quoted message alert

apps/ios/Shared/Model/SimpleXAPI.swift

@@ -322,13 +322,13 @@ let loadItemsPerPage = 50
 
 func apiGetChat(type: ChatType, id: Int64, search: String = "") async throws -> Chat {
     let r = await chatSendCmd(.apiGetChat(type: type, id: id, pagination: .last(count: loadItemsPerPage), search: search))
-    if case let .apiChat(_, chat) = r { return Chat.init(chat) }
+    if case let .apiChat(_, chat, _) = r { return Chat.init(chat) }
     throw r
 }
 
 func apiGetChatItems(type: ChatType, id: Int64, pagination: ChatPagination, search: String = "") async throws -> [ChatItem] {
     let r = await chatSendCmd(.apiGetChat(type: type, id: id, pagination: pagination, search: search))
-    if case let .apiChat(_, chat) = r { return chat.chatItems }
+    if case let .apiChat(_, chat, _) = r { return chat.chatItems }
     throw r
 }
 

apps/ios/Shared/Views/Chat/ChatItem/FramedItemView.swift

@@ -13,6 +13,7 @@ struct FramedItemView: View {
     @EnvironmentObject var m: ChatModel
     @EnvironmentObject var theme: AppTheme
     @EnvironmentObject var scrollModel: ReverseListScrollModel
+    @EnvironmentObject var sectionModel: ReverseListSectionModel
     @ObservedObject var chat: Chat
     var chatItem: ChatItem
     var preview: UIImage?
@@ -46,12 +47,43 @@ struct FramedItemView: View {
                 }
 
                 if let qi = chatItem.quotedItem {
+                    let notFoundItemTitle = NSLocalizedString("Message no longer available", comment: "alert title")
+                    let notFoundItemMessage = NSLocalizedString("The quoted message you are trying to view has been deleted.", comment: "alert message")
+
                     ciQuoteView(qi)
                         .onTapGesture {
-                            if let ci = ItemsModel.shared.reversedChatItems.first(where: { $0.id == qi.itemId }) {
+                            if let itemId = qi.itemId {
-                                withAnimation {
+                                Task {
-                                    scrollModel.scrollToItem(id: ci.id)
+                                    if let reversedPage = await loadItemsAround(chat.chatInfo, itemId) {
+                                        await MainActor.run {
+                                            let im = ItemsModel.shared
+                                            let reversedPageToAppend = self.sectionModel.handleSectionInsertion(
+                                                candidateSection: .destination,
+                                                reversedPage: reversedPage,
+                                                allItems: im.reversedChatItems
+                                            )
+                                            im.reversedChatItems.append(contentsOf: reversedPageToAppend)
+                                            
+                                            withAnimation {
+                                                scrollModel.scrollToItem(id: itemId)
+                                            }
+                                        }
+                                    } else {
+                                        AlertManager.shared.showAlert(
+                                            Alert(
+                                                title: Text(notFoundItemTitle),
+                                                message: Text(notFoundItemMessage)
+                                            )
+                                        )
+                                    }
                                 }
+                            } else {
+                                AlertManager.shared.showAlert(
+                                    Alert(
+                                        title: Text(notFoundItemTitle),
+                                        message: Text(notFoundItemMessage)
+                                    )
+                                )
                             }
                         }
                 } else if let itemForwarded = chatItem.meta.itemForwarded {

