refactor and cleanup [skip ci]

submodules/Postbox/Sources/AdditionalChatListItemsTable.swift

@@ -0,0 +1,85 @@
+import Foundation
+
+final class AdditionalChatListItemsTable: Table {
+    static func tableSpec(_ id: Int32) -> ValueBoxTable {
+        return ValueBoxTable(id: id, keyType: .binary, compactValuesOnCreation: true)
+    }
+    
+    private var cachedItems: [PeerId]?
+    private var updatedItems = false
+    
+    private func key(_ index: Int32) -> ValueBoxKey {
+        let key = ValueBoxKey(length: 4)
+        key.setInt32(0, value: index)
+        return key
+    }
+    
+    private func lowerBound() -> ValueBoxKey {
+        let key = ValueBoxKey(length: 1)
+        key.setInt8(0, value: 0)
+        return key
+    }
+    
+    private func upperBound() -> ValueBoxKey {
+        let key = ValueBoxKey(length: 4)
+        key.setInt32(0, value: Int32.max)
+        return key
+    }
+    
+    func set(_ items: [PeerId]) -> Bool {
+        if self.get() == items {
+            return false
+        }
+        self.cachedItems = items
+        self.updatedItems = true
+        
+        return true
+    }
+    
+    func get() -> [PeerId] {
+        if let cachedItems = self.cachedItems {
+            return cachedItems
+        }
+        var items: [PeerId] = []
+        self.valueBox.range(self.table, start: self.lowerBound(), end: self.upperBound(), values: { key, value in
+            assert(key.getInt32(0) == Int32(items.count))
+            var peerIdValue: Int64 = 0
+            value.read(&peerIdValue, offset: 0, length: 8)
+            items.append(PeerId(peerIdValue))
+            return true
+        }, limit: 0)
+        self.cachedItems = items
+        return items
+    }
+    
+    override func clearMemoryCache() {
+        self.cachedItems = nil
+        assert(!self.updatedItems)
+    }
+    
+    override func beforeCommit() {
+        if self.updatedItems {
+            var keys: [ValueBoxKey] = []
+            self.valueBox.range(self.table, start: self.lowerBound(), end: self.upperBound(), keys: { key in
+                keys.append(key)
+                return true
+            }, limit: 0)
+            for key in keys {
+                self.valueBox.remove(self.table, key: key, secure: false)
+            }
+            
+            if let items = self.cachedItems {
+                var index: Int32 = 0
+                for item in items {
+                    var peerIdValue = item.toInt64()
+                    self.valueBox.set(self.table, key: self.key(index), value: MemoryBuffer(memory: &peerIdValue, capacity: 8, length: 8, freeWhenDone: false))
+                    index += 1
+                }
+            } else {
+                assertionFailure()
+            }
+            
+            self.updatedItems = false
+        }
+    }
+}