Make sure we do not return outdated rates

# Conflicts:
#	BTCPayServer/BTCPayServer.csproj

BTCPayServer.Tests/BTCPayServerTester.cs

@@ -120,36 +120,67 @@ namespace BTCPayServer.Tests
                     .Build();
             _Host.Start();
             InvoiceRepository = (InvoiceRepository)_Host.Services.GetService(typeof(InvoiceRepository));
-            StoreRepository = (StoreRepository)_Host.Services.GetService(typeof(StoreRepository)); 
-            var rateProvider = (BTCPayRateProviderFactory)_Host.Services.GetService(typeof(BTCPayRateProviderFactory));
-            rateProvider.DirectProviders.Clear();
+            StoreRepository = (StoreRepository)_Host.Services.GetService(typeof(StoreRepository));
 
-            var coinAverageMock = new MockRateProvider();
-            coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
+            if (MockRates)
             {
-                Exchange = "coinaverage",
-                CurrencyPair = CurrencyPair.Parse("BTC_USD"),
-                BidAsk = new BidAsk(5000m)
-            });
-            coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
-            {
-                Exchange = "coinaverage",
-                CurrencyPair = CurrencyPair.Parse("BTC_CAD"),
-                BidAsk = new BidAsk(4500m)
-            });
-            coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
-            {
-                Exchange = "coinaverage",
-                CurrencyPair = CurrencyPair.Parse("LTC_BTC"),
-                BidAsk = new BidAsk(0.001m)
-            });
-            coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
-            {
-                Exchange = "coinaverage",
-                CurrencyPair = CurrencyPair.Parse("LTC_USD"),
-                BidAsk = new BidAsk(500m)
-            });
-            rateProvider.DirectProviders.Add("coinaverage", coinAverageMock);
+                var rateProvider = (RateProviderFactory)_Host.Services.GetService(typeof(RateProviderFactory));
+                rateProvider.Providers.Clear();
+
+                var coinAverageMock = new MockRateProvider();
+                coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "coinaverage",
+                    CurrencyPair = CurrencyPair.Parse("BTC_USD"),
+                    BidAsk = new BidAsk(5000m)
+                });
+                coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "coinaverage",
+                    CurrencyPair = CurrencyPair.Parse("BTC_CAD"),
+                    BidAsk = new BidAsk(4500m)
+                });
+                coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "coinaverage",
+                    CurrencyPair = CurrencyPair.Parse("LTC_BTC"),
+                    BidAsk = new BidAsk(0.001m)
+                });
+                coinAverageMock.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "coinaverage",
+                    CurrencyPair = CurrencyPair.Parse("LTC_USD"),
+                    BidAsk = new BidAsk(500m)
+                });
+                rateProvider.Providers.Add("coinaverage", coinAverageMock);
+
+                var bitflyerMock = new MockRateProvider();
+                bitflyerMock.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "bitflyer",
+                    CurrencyPair = CurrencyPair.Parse("BTC_JPY"),
+                    BidAsk = new BidAsk(700000m)
+                });
+                rateProvider.Providers.Add("bitflyer", bitflyerMock);
+
+                var quadrigacx = new MockRateProvider();
+                quadrigacx.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "quadrigacx",
+                    CurrencyPair = CurrencyPair.Parse("BTC_CAD"),
+                    BidAsk = new BidAsk(6000m)
+                });
+                rateProvider.Providers.Add("quadrigacx", quadrigacx);
+
+                var bittrex = new MockRateProvider();
+                bittrex.ExchangeRates.Add(new Rating.ExchangeRate()
+                {
+                    Exchange = "bittrex",
+                    CurrencyPair = CurrencyPair.Parse("DOGE_BTC"),
+                    BidAsk = new BidAsk(0.004m)
+                });
+                rateProvider.Providers.Add("bittrex", bittrex);
+            }
         }
 
         public string HostName
@@ -177,7 +208,7 @@ namespace BTCPayServer.Tests
             {
                 context.User = new ClaimsPrincipal(new ClaimsIdentity(new[] { new Claim(ClaimTypes.NameIdentifier, userId) }, Policies.CookieAuthentication));
             }
-            if(storeId != null)
+            if (storeId != null)
             {
                 context.SetStoreData(GetService<StoreRepository>().FindStore(storeId, userId).GetAwaiter().GetResult());
             }

BTCPayServer.Tests/TestAccount.cs

@@ -14,6 +14,7 @@ using Xunit;
 using NBXplorer.DerivationStrategy;
 using BTCPayServer.Payments;
 using BTCPayServer.Payments.Lightning;
+using BTCPayServer.Tests.Logging;
 
 namespace BTCPayServer.Tests
 {

BTCPayServer.Tests/UnitTest1.cs

@@ -398,6 +398,7 @@ namespace BTCPayServer.Tests
         }
 
         [Fact]
+        [Trait("Flaky", "Flaky")]
         public void CanSetLightningServer()
         {
             using (var tester = ServerTester.Create())
@@ -546,18 +547,21 @@ namespace BTCPayServer.Tests
         }
 
         [Fact]
+        [Trait("Flaky", "Flaky")]
         public void CanSendLightningPaymentCLightning()
         {
             ProcessLightningPayment(LightningConnectionType.CLightning);
         }
 
         [Fact]
+        [Trait("Flaky", "Flaky")]
         public void CanSendLightningPaymentCharge()
         {
             ProcessLightningPayment(LightningConnectionType.Charge);
         }
 