apps/ios/Shared/Views/Chat/ChatView.swift

@@ -23,6 +23,7 @@ struct ChatView: View {
     @Environment(\.scenePhase) var scenePhase
     @State @ObservedObject var chat: Chat
     @StateObject private var scrollModel = ReverseListScrollModel()
+    @StateObject private var sectionModel = ReverseListSectionModel()
     @State private var showChatInfoSheet: Bool = false
     @State private var showAddMembersSheet: Bool = false
     @State private var composeState = ComposeState()
@@ -31,7 +32,6 @@ struct ChatView: View {
     @State private var customUserProfile: Profile?
     @State private var connectionCode: String?
     @State private var loadingItems = false
-    @State private var firstPage = false
     @State private var revealedChatItem: ChatItem?
     @State private var searchMode = false
     @State private var searchText: String = ""
@@ -168,7 +168,6 @@ struct ChatView: View {
         .onChange(of: chatModel.chatId) { cId in
             showChatInfoSheet = false
             selectedChatItems = nil
-            scrollModel.scrollToBottom()
             stopAudioPlayer()
             if let cId {
                 if let c = chatModel.getChat(cId) {
@@ -187,10 +186,11 @@ struct ChatView: View {
             if !isLoading,
                im.reversedChatItems.count <= loadItemsPerPage,
                filtered(im.reversedChatItems).count < 10 {
-                loadChatItems(chat.chatInfo)
+                loadChatItems(chat.chatInfo, .toOldest, .bottom, nil)
             }
         }
         .environmentObject(scrollModel)
+        .environmentObject(sectionModel)
         .onDisappear {
             VideoPlayerView.players.removeAll()
             stopAudioPlayer()
@@ -363,6 +363,34 @@ struct ChatView: View {
             }
         }
         ChatView.FloatingButtonModel.shared.totalUnread = chat.chatStats.unreadCount
+        sectionModel.resetSections(items: im.reversedChatItems)
+        
+        let minUnreadItemId = chat.chatStats.minUnreadItemId
+        if minUnreadItemId > 0 {
+            if im.reversedChatItems.contains(where: { $0.id == minUnreadItemId }) {
+                withAnimation {
+                    scrollModel.scrollToItem(id: minUnreadItemId, position: .middle)
+                }
+            } else {
+                Task {
+                    if let reversedPage = await loadItemsAround(chat.chatInfo, minUnreadItemId) {
+                        await MainActor.run {
+                            let reversedPageToAppend = self.sectionModel.handleSectionInsertion(
+                                candidateSection: .current,
+                                reversedPage: reversedPage,
+                                allItems: im.reversedChatItems
+                            )
+                            im.reversedChatItems.append(contentsOf: reversedPageToAppend)
+                            withAnimation {
+                                scrollModel.scrollToItem(id: minUnreadItemId, position: .middle, animated: false)
+                            }
+                        }
+                    }
+                }
+            }
+        } else {
+            scrollModel.scrollToBottom()
+        }
     }
 
     private func searchToolbar() -> some View {
@@ -400,25 +428,11 @@ struct ChatView: View {
         ci.content.msgContent?.isVoice == true && ci.content.text.count == 0 && ci.quotedItem == nil && ci.meta.itemForwarded == nil
     }
 
-    private func filtered(_ reversedChatItems: Array<ChatItem>) -> Array<ChatItem> {
-        reversedChatItems
-            .enumerated()
-            .filter { (index, chatItem) in
-                if let mergeCategory = chatItem.mergeCategory, index > 0 {
-                    mergeCategory != reversedChatItems[index - 1].mergeCategory
-                } else {
-                    true
-                }
-            }
-            .map { $0.element }
-    }
-
-
     private func chatItemsList() -> some View {
         let cInfo = chat.chatInfo
         let mergedItems = filtered(im.reversedChatItems)
         return GeometryReader { g in
-            ReverseList(items: mergedItems, scrollState: $scrollModel.state) { ci in
+            ReverseList(items: mergedItems, scrollState: $scrollModel.state, sectionModel: sectionModel) { ci in
                 let voiceNoFrame = voiceWithoutFrame(ci)
                 let maxWidth = cInfo.chatType == .group
                                 ? voiceNoFrame
@@ -438,18 +452,22 @@ struct ChatView: View {
                     forwardedChatItems: $forwardedChatItems
                 )
                 .id(ci.id) // Required to trigger `onAppear` on iOS15
-            } loadPage: {
+            } loadPage: { (direction, section, chatItemId) in
-                loadChatItems(cInfo)
+                loadChatItems(cInfo, direction, section, chatItemId)
             }
             .opacity(ItemsModel.shared.isLoading ? 0 : 1)
             .padding(.vertical, -InvertedTableView.inset)
             .onTapGesture { hideKeyboard() }
             .onChange(of: searchText) { _ in
-                Task { await loadChat(chat: chat, search: searchText) }
+                Task {
+                    await loadChat(chat: chat, search: searchText)
+                    sectionModel.resetSections(items: im.reversedChatItems)
+                }
             }
             .onChange(of: im.itemAdded) { added in
                 if added {
                     im.itemAdded = false
+                    sectionModel.resetSections(items: im.reversedChatItems)
                     if FloatingButtonModel.shared.isReallyNearBottom {
                         scrollModel.scrollToBottom()
                     }
@@ -839,9 +857,17 @@ struct ChatView: View {
         }
     }
     
