refactor and cleanup [skip ci]

submodules/Postbox/Sources/PeerPresencesView.swift

@@ -0,0 +1,41 @@
+import Foundation
+
+final class MutablePeerPresencesView: MutablePostboxView {
+    fileprivate let ids: Set<PeerId>
+    fileprivate var presences: [PeerId: PeerPresence] = [:]
+    
+    init(postbox: Postbox, ids: Set<PeerId>) {
+        self.ids = ids
+        for id in ids {
+            if let presence = postbox.peerPresenceTable.get(id) {
+                self.presences[id] = presence
+            }
+        }
+    }
+    
+    func replay(postbox: Postbox, transaction: PostboxTransaction) -> Bool {
+        var updated = false
+        if !transaction.currentUpdatedPeerPresences.isEmpty {
+            for (id, presence) in transaction.currentUpdatedPeerPresences {
+                if self.ids.contains(id) {
+                    self.presences[id] = presence
+                    updated = true
+                }
+            }
+        }
+        
+        return updated
+    }
+    
+    func immutableView() -> PostboxView {
+        return PeerPresencesView(self)
+    }
+}
+
+public final class PeerPresencesView: PostboxView {
+    public let presences: [PeerId: PeerPresence]
+    
+    init(_ view: MutablePeerPresencesView) {
+        self.presences = view.presences
+    }
+}