         [Fact]
+        [Trait("Flaky", "Flaky")]
         public void CanSendLightningPaymentLnd()
         {
             ProcessLightningPayment(LightningConnectionType.LndREST);
@@ -943,8 +947,8 @@ namespace BTCPayServer.Tests
                 user.RegisterDerivationScheme("BTC");
                 List<decimal> rates = new List<decimal>();
                 rates.Add(CreateInvoice(tester, user, "coinaverage"));
-                var bitflyer = CreateInvoice(tester, user, "bitflyer");
-                var bitflyer2 = CreateInvoice(tester, user, "bitflyer");
+                var bitflyer = CreateInvoice(tester, user, "bitflyer", "JPY");
+                var bitflyer2 = CreateInvoice(tester, user, "bitflyer", "JPY");
                 Assert.Equal(bitflyer, bitflyer2); // Should be equal because cache
                 rates.Add(bitflyer);
 
@@ -955,7 +959,7 @@ namespace BTCPayServer.Tests
             }
         }
 
-        private static decimal CreateInvoice(ServerTester tester, TestAccount user, string exchange)
+        private static decimal CreateInvoice(ServerTester tester, TestAccount user, string exchange, string currency = "USD")
         {
             var storeController = user.GetController<StoresController>();
             var vm = (RatesViewModel)((ViewResult)storeController.Rates()).Model;
@@ -964,7 +968,7 @@ namespace BTCPayServer.Tests
             var invoice2 = user.BitPay.CreateInvoice(new Invoice()
             {
                 Price = 5000.0m,
-                Currency = "USD",
+                Currency = currency,
                 PosData = "posData",
                 OrderId = "orderId",
                 ItemDesc = "Some description",
@@ -978,12 +982,10 @@ namespace BTCPayServer.Tests
         {
             using (var tester = ServerTester.Create())
             {
-                tester.PayTester.MockRates = false;
                 tester.Start();
                 var user = tester.NewAccount();
                 user.GrantAccess();
                 user.RegisterDerivationScheme("BTC");
-
                 // First we try payment with a merchant having only BTC
                 var invoice1 = user.BitPay.CreateInvoice(new Invoice()
                 {
@@ -994,7 +996,7 @@ namespace BTCPayServer.Tests
                     ItemDesc = "Some description",
                     FullNotifications = true
                 }, Facade.Merchant);
-
+                Assert.Equal(Money.Coins(1.0m), invoice1.BtcPrice);
 
                 var storeController = user.GetController<StoresController>();
                 var vm = (RatesViewModel)((ViewResult)storeController.Rates()).Model;
@@ -1013,11 +1015,9 @@ namespace BTCPayServer.Tests
                     FullNotifications = true
                 }, Facade.Merchant);
 
-                // The rate was 5000 USD per BTC
-                // Now it should be 3000 USD per BTC
-                // So the expected price should be
-                var expected = Money.Coins(5000m / 3000m);
-                Assert.True(invoice2.BtcPrice.Almost(expected, 0.00001m));
+                var expectedRate = 5000.0m * 0.6m;
+                var expectedCoins = invoice2.Price / expectedRate;
+                Assert.True(invoice2.BtcPrice.Almost(Money.Coins(expectedCoins), 0.00001m));
             }
         }
 
@@ -1132,7 +1132,7 @@ namespace BTCPayServer.Tests
                 rateVm.ScriptTest = "BTC_USD,BTC_CAD,DOGE_USD,DOGE_CAD";
                 rateVm.Script = "DOGE_X = bittrex(DOGE_BTC) * BTC_X;\n" +
                                 "X_CAD = quadrigacx(X_CAD);\n" +
-                                 "X_X = gdax(X_X);";
+                                 "X_X = coinaverage(X_X);";
                 rateVm.Spread = 50;
                 rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates(rateVm, "Test").Result).Model);
                 Assert.True(rateVm.TestRateRules.All(t => !t.Error));
@@ -1666,15 +1666,17 @@ namespace BTCPayServer.Tests
         [Fact]
         public void CanQueryDirectProviders()
         {
-            var provider = new BTCPayNetworkProvider(NetworkType.Mainnet);
-            var factory = CreateBTCPayRateFactory(provider);
+            var factory = CreateBTCPayRateFactory();
 
             foreach (var result in factory
-                .DirectProviders
-                .Select(p => (ExpectedName: p.Key, ResultAsync: p.Value.GetRatesAsync()))
+                .Providers
+                .Where(p => p.Value is BackgroundFetcherRateProvider)
+                .Select(p => (ExpectedName: p.Key, ResultAsync: p.Value.GetRatesAsync(), Fetcher: (BackgroundFetcherRateProvider)p.Value))
                 .ToList())
             {
+                result.Fetcher.InvalidateCache();
                 var exchangeRates = result.ResultAsync.Result;
+                result.Fetcher.InvalidateCache();
                 Assert.NotNull(exchangeRates);
                 Assert.NotEmpty(exchangeRates);
                 Assert.NotEmpty(exchangeRates.ByExchange[result.ExpectedName]);
@@ -1687,21 +1689,23 @@ namespace BTCPayServer.Tests
                                && e.BidAsk.Bid > 1.0m // 1BTC will always be more than 1USD
                                );
             }
+            // Kraken emit one request only after first GetRates
+            factory.Providers["kraken"].GetRatesAsync().GetAwaiter().GetResult();
         }
 
