fix: verify input VTXOs are spent before breaking poll loop

PostSpendVtxoPollingHandler broke out of the retry loop as soon as any
VTXO was returned (found > 0). When arkd returned the new output VTXOs
before marking the input VTXOs as spent, the handler exited early and
the input VTXOs remained "unspent" in local storage.

Now the handler checks that all input VTXOs have SpentByTransactionId
set before breaking the loop, ensuring the local state accurately
reflects the spend.

Author: Kukks

NArk.Core/Events/PostSpendVtxoPollingHandler.cs

@@ -47,6 +47,7 @@ public async Task HandleAsync(PostCoinsSpendActionEvent @event, CancellationToke
 
 
             var inputScripts = @event.ArkCoins.Select(c => c.ScriptPubKey.ToHex()).ToHashSet();
+            var inputOutpoints = @event.ArkCoins.Select(c => c.Outpoint).ToHashSet();
             var outputScripts = @event.Psbt.Outputs.Select(o => o.ScriptPubKey.ToHex()).ToHashSet();
             outputScripts.Remove("51024e73");
 
@@ -59,6 +60,9 @@ public async Task HandleAsync(PostCoinsSpendActionEvent @event, CancellationToke
                 string.Join(", ", outputScripts));
 
             // Retry with backoff — arkd's indexer may not have processed the VTXOs yet
+            // We must verify that input VTXOs are marked as spent, not just that any VTXO was found.
+            // Breaking early on `found > 0` caused input VTXOs to remain "unspent" locally
+            // when arkd returned the new output VTXOs before updating the spent state of inputs.
             const int maxAttempts = 5;
             for (var attempt = 1; attempt <= maxAttempts; attempt++)
             {
@@ -68,7 +72,18 @@ public async Task HandleAsync(PostCoinsSpendActionEvent @event, CancellationToke
                     attempt, maxAttempts, @event.TransactionId, found);
 
                 if (found > 0)
-                    break;
+                {
+                    // Verify input VTXOs are now marked as spent in local storage
+                    var inputVtxos = await vtxoSyncService.GetVtxosByOutpoints(inputOutpoints, cancellationToken);
+                    var allInputsSpent = inputVtxos.Count > 0 && inputVtxos.All(v => v.IsSpent());
+                    if (allInputsSpent)
+                        break;
+
+                    logger?.LogInformation(
+                        "PostSpendVtxoPolling: attempt {Attempt}/{Max} for TxId={TxId} — output VTXOs found but {Unspent} input(s) still unspent",
+                        attempt, maxAttempts, @event.TransactionId,
+                        inputVtxos.Count(v => !v.IsSpent()));
+                }
 
                 if (attempt < maxAttempts)
                     await Task.Delay(delay, cancellationToken);

NArk.Core/Services/VtxoSynchronizationService.cs

@@ -4,6 +4,7 @@
 using NArk.Abstractions.Scripts;
 using NArk.Abstractions.VTXOs;
 using NArk.Core.Transport;
+using NBitcoin;
 
 namespace NArk.Core.Services;
 
@@ -248,6 +249,16 @@ public async Task<int> PollScriptsForVtxos(IReadOnlySet<string> scripts, Cancell
         return count;
     }
 
+    /// <summary>
+    /// Retrieves VTXOs from local storage by their outpoints (including spent ones).
+    /// </summary>
+    public async Task<IReadOnlyCollection<ArkVtxo>> GetVtxosByOutpoints(
+        IReadOnlyCollection<OutPoint> outpoints, CancellationToken cancellationToken = default)
+    {
+        return await _vtxoStorage.GetVtxos(outpoints: outpoints.ToList(), includeSpent: true,
+            cancellationToken: cancellationToken);
+    }
+
     public async ValueTask DisposeAsync()
     {
         _logger?.LogDebug("Disposing VTXO synchronization service");