Use Websocket for blockchain notifications

BTCPayServer/HostedServices/InvoiceNotificationManager.cs

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+using Hangfire;
+using Hangfire.Common;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Hangfire.Annotations;
+using System.Reflection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using System.Net.Http;
+using System.Text;
+using System.Threading;
+using NBitpayClient;
+using Newtonsoft.Json.Linq;
+using Newtonsoft.Json;
+using System.Collections.Concurrent;
+using Microsoft.Extensions.Hosting;
+using BTCPayServer.Events;
+using NBXplorer;
+using BTCPayServer.Services.Invoices;
+
+namespace BTCPayServer.HostedServices
+{
+    public class InvoiceNotificationManager : IHostedService
+    {
+        public static HttpClient _Client = new HttpClient();
+
+        public class ScheduledJob
+        {
+            public int TryCount
+            {
+                get; set;
+            }
+
+            public InvoiceEntity Invoice
+            {
+                get; set;
+            }
+        }
+
+        public ILogger Logger
+        {
+            get; set;
+        }
+
+        IBackgroundJobClient _JobClient;
+        EventAggregator _EventAggregator;
+        InvoiceRepository _InvoiceRepository;
+        BTCPayNetworkProvider _NetworkProvider;
+
+        public InvoiceNotificationManager(
+            IBackgroundJobClient jobClient,
+            EventAggregator eventAggregator,
+            InvoiceRepository invoiceRepository,
+            BTCPayNetworkProvider networkProvider,
+            ILogger<InvoiceNotificationManager> logger)
+        {
+            Logger = logger as ILogger ?? NullLogger.Instance;
+            _JobClient = jobClient;
+            _EventAggregator = eventAggregator;
+            _InvoiceRepository = invoiceRepository;
+            _NetworkProvider = networkProvider;
+        }
+
+        async Task Notify(InvoiceEntity invoice)
+        {
+            CancellationTokenSource cts = new CancellationTokenSource(10000);
+            try
+            {
+                await SendNotification(invoice, cts.Token);
+                return;
+            }
+            catch // It fails, it is OK because we try with hangfire after
+            {
+            }
+            var invoiceStr = NBitcoin.JsonConverters.Serializer.ToString(new ScheduledJob() { TryCount = 0, Invoice = invoice });
+            if (!string.IsNullOrEmpty(invoice.NotificationURL))
+                _JobClient.Schedule(() => NotifyHttp(invoiceStr), TimeSpan.Zero);
+        }
+
+        ConcurrentDictionary<string, string> _Executing = new ConcurrentDictionary<string, string>();
+        public async Task NotifyHttp(string invoiceData)
+        {
+            var job = NBitcoin.JsonConverters.Serializer.ToObject<ScheduledJob>(invoiceData);
+            var jobId = GetHttpJobId(job.Invoice);
+
+            if (!_Executing.TryAdd(jobId, jobId))
+                return; //For some reason, Hangfire fire the job several time
+
+            Logger.LogInformation("Running " + jobId);
+            bool reschedule = false;
+            CancellationTokenSource cts = new CancellationTokenSource(10000);
+            try
+            {
+                HttpResponseMessage response = await SendNotification(job.Invoice, cts.Token);
+                reschedule = response.StatusCode != System.Net.HttpStatusCode.OK;
+                Logger.LogInformation("Job " + jobId + " returned " + response.StatusCode);
+            }
+            catch (Exception ex)
+            {
+                reschedule = true;
+                Logger.LogInformation("Job " + jobId + " threw exception " + ex.Message);
+            }
+            finally { cts.Dispose(); _Executing.TryRemove(jobId, out jobId); }
+
+            job.TryCount++;
+
+            if (job.TryCount < MaxTry && reschedule)
+            {
+                Logger.LogInformation("Rescheduling " + jobId + " in 10 minutes, remaining try " + (MaxTry - job.TryCount));
+
+                invoiceData = NBitcoin.JsonConverters.Serializer.ToString(job);
+                _JobClient.Schedule(() => NotifyHttp(invoiceData), TimeSpan.FromMinutes(10.0));
+            }
+        }
+
+        private async Task<HttpResponseMessage> SendNotification(InvoiceEntity invoice, CancellationToken cancellation)
+        {
+            var request = new HttpRequestMessage();
+            request.Method = HttpMethod.Post;
+
+            var dto = invoice.EntityToDTO(_NetworkProvider);
+            InvoicePaymentNotification notification = new InvoicePaymentNotification()
+            {
+                Id = dto.Id,
+                Currency = dto.Currency,
+                CurrentTime = dto.CurrentTime,
+                ExceptionStatus = dto.ExceptionStatus,
+                ExpirationTime = dto.ExpirationTime,
+                InvoiceTime = dto.InvoiceTime,
+                PosData = dto.PosData,
+                Price = dto.Price,
+                Status = dto.Status,
+                BuyerFields = invoice.RefundMail == null ? null : new Newtonsoft.Json.Linq.JObject() { new JProperty("buyerEmail", invoice.RefundMail) }
+            };
+
+            // We keep backward compatibility with bitpay by passing BTC info to the notification
+            // we don't pass other info, as it is a bad idea to use IPN data for logic processing (can be faked)
+            var btcCryptoInfo = dto.CryptoInfo.FirstOrDefault(c => c.CryptoCode == "BTC");
+            if(btcCryptoInfo != null)
+            {
+#pragma warning disable CS0618
+                notification.Rate = (double)dto.Rate;
+                notification.Url = dto.Url;
+                notification.BTCDue = dto.BTCDue;
+                notification.BTCPaid = dto.BTCPaid;
+                notification.BTCPrice = dto.BTCPrice;
+#pragma warning restore CS0618
+            }
+            request.RequestUri = new Uri(invoice.NotificationURL, UriKind.Absolute);
+            request.Content = new StringContent(JsonConvert.SerializeObject(notification), Encoding.UTF8, "application/json");
+            var response = await _Client.SendAsync(request, cancellation);
+            return response;
+        }
+
+        int MaxTry = 6;
+
+        private static string GetHttpJobId(InvoiceEntity invoice)
+        {
+            return $"{invoice.Id}-{invoice.Status}-HTTP";
+        }
+
+        CompositeDisposable leases = new CompositeDisposable();
+        public Task StartAsync(CancellationToken cancellationToken)
+        {
+            leases.Add(_EventAggregator.Subscribe<InvoiceStatusChangedEvent>(async e => 
+            {
+                var invoice = await _InvoiceRepository.GetInvoice(null, e.InvoiceId);
+
+                // we need to use the status in the event and not in the invoice. The invoice might now be in another status.
+                if (invoice.FullNotifications)
+                {
+                    if (e.NewState == "expired" ||
+                       e.NewState == "paid" ||
+                       e.NewState == "invalid" ||
+                       e.NewState == "complete"
+                     )
+                        await Notify(invoice);
+                }
+                
+                if(e.NewState == "confirmed")
+                {
+                    await Notify(invoice);
+                }
+            }));
+            return Task.CompletedTask;
+        }
+
+        public Task StopAsync(CancellationToken cancellationToken)
+        {
+            leases.Dispose();
+            return Task.CompletedTask;
+        }
+    }
+}