         [Fact]
         public void CanGetRateCryptoCurrenciesByDefault()
         {
             var provider = new BTCPayNetworkProvider(NetworkType.Mainnet);
-            var factory = CreateBTCPayRateFactory(provider);
-
+            var factory = CreateBTCPayRateFactory();
+            var fetcher = new RateFetcher(factory);
             var pairs =
                     provider.GetAll()
                     .Select(c => new CurrencyPair(c.CryptoCode, "USD"))
                     .ToHashSet();
 
             var rules = new StoreBlob().GetDefaultRateRules(provider);
-            var result = factory.FetchRates(pairs, rules);
+            var result = fetcher.FetchRates(pairs, rules);
             foreach (var value in result)
             {
                 var rateResult = value.Value.GetAwaiter().GetResult();
@@ -1709,46 +1713,93 @@ namespace BTCPayServer.Tests
             }
         }
 
-        private static BTCPayRateProviderFactory CreateBTCPayRateFactory(BTCPayNetworkProvider provider)
+        private static RateProviderFactory CreateBTCPayRateFactory()
         {
-            return new BTCPayRateProviderFactory(new MemoryCacheOptions() { ExpirationScanFrequency = TimeSpan.FromSeconds(1.0) }, provider, new CoinAverageSettings());
+            return new RateProviderFactory(CreateMemoryCache(), null, new CoinAverageSettings());
+        }
+
+        private static MemoryCacheOptions CreateMemoryCache()
+        {
+            return new MemoryCacheOptions() { ExpirationScanFrequency = TimeSpan.FromSeconds(1.0) };
+        }
+
+        class SpyRateProvider : IRateProvider
+        {
+            public bool Hit { get; set; }
+            public Task<ExchangeRates> GetRatesAsync()
+            {
+                Hit = true;
+                var rates = new ExchangeRates();
+                rates.Add(new ExchangeRate("coinaverage", CurrencyPair.Parse("BTC_USD"), new BidAsk(5000)));
+                return Task.FromResult(rates);
+            }
+
+            public void AssertHit()
+            {
+                Assert.True(Hit, "Should have hit the provider");
+                Hit = false;
+            }
+            public void AssertNotHit()
+            {
+                Assert.False(Hit, "Should have not hit the provider");
+                Hit = false;
+            }
         }
 
         [Fact]
         public void CheckRatesProvider()
         {
-            var provider = new BTCPayNetworkProvider(NetworkType.Mainnet);
-            var coinAverage = new CoinAverageRateProvider();
-            var rates = coinAverage.GetRatesAsync().GetAwaiter().GetResult();
-            Assert.NotNull(rates.GetRate("coinaverage", new CurrencyPair("BTC", "JPY")));
-            var ratesBitpay = new BitpayRateProvider(new Bitpay(new Key(), new Uri("https://bitpay.com/"))).GetRatesAsync().GetAwaiter().GetResult();
-            Assert.NotNull(ratesBitpay.GetRate("bitpay", new CurrencyPair("BTC", "JPY")));
-
+            var spy = new SpyRateProvider();
             RateRules.TryParse("X_X = coinaverage(X_X);", out var rateRules);
 
-            var factory = CreateBTCPayRateFactory(provider);
-            factory.CacheSpan = TimeSpan.FromSeconds(10);
+            var factory = CreateBTCPayRateFactory();
+            factory.Providers.Clear();
+            factory.Providers.Add("coinaverage", new CachedRateProvider("coinaverage", spy, new MemoryCache(CreateMemoryCache())));
+            factory.Providers.Add("bittrex", new CachedRateProvider("bittrex", spy, new MemoryCache(CreateMemoryCache())));
+            factory.CacheSpan = TimeSpan.FromSeconds(1);
 
-            var fetchedRate = factory.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
-            Assert.False(fetchedRate.Cached);
-            fetchedRate = factory.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
-            Assert.True(fetchedRate.Cached);
+            var fetcher = new RateFetcher(factory);
 
-            Thread.Sleep(11000);
-            fetchedRate = factory.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
-            Assert.False(fetchedRate.Cached);
-            fetchedRate = factory.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
-            Assert.True(fetchedRate.Cached);
+            var fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertHit();
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertNotHit();
+
+            Thread.Sleep(3000);
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertHit();
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertNotHit();
             // Should cache at exchange level so this should hit the cache
-            var fetchedRate2 = factory.FetchRate(CurrencyPair.Parse("LTC_USD"), rateRules).GetAwaiter().GetResult();
-            Assert.True(fetchedRate.Cached);
-            Assert.NotEqual(fetchedRate.BidAsk.Bid, fetchedRate2.BidAsk.Bid);
+            var fetchedRate2 = fetcher.FetchRate(CurrencyPair.Parse("LTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertNotHit();
+            Assert.Null(fetchedRate2.BidAsk);
+            Assert.Equal(RateRulesErrors.RateUnavailable, fetchedRate2.Errors.First());
 
             // Should cache at exchange level this should not hit the cache as it is different exchange
             RateRules.TryParse("X_X = bittrex(X_X);", out rateRules);
-            fetchedRate = factory.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
-            Assert.False(fetchedRate.Cached);
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertHit();
 
+            factory.Providers.Clear();
+            var fetch = new BackgroundFetcherRateProvider(spy);
+            factory.Providers.Add("bittrex", fetch);
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertHit();
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertNotHit();
+            fetch.UpdateIfNecessary().GetAwaiter().GetResult();
+            spy.AssertNotHit();
+            fetch.RefreshRate = TimeSpan.FromSeconds(1.0);
+            Thread.Sleep(1020);
+            fetchedRate = fetcher.FetchRate(CurrencyPair.Parse("BTC_USD"), rateRules).GetAwaiter().GetResult();
+            spy.AssertNotHit();
+            fetch.ValidatyTime = TimeSpan.FromSeconds(1.0);
+            fetch.UpdateIfNecessary().GetAwaiter().GetResult();
+            spy.AssertHit();
+            fetch.GetRatesAsync().GetAwaiter().GetResult();
+            Thread.Sleep(1000);
+            Assert.Throws<InvalidOperationException>(() => fetch.GetRatesAsync().GetAwaiter().GetResult());
         }
 
         private static bool IsMapped(Invoice invoice, ApplicationDbContext ctx)