-    private func loadChatItems(_ cInfo: ChatInfo) {
+    private func boundaryReached(_ direction: ChatScrollDirection) -> Bool {
+        return (direction == .toLatest && sectionModel.boundaries.latest) || (direction == .toOldest && sectionModel.boundaries.oldest)
+    }
+    
+    private func setBoundary(_ direction: ChatScrollDirection) {
+        direction == .toLatest ? (sectionModel.boundaries.latest = true) : (sectionModel.boundaries.oldest = true)
+    }
+
+    private func loadChatItems(_ cInfo: ChatInfo, _ direction: ChatScrollDirection, _ section: ChatSection, _ chatItem: ChatItem?) {
         Task {
-            if loadingItems || firstPage { return }
+            if loadingItems || boundaryReached(direction)  { return }
             loadingItems = true
             do {
                 var reversedPage = Array<ChatItem>()
@@ -849,11 +875,14 @@ struct ChatView: View {
                 // Load additional items until the page is +50 large after merging
                 while chatItemsAvailable && filtered(reversedPage).count < loadItemsPerPage {
                     let pagination: ChatPagination =
-                        if let lastItem = reversedPage.last ?? im.reversedChatItems.last {
+                    if direction == .toOldest, let lastItem = chatItem ?? reversedPage.last ?? im.reversedChatItems.last {
-                            .before(chatItemId: lastItem.id, count: loadItemsPerPage)
+                        .before(chatItemId: lastItem.id, count: loadItemsPerPage)
-                        } else {
+                    } else if direction == .toLatest, let firstItem = chatItem ?? reversedPage.first ?? im.reversedChatItems.first {
-                            .last(count: loadItemsPerPage)
+                        .after(chatItemId: firstItem.id, count: loadItemsPerPage)
-                        }
+                    } else {
+                        .last(count: loadItemsPerPage)
+                    }
+
                     let chatItems = try await apiGetChatItems(
                         type: cInfo.chatType,
                         id: cInfo.apiId,
@@ -863,12 +892,29 @@ struct ChatView: View {
                     chatItemsAvailable = !chatItems.isEmpty
                     reversedPage.append(contentsOf: chatItems.reversed())
                 }
+
                 await MainActor.run {
-                    if reversedPage.count == 0 {
+                    if reversedPage.count == 0  {
-                        firstPage = true
+                        setBoundary(direction)
                     } else {
-                        im.reversedChatItems.append(contentsOf: reversedPage)
+                        let reversedPageToAppend = self.sectionModel.handleSectionInsertion(
+                            candidateSection: section,
+                            reversedPage: reversedPage,
+                            allItems: im.reversedChatItems
+                        )
+                        
+                        if direction == .toLatest {
+                            let at = if let chatItemId = chatItem?.id, let index = im.reversedChatItems.firstIndex(where: { $0.id == chatItemId }) {
+                                index
+                            } else {
+                                0
+                            }
+                            im.reversedChatItems.insert(contentsOf: reversedPageToAppend, at: at)
+                        } else {
+                            im.reversedChatItems.append(contentsOf: reversedPageToAppend)
+                        }
                     }
+                    self.sectionModel.manageActiveSection(scrollDirection: direction)
                     loadingItems = false
                 }
             } catch let error {
@@ -1886,6 +1932,36 @@ func updateChatSettings(_ chat: Chat, chatSettings: ChatSettings) {
         }
     }
 }
+private func filtered(_ reversedChatItems: Array<ChatItem>) -> Array<ChatItem> {
+    reversedChatItems
+        .enumerated()
+        .filter { (index, chatItem) in
+            if let mergeCategory = chatItem.mergeCategory, index > 0 {
+                mergeCategory != reversedChatItems[index - 1].mergeCategory
+            } else {
+                true
+            }
+        }
+        .map { $0.element }
+}
+
+func loadItemsAround(_ cInfo: ChatInfo, _ chatItemId: Int64) async -> [ChatItem]? {
+    do {
+        var reversedPage = Array<ChatItem>()
+        let pagination: ChatPagination = .around(chatItemId: chatItemId, count: loadItemsPerPage * 2)
+        var chatItems = try await apiGetChatItems(
+            type: cInfo.chatType,
+            id: cInfo.apiId,
+            pagination: pagination,
+            search: ""
+        )
+            
+        return chatItems.reversed()
+    } catch let error {
+        logger.error("apiGetChat error: \(responseError(error))")
+        return nil
+    }
+}
 
