From fa13a2874e43a2cbbcf90f0b64b5b52423243b47 Mon Sep 17 00:00:00 2001
From: "nicolas.dorier" <nicolas.dorier@gmail.com>
Date: Fri, 8 Dec 2017 15:04:47 +0900
Subject: [PATCH] Estimate rate with BTCPay if BitcoinAverage stops works

---
 BTCPayServer/BTCPayServer.csproj              |  2 +-
 BTCPayServer/Hosting/BTCPayServerServices.cs  |  4 +-
 .../Services/Rates/FallbackRateProvider.cs    | 43 +++++++++++++++++++
 3 files changed, 47 insertions(+), 2 deletions(-)
 create mode 100644 BTCPayServer/Services/Rates/FallbackRateProvider.cs

diff --git a/BTCPayServer/BTCPayServer.csproj b/BTCPayServer/BTCPayServer.csproj
index fc422f0a8..f0d9b42fa 100644
--- a/BTCPayServer/BTCPayServer.csproj
+++ b/BTCPayServer/BTCPayServer.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.0</TargetFramework>
-		<Version>1.0.0.38</Version>
+		<Version>1.0.0.39</Version>
   </PropertyGroup>
   <ItemGroup>
     <Compile Remove="Build\dockerfiles\**" />
diff --git a/BTCPayServer/Hosting/BTCPayServerServices.cs b/BTCPayServer/Hosting/BTCPayServerServices.cs
index c970ef178..756923dd2 100644
--- a/BTCPayServer/Hosting/BTCPayServerServices.cs
+++ b/BTCPayServer/Hosting/BTCPayServerServices.cs
@@ -141,7 +141,9 @@ namespace BTCPayServer.Hosting
             });
             services.TryAddSingleton<IRateProvider>(o =>
             {
-                return new CachedRateProvider(new CoinAverageRateProvider(), o.GetRequiredService<IMemoryCache>()) { CacheSpan = TimeSpan.FromMinutes(1.0) };
+                var coinaverage = new CoinAverageRateProvider();
+                var bitpay = new BitpayRateProvider(new Bitpay(new Key(), new Uri("https://bitpay.com/")));
+                return new CachedRateProvider(new FallbackRateProvider(new IRateProvider[] { coinaverage, bitpay }), o.GetRequiredService<IMemoryCache>()) { CacheSpan = TimeSpan.FromMinutes(1.0) };
             });
             services.TryAddSingleton<InvoiceWatcher>();
             services.TryAddSingleton<InvoiceNotificationManager>();
diff --git a/BTCPayServer/Services/Rates/FallbackRateProvider.cs b/BTCPayServer/Services/Rates/FallbackRateProvider.cs
new file mode 100644
index 000000000..59e57c0f3
--- /dev/null
+++ b/BTCPayServer/Services/Rates/FallbackRateProvider.cs
@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Services.Rates
+{
+    public class FallbackRateProvider : IRateProvider
+    {
+        IRateProvider[] _Providers;
+        public FallbackRateProvider(IRateProvider[] providers)
+        {
+            if (providers == null)
+                throw new ArgumentNullException(nameof(providers));
+            _Providers = providers;
+        }
+        public async Task<decimal> GetRateAsync(string currency)
+        {
+            foreach(var p in _Providers)
+            {
+                try
+                {
+                    return await p.GetRateAsync(currency).ConfigureAwait(false);
+                }
+                catch { }
+            }
+            throw new RateUnavailableException(currency);
+        }
+
+        public async Task<ICollection<Rate>> GetRatesAsync()
+        {
+            foreach (var p in _Providers)
+            {
+                try
+                {
+                    return await p.GetRatesAsync().ConfigureAwait(false);
+                }
+                catch { }
+            }
+            throw new RateUnavailableException("ALL");
+        }
+    }
+}