Use websockets in checkout page to get notified of paid invoices

BTCPayServer/Controllers/InvoiceController.UI.cs

@@ -16,12 +16,14 @@ using System.Security.Claims;
 using System.Text;
 using System.Threading.Tasks;
 using BTCPayServer.Services.Rates;
+using System.Net.WebSockets;
+using System.Threading;
+using BTCPayServer.Events;
 
 namespace BTCPayServer.Controllers
 {
     public partial class InvoiceController
     {
-
         [HttpPost]
         [Route("invoices/{invoiceId}")]
         public IActionResult Invoice(string invoiceId, string command)
@@ -169,6 +171,73 @@ namespace BTCPayServer.Controllers
             return Json(model);
         }
 
+        [HttpGet]
+        [Route("i/{invoiceId}/status/ws")]
+        public async Task<IActionResult> GetStatusWebSocket(string invoiceId)
+        {
+            if (!HttpContext.WebSockets.IsWebSocketRequest)
+                return NotFound();
+            var invoice = await _InvoiceRepository.GetInvoice(null, invoiceId);
+            if (invoice == null || invoice.Status == "complete" || invoice.Status == "invalid" || invoice.Status == "expired")
+                return NotFound();
+            var webSocket = await HttpContext.WebSockets.AcceptWebSocketAsync();
+            CompositeDisposable leases = new CompositeDisposable();
+            try
+            {
+                _EventAggregator.Subscribe<Events.InvoiceDataChangedEvent>(async o => await NotifySocket(webSocket, o.InvoiceId, invoiceId));
+                _EventAggregator.Subscribe<Events.InvoicePaymentEvent>(async o => await NotifySocket(webSocket, o.InvoiceId, invoiceId));
+                _EventAggregator.Subscribe<Events.InvoiceStatusChangedEvent>(async o => await NotifySocket(webSocket, o.InvoiceId, invoiceId));
+                while (true)
+                {
+                    var message = await webSocket.ReceiveAsync(DummyBuffer, default(CancellationToken));
+                    if (message.MessageType == WebSocketMessageType.Close)
+                        break;
+                }
+            }
+            finally
+            {
+                leases.Dispose();
+                await CloseSocket(webSocket);
+            }
+            return new NoResponse();
+        }
+
+        class NoResponse : IActionResult
+        {
+            public Task ExecuteResultAsync(ActionContext context)
+            {
+                return Task.CompletedTask;
+            }
+        }
+
+        ArraySegment<Byte> DummyBuffer = new ArraySegment<Byte>(new Byte[1]);
+        private async Task NotifySocket(WebSocket webSocket, string invoiceId, string expectedId)
+        {
+            if (invoiceId != expectedId || webSocket.State != WebSocketState.Open)
+                return;
+            CancellationTokenSource cts = new CancellationTokenSource();
+            cts.CancelAfter(5000);
+            try
+            {
+                await webSocket.SendAsync(DummyBuffer, WebSocketMessageType.Binary, true, cts.Token);
+            }
+            catch { await CloseSocket(webSocket); }
+        }
+
+        private static async Task CloseSocket(WebSocket webSocket)
+        {
+            try
+            {
+                if (webSocket.State == WebSocketState.Open)
+                {
+                    CancellationTokenSource cts = new CancellationTokenSource();
+                    cts.CancelAfter(5000);
+                    await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", cts.Token);
+                }
+            }
+            finally { webSocket.Dispose(); }
+        }
+
         [HttpPost]
         [Route("i/{invoiceId}/UpdateCustomer")]
         public async Task<IActionResult> UpdateCustomer(string invoiceId, [FromBody]UpdateCustomerModel data)

BTCPayServer/Controllers/InvoiceController.cs

@@ -53,7 +53,7 @@ namespace BTCPayServer.Controllers
         IFeeProvider _FeeProvider;
         private CurrencyNameTable _CurrencyNameTable;
         ExplorerClient _Explorer;
-
+        EventAggregator _EventAggregator;
         public InvoiceController(
             Network network,
             InvoiceRepository invoiceRepository,
@@ -62,6 +62,7 @@ namespace BTCPayServer.Controllers
             BTCPayWallet wallet,
             IRateProvider rateProvider,
             StoreRepository storeRepository,
+            EventAggregator eventAggregator,
             InvoiceWatcherAccessor watcher,
             ExplorerClient explorerClient,
             IFeeProvider feeProvider)
@@ -76,6 +77,7 @@ namespace BTCPayServer.Controllers
             _Watcher = (watcher ?? throw new ArgumentNullException(nameof(watcher))).Instance;
             _UserManager = userManager;
             _FeeProvider = feeProvider ?? throw new ArgumentNullException(nameof(feeProvider));
+            _EventAggregator = eventAggregator;
         }
 
         internal async Task<DataWrapper<InvoiceResponse>> CreateInvoiceCore(Invoice invoice, StoreData store, string serverUrl, double expiryMinutes = 15)

BTCPayServer/Hosting/BTCpayMiddleware.cs

@@ -29,13 +29,11 @@ namespace BTCPayServer.Hosting
     {
         TokenRepository _TokenRepository;
         RequestDelegate _Next;
-        CallbackController _CallbackController;
         BTCPayServerOptions _Options;
 
         public BTCPayMiddleware(RequestDelegate next,
             TokenRepository tokenRepo,
-            BTCPayServerOptions options,
-            CallbackController callbackController)
+            BTCPayServerOptions options)
         {
             _TokenRepository = tokenRepo ?? throw new ArgumentNullException(nameof(tokenRepo));
             _Next = next ?? throw new ArgumentNullException(nameof(next));
@@ -43,12 +41,9 @@ namespace BTCPayServer.Hosting
         }
 
 
-
-        bool _Registered;
         public async Task Invoke(HttpContext httpContext)
         {
             RewriteHostIfNeeded(httpContext);
-
             httpContext.Request.Headers.TryGetValue("x-signature", out StringValues values);
             var sig = values.FirstOrDefault();
             httpContext.Request.Headers.TryGetValue("x-identity", out values);

BTCPayServer/Hosting/Startup.cs

@@ -144,6 +144,7 @@ namespace BTCPayServer.Hosting
             app.UseAuthentication();
             app.UseHangfireServer();
             app.UseHangfireDashboard("/hangfire", new DashboardOptions() { Authorization = new[] { new NeedRole(Roles.ServerAdmin) } });
+            app.UseWebSockets();
             app.UseMvc(routes =>
             {
                 routes.MapRoute(

BTCPayServer/wwwroot/js/core.js

@@ -191,7 +191,7 @@ function onDataCallback(jsonData) {
     checkoutCtrl.srvModel = jsonData;
 }
 
-var watcher = setInterval(function () {
+function fetchStatus() {
     var path = srvModel.serverUrl + "/i/" + srvModel.invoiceId + "/status";
     $.ajax({
         url: path,
@@ -201,6 +201,21 @@ var watcher = setInterval(function () {
     }).fail(function (jqXHR, textStatus, errorThrown) {
 
     });
+}
+
+var supportsWebSockets = 'WebSocket' in window && window.WebSocket.CLOSING === 2;
+if (supportsWebSockets) {
+    var path = srvModel.serverUrl + "/i/" + srvModel.invoiceId + "/status/ws";
+    path = path.replace("https://", "wss://");
+    path = path.replace("http://", "ws://");
+    var socket = new WebSocket(path);
+    socket.onmessage = function (e) {
+        fetchStatus();
+    };
+}
+
+var watcher = setInterval(function () {
+    fetchStatus();
 }, 2000);
 
 $(".menu__item").click(function () {