refactor(ads): improve interstitial ad frequency logic

- Remove _getRequiredTransitions method
- Use frequency config specific to user role
- Add check for disabled frequency config
- Simplify ad showing and preloading process

Author: fulleni

lib/ads/interstitial_ad_manager.dart

@@ -124,6 +124,7 @@ class InterstitialAdManager {
       final ad = await _adService.getInterstitialAd(
         adConfig: adConfig,
         adThemeStyle: adThemeStyle,
+        userRole: _userRole ?? AppUserRole.guestUser,
       );
 
       if (ad != null) {
@@ -165,14 +166,17 @@ class InterstitialAdManager {
     }
 
     final frequencyConfig =
-        adConfig.interstitialAdConfiguration.feedInterstitialAdFrequencyConfig;
-    final requiredTransitions = _getRequiredTransitions(frequencyConfig);
+        adConfig.interstitialAdConfiguration.visibleTo[_userRole];
+
+    // If no frequency config is found for the user role, or if it's explicitly
+    // disabled (transitionsBeforeShowingInterstitialAds == 0), then no ad should be shown.
+    final requiredTransitions =
+        frequencyConfig?.transitionsBeforeShowingInterstitialAds ?? 0;
 
     if (requiredTransitions > 0 && _transitionCount >= requiredTransitions) {
       _logger.info('Transition count meets threshold. Attempting to show ad.');
       await _showAd();
-      _transitionCount =
-          0; // Reset counter after showing (or attempting to show)
+      _transitionCount = 0;
     } else {
       _logger.info(
         'Transition count ($_transitionCount) has not met threshold ($requiredTransitions).',
@@ -197,7 +201,7 @@ class InterstitialAdManager {
     }
 
     final adToShow = _preloadedAd!;
-    _preloadedAd = null; // Clear the pre-loaded ad before showing
+    _preloadedAd = null;
 
     try {
       switch (adToShow.provider) {
@@ -230,7 +234,7 @@ class InterstitialAdManager {
     } finally {
       // After the ad is shown or fails to show, dispose of it and
       // start pre-loading the next one for the next opportunity.
-      _disposePreloadedAd(); // Ensure the ad object is disposed
+      _disposePreloadedAd();
       unawaited(_maybePreloadAd(_appBloc.state));
     }
   }
@@ -268,7 +272,7 @@ class InterstitialAdManager {
     // Await the result of showDialog, which completes when the dialog is popped.
     await showDialog<void>(
       context: context,
-      barrierDismissible: false, // Prevent dismissing by tapping outside
+      barrierDismissible: false,
       builder: (_) => LocalInterstitialAdDialog(
         localInterstitialAd: ad.adObject as LocalInterstitialAd,
       ),
@@ -279,22 +283,8 @@ class InterstitialAdManager {
     // Await the result of showDialog, which completes when the dialog is popped.
     await showDialog<void>(
       context: context,
-      barrierDismissible: false, // Prevent dismissing by tapping outside
+      barrierDismissible: false,
       builder: (_) => const DemoInterstitialAdDialog(),
     );
   }
-
-  /// Determines the required number of transitions based on the user's role.
-  int _getRequiredTransitions(InterstitialAdFrequencyConfig config) {
-    switch (_userRole) {
-      case AppUserRole.guestUser:
-        return config.guestTransitionsBeforeShowingInterstitialAds;
-      case AppUserRole.standardUser:
-        return config.standardUserTransitionsBeforeShowingInterstitialAds;
-      case AppUserRole.premiumUser:
-        return config.premiumUserTransitionsBeforeShowingInterstitialAds;
-      case null:
-        return config.guestTransitionsBeforeShowingInterstitialAds;
-    }
-  }
 }