refactor and cleanup [skip ci]

submodules/Postbox/Sources/MessageView.swift

@@ -0,0 +1,55 @@
+import Foundation
+
+final class MutableMessageView {
+    let messageId: MessageId
+    var stableId: UInt32?
+    var message: Message?
+    
+    init(messageId: MessageId, message: Message?) {
+        self.messageId = messageId
+        self.message = message
+        self.stableId = message?.stableId
+    }
+    
+    func replay(_ operations: [MessageHistoryOperation], updatedMedia: [MediaId: Media?], renderIntermediateMessage: (IntermediateMessage) -> Message) -> Bool {
+        var updated = false
+        for operation in operations {
+            switch operation {
+                case let .Remove(indices):
+                    if let message = self.message {
+                        let messageIndex = message.index
+                        for (index, _) in indices {
+                            if index == messageIndex {
+                                self.message = nil
+                                updated = true
+                                break
+                            }
+                        }
+                    }
+                case let .InsertMessage(message):
+                    if message.id == self.messageId || message.stableId == self.stableId {
+                        self.message = renderIntermediateMessage(message)
+                        self.stableId = message.stableId
+                        updated = true
+                    }
+                case .UpdateEmbeddedMedia:
+                    break
+                case .UpdateTimestamp:
+                    break
+                default:
+                    break
+            }
+        }
+        return updated
+    }
+}
+
+public final class MessageView {
+    public let messageId: MessageId
+    public let message: Message?
+    
+    init(_ view: MutableMessageView) {
+        self.messageId = view.messageId
+        self.message = view.message
+    }
+}