feat(AuthHub): Added GetPublicKeyAsync method to send the key to caller

src/DigitalData.Auth.API/Hubs/AuthHub.cs

@@ -1,10 +1,47 @@
 using DigitalData.Auth.Abstractions;
+using DigitalData.Core.Abstractions.Security;
 using Microsoft.AspNetCore.SignalR;
+using Microsoft.Extensions.Caching.Memory;
 
 namespace DigitalData.Auth.API.Hubs;
 
 public class AuthHub : Hub<IAuthListenHandler>, IAuthSenderHandler
 {
+    private readonly ICryptoFactory _cFactory;
+
+    private readonly ILogger _logger;
+
+    private readonly IMemoryCache _cache;
+
+    private readonly static string CacheId = Guid.NewGuid().ToString();
+
+    public AuthHub(ICryptoFactory cryptoFactory, ILogger logger, IMemoryCache cache)
+    {
+        _cFactory = cryptoFactory;
+        _logger = logger;
+        _cache = cache;
+    }
+
+    public async Task GetPublicKeyAsync(string issuer, string audience)
+    {
+        if(_cFactory.TokenDescriptors.TryGet(issuer, audience, out var tDesc))
+        {
+            await Clients.Caller.ReceivePublicKeyAsync(issuer, audience, tDesc.PublicKey.Content);
+        }
+        else
+        {
+            await Clients.Caller.ReceivePublicKeyAsync(issuer, audience, string.Empty);
+
+            // Log this warning only once per minute to avoid unnecessary repetition.
+            _cache.GetOrCreate(CacheId + "LastLoggingDate", e =>
+            {
+                _logger.LogWarning("Token description is not found. Issuer: {issuer} Audience: {audience}", issuer, audience);
+                e.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(1);
+                return true;
+            });
+        }
+    }
+
     public async Task SendPublicKeyAsync(string issuer, string audience, string value)
         => await Clients.All.ReceivePublicKeyAsync(issuer, audience, value);
 }