BTCPayServer.Tests/docker-compose.yml

@@ -63,7 +63,7 @@ services:
 
 
   nbxplorer:
-    image: nicolasdorier/nbxplorer:1.0.2.14
+    image: nicolasdorier/nbxplorer:1.0.2.31
     ports:
       - "32838:32838"
     expose: 

BTCPayServer/BTCPayServer.csproj

@@ -2,9 +2,12 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.1</TargetFramework>
-		<Version>1.0.2.90</Version>
+		<Version>1.0.2.96</Version>
     <NoWarn>NU1701,CA1816,CA1308,CA1810,CA2208</NoWarn>
   </PropertyGroup>
+  <PropertyGroup>
+    <LangVersion>7.3</LangVersion>
+  </PropertyGroup>
   <ItemGroup>
     <Compile Remove="Build\dockerfiles\**" />
     <Compile Remove="wwwroot\bundles\jqueryvalidate\**" />
@@ -31,22 +34,22 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="BuildBundlerMinifier" Version="2.7.385" />
-    <PackageReference Include="DigitalRuby.ExchangeSharp" Version="0.4.1" />
+    <PackageReference Include="DigitalRuby.ExchangeSharp" Version="0.5.3" />
     <PackageReference Include="Hangfire" Version="1.6.19" />
     <PackageReference Include="Hangfire.MemoryStorage" Version="1.5.2" />
     <PackageReference Include="Hangfire.PostgreSql" Version="1.4.8.2" />
-    <PackageReference Include="LedgerWallet" Version="2.0.0" />
+    <PackageReference Include="LedgerWallet" Version="2.0.0.1" />
     <PackageReference Include="Meziantou.AspNetCore.BundleTagHelpers" Version="2.0.0" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="2.1.0" />
     <PackageReference Include="Microsoft.Extensions.Logging.Filter" Version="1.1.2" />
     <PackageReference Include="Microsoft.NetCore.Analyzers" Version="2.6.0" />
-    <PackageReference Include="NBitcoin" Version="4.1.1.32" />
+    <PackageReference Include="NBitcoin" Version="4.1.1.45" />
     <PackageReference Include="NBitpayClient" Version="1.0.0.29" />	  
     <PackageReference Include="DBreeze" Version="1.87.0" />
-    <PackageReference Include="NBXplorer.Client" Version="1.0.2.15" />
+    <PackageReference Include="NBXplorer.Client" Version="1.0.2.18" />
     <PackageReference Include="NicolasDorier.CommandLine" Version="1.0.0.2" />
     <PackageReference Include="NicolasDorier.CommandLine.Configuration" Version="1.0.0.3" />
-    <PackageReference Include="NicolasDorier.StandardConfiguration" Version="1.0.0.16" />
+    <PackageReference Include="NicolasDorier.StandardConfiguration" Version="1.0.0.17" />
     <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="2.1.0" />
     <PackageReference Include="SSH.NET" Version="2016.1.0" />
     <PackageReference Include="System.Xml.XmlSerializer" Version="4.3.0" />
@@ -116,7 +119,16 @@
 	</ItemGroup>
 
 	<ItemGroup>
-	  <Content Update="Views\Server\SSHService.cshtml">
+    <Content Update="Views\Server\SSHService.cshtml">
+      <Pack>$(IncludeRazorContentInPack)</Pack>
+    </Content>
+	  <Content Update="Views\Stores\PayButton.cshtml">
+	    <Pack>$(IncludeRazorContentInPack)</Pack>
+	  </Content>
+	  <Content Update="Views\Stores\PayButtonHandle.cshtml">
+	    <Pack>$(IncludeRazorContentInPack)</Pack>
+	  </Content>
+	  <Content Update="Views\Stores\PayButtonTest.cshtml">
 	    <Pack>$(IncludeRazorContentInPack)</Pack>
 	  </Content>
 	  <Content Update="Views\Server\LNDGRPCServices.cshtml">

BTCPayServer/Controllers/AppsController.PointOfSale.cs

@@ -163,7 +163,7 @@ namespace BTCPayServer.Controllers
             using (var ctx = _ContextFactory.CreateContext())
             {
                 return await ctx.Apps
-                                .Where(us => us.Id == appId && 
+                                .Where(us => us.Id == appId &&
                                              us.AppType == appType.ToString())
                                 .FirstOrDefaultAsync();
             }
@@ -263,14 +263,6 @@ namespace BTCPayServer.Controllers
             return Redirect(invoice.Data.Url);
         }
 
-        private async Task<StoreData> GetStore(AppData app)
-        {
-            using (var ctx = _ContextFactory.CreateContext())
-            {
-                return await ctx.Stores.FirstOrDefaultAsync(s => s.Id == app.StoreDataId);
-            }
-        }
-
         private async Task UpdateAppSettings(AppData app)
         {
             using (var ctx = _ContextFactory.CreateContext())