 struct ChatView_Previews: PreviewProvider {
     static var previews: some View {

apps/ios/Shared/Views/Chat/ReverseList.swift

@@ -10,16 +10,28 @@ import SwiftUI
 import Combine
 import SimpleXChat
 
+enum ChatScrollDirection {
+    case toLatest
+    case toOldest
+    case none
+}
+
+enum ChatSection: CaseIterable {
+    case current
+    case destination
+    case bottom
+}
+
 /// A List, which displays it's items in reverse order - from bottom to top
 struct ReverseList<Content: View>: UIViewControllerRepresentable {
     let items: Array<ChatItem>
 
     @Binding var scrollState: ReverseListScrollModel.State
-
+    @ObservedObject var sectionModel: ReverseListSectionModel
     /// Closure, that returns user interface for a given item
     let content: (ChatItem) -> Content
 
-    let loadPage: () -> Void
+    let loadPage: (ChatScrollDirection, ChatSection, ChatItem?) -> Void
     
     func makeUIViewController(context: Context) -> Controller {
         Controller(representer: self)
@@ -32,10 +44,10 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
             switch destination {
             case .nextPage:
                 controller.scrollToNextPage()
-            case let .item(id):
+            case let .item(id, position, animated):
-                controller.scroll(to: items.firstIndex(where: { $0.id == id }), position: .bottom)
+                controller.scrollToItem(id: id, position: position, animated: animated)
             case .bottom:
-                controller.scroll(to: 0, position: .top)
+                controller.scroll(to: 0, position: .top, section: .bottom, shouldTryAnimate: true)
             }
         } else {
             controller.update(items: items)
@@ -44,12 +56,14 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
 
     /// Controller, which hosts SwiftUI cells
     class Controller: UITableViewController {
-        private enum Section { case main }
         var representer: ReverseList
-        private var dataSource: UITableViewDiffableDataSource<Section, ChatItem>!
+        private var dataSource: UITableViewDiffableDataSource<ChatSection, ChatItem>!
         private var itemCount: Int = 0
         private let updateFloatingButtons = PassthroughSubject<Void, Never>()
         private var bag = Set<AnyCancellable>()
+        private var lastContentOffset: CGFloat = 0
+        private var scrollDirection: ChatScrollDirection = .none
+        private var requestedRange = false
         
         init(representer: ReverseList) {
             self.representer = representer
@@ -75,11 +89,22 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
             }
             
             // 3. Configure data source
-            self.dataSource = UITableViewDiffableDataSource<Section, ChatItem>(
+            self.dataSource = UITableViewDiffableDataSource<ChatSection, ChatItem>(
                 tableView: tableView
             ) { (tableView, indexPath, item) -> UITableViewCell? in
-                if indexPath.item > self.itemCount - 8 {
+                if let section = self.dataSource.sectionIdentifier(for: indexPath.section), self.representer.scrollState == .atDestination, !self.requestedRange {
-                    self.representer.loadPage()
+                    if self.representer.sectionModel.activeSection == section {
+                        let itemCount = self.getTotalItemsInItemSection(indexPath: indexPath)
+                        if self.scrollDirection == .toOldest, indexPath.item > itemCount - 8 {
+                            let lastItem = self.getLastItemInItemSection(indexPath: indexPath)
+                            self.requestedRange = !self.representer.sectionModel.boundaries.oldest
+                            self.representer.loadPage(.toOldest, section, lastItem)
+                        } else if self.scrollDirection == .toLatest, indexPath.item < 8 {
+                            self.requestedRange = !self.representer.sectionModel.boundaries.latest
+                            let firstItem = self.getFirstItemInItemSection(indexPath: indexPath)
+                            self.representer.loadPage(.toLatest, section, firstItem)
+                        }
+                    }
                 }
                 let cell = tableView.dequeueReusableCell(withIdentifier: cellReuseId, for: indexPath)
                 if #available(iOS 16.0, *) {
@@ -162,16 +187,34 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
             Task { representer.scrollState = .atDestination }
         }
         
