refactor and cleanup [skip ci]

submodules/Postbox/Sources/PeerChatStateTable.swift

@@ -0,0 +1,57 @@
+import Foundation
+
+final class PeerChatStateTable: Table {
+    static func tableSpec(_ id: Int32) -> ValueBoxTable {
+        return ValueBoxTable(id: id, keyType: .int64, compactValuesOnCreation: false)
+    }
+    
+    private var cachedPeerChatStates: [PeerId: PostboxCoding?] = [:]
+    private var updatedPeerIds = Set<PeerId>()
+    
+    private let sharedKey = ValueBoxKey(length: 8)
+    
+    private func key(_ id: PeerId) -> ValueBoxKey {
+        self.sharedKey.setInt64(0, value: id.toInt64())
+        return self.sharedKey
+    }
+    
+    func get(_ id: PeerId) -> PostboxCoding? {
+        if let state = self.cachedPeerChatStates[id] {
+            return state
+        } else {
+            if let value = self.valueBox.get(self.table, key: self.key(id)), let state = PostboxDecoder(buffer: value).decodeRootObject() {
+                self.cachedPeerChatStates[id] = state
+                return state
+            } else {
+                self.cachedPeerChatStates[id] = nil
+                return nil
+            }
+        }
+    }
+    
+    func set(_ id: PeerId, state: PostboxCoding?) {
+        self.cachedPeerChatStates[id] = state
+        self.updatedPeerIds.insert(id)
+    }
+    
+    override func clearMemoryCache() {
+        self.cachedPeerChatStates.removeAll()
+        self.updatedPeerIds.removeAll()
+    }
+    
+    override func beforeCommit() {
+        if !self.updatedPeerIds.isEmpty {
+            let sharedEncoder = PostboxEncoder()
+            for id in self.updatedPeerIds {
+                if let wrappedState = self.cachedPeerChatStates[id], let state = wrappedState {
+                    sharedEncoder.reset()
+                    sharedEncoder.encodeRootObject(state)
+                    self.valueBox.set(self.table, key: self.key(id), value: sharedEncoder.readBufferNoCopy())
+                } else {
+                    self.valueBox.remove(self.table, key: self.key(id), secure: false)
+                }
+            }
+            self.updatedPeerIds.removeAll()
+        }
+    }
+}