BTCPayServer/Controllers/AppsController.cs

@@ -1,18 +1,17 @@
 using System;
-using Microsoft.EntityFrameworkCore;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using BTCPayServer.Data;
 using BTCPayServer.Models;
 using BTCPayServer.Models.AppViewModels;
-using Microsoft.AspNetCore.Authorization;
-using Microsoft.AspNetCore.Identity;
-using Microsoft.AspNetCore.Mvc;
-using NBitcoin.DataEncoders;
-using NBitcoin;
 using BTCPayServer.Services.Apps;
 using BTCPayServer.Services.Rates;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using NBitcoin;
+using NBitcoin.DataEncoders;
 
 namespace BTCPayServer.Controllers
 {
@@ -24,6 +23,7 @@ namespace BTCPayServer.Controllers
         UserManager<ApplicationUser> _UserManager;
         CurrencyNameTable _Currencies;
         InvoiceController _InvoiceController;
+        BTCPayNetworkProvider _NetworkProvider;
 
         [TempData]
         public string StatusMessage { get; set; }
@@ -32,12 +32,14 @@ namespace BTCPayServer.Controllers
             UserManager<ApplicationUser> userManager,
             ApplicationDbContextFactory contextFactory,
             CurrencyNameTable currencies,
-            InvoiceController invoiceController)
+            InvoiceController invoiceController,
+            BTCPayNetworkProvider networkProvider)
         {
             _InvoiceController = invoiceController;
             _UserManager = userManager;
             _ContextFactory = contextFactory;
             _Currencies = currencies;
+            _NetworkProvider = networkProvider;
         }
         public async Task<IActionResult> ListApps()
         {
@@ -199,5 +201,13 @@ namespace BTCPayServer.Controllers
         {
             return _UserManager.GetUserId(User);
         }
+
+        private async Task<StoreData> GetStore(AppData app)
+        {
+            using (var ctx = _ContextFactory.CreateContext())
+            {
+                return await ctx.Stores.FirstOrDefaultAsync(s => s.Id == app.StoreDataId);
+            }
+        }
     }
 }

BTCPayServer/Controllers/InvoiceController.UI.cs

@@ -34,7 +34,6 @@ namespace BTCPayServer.Controllers
         {
             var invoice = (await _InvoiceRepository.GetInvoices(new InvoiceQuery()
             {
-                UserId = GetUserId(),
                 InvoiceId = invoiceId,
                 IncludeAddresses = true,
                 IncludeEvents = true

BTCPayServer/Controllers/InvoiceController.cs

@@ -49,7 +49,7 @@ namespace BTCPayServer.Controllers
     {
         InvoiceRepository _InvoiceRepository;
         ContentSecurityPolicies _CSP;
-        BTCPayRateProviderFactory _RateProvider;
+        RateFetcher _RateProvider;
         StoreRepository _StoreRepository;
         UserManager<ApplicationUser> _UserManager;
         private CurrencyNameTable _CurrencyNameTable;
@@ -62,7 +62,7 @@ namespace BTCPayServer.Controllers
             InvoiceRepository invoiceRepository,
             CurrencyNameTable currencyNameTable,
             UserManager<ApplicationUser> userManager,
-            BTCPayRateProviderFactory rateProvider,
+            RateFetcher rateProvider,
             StoreRepository storeRepository,
             EventAggregator eventAggregator,
             BTCPayWalletProvider walletProvider,
@@ -195,12 +195,9 @@ namespace BTCPayServer.Controllers
                     var allRateRuleErrors = string.Join(", ", rateResult.Errors.ToArray());
                     logs.Write($"{pair.Key}: Rate rule error ({allRateRuleErrors})");
                 }
-                if (rateResult.ExchangeExceptions.Count != 0)
+                foreach (var ex in rateResult.ExchangeExceptions)
                 {
-                    foreach (var ex in rateResult.ExchangeExceptions)
-                    {
-                        logs.Write($"{pair.Key}: Exception reaching exchange {ex.ExchangeName} ({ex.Exception.Message})");
-                    }
+                    logs.Write($"{pair.Key}: Exception reaching exchange {ex.ExchangeName} ({ex.Exception.Message})");
                 }
             }).ToArray());
         }
@@ -210,6 +207,7 @@ namespace BTCPayServer.Controllers
             try
             {
                 var storeBlob = store.GetStoreBlob();
+                var preparePayment = handler.PreparePayment(supportedPaymentMethod, store, network);
                 var rate = await fetchingByCurrencyPair[new CurrencyPair(network.CryptoCode, entity.ProductInformation.Currency)];
                 if (rate.BidAsk == null)
                 {
@@ -220,7 +218,7 @@ namespace BTCPayServer.Controllers
                 paymentMethod.Network = network;
                 paymentMethod.SetId(supportedPaymentMethod.PaymentId);
                 paymentMethod.Rate = rate.BidAsk.Bid;
-                var paymentDetails = await handler.CreatePaymentMethodDetails(supportedPaymentMethod, paymentMethod, store, network);
+                var paymentDetails = await handler.CreatePaymentMethodDetails(supportedPaymentMethod, paymentMethod, store, network, preparePayment);
                 if (storeBlob.NetworkFeeDisabled)
                     paymentDetails.SetNoTxFee();
                 paymentMethod.SetPaymentMethodDetails(paymentDetails);

BTCPayServer/Controllers/RateController.cs

@@ -15,12 +15,12 @@ namespace BTCPayServer.Controllers
 {
     public class RateController : Controller
     {
-        BTCPayRateProviderFactory _RateProviderFactory;
+        RateFetcher _RateProviderFactory;
         BTCPayNetworkProvider _NetworkProvider;
         CurrencyNameTable _CurrencyNameTable;
         StoreRepository _StoreRepo;
         public RateController(
-            BTCPayRateProviderFactory rateProviderFactory,
+            RateFetcher rateProviderFactory,
             BTCPayNetworkProvider networkProvider,
             StoreRepository storeRepo,
             CurrencyNameTable currencyNameTable)