+        /// Scrolls to a given item
+        func scrollToItem(id: Int64, position: UITableView.ScrollPosition, animated: Bool) {
+            if let loadedIndex = self.representer.items.firstIndex(where: { $0.id == id }) {
+                let ci = representer.items[loadedIndex]
+                if let indexPath = dataSource.indexPath(for: ci),
+                   let section = dataSource.sectionIdentifier(for: indexPath.section) {
+                    self.scroll(to: indexPath.row, position: position, section: section, shouldTryAnimate: animated)
+                }
+            }
+        }
+
         /// Scrolls to Item at index path
         /// - Parameter indexPath: Item to scroll to - will scroll to beginning of the list, if `nil`
-        func scroll(to index: Int?, position: UITableView.ScrollPosition) {
+        func scroll(to index: Int?, position: UITableView.ScrollPosition, section: ChatSection, shouldTryAnimate: Bool) {
+            let activeSectionBeforeScroll = representer.sectionModel.activeSection
+            
+            if section != activeSectionBeforeScroll {
+                Task {
+                    representer.sectionModel.changeActiveSection(section)
+                }
+            }
             var animated = false
             if #available(iOS 16.0, *) {
-                animated = true
+                animated = shouldTryAnimate
             }
-            if let index, tableView.numberOfRows(inSection: 0) != 0 {
+            if let index, let sectionIndex = dataSource.index(for: section), tableView.numberOfRows(inSection: sectionIndex) != 0 {
                 tableView.scrollToRow(
-                    at: IndexPath(row: index, section: 0),
+                    at: IndexPath(row: index, section: sectionIndex),
                     at: position,
                     animated: animated
                 )
@@ -181,13 +224,25 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
                     animated: animated
                 )
             }
-            Task { representer.scrollState = .atDestination }
+            Task {
+                representer.scrollState = .atDestination
+                if activeSectionBeforeScroll != section {
+                    representer.sectionModel.maybeDropSection(activeSectionBeforeScroll)
+                }
+            }
         }
 
         func update(items: [ChatItem]) {
-            var snapshot = NSDiffableDataSourceSnapshot<Section, ChatItem>()
+            requestedRange = false
-            snapshot.appendSections([.main])
+            var snapshot = NSDiffableDataSourceSnapshot<ChatSection, ChatItem>()
-            snapshot.appendItems(items)
+            let sections = self.representer.sectionModel.getSectionsOrdered()
+            let itemsBySection = self.itemsBySection(items: items)
+            snapshot.appendSections(sections)
+            sections.forEach { sec in
+                if let sectionItems = itemsBySection[sec] {
+                    snapshot.appendItems(sectionItems, toSection: sec)
+                }
+            }
             dataSource.defaultRowAnimation = .none
             dataSource.apply(
                 snapshot,
@@ -205,6 +260,15 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
         }
 
         override func scrollViewDidScroll(_ scrollView: UIScrollView) {
+            let currentOffset = scrollView.contentOffset.y
+            if currentOffset > lastContentOffset {
+                scrollDirection = .toOldest
+            } else if currentOffset < lastContentOffset {
+                scrollDirection = .toLatest
+            } else {
+                scrollDirection = .none
+            }
+            lastContentOffset = currentOffset
             updateFloatingButtons.send()
         }
 
