refactor and cleanup [skip ci]

submodules/Postbox/Sources/MessagesView.swift

@@ -0,0 +1,66 @@
+import Foundation
+
+final class MutableMessagesView: MutablePostboxView {
+    fileprivate let ids: Set<MessageId>
+    private let peerIds: Set<PeerId>
+    fileprivate var messages: [MessageId: Message] = [:]
+    
+    init(postbox: Postbox, ids: Set<MessageId>) {
+        self.ids = ids
+        self.peerIds = Set(ids.map { $0.peerId })
+        for id in ids {
+            if let message = postbox.getMessage(id) {
+                self.messages[message.id] = message
+            }
+        }
+    }
+    
+    func replay(postbox: Postbox, transaction: PostboxTransaction) -> Bool {
+        var updatedIds = Set<MessageId>()
+        for peerId in self.peerIds {
+            if let operations = transaction.currentOperationsByPeerId[peerId] {
+                for operation in operations {
+                    switch operation {
+                        case let .InsertMessage(message):
+                            if self.ids.contains(message.id) {
+                                updatedIds.insert(message.id)
+                            }
+                        case let .Remove(indices):
+                            for index in indices {
+                                if self.ids.contains(index.0.id) {
+                                    updatedIds.insert(index.0.id)
+                                }
+                            }
+                        default:
+                            break
+                    }
+                }
+            }
+        }
+        if !updatedIds.isEmpty {
+            for id in updatedIds {
+                if let message = postbox.getMessage(id) {
+                    self.messages[message.id] = message
+                } else {
+                    self.messages.removeValue(forKey: id)
+                }
+            }
+            
+            return true
+        } else {
+            return false
+        }
+    }
+    
+    func immutableView() -> PostboxView {
+        return MessagesView(self)
+    }
+}
+
+public final class MessagesView: PostboxView {
+    public var messages: [MessageId: Message] = [:]
+    
+    init(_ view: MutableMessagesView) {
+        self.messages = view.messages
+    }
+}