BTCPayServer/Controllers/ServerController.cs

@@ -33,14 +33,14 @@ namespace BTCPayServer.Controllers
         private UserManager<ApplicationUser> _UserManager;
         SettingsRepository _SettingsRepository;
         private readonly NBXplorerDashboard _dashBoard;
-        private BTCPayRateProviderFactory _RateProviderFactory;
+        private RateFetcher _RateProviderFactory;
         private StoreRepository _StoreRepository;
         LightningConfigurationProvider _LnConfigProvider;
         BTCPayServerOptions _Options;
 
         public ServerController(UserManager<ApplicationUser> userManager,
             Configuration.BTCPayServerOptions options,
-            BTCPayRateProviderFactory rateProviderFactory,
+            RateFetcher rateProviderFactory,
             SettingsRepository settingsRepository,
             NBXplorerDashboard dashBoard,
             LightningConfigurationProvider lnConfigProvider,
@@ -180,6 +180,8 @@ namespace BTCPayServer.Controllers
                     return View(vm);
                 }
                 vm.DNSDomain = vm.DNSDomain.Trim().ToLowerInvariant();
+                if (vm.DNSDomain.Equals(this.Request.Host.Host, StringComparison.OrdinalIgnoreCase))
+                    return View(vm);
                 if (IPAddress.TryParse(vm.DNSDomain, out var unused))
                 {
                     ModelState.AddModelError(nameof(vm.DNSDomain), $"This should be a domain name");
@@ -200,12 +202,13 @@ namespace BTCPayServer.Controllers
                     {
                         builder.Scheme = this.Request.Scheme;
                         builder.Host = vm.DNSDomain;
-                        if (this.Request.Host.Port != null)
-                            builder.Port = this.Request.Host.Port.Value;
-                        builder.Path = "runid";
-                        builder.Query = $"expected={RunId}";
-                        var response = await client.GetAsync(builder.Uri);
-                        if (!response.IsSuccessStatusCode)
+                        var addresses1 = Dns.GetHostAddressesAsync(this.Request.Host.Host);
+                        var addresses2 = Dns.GetHostAddressesAsync(vm.DNSDomain);
+                        await Task.WhenAll(addresses1, addresses2);
+
+                        var addressesSet = addresses1.GetAwaiter().GetResult().Select(c => c.ToString()).ToHashSet();
+                        var hasCommonAddress = addresses2.GetAwaiter().GetResult().Select(c => c.ToString()).Any(s => addressesSet.Contains(s));
+                        if (!hasCommonAddress)
                         {
                             ModelState.AddModelError(nameof(vm.DNSDomain), $"Invalid host ({vm.DNSDomain} is not pointing to this BTCPay instance)");
                             return View(vm);

BTCPayServer/Controllers/StoresController.cs

@@ -1,8 +1,13 @@
-using BTCPayServer.Authentication;
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Authentication;
 using BTCPayServer.Configuration;
 using BTCPayServer.Data;
-using BTCPayServer.HostedServices;
 using BTCPayServer.Models;
+using BTCPayServer.Models.AppViewModels;
 using BTCPayServer.Models.StoreViewModels;
 using BTCPayServer.Rating;
 using BTCPayServer.Security;
@@ -11,21 +16,13 @@ using BTCPayServer.Services.Rates;
 using BTCPayServer.Services.Stores;
 using BTCPayServer.Services.Wallets;
 using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Cors;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Rendering;
-using Microsoft.Extensions.Options;
 using NBitcoin;
 using NBitcoin.DataEncoders;
-using NBXplorer.DerivationStrategy;
-using System;
-using System.Collections.Generic;
-using System.Globalization;
-using System.Linq;
-using System.Net.Http;
-using System.Threading;
-using System.Threading.Tasks;
 
 namespace BTCPayServer.Controllers
 {
@@ -35,7 +32,7 @@ namespace BTCPayServer.Controllers
     [AutoValidateAntiforgeryToken]
     public partial class StoresController : Controller
     {
-        BTCPayRateProviderFactory _RateFactory;
+        RateFetcher _RateFactory;
         public string CreatedStoreId { get; set; }
         public StoresController(
             IServiceProvider serviceProvider,
@@ -47,11 +44,12 @@ namespace BTCPayServer.Controllers
             AccessTokenController tokenController,
             BTCPayWalletProvider walletProvider,
             BTCPayNetworkProvider networkProvider,
-            BTCPayRateProviderFactory rateFactory,
+            RateFetcher rateFactory,
             ExplorerClientProvider explorerProvider,
             IFeeProviderFactory feeRateProvider,
             LanguageService langService,
-            IHostingEnvironment env)
+            IHostingEnvironment env,
+            InvoiceController invoiceController)
         {
             _RateFactory = rateFactory;
             _Repo = repo;
@@ -67,6 +65,7 @@ namespace BTCPayServer.Controllers
             _ServiceProvider = serviceProvider;
             _BtcpayServerOptions = btcpayServerOptions;
             _BTCPayEnv = btcpayEnv;
+            _InvoiceController = invoiceController;
         }
         BTCPayServerOptions _BtcpayServerOptions;
         BTCPayServerEnvironment _BTCPayEnv;
@@ -81,6 +80,7 @@ namespace BTCPayServer.Controllers
         UserManager<ApplicationUser> _UserManager;
         private LanguageService _LangService;
         IHostingEnvironment _Env;
+        InvoiceController _InvoiceController;
 