@@ -212,15 +276,18 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
             if let visibleRows = tableView.indexPathsForVisibleRows,
                 visibleRows.last?.item ?? 0 < representer.items.count {
                 let scrollOffset: Double = tableView.contentOffset.y + InvertedTableView.inset
+            
                 let topItemDate: Date? =
-                    if let lastVisible = visibleRows.last(where: { isVisible(indexPath: $0) }) {
+                    if let lastVisible = visibleRows.last(where: { isVisible(indexPath: $0) }),
-                        representer.items[lastVisible.item].meta.itemTs
+                       let cI = self.dataSource.itemIdentifier(for: lastVisible) {
+                        cI.meta.itemTs
                     } else {
                         nil
                     }
                 let bottomItemId: ChatItem.ID? =
-                    if let firstVisible = visibleRows.first(where: { isVisible(indexPath: $0) }) {
+                    if let firstVisible = visibleRows.first(where: { isVisible(indexPath: $0) }),
-                        representer.items[firstVisible.item].id
+                       let cI = self.dataSource.itemIdentifier(for: firstVisible) {
+                        cI.id
                     } else {
                         nil
                     }
@@ -238,6 +305,40 @@ struct ReverseList<Content: View>: UIViewControllerRepresentable {
                 relativeFrame.minY < tableView.frame.height - InvertedTableView.inset
             } else { false }
         }
+        
+        private func getTotalItemsInItemSection(indexPath: IndexPath) -> Int {
+            return self.tableView.numberOfRows(inSection: indexPath.section)
+        }
+        
+        private func getLastItemInItemSection(indexPath: IndexPath) -> ChatItem? {
+            let numberOfRows = self.getTotalItemsInItemSection(indexPath: indexPath)
+            
+            return if numberOfRows > 0,
+                      let lastItem = self.dataSource.itemIdentifier(for: IndexPath(row: numberOfRows - 1, section: indexPath.section)) {
+                lastItem
+            } else {
+                nil
+            }
+        }
+        
+        private func getFirstItemInItemSection(indexPath: IndexPath) -> ChatItem? {
+            let firstIndexPath = IndexPath(item: 0, section: indexPath.section)
+            return if let firstItem = self.dataSource.itemIdentifier(for: firstIndexPath) {
+                firstItem
+            } else {
+                nil
+            }
+        }
+        
+        private func itemsBySection(items: [ChatItem]) -> [ChatSection: [ChatItem]] {
+            let itemsBySection = items.reduce(into: [ChatSection: [ChatItem]]()) { result, ci in
+                if let sec = self.representer.sectionModel.getItemSection(ci.id) {
+                    result[sec, default: []].append(ci)
+                }
+            }
+            
+            return itemsBySection
+        }
     }
 
     /// `UIHostingConfiguration` back-port for iOS14 and iOS15
@@ -292,7 +393,7 @@ class ReverseListScrollModel: ObservableObject {
     enum State: Equatable {
         enum Destination: Equatable {
             case nextPage
-            case item(ChatItem.ID)
+            case item(ChatItem.ID, UITableView.ScrollPosition, Bool)
             case bottom
         }
 
@@ -310,8 +411,177 @@ class ReverseListScrollModel: ObservableObject {
         state = .scrollingTo(.bottom)
     }
 
