
+    )
+}

libraries/matrix/api/build.gradle.kts

@@ -42,6 +42,7 @@ dependencies {
     implementation(libs.serialization.json)
     api(projects.libraries.sessionStorage.api)
     implementation(libs.coroutines.core)
+    api(projects.libraries.architecture)
 
     testImplementation(libs.test.junit)
     testImplementation(libs.test.truth)

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

@@ -17,14 +17,16 @@
 package io.element.android.libraries.matrix.api.timeline
 
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.first
 
 /**
  * This interface defines a way to get the active timeline.
- * It could be the current room timeline, or a timeline for a specific event.
+ * It could be the live timeline, a pinned timeline or a detached timeline.
+ * By default, the active timeline is the live timeline.
  */
 interface TimelineProvider {
-    fun activeTimelineFlow(): StateFlow<Timeline>
+    fun activeTimelineFlow(): StateFlow<Timeline?>
 }
 
-suspend fun TimelineProvider.getActiveTimeline(): Timeline = activeTimelineFlow().first()
+suspend fun TimelineProvider.getActiveTimeline(): Timeline = activeTimelineFlow().filterNotNull().first()