         [TempData]
         public string StatusMessage
@@ -521,7 +521,7 @@ namespace BTCPayServer.Controllers
 
         private CoinAverageExchange[] GetSupportedExchanges()
         {
-            return _RateFactory.GetSupportedExchanges()
+            return _RateFactory.RateProviderFactory.GetSupportedExchanges()
                     .Select(c => c.Value)
                     .OrderBy(s => s.Name, StringComparer.OrdinalIgnoreCase)
                     .ToArray();
@@ -767,5 +767,65 @@ namespace BTCPayServer.Controllers
                 return null;
             return _UserManager.GetUserId(User);
         }
+
+
+
+        // TODO: Need to have talk about how architect default currency implementation
+        // For now we have also hardcoded USD for Store creation and then Invoice creation
+        const string DEFAULT_CURRENCY = "USD";
+
+        [Route("{storeId}/paybutton")]
+        public IActionResult PayButton()
+        {
+            var store = StoreData;
+
+            var appUrl = HttpContext.Request.GetAbsoluteRoot().WithTrailingSlash();
+            var model = new PayButtonViewModel
+            {
+                Price = 10,
+                Currency = DEFAULT_CURRENCY,
+                ButtonSize = 2,
+                UrlRoot = appUrl,
+                PayButtonImageUrl = appUrl + "img/paybutton/pay.png",
+                StoreId = store.Id
+            };
+            return View(model);
+        }
+
+        [HttpPost]
+        [Route("{storeId}/pay")]
+        [IgnoreAntiforgeryToken]
+        [EnableCors(CorsPolicies.All)]
+        public async Task<IActionResult> PayButtonHandle(string storeId, [FromForm]PayButtonViewModel model)
+        {
+            var store = StoreData;
+
+            // TODO: extract validation to model
+            if (model.Price <= 0)
+                ModelState.AddModelError("Price", "Price must be greater than 0");
+
+            if (!ModelState.IsValid)
+                return View();
+
+            var invoice = await _InvoiceController.CreateInvoiceCore(new NBitpayClient.Invoice()
+            {
+                Price = model.Price,
+                Currency = model.Currency,
+                ItemDesc = model.CheckoutDesc,
+                OrderId = model.OrderId,
+                BuyerEmail = model.NotifyEmail,
+                NotificationURL = model.ServerIpn,
+                RedirectURL = model.BrowserRedirect,
+                FullNotifications = true
+            }, store, HttpContext.Request.GetAbsoluteRoot());
+            return Redirect(invoice.Data.Url);
+        }
+
+        [HttpGet]
+        [Route("{storeId}/paybuttontest")]
+        public IActionResult PayButtonTest(string storeId)
+        {
+            return View();
+        }
     }
 }

BTCPayServer/Controllers/WalletsController.cs

@@ -42,7 +42,7 @@ namespace BTCPayServer.Controllers
         private readonly ExplorerClientProvider _explorerProvider;
         private readonly IFeeProviderFactory _feeRateProvider;
         private readonly BTCPayWalletProvider _walletProvider;
-        BTCPayRateProviderFactory _RateProvider;
+        RateFetcher _RateProvider;
         CurrencyNameTable _currencyTable;
         public WalletsController(StoreRepository repo,
                                  CurrencyNameTable currencyTable,
@@ -50,7 +50,7 @@ namespace BTCPayServer.Controllers
                                  UserManager<ApplicationUser> userManager,
                                  IOptions<MvcJsonOptions> mvcJsonOptions,
                                  NBXplorerDashboard dashboard,
-                                 BTCPayRateProviderFactory rateProvider,
+                                 RateFetcher rateProvider,
                                  ExplorerClientProvider explorerProvider,
                                  IFeeProviderFactory feeRateProvider,
                                  BTCPayWalletProvider walletProvider)

BTCPayServer/Data/StoreData.cs

@@ -199,7 +199,7 @@ namespace BTCPayServer.Data
 #pragma warning disable CS0618
         public string GetDefaultCrypto(BTCPayNetworkProvider networkProvider = null)
         {
-            return DefaultCrypto ?? (networkProvider == null ? "BTC" : GetSupportedPaymentMethods(networkProvider).First().PaymentId.CryptoCode);
+            return DefaultCrypto ?? (networkProvider == null ? "BTC" : GetSupportedPaymentMethods(networkProvider).Select(p => p.PaymentId.CryptoCode).FirstOrDefault() ?? "BTC");
         }
         public void SetDefaultCrypto(string defaultCryptoCurrency)
         {