-    func scrollToItem(id: ChatItem.ID) {
+    func scrollToItem(id: ChatItem.ID, position: UITableView.ScrollPosition? = .bottom, animated: Bool = true) {
-        state = .scrollingTo(.item(id))
+        state = .scrollingTo(.item(id, position ?? .bottom, animated))
+    }
+}
+
+struct SectionBoundaryReached {
+    var oldest: Bool
+    var latest: Bool
+}
+
+/// Manages ``ReverseList`` sections
+class ReverseListSectionModel: ObservableObject {
+    static let shared = ReverseListSectionModel()
+    static let MAX_SECTION_SIZE = 500
+    static let MIN_SECTION_SIZE = 200
+    @Published private(set) var activeSection: ChatSection = .bottom
+    @Published var boundaries = SectionBoundaryReached(oldest: false, latest: false)
+    @Published private var itemSection: [Int64: ChatSection] = [:]
+    @Published private var sections = Set<ChatSection>()
+
+    func getItemSection(_ id: Int64) -> ChatSection? {
+        return itemSection[id]
+    }
+    
+    func changeActiveSection(_ section: ChatSection) {
+        activeSection = section
+        boundaries.latest = false
+        boundaries.oldest = false
+    }
+    
+    func maybeDropSection(_ section: ChatSection) {
+        if section == .bottom { return }
+        let im = ItemsModel.shared
+        
+        sections.remove(section)
+        im.reversedChatItems = im.reversedChatItems.filter { it in itemSection[it.id] != section }
+    }
+    
+    private func activeSectionItemsCount() -> Int {
+        // TODO: check
+        return itemSection.values.filter { $0 == self.activeSection }.count
+    }
+    
+    private func splitSection(originalSection: ChatSection, newSection: ChatSection) {
+        var originalSectionCount = 0
+        let im = ItemsModel.shared
+
+        im.reversedChatItems.forEach { it in
+            if itemSection[it.id] == originalSection {
+                if originalSectionCount < ReverseListSectionModel.MIN_SECTION_SIZE {
+                    originalSectionCount += 1
+                } else {
+                    itemSection[it.id] = newSection
+                }
+            }
+        }
+    }
+    
+    private func trimSection(scrollDirection: ChatScrollDirection, section: ChatSection) {
+        let im = ItemsModel.shared
+        var i = scrollDirection == .toLatest ? 0 : im.reversedChatItems.count - 1
+        let moveToNextIndex: () -> Bool = {
+            if scrollDirection == .toLatest {
+                if i < im.reversedChatItems.count - 1 {
+                    i += 1
+                    return false
+                } else {
+                    return true
+                }
+            } else {
+                if i > 0 {
+                    i -= 1
+                    return false
+                } else {
+                    return true
+                }
+            }
+        }
+        var sectionCount = 0
+        var completed = false
+        var toRemoveIndexes = IndexSet()
+        
+        while (!completed) {
+            let it = im.reversedChatItems[i]
+            if itemSection[it.id] == section {
+                if sectionCount >= ReverseListSectionModel.MAX_SECTION_SIZE {
+                    toRemoveIndexes.insert(i)
+                    itemSection.removeValue(forKey: it.id)
+                } else {
+                    sectionCount += 1
+                }
+            }
+            completed = moveToNextIndex()
+        }
+        
+        if (!toRemoveIndexes.isEmpty) {
+            im.reversedChatItems.remove(atOffsets: toRemoveIndexes)
+        }
+    }
+    
+    func manageActiveSection(scrollDirection: ChatScrollDirection) {
+        let activeSectionCount = activeSectionItemsCount()
+
+        switch self.activeSection {
+        case .bottom:
+            if activeSectionCount > ReverseListSectionModel.MAX_SECTION_SIZE {
+                if scrollDirection == .toLatest {
+                boundaries.oldest = false
+                self.trimSection(scrollDirection: scrollDirection, section: self.activeSection)
+                } else {
+                    splitSection(originalSection: .bottom, newSection: .current)
+                    changeActiveSection(.current)
+                    sections.insert(.current)
+                }
+            }
+            break;
+        default:
+            if activeSectionCount > ReverseListSectionModel.MAX_SECTION_SIZE {
+                if scrollDirection == .toLatest {
+                    boundaries.oldest = false
+                } else {
+                    boundaries.latest = false
+                }
+                self.trimSection(scrollDirection: scrollDirection, section: self.activeSection)
+            }
+        }
+    }
+    
+    func getSectionsOrdered() -> [ChatSection] {
+        var orderedSections: [ChatSection] = [.bottom]
+        
+        if (sections.contains(.current)) {
+            orderedSections.append(.current)
+        }
+        
+        if (sections.contains(.destination)) {
+            orderedSections.append(.destination)
+        }
+        
+        return orderedSections
+    }
+    
+    func resetSections(items: [ChatItem]) {
+        itemSection = Dictionary(uniqueKeysWithValues: items.map { ($0.id, .bottom) })
+    }
+    
+    func handleSectionInsertion(candidateSection: ChatSection, reversedPage: [ChatItem], allItems: [ChatItem]) -> [ChatItem] {
+        var reversedPageToAppend = Array<ChatItem>()
+        var targetSection = candidateSection
+        
+        if let sectionIntersectionItem = reversedPage.first(where: { itemSection[$0.id] != nil && itemSection[$0.id] != candidateSection }) {
+            let sectionToDrop = itemSection[sectionIntersectionItem.id] == .bottom ? candidateSection : (itemSection[sectionIntersectionItem.id] ?? .destination)
+            targetSection = itemSection[sectionIntersectionItem.id] == .bottom ? .bottom : candidateSection
+            itemSection = itemSection.mapValues { section in
+                section == sectionToDrop ? targetSection : section
+            }
+            if (sectionToDrop != targetSection) {
+                sections.remove(sectionToDrop)
+            }
+        }
+        
+        reversedPage.forEach { ci in
+            if itemSection[ci.id] == nil {
+                reversedPageToAppend.append(ci)
+                itemSection[ci.id] = targetSection
+            }
+        }
+        sections.insert(targetSection)
+        self.activeSection = targetSection
+        
+        return reversedPageToAppend
     }
 }
 

