android, desktop, ios: simplify pending-invitee preview selection

Collapse the four nested branches in addChatItem's preview pick into a
single "keep the current preview" predicate: the new item wins by default,
and only the comparison criterion changes for a pending invitee. Same
behaviour, addresses review feedback (4 branches for 2 outcomes).

apps/ios/Shared/Model/ChatModel.swift

@@ -658,24 +658,17 @@ final class ChatModel: ObservableObject {
         if let i = getChatIndex(cInfo.id) {
             // update preview
             if cInfo.groupChatScope() == nil || cInfo.groupInfo?.membership.memberPending ?? false {
-                chats[i].chatItems = switch cInfo {
-                case .group:
-                    if let currentPreviewItem = chats[i].chatItems.first {
-                        // Pending invitee: surface the latest support message (broker vs local itemTs
-                        // aren't comparable); don't let a no-content event re-cover an already-shown message.
-                        if cInfo.groupInfo?.membership.memberPending ?? false {
-                            (cItem.content.msgContent != nil || currentPreviewItem.content.msgContent == nil) ? [cItem] : [currentPreviewItem]
-                        } else if cItem.meta.itemTs >= currentPreviewItem.meta.itemTs {
-                            [cItem]
-                        } else {
-                            [currentPreviewItem]
-                        }
-                    } else {
-                        [cItem]
-                    }
-                default:
-                    [cItem]
+                let memberPending = cInfo.groupInfo?.membership.memberPending ?? false
+                let currentPreviewItem: ChatItem? = if case .group = cInfo { chats[i].chatItems.first } else { nil }
+                // the new item becomes the preview unless it is older - or, for a pending invitee, unless it is
+                // a no-content event that would re-cover an already shown support message (broker vs local
+                // itemTs aren't comparable there, so content presence is the criterion instead)
+                let keptPreviewItem = currentPreviewItem.flatMap { current in
+                    (memberPending
+                     ? cItem.content.msgContent == nil && current.content.msgContent != nil
+                     : cItem.meta.itemTs < current.meta.itemTs) ? current : nil
                 }
+                chats[i].chatItems = [keptPreviewItem ?? cItem]
                 if case .rcvNew = cItem.meta.itemStatus {
                     unreadCollector.changeUnreadCounter(cInfo.id, by: 1, unreadMentions: cItem.meta.userMention ? 1 : 0)
                 }

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/model/ChatModel.kt

@@ -541,26 +541,15 @@ object ChatModel {
         chat = chats[i]
         // update preview (for chat from main scope to show new items for invitee in pending status)
         if (cInfo.groupChatScope() == null || cInfo.groupInfo_?.membership?.memberPending == true) {
-          val newPreviewItem = when (cInfo) {
-            is ChatInfo.Group -> {
-              val currentPreviewItem = chat.chatItems.firstOrNull()
-              if (currentPreviewItem != null) {
-                // Pending invitee: surface the latest support message (broker vs local itemTs aren't
-                // comparable); don't let a no-content event re-cover an already-shown message.
-                if (cInfo.groupInfo_?.membership?.memberPending == true) {
-                  if (cItem.content.msgContent != null || currentPreviewItem.content.msgContent == null) cItem else currentPreviewItem
-                } else if (cItem.meta.itemTs >= currentPreviewItem.meta.itemTs) {
-                  cItem
-                } else {
-                  currentPreviewItem
-                }
-              } else {
-                cItem
-              }
-            }
-
-            else -> cItem
-          }
+          val memberPending = cInfo.groupInfo_?.membership?.memberPending == true
+          val currentPreviewItem = if (cInfo is ChatInfo.Group) chat.chatItems.firstOrNull() else null
+          // the new item becomes the preview unless it is older - or, for a pending invitee, unless it is
+          // a no-content event that would re-cover an already shown support message (broker vs local
+          // itemTs aren't comparable there, so content presence is the criterion instead)
+          val newPreviewItem = currentPreviewItem?.takeIf {
+            if (memberPending) cItem.content.msgContent == null && it.content.msgContent != null
+            else cItem.meta.itemTs < it.meta.itemTs
+          } ?: cItem
           val wasUnread = chat.unreadTag
           chats[i] = chat.copy(
             chatItems = arrayListOf(newPreviewItem),

plans/2026-06-13-fix-wrong-chat-preview-addchatitem.md

@@ -158,11 +158,14 @@ Sent items win only because their `itemTs` is the same device's local clock.
 
 **Fix (two parts):** for a pending invitee, (1) **bypass the cross-clock comparison** so the
 support message surfaces, and (2) **prefer a message over a no-content event** so an event can't
-re-cover an already-shown message (Kotlin + iOS):
+re-cover an already-shown message (Kotlin + iOS). Expressed as a single *keep the current
+preview* predicate — the new item wins by default, and only the criterion for keeping the old
+one changes with `memberPending` (no extra branches per outcome):
 ```
-if (memberPending)
-  if (cItem.content.msgContent != null || currentPreviewItem.content.msgContent == null) cItem else currentPreviewItem
-else if (cItem.meta.itemTs >= currentPreviewItem.meta.itemTs) cItem else currentPreviewItem
+newPreviewItem = currentPreviewItem?.takeIf {
+  if (memberPending) cItem.content.msgContent == null && it.content.msgContent != null
+  else cItem.meta.itemTs < it.meta.itemTs
+} ?: cItem
 ```
 Part (2) (`5b37cf881`) fixes a follow-up symptom — **"reviewed by admins" reappearing after the
 first message**: a pending invitee's member-support no-content events arrive as new chat items in