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// AppDelegate.swift

var canSendCSMatchingKey = false

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // ... your existing code ..
    MobileCore.registerExtensions([Identity.self, Analytics.self, ....], {
        // ... your existing code ..

        self.canSendCSMatchingKey = true
        self.sendCSMatchingKeyIfNeeded()
    })

    // When going back to foreground, more than 30 minutes may have elapsed.
    // In this situation Contentsquare SDK may create a new session
    // This is why `sendCSMatchingKeyIfNeeded` must be called in this situation
    NotificationCenter.default.addObserver(self,
                                           selector: #selector(sendCSMatchingKeyIfNeeded),
                                           name: UIApplication.didBecomeActiveNotification,
                                           object: nil)

    // ... your existing code ..
}

@objc
func sendCSMatchingKeyIfNeeded() {
  guard canSendCSMatchingKey else { return }

  let csMatchingKeyTimestampKey = "csMatchingKey_ts"
  let csMatchingKeyValidityMs = 1_800_000 // 30 minutes

  let currentTimestamp = Int(Date().timeIntervalSince1970 * 1000)
  let csMatchingKeyIsPreviousTimestamp = UserDefaults.standard.integer(forKey: csMatchingKeyTimestampKey)

  guard (currentTimestamp - csMatchingKeyIsPreviousTimestamp) > csMatchingKeyValidityMs else {
    return
  }

  UserDefaults.standard.set(currentTimestamp, forKey: csMatchingKeyTimestampKey)

  let csMatchingKey = "csMatchingKey"
  let csMatchingKeyValue = "\(Double.random(in: 0..<1))_\(currentTimestamp)"

  Contentsquare.send(dynamicVar: DynamicVar(key: csMatchingKey, value: csMatchingKeyValue))
  MobileCore.track(state: "csMatchingKey_state", data: [csMatchingKey: csMatchingKeyValue])
}

// AppDelegate.m
@interface AppDelegate ()

@property (nonatomic, assign) BOOL canSendCSMatchingKey;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.canSendCSMatchingKey = NO;

    // ... your existing code ..
    [AEPMobileCore registerExtensions:@[AEPMobileEdgeIdentity.class, AEPMobileAnalytics.class] completion:^{
        // ... your existing code ..

        self.canSendCSMatchingKey = YES;
        [self sendCSMatchingKeyIfNeeded];
    }];

    // When going back to foreground, more than 30 minutes may have elapsed.
    // In this situation Contentsquare SDK may create a new session
    // This is why `sendCSMatchingKeyIfNeeded` must be called in this situation
    [[NSNotificationCenter defaultCenter] addObserver:self
                                            selector:@selector(sendKeyIfNeeded)
                                                name:UIApplicationDidBecomeActiveNotification
                                              object:nil];

    // ... your existing code ..
    return YES;
}

- (void)sendCSMatchingKeyIfNeeded {
    if (!self.canSendCSMatchingKey) {
      return;
    }

    NSString *csMatchingKeyTimestampKey = @"csMatchingKey_ts";
    NSInteger csMatchingKeyValidityMs = 1800000; // 30 minutes

    NSInteger currentTimestamp = (NSInteger)([[NSDate date] timeIntervalSince1970] * 1000);
    NSInteger csMatchingKeyIsPreviousTimestamp = [[NSUserDefaults standardUserDefaults] integerForKey:csMatchingKeyTimestampKey];

    if ((currentTimestamp - csMatchingKeyIsPreviousTimestamp) <= csMatchingKeyValidityMs) {
        return;
    }

    [[NSUserDefaults standardUserDefaults] setInteger:currentTimestamp forKey:csMatchingKeyTimestampKey];

    NSString *csMatchingKey = @"csMatchingKey";
    NSString *csMatchingKeyValue = [NSString stringWithFormat:@"%f_%f", (double)arc4random() / UINT32_MAX, currentTimestamp];

    DynamicVar *csMatchingKeyDynamicVar = [[DynamicVar alloc] initWithKey:csMatchingKey
                                                      stringValue:csMatchingKeyValue
                                                            error:(NSError * _Nullable __autoreleasing * _Nullable)];
    [Contentsquare sendWithDynamicVar:csMatchingKeyDynamicVar];
    [AEPMobileCore trackState:@"csMatchingKey_state" data:@{csMatchingKey:csMatchingKeyValue}];
}

@end