Document [TimelineItemGroupPosition] and improve preview of [MessageEventBubble].

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineStateProvider.kt

@@ -94,7 +94,7 @@ internal fun aTimelineItemEvent(
     eventId: EventId = EventId("\$" + Random.nextInt().toString()),
     isMine: Boolean = false,
     content: TimelineItemEventContent = aTimelineItemTextContent(),
-    groupPosition: TimelineItemGroupPosition = TimelineItemGroupPosition.First,
+    groupPosition: TimelineItemGroupPosition = TimelineItemGroupPosition.None,
     sendState: EventSendState = EventSendState.Sent(eventId),
 ): TimelineItem.Event {
     return TimelineItem.Event(

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/MessageEventBubble.kt

@@ -20,7 +20,6 @@ import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.interaction.MutableInteractionSource
 import androidx.compose.foundation.layout.Box
-import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
@@ -35,13 +34,16 @@ import androidx.compose.ui.graphics.Shape
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
 import io.element.android.features.messages.impl.timeline.model.TimelineItemGroupPosition
 import io.element.android.features.messages.impl.timeline.model.bubble.BubbleState
 import io.element.android.features.messages.impl.timeline.model.bubble.BubbleStateProvider
+import io.element.android.libraries.core.extensions.to01
 import io.element.android.libraries.designsystem.preview.ElementPreviewDark
 import io.element.android.libraries.designsystem.preview.ElementPreviewLight
 import io.element.android.libraries.designsystem.theme.ElementTheme
 import io.element.android.libraries.designsystem.theme.components.Surface
+import io.element.android.libraries.designsystem.theme.components.Text
 
 private val BUBBLE_RADIUS = 16.dp
 
@@ -141,7 +143,14 @@ private fun ContentToPreview(state: BubbleState) {
             state = state,
             interactionSource = MutableInteractionSource(),
         ) {
-            Spacer(modifier = Modifier.size(width = 120.dp, height = 32.dp))
+            // Render the state as a text to better understand the previews
+            Text(
+                modifier = Modifier
+                    .size(width = 120.dp, height = 32.dp)
+                    .padding(horizontal = 12.dp, vertical = 6.dp),
+                fontSize = 10.sp,
+                text = "${state.groupPosition.javaClass.simpleName} m:${state.isMine.to01()} h:${state.isHighlighted.to01()}"
+            )
         }
     }
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/factories/event/TimelineItemEventFactory.kt

@@ -105,7 +105,7 @@ class TimelineItemEventFactory @Inject constructor(
         return when {
             previousSender != currentSender && nextSender == currentSender -> TimelineItemGroupPosition.First
             previousSender == currentSender && nextSender == currentSender -> TimelineItemGroupPosition.Middle
-            previousSender == currentSender && nextSender != currentSender -> TimelineItemGroupPosition.Last
+            previousSender == currentSender /* && nextSender != currentSender (== true) */ -> TimelineItemGroupPosition.Last
             else -> TimelineItemGroupPosition.None
         }
     }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/TimelineItemGroupPosition.kt

@@ -18,13 +18,48 @@ package io.element.android.features.messages.impl.timeline.model
 
 import androidx.compose.runtime.Immutable
 
+/**
+ * Attribute for a TimelineItem, used to render successive events from the same sender differently.
+ *
+ * Possible sequences in the timeline will be:
+ *
+ * Only one Event:
+ * - [None]
+ *
+ * Two Events
+ * - [First]
+ * - [Last]
+ *
+ * Many Events:
+ * - [First]
+ * - [Middle] (repeated if necessary)
+ * - [Last]
+ */
 @Immutable
 sealed interface TimelineItemGroupPosition {
+    /**
+     * The event is part of a group of events from the same sender and is the first sent Event.
+     */
     object First : TimelineItemGroupPosition
+
+    /**
+     * The event is part of a group of events from the same sender and is neither the first nor the last sent Event.
+     */
     object Middle : TimelineItemGroupPosition
+
+    /**
+     * The event is part of a group of events from the same sender and is the last sent Event.
+     */
     object Last : TimelineItemGroupPosition
+
+    /**
+     * The event is not part of a group of events. Sender of previous event is different, and sender of next event is different.
+     */
     object None : TimelineItemGroupPosition
 
+    /**
+     * Return true if the previous sender of the event is a different sender.
+     */
     fun isNew(): Boolean = when (this) {
         First, None -> true
         else -> false

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/bubble/BubbleStateProvider.kt

@@ -25,6 +25,7 @@ open class BubbleStateProvider : PreviewParameterProvider<BubbleState> {
             TimelineItemGroupPosition.First,
             TimelineItemGroupPosition.Middle,
             TimelineItemGroupPosition.Last,
+            TimelineItemGroupPosition.None,
         ).map { groupPosition ->
             sequenceOf(false, true).map { isMine ->
                 sequenceOf(false, true).map { isHighlighted ->

libraries/core/src/main/kotlin/io/element/android/libraries/core/extensions/BasicExtensions.kt

@@ -17,6 +17,7 @@
 package io.element.android.libraries.core.extensions
 
 fun Boolean.toOnOff() = if (this) "ON" else "OFF"
+fun Boolean.to01() = if (this) "1" else "0"
 
 inline fun <T> T.ooi(block: (T) -> Unit): T = also(block)