Merge commit '7621e2f8dec938cf48181c8b10afc9b01f444e68' into beta

submodules/TelegramUI/Sources/ChatHistoryNavigationStack.swift

@@ -0,0 +1,30 @@
+import Foundation
+import UIKit
+import Postbox
+
+struct ChatHistoryNavigationStack {
+    private var messageIndices: [MessageIndex] = []
+    
+    mutating func add(_ index: MessageIndex) {
+        self.messageIndices.append(index)
+    }
+    
+    mutating func removeLast() -> MessageIndex? {
+        if messageIndices.isEmpty {
+            return nil
+        }
+        return messageIndices.removeLast()
+    }
+    
+    var isEmpty: Bool {
+        return self.messageIndices.isEmpty
+    }
+    
+    mutating func filterOutIndicesLessThan(_ index: MessageIndex) {
+        for i in (0 ..< self.messageIndices.count).reversed() {
+            if self.messageIndices[i] <= index {
+                self.messageIndices.remove(at: i)
+            }
+        }
+    }
+}