Rework notifications refresh initial page algorithm to make more robust

lib/services/notifications_manager.dart

@@ -80,32 +80,52 @@ class NotificationsManager extends ChangeNotifier {
           continue;
         }
         final page = _pm.pages[i];
-        PagingData? pd;
         if (i == 0) {
-          if (page.next == null) {
-            _logger.severe(
-                "Expected first page to have a next page so can query on this page of data but doesn't exist.");
-            continue;
-          }
-          final response = await _clientGetNotificationsRequest(page.next!);
-          response.match(
-              onSuccess: (response) => pd = response.previous,
-              onError: (error) =>
-                  _logger.severe('Error getting previous page: $error'));
-          if (pd == null && page.previous == null) {
-            _logger.severe(
-                'Next page returned no results and no previous page so need to re-initalize');
-          } else {
-            final response = await _clientGetNotificationsRequest(pd!);
+          PagingData? pd;
+          bool initializedFirstPage = false;
+          if (page.next != null) {
+            final response = await _clientGetNotificationsRequest(page.next!);
             response.match(
-                onSuccess: (response) => pd = response.next,
+                onSuccess: (response) => pd = response.previous,
                 onError: (error) =>
                     _logger.severe('Error getting previous page: $error'));
+            if (pd != null) {
+              final response = await _clientGetNotificationsRequest(pd!);
+              response.match(
+                  onSuccess: (response) {
+                    initializedFirstPage = true;
+                    notificationsFromRefresh.addAll(response.data);
+                  },
+                  onError: (error) =>
+                      _logger.severe('Error getting previous page: $error'));
+            } else if (pd == null && page.previous != null) {
+              final response = await _clientGetNotificationsRequest(
+                      page.previous!)
+                  .andThenAsync((previousData) async => previousData.next !=
+                          null
+                      ? await _clientGetNotificationsRequest(previousData.next!)
+                      : buildErrorResult(
+                          type: ErrorType.rangeError,
+                          message: 'No "next" page from previous data either'));
+              response.match(
+                  onSuccess: (response) {
+                    initializedFirstPage = true;
+                    notificationsFromRefresh.addAll(response.data);
+                  },
+                  onError: (error) =>
+                      _logger.severe('Error getting previous page: $error'));
+            } else if (pd == null && page.previous == null) {
+              _logger.severe(
+                  'Next page returned no results and no previous page so will need to re-initalize');
+            }
+          } else {
+            _logger.severe(
+                'There is no next page to query so will be forced to reset');
           }
 
-          if (pd == null) {
+          if (!initializedFirstPage) {
             _logger.severe(
-                'Previous and next page both returned nulls so need to reinitialize');
+                'Unable to determine call to rebuild initial page so resetting');
             _pm.clear();
             final result = await _pm.initialize(initialPull);
             result.andThenSuccess(
@@ -126,7 +146,7 @@ class NotificationsManager extends ChangeNotifier {
             onSuccess: (response) =>
                 notificationsFromRefresh.addAll(response.data),
             onError: (error) =>
-                _logger.severe('Error getting previous page: $error'));
+                _logger.severe('Error getting next page: $error'));
       }
     }