btcpayserver/BTCPayServer/Services/Invoices/InvoiceNotificationManager.cs

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;

namespace BTCPayServer.Servcices.Invoices
{
	public class InvoiceNotificationManager
	{
		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;
		public InvoiceNotificationManager(
			IBackgroundJobClient jobClient,
			ILogger<InvoiceNotificationManager> logger)
		{
			Logger = logger as ILogger ?? NullLogger.Instance;
			_JobClient = jobClient;
		}

		public void Notify(InvoiceEntity invoice)
		{
			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
			{
				var request = new HttpRequestMessage();
				request.Method = HttpMethod.Post;

				var dto = job.Invoice.EntityToDTO();
				InvoicePaymentNotification notification = new InvoicePaymentNotification()
				{
					Id = dto.Id,
					Url = dto.Url,
					BTCDue = dto.BTCDue,
					BTCPaid = dto.BTCPaid,
					BTCPrice = dto.BTCPrice,
					Currency = dto.Currency,
					CurrentTime = dto.CurrentTime,
					ExceptionStatus = dto.ExceptionStatus,
					ExpirationTime = dto.ExpirationTime,
					InvoiceTime = dto.InvoiceTime,
					PosData = dto.PosData,
					Price = dto.Price,
					Rate = dto.Rate,
					Status = dto.Status,
					BuyerFields = job.Invoice.RefundMail == null ? null : new Newtonsoft.Json.Linq.JObject() { new JProperty("buyerEmail", job.Invoice.RefundMail) }
				};
				request.RequestUri = new Uri(job.Invoice.NotificationURL, UriKind.Absolute);
				request.Content = new StringContent(JsonConvert.SerializeObject(notification), Encoding.UTF8, "application/json");
				var response = await _Client.SendAsync(request, 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));
			}
		}

		int MaxTry = 6;

		private static string GetHttpJobId(InvoiceEntity invoice)
		{
			return $"{invoice.Id}-{invoice.Status}-HTTP";
		}
	}
}