Instrument metrics for iOS for the IA project #5401

- Added last needed metrics

Riot/Modules/Analytics/AnalyticsSpaceTracker.swift

@@ -0,0 +1,72 @@
+// 
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+
+class AnalyticsSpaceTracker {
+    // MARK: - Constants
+
+    private enum Constants {
+        static let lastNumberOfSpaces: String = "AnalyticsSpaceTracker.lastNumberOfSpaces"
+    }
+    
+    // Last number of spaces tracked
+    private var lastNumberOfSpaces: Int? {
+        get {
+            guard let value = UserDefaults.standard.value(forKey: Constants.lastNumberOfSpaces) as? NSNumber else {
+                return nil
+            }
+            
+            return value.intValue
+        }
+        
+        set {
+            guard let value = newValue else {
+                UserDefaults.standard.removeObject(forKey: Constants.lastNumberOfSpaces)
+                return
+            }
+            
+            UserDefaults.standard.setValue(NSNumber(value: value), forKey: Constants.lastNumberOfSpaces)
+        }
+    }
+
+    // MARK: - Setup
+    
+    init() {
+        NotificationCenter.default.addObserver(self, selector: #selector(self.spaceGraphDidUpdate(notification:)), name: MXSpaceService.didBuildSpaceGraph, object: nil)
+    }
+    
+    @objc private func spaceGraphDidUpdate(notification: Notification) {
+        guard let spaceService = notification.object as? MXSpaceService else {
+            return
+        }
+        
+        trackSpaceNumber(with: spaceService)
+    }
+    
+    // MARK: - Private
+    
+    private func trackSpaceNumber(with spaceService: MXSpaceService) {
+        let spaceNumber = spaceService.spaceSummaries.filter { $0.membership == .join }.count
+        
+        guard lastNumberOfSpaces != spaceNumber else {
+            return
+        }
+        
+        Analytics.shared.updateUserProperties(numSpaces: spaceNumber)
+        lastNumberOfSpaces = spaceNumber
+    }
+}