BTCPayServer/HostedServices/RatesHostedService.cs

@@ -18,9 +18,9 @@ namespace BTCPayServer.HostedServices
     {
         private SettingsRepository _SettingsRepository;
         private CoinAverageSettings _coinAverageSettings;
-        BTCPayRateProviderFactory _RateProviderFactory;
+        RateProviderFactory _RateProviderFactory;
         public RatesHostedService(SettingsRepository repo,
-                                  BTCPayRateProviderFactory rateProviderFactory,
+                                  RateProviderFactory rateProviderFactory,
                                   CoinAverageSettings coinAverageSettings)
         {
             this._SettingsRepository = repo;
@@ -33,16 +33,41 @@ namespace BTCPayServer.HostedServices
             return new[]
             {
                 CreateLoopTask(RefreshCoinAverageSupportedExchanges),
-                CreateLoopTask(RefreshCoinAverageSettings)
+                CreateLoopTask(RefreshCoinAverageSettings),
+                CreateLoopTask(RefreshRates)
             };
         }
+        async Task RefreshRates()
+        {
+
+            using (var timeout = CancellationTokenSource.CreateLinkedTokenSource(Cancellation))
+            {
+                timeout.CancelAfter(TimeSpan.FromSeconds(20.0));
+                try
+                {
+                    await Task.WhenAll(_RateProviderFactory.Providers
+                                    .Select(p => (Fetcher: p.Value as BackgroundFetcherRateProvider, ExchangeName: p.Key)).Where(p => p.Fetcher != null)
+                                    .Select(p => p.Fetcher.UpdateIfNecessary().ContinueWith(t =>
+                                    {
+                                        if (t.Result.Exception != null)
+                                        {
+                                            Logs.PayServer.LogWarning($"Error while contacting {p.ExchangeName}: {t.Result.Exception.Message}");
+                                        }
+                                    }, TaskScheduler.Default))
+                                    .ToArray()).WithCancellation(timeout.Token);
+                }
+                catch (OperationCanceledException) when (timeout.IsCancellationRequested)
+                {
+                }
+            }
+            await Task.Delay(TimeSpan.FromSeconds(30), Cancellation);
+        }
 
         async Task RefreshCoinAverageSupportedExchanges()
         {
-            await new SynchronizationContextRemover();
             var tickers = await new CoinAverageRateProvider() { Authenticator = _coinAverageSettings }.GetExchangeTickersAsync();
             var exchanges = new CoinAverageExchanges();
-            foreach(var item in tickers
+            foreach (var item in tickers
                 .Exchanges
                 .Select(c => new CoinAverageExchange(c.Name, c.DisplayName)))
             {
@@ -54,7 +79,6 @@ namespace BTCPayServer.HostedServices
 
         async Task RefreshCoinAverageSettings()
         {
-            await new SynchronizationContextRemover();
             var rates = (await _SettingsRepository.GetSettingAsync<RatesSetting>()) ?? new RatesSetting();
             _RateProviderFactory.CacheSpan = TimeSpan.FromMinutes(rates.CacheInMinutes);
             if (!string.IsNullOrWhiteSpace(rates.PrivateKey) && !string.IsNullOrWhiteSpace(rates.PublicKey))

BTCPayServer/Hosting/BTCPayServerServices.cs

@@ -53,6 +53,7 @@ namespace BTCPayServer.Hosting
                 var factory = provider.GetRequiredService<ApplicationDbContextFactory>();
                 factory.ConfigureBuilder(o);
             });
+            services.AddHttpClient();
             services.TryAddSingleton<SettingsRepository>();
             services.TryAddSingleton<InvoicePaymentNotification>();
             services.TryAddSingleton<BTCPayServerOptions>(o => o.GetRequiredService<IOptions<BTCPayServerOptions>>().Value);
@@ -137,7 +138,8 @@ namespace BTCPayServer.Hosting
                 else
                     return new Bitpay(new Key(), new Uri("https://test.bitpay.com/"));
             });
-            services.TryAddSingleton<BTCPayRateProviderFactory>();
+            services.TryAddSingleton<RateProviderFactory>();
+            services.TryAddSingleton<RateFetcher>();
 
             services.TryAddScoped<IHttpContextAccessor, HttpContextAccessor>();
             services.AddTransient<AccessTokenController>();

BTCPayServer/Models/AppViewModels/ListAppsViewModel.cs

@@ -15,6 +15,7 @@ namespace BTCPayServer.Models.AppViewModels
             public string AppName { get; set; }
             public string AppType { get; set; }
             public bool IsOwner { get; set; }
+
             public string UpdateAction { get { return "Update" + AppType; } }
             public string ViewAction { get { return "View" + AppType; } }
         }

BTCPayServer/Models/StoreViewModels/PayButtonViewModel.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Models.StoreViewModels
+{
+    public class PayButtonViewModel
+    {
+        public decimal Price { get; set; }
+        [Required]
+        public string Currency { get; set; }
+        public string CheckoutDesc { get; set; }
+        public string OrderId { get; set; }
+        public int ButtonSize { get; set; }
+        [Url]
+        public string ServerIpn { get; set; }
+        [Url]
+        public string BrowserRedirect { get; set; }
+        [EmailAddress]
+        public string NotifyEmail { get; set; }
+
+        public string StoreId { get; set; }
+
+        // Data that influences Pay Button UI, but not invoice creation
+        public string UrlRoot { get; set; }
+        public List<string> CurrencyDropdown { get; set; }
+        public string PayButtonImageUrl { get; set; }
+    }
+}

BTCPayServer/Payments/Bitcoin/BitcoinLikePaymentHandler.cs

@@ -27,16 +27,30 @@ namespace BTCPayServer.Payments.Bitcoin
             _WalletProvider = walletProvider;
         }
 
-        public override async Task<IPaymentMethodDetails> CreatePaymentMethodDetails(DerivationStrategy supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network)
+        class Prepare
+        {
+            public Task<FeeRate> GetFeeRate;
+            public Task<BitcoinAddress> ReserveAddress;
+        }
+
+        public override object PreparePayment(DerivationStrategy supportedPaymentMethod, StoreData store, BTCPayNetwork network)
+        {
+            return new Prepare()
+            {
+                GetFeeRate = _FeeRateProviderFactory.CreateFeeProvider(network).GetFeeRateAsync(),
+                ReserveAddress = _WalletProvider.GetWallet(network).ReserveAddressAsync(supportedPaymentMethod.DerivationStrategyBase)
+            };
+        }
+
+        public override async Task<IPaymentMethodDetails> CreatePaymentMethodDetails(DerivationStrategy supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network, