Remember parsed target

PayForReactions/ZapperRelay.cs

@@ -1,4 +1,5 @@
 using FASTER.core;
+using Microsoft.Extensions.Caching.Memory;
 using Nostr.Client.Json;
 using Nostr.Client.Keys;
 using Nostr.Client.Messages;
@@ -13,6 +14,7 @@ namespace PayForReactions;
 public class ZapperRelay : INostrRelay, IDisposable
 {
     private readonly ILogger<ZapperRelay> _logger;
+    private readonly IMemoryCache _cache;
     private readonly Config _config;
     private readonly Lnurl _lnurl;
     private readonly AlbyApi _albyApi;
@@ -20,13 +22,14 @@ public class ZapperRelay : INostrRelay, IDisposable
     private readonly EventSession _session;
 
     public ZapperRelay(Lnurl lnurl, AlbyApi albyApi, NostrServicesClient nostrServices, Config config, NostrStore store,
-        ILogger<ZapperRelay> logger)
+        ILogger<ZapperRelay> logger, IMemoryCache cache)
     {
         _lnurl = lnurl;
         _albyApi = albyApi;
         _nostrServices = nostrServices;
         _config = config;
         _logger = logger;
+        _cache = cache;
         _session = store.MainStore.For(new SimpleFunctions<byte[], byte[]>()).NewSession<SimpleFunctions<byte[], byte[]>>();
     }
 
@@ -108,6 +111,15 @@ public class ZapperRelay : INostrRelay, IDisposable
                 return new(false, "blocked: wallet is down, no zap for you!");
             }
 
+            var keyEventWalletSeen = $"zapaped:{refEvent.Id}:{parsedTarget}";
+            var eventWalletZapTry = _cache.Get<int>(keyEventWalletSeen);
+            if (eventWalletZapTry > 0)
+            {
+                return new(false, $"blocked: hey i already zapped you! (count={eventWalletZapTry}");
+            }
+
+            _cache.Set(keyEventWalletSeen, ++eventWalletZapTry);
+
             var key = NostrPrivateKey.FromBech32(_config.PrivateKey);
             var myPubkey = key.DerivePublicKey().Hex;
             var zap = new NostrEvent