calling store.UpdateFeed and store.UpdateFeedError in a defer function

This makes sure that we are always calling the following functions:
* originalFeed.ScheduleNextCheck
* store.UpdateFeed
* store.UpdateFeedError
And we only call them in a single place regardless which branch is taken inside function.

The store functions within them will udpate the value in database.

This change aims to reduce "unknown unknowns" in the codes. With this change, we won't miss calling above functions.

internal/reader/handler/handler.go

@@ -188,12 +188,13 @@ func CreateFeed(store *storage.Storage, userID int64, feedCreationRequest *model
 }
 
 // RefreshFeed refreshes a feed.
-func RefreshFeed(store *storage.Storage, userID, feedID int64, forceRefresh bool) *locale.LocalizedErrorWrapper {
+func RefreshFeed(store *storage.Storage, userID, feedID int64, forceRefresh bool) (localizedError *locale.LocalizedErrorWrapper) {
 	slog.Debug("Begin feed refresh process",
 		slog.Int64("user_id", userID),
 		slog.Int64("feed_id", feedID),
 		slog.Bool("force_refresh", forceRefresh),
 	)
+	localizedError = nil
 
 	user, storeErr := store.UserByID(userID)
 	if storeErr != nil {
@@ -220,7 +221,31 @@ func RefreshFeed(store *storage.Storage, userID, feedID int64, forceRefresh bool
 	}
 
 	originalFeed.CheckedNow()
-	originalFeed.ScheduleNextCheck(weeklyEntryCount, refreshDelayInMinutes)
+	// Commit the result to the database at the end of this function.
+	// If we met an error before entering the defer function, localizedError would not be nil.
+	defer func() {
+		originalFeed.ScheduleNextCheck(weeklyEntryCount, refreshDelayInMinutes)
+		slog.Debug("Updated next check date",
+			slog.Int64("user_id", userID),
+			slog.Int64("feed_id", feedID),
+			slog.Int("weeklyEntryCount", weeklyEntryCount),
+			slog.Int("retry_delay_in_seconds", retryDelayInSeconds),
+			slog.Int("refresh_delay_in_minutes", refreshDelayInMinutes),
+			slog.Time("new_next_check_at", originalFeed.NextCheckAt),
+		)
+		if localizedError == nil {
+			// We have not encountered any error before entering this delay function.
+			originalFeed.ResetErrorCounter()
+			if storeErr := store.UpdateFeed(originalFeed); storeErr != nil {
+				// Update the return value when there is an error.
+				localizedError = locale.NewLocalizedErrorWrapper(storeErr, "error.database_error", storeErr)
+			}
+		}
+		if localizedError != nil {
+			originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language))
+			store.UpdateFeedError(originalFeed)
+		}
+	}()
 
 	requestBuilder := fetcher.NewRequestBuilder()
 	requestBuilder.WithUsernameAndPassword(originalFeed.Username, originalFeed.Password)
@@ -254,17 +279,13 @@ func RefreshFeed(store *storage.Storage, userID, feedID int64, forceRefresh bool
 		)
 	}
 
-	if localizedError := responseHandler.LocalizedError(); localizedError != nil {
+	if localizedError = responseHandler.LocalizedError(); localizedError != nil {
 		slog.Warn("Unable to fetch feed", slog.String("feed_url", originalFeed.FeedURL), slog.Any("error", localizedError.Error()))
-		originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language))
-		store.UpdateFeedError(originalFeed)
 		return localizedError
 	}
 
 	if store.AnotherFeedURLExists(userID, originalFeed.ID, responseHandler.EffectiveURL()) {
-		localizedError := locale.NewLocalizedErrorWrapper(ErrDuplicatedFeed, "error.duplicated_feed")
-		originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language))
-		store.UpdateFeedError(originalFeed)
+		localizedError = locale.NewLocalizedErrorWrapper(ErrDuplicatedFeed, "error.duplicated_feed")
 		return localizedError
 	}
 
@@ -284,40 +305,25 @@ func RefreshFeed(store *storage.Storage, userID, feedID int64, forceRefresh bool
 
 		updatedFeed, parseErr := parser.ParseFeed(responseHandler.EffectiveURL(), bytes.NewReader(responseBody))
 		if parseErr != nil {
-			localizedError := locale.NewLocalizedErrorWrapper(parseErr, "error.unable_to_parse_feed", parseErr)
-
 			if errors.Is(parseErr, parser.ErrFeedFormatNotDetected) {
 				localizedError = locale.NewLocalizedErrorWrapper(parseErr, "error.feed_format_not_detected", parseErr)
+			} else {
+				localizedError = locale.NewLocalizedErrorWrapper(parseErr, "error.unable_to_parse_feed", parseErr)
 			}
-
-			originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language))
-			store.UpdateFeedError(originalFeed)
 			return localizedError
 		}
 
 		// If the feed has a TTL defined, we use it to make sure we don't check it too often.
 		refreshDelayInMinutes = updatedFeed.TTL
 
-		// Set the next check at with updated arguments.
-		originalFeed.ScheduleNextCheck(weeklyEntryCount, refreshDelayInMinutes)
-
-		slog.Debug("Updated next check date",
-			slog.Int64("user_id", userID),
-			slog.Int64("feed_id", feedID),
-			slog.Int("refresh_delay_in_minutes", refreshDelayInMinutes),
-			slog.Time("new_next_check_at", originalFeed.NextCheckAt),
-		)
-
 		originalFeed.Entries = updatedFeed.Entries
 		processor.ProcessFeedEntries(store, originalFeed, user, forceRefresh)
 
 		// We don't update existing entries when the crawler is enabled (we crawl only inexisting entries). Unless it is forced to refresh
 		updateExistingEntries := forceRefresh || !originalFeed.Crawler
 		newEntries, storeErr := store.RefreshFeedEntries(originalFeed.UserID, originalFeed.ID, originalFeed.Entries, updateExistingEntries)
 		if storeErr != nil {
-			localizedError := locale.NewLocalizedErrorWrapper(storeErr, "error.database_error", storeErr)
-			originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language))
-			store.UpdateFeedError(originalFeed)
+			localizedError = locale.NewLocalizedErrorWrapper(storeErr, "error.database_error", storeErr)
 			return localizedError
 		}
 
@@ -354,14 +360,5 @@ func RefreshFeed(store *storage.Storage, userID, feedID int64, forceRefresh bool
 		}
 	}
 
-	originalFeed.ResetErrorCounter()
-
-	if storeErr := store.UpdateFeed(originalFeed); storeErr != nil {
-		localizedError := locale.NewLocalizedErrorWrapper(storeErr, "error.database_error", storeErr)
-		originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language))
-		store.UpdateFeedError(originalFeed)
-		return localizedError
-	}
-
-	return nil
+	return localizedError
 }