fix(library): sync again after a Steam ID change and keep library on empty result

An empty Steam answer (error, private profile, wrong ID) was stored as OK and
soft-deleted the whole library. It is now FAILED, keeps the library and is
retried after 15 minutes (app.library.failed-retry-minutes).

The automatic sync now also runs when the Steam ID in the token differs from
the stored one, and removes the games of the previous Steam account.

src/main/java/core_service/modules/library/service/LibrarySyncService.java

@@ -27,19 +27,22 @@ public class LibrarySyncService {
     @Value("${app.library.running-stale-minutes:5}")
     private long runningStaleMinutes;
 
+    @Value("${app.library.failed-retry-minutes:15}")
+    private long failedRetryMinutes;
+
     /**
-     * Trigger sync only if data is older than TTL. Cheap gate check on caller thread,
-     * actual sync runs async via worker.
+     * Trigger sync only if data is older than TTL or was synced for another Steam ID.
+     * Cheap gate check on caller thread, actual sync runs async via worker.
      */
     public void syncIfStale(Long userId, String steamId) {
         UserSteamSync sync = userSteamSyncRepository.findById(userId).orElse(null);
-        if (sync != null && !isStale(sync)) {
-            return;
-        }
         if (sync != null && isAlreadyRunning(sync)) {
             log.debug("Sync already running for user {}", userId);
             return;
         }
+        if (sync != null && steamId.equals(sync.getSteamId()) && !isStale(sync)) {
+            return;
+        }
         worker.runSync(userId, steamId);
     }
 
@@ -62,7 +65,10 @@ public class LibrarySyncService {
 
     private boolean isStale(UserSteamSync sync) {
         if (sync.getLastSyncedAt() == null) return true;
-        return sync.getLastSyncedAt().isBefore(Instant.now().minus(Duration.ofHours(syncTtlHours)));
+        Duration maxAge = sync.getLastSyncStatus() == UserSteamSync.Status.FAILED
+                ? Duration.ofMinutes(failedRetryMinutes)
+                : Duration.ofHours(syncTtlHours);
+        return sync.getLastSyncedAt().isBefore(Instant.now().minus(maxAge));
     }
 
     private boolean isAlreadyRunning(UserSteamSync sync) {

src/main/java/core_service/modules/library/service/LibrarySyncWorker.java

@@ -3,6 +3,7 @@ package core_service.modules.library.service;
 import core_service.modules.library.domain.SteamGame;
 import core_service.modules.library.domain.UserGame;
 import core_service.modules.library.domain.UserGameId;
+import core_service.modules.library.domain.UserSteamSync;
 import core_service.modules.library.repo.SteamGameRepository;
 import core_service.modules.library.repo.UserGameRepository;
 import core_service.modules.library.repo.UserSteamSyncRepository;
@@ -43,6 +44,9 @@ public class LibrarySyncWorker {
     @Transactional
     public void runSync(Long userId, String steamId) {
         Instant runningStaleBefore = Instant.now().minus(Duration.ofMinutes(runningStaleMinutes));
+        String previousSteamId = userSteamSyncRepository.findById(userId)
+                .map(UserSteamSync::getSteamId)
+                .orElse(null);
         int claimed = userSteamSyncRepository.tryClaimRun(userId, steamId, runningStaleBefore);
         if (claimed == 0) {
             log.info("Sync skipped for user {} — another run already in flight", userId);
@@ -52,8 +56,17 @@ public class LibrarySyncWorker {
         Instant syncStartedAt = Instant.now();
         Status finalStatus = Status.FAILED;
         try {
+            if (previousSteamId != null && !previousSteamId.equals(steamId)) {
+                // The old games belong to the previous Steam account. The upserts below restore the games this account also owns.
+                userGameRepository.softDeleteMissingSince(userId, syncStartedAt, Instant.now());
+            }
             List<SteamOwnedGamesResponse.Game> games = steamApiService.getOwnedGames(steamId);
             log.info("Sync user={} fetched {} games from Steam", userId, games.size());
+            if (games.isEmpty()) {
+                // Steam errors and a private "Game details" setting also end here. A soft-delete would wipe the library.
+                log.warn("Sync user={} got no games for SteamID {}", userId, steamId);
+                return;
+            }
 
             for (SteamOwnedGamesResponse.Game g : games) {
                 if (g.appid() == null) continue;