Use callback to update invoice state instead of long polling

BTCPayServer/Controllers/CallbackController.cs

@@ -0,0 +1,116 @@
+using BTCPayServer.Logging;
+using BTCPayServer.Servcices.Invoices;
+using BTCPayServer.Services;
+using BTCPayServer.Services.Wallets;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using NBitcoin;
+using NBXplorer;
+using Microsoft.Extensions.Logging;
+using NBXplorer.DerivationStrategy;
+using NBXplorer.Models;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Controllers
+{
+	public class CallbackController : Controller
+	{
+		public class CallbackSettings
+		{
+			public string Token
+			{
+				get; set;
+			}
+		}
+		SettingsRepository _Settings;
+		Network _Network;
+		InvoiceWatcher _Watcher;
+		ExplorerClient _Explorer;
+
+		public CallbackController(SettingsRepository repo,
+								  ExplorerClient explorer,
+								  InvoiceWatcher watcher,
+								  Network network)
+		{
+			_Settings = repo;
+			_Network = network;
+			_Watcher = watcher;
+			_Explorer = explorer;
+		}
+
+		[Route("callbacks/transactions")]
+		[HttpPost]
+		public async Task NewTransaction(string token)
+		{
+			await AssertToken(token);
+			Logs.PayServer.LogInformation("New transaction callback");
+			//We don't want to register all the json converter at MVC level, so we parse here
+			var serializer = new NBXplorer.Serializer(_Network);
+			var content = await new StreamReader(Request.Body, new UTF8Encoding(false), false, 1024, true).ReadToEndAsync();
+			var match = serializer.ToObject<TransactionMatch>(content);
+
+			foreach(var output in match.Outputs)
+			{
+				await _Watcher.NotifyReceived(output.ScriptPubKey);
+			}
+		}
+
+		[Route("callbacks/blocks")]
+		[HttpPost]
+		public async Task NewBlock(string token)
+		{
+			await AssertToken(token);
+			Logs.PayServer.LogInformation("New block callback");
+			await _Watcher.NotifyBlock();
+		}
+
+		private async Task AssertToken(string token)
+		{
+			var callback = await _Settings.GetSettingAsync<CallbackSettings>();
+			if(await GetToken() != token)
+				throw new BTCPayServer.BitpayHttpException(400, "invalid-callback-token");
+		}
+
+		public async Task<Uri> GetCallbackUriAsync(HttpRequest request)
+		{
+			string token = await GetToken();
+			return new Uri(request.GetAbsoluteRoot() + "/callbacks/transactions?token=" + token);
+		}
+
+		public async Task RegisterCallbackUriAsync(DerivationStrategyBase derivationScheme, HttpRequest request)
+		{
+			var uri = await GetCallbackUriAsync(request);
+			await _Explorer.SubscribeToWalletAsync(uri, derivationScheme);
+		}
+
+		private async Task<string> GetToken()
+		{
+			var callback = await _Settings.GetSettingAsync<CallbackSettings>();
+			if(callback == null)
+			{
+				callback = new CallbackSettings() { Token = Guid.NewGuid().ToString() };
+				await _Settings.UpdateSetting(callback);
+			}
+			var token = callback.Token;
+			return token;
+		}
+
+		public async Task<Uri> GetCallbackBlockUriAsync(HttpRequest request)
+		{
+			string token = await GetToken();
+			return new Uri(request.GetAbsoluteRoot() + "/callbacks/blocks?token=" + token);
+		}
+
+		public async Task<Uri> RegisterCallbackBlockUriAsync(HttpRequest request)
+		{
+			var uri = await GetCallbackBlockUriAsync(request);
+			await _Explorer.SubscribeToBlocksAsync(uri);
+			return uri;
+		}
+	}
+}