apps/ios/SimpleXChat/API.swift

@@ -213,8 +213,10 @@ public func chatResponse(_ s: String) -> ChatResponse {
                 if let jApiChat = jResp["apiChat"] as? NSDictionary,
                    let user: UserRef = try? decodeObject(jApiChat["user"] as Any),
                    let jChat = jApiChat["chat"] as? NSDictionary,
-                   let chat = try? parseChatData(jChat) {
+                   let jSection = jApiChat["section"] as? String,
-                    return .apiChat(user: user, chat: chat)
+                   let chat = try? parseChatData(jChat),
+                   let section = ChatLandingSection(rawValue: jSection) {
+                    return .apiChat(user: user, chat: chat, section: section)
                 }
             } else if type == "chatCmdError" {
                 if let jError = jResp["chatCmdError"] as? NSDictionary {

apps/ios/SimpleXChat/APITypes.swift

@@ -546,7 +546,7 @@ public enum ChatResponse: Decodable, Error {
     case chatStopped
     case chatSuspended
     case apiChats(user: UserRef, chats: [ChatData])
-    case apiChat(user: UserRef, chat: ChatData)
+    case apiChat(user: UserRef, chat: ChatData, section: ChatLandingSection)
     case chatItemInfo(user: UserRef, chatItem: AChatItem, chatItemInfo: ChatItemInfo)
     case userProtoServers(user: UserRef, servers: UserProtoServers)
     case serverTestResult(user: UserRef, testServer: String, testFailure: ProtocolTestFailure?)
@@ -888,7 +888,7 @@ public enum ChatResponse: Decodable, Error {
             case .chatStopped: return noDetails
             case .chatSuspended: return noDetails
             case let .apiChats(u, chats): return withUser(u, String(describing: chats))
-            case let .apiChat(u, chat): return withUser(u, String(describing: chat))
+            case let .apiChat(u, chat, section): return withUser(u, "section: \(String(describing: section))\n\(String(describing: chat))")
             case let .chatItemInfo(u, chatItem, chatItemInfo): return withUser(u, "chatItem: \(String(describing: chatItem))\nchatItemInfo: \(String(describing: chatItemInfo))")
             case let .userProtoServers(u, servers): return withUser(u, "servers: \(String(describing: servers))")
             case let .serverTestResult(u, server, testFailure): return withUser(u, "server: \(server)\nresult: \(String(describing: testFailure))")
@@ -1133,12 +1133,16 @@ public enum ChatPagination {
     case last(count: Int)
     case after(chatItemId: Int64, count: Int)
     case before(chatItemId: Int64, count: Int)
+    case around(chatItemId: Int64, count: Int)
+    case initial(count: Int)
 
     var cmdString: String {
         switch self {
         case let .last(count): return "count=\(count)"
         case let .after(chatItemId, count): return "after=\(chatItemId) count=\(count)"
         case let .before(chatItemId, count): return "before=\(chatItemId) count=\(count)"
+        case let .around(chatItemId, count): return "around=\(chatItemId) count=\(count)"
+        case let .initial(count): return "initial=\(count)"
         }
     }
 }

apps/ios/SimpleXChat/ChatTypes.swift

@@ -1619,6 +1619,11 @@ public struct Contact: Identifiable, Decodable, NamedChat, Hashable {
     )
 }
 
+public enum ChatLandingSection: String, Decodable, Hashable {
+    case latest = "latest"
+    case unread = "unread"
+}
+
 public enum ContactStatus: String, Decodable, Hashable {
     case active = "active"
     case deleted = "deleted"