Handle updating of wrongly formatted timestamps

Handle rewriting timestamps from the specific RSS feed's format to a
more unified Instant string format.

If a DateTimeParseException is thrown while attempting to work with the
date format, use that opportunity to attempt to parse that original date
with the given date format pattern, then convert it into a string using
'Instant#toString'.

If the conversion fails, simply return an empty Optional and let the
rest of the code handle it from there since the new value will be
overwritten in any case.

Signed-off-by: Chris Sdogkos <work@chris-sdogkos.com>

Author: christolis

application/src/main/java/org/togetherjava/tjbot/features/rss/RSSHandlerRoutine.java

@@ -29,6 +29,7 @@
 
 import java.io.IOException;
 import java.time.Instant;
+import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 import java.time.format.DateTimeParseException;
 import java.time.temporal.ChronoUnit;
@@ -188,16 +189,24 @@ private Optional<Predicate<Item>> prepareItemPostPredicate(RSSFeed feedConfig,
             return Optional.empty();
         }
 
-        Optional<Instant> lastSavedDate =
-                getLastSavedDateFromDatabaseRecord(rssFeedRecord.orElseThrow());
+        Instant lastSavedDate;
+        try {
+            lastSavedDate = getLastSavedDateFromDatabaseRecord(rssFeedRecord.orElseThrow());
+        } catch (DateTimeParseException _) {
+            Optional<Instant> convertedDate = convertDateTimeToInstant(feedConfig);
 
-        if (lastSavedDate.isEmpty()) {
-            return Optional.empty();
+            if (convertedDate.isEmpty()) {
+                return Optional.empty();
+            }
+
+            lastSavedDate = convertedDate.get();
         }
 
+        final Instant convertedLastSavedDate = lastSavedDate;
+
         return Optional.of(item -> {
             Instant itemPubDate = getDateTimeFromItem(item, feedConfig.dateFormatterPattern());
-            return itemPubDate.isAfter(lastSavedDate.orElseThrow());
+            return itemPubDate.isAfter(convertedLastSavedDate);
         });
     }
 
@@ -222,13 +231,9 @@ private Optional<RssFeedRecord> getRssFeedRecordFromDatabase(RSSFeed feedConfig)
      * @return An {@link Optional} containing the last saved date if it could be retrieved and
      *         parsed successfully, otherwise an empty {@link Optional}
      */
-    private Optional<Instant> getLastSavedDateFromDatabaseRecord(RssFeedRecord rssRecord)
+    private Instant getLastSavedDateFromDatabaseRecord(RssFeedRecord rssRecord)
             throws DateTimeParseException {
-        try {
-            return Optional.of(Instant.parse(rssRecord.getLastDate()));
-        } catch (DateTimeParseException _) {
-            return Optional.empty();
-        }
+        return Instant.parse(rssRecord.getLastDate());
     }
 
     /**
@@ -332,6 +337,31 @@ private static boolean isValidDateFormat(Item rssItem, RSSFeed feedConfig) {
         return true;
     }
 
+    private Optional<Instant> convertDateTimeToInstant(RSSFeed feedConfig) {
+        Optional<RssFeedRecord> feedOptional = getRssFeedRecordFromDatabase(feedConfig);
+        String dateTimeFormat = feedConfig.dateFormatterPattern();
+
+        if (feedOptional.isEmpty() || dateTimeFormat.isEmpty()) {
+            return Optional.empty();
+        }
+
+        RssFeedRecord feedRecord = feedOptional.get();
+        String lastDate = feedRecord.getLastDate();
+
+        ZonedDateTime zonedDateTime;
+        try {
+            zonedDateTime =
+                    ZonedDateTime.parse(lastDate, DateTimeFormatter.ofPattern(dateTimeFormat));
+        } catch (DateTimeParseException exception) {
+            logger.error(
+                    "Attempted to convert date time from database ({}) to instant, but failed:",
+                    lastDate, exception);
+            return Optional.empty();
+        }
+
+        return Optional.of(zonedDateTime.toInstant());
+    }
+
     /**
      * Attempts to find text channels from a given RSS feed configuration.
      *