Add preliminary support for buttons

PluralKit.Bot/Services/InteractionDispatchService.cs

@@ -0,0 +1,92 @@
+using System;
+using System.Collections.Concurrent;
+using System.Threading;
+using System.Threading.Tasks;
+
+using NodaTime;
+
+using Serilog;
+
+namespace PluralKit.Bot
+{
+    public class InteractionDispatchService: IDisposable
+    {
+        private static readonly Duration DefaultExpiry = Duration.FromMinutes(15);
+
+        private readonly ConcurrentDictionary<Guid, RegisteredInteraction> _handlers = new();
+        private readonly CancellationTokenSource _cts = new();
+        private readonly IClock _clock;
+        private readonly ILogger _logger;
+        private readonly Task _cleanupWorker;
+        
+        public InteractionDispatchService(IClock clock, ILogger logger)
+        {
+            _clock = clock;
+            _logger = logger.ForContext<InteractionDispatchService>();
+
+            _cleanupWorker = CleanupLoop(_cts.Token);
+        }
+
+        public async ValueTask<bool> Dispatch(string customId, InteractionContext context)
+        {
+            if (!Guid.TryParse(customId, out var customIdGuid))
+                return false;
+            
+            if (!_handlers.TryGetValue(customIdGuid, out var handler))
+                return false;
+
+            await handler.Callback.Invoke(context);
+            return true;
+        }
+
+        public string Register(Func<InteractionContext, Task> callback, Duration? expiry = null)
+        {
+            var key = Guid.NewGuid();
+            var handler = new RegisteredInteraction
+            {
+                Callback = callback, 
+                Expiry = _clock.GetCurrentInstant() + (expiry ?? DefaultExpiry)
+            };
+            
+            _handlers[key] = handler;
+            return key.ToString();
+        }
+
+        private async Task CleanupLoop(CancellationToken ct)
+        {
+            while (true)
+            {
+                DoCleanup();
+                await Task.Delay(TimeSpan.FromMinutes(1), ct);
+            }
+        }
+
+        private void DoCleanup()
+        {
+            var now = _clock.GetCurrentInstant();
+            var removedCount = 0;
+            foreach (var (key, value) in _handlers.ToArray())
+            {
+                if (value.Expiry < now)
+                {
+                    _handlers.TryRemove(key, out _);
+                    removedCount++;
+                }
+            }
+
+            _logger.Debug("Removed {ExpiredInteractions} expired interactions", removedCount);
+        }
+
+        private struct RegisteredInteraction
+        {
+            public Instant Expiry;
+            public Func<InteractionContext, Task> Callback;
+        }
+
+        public void Dispose()
+        {
+            _cts.Cancel(); 
+            _cts.Dispose();
+        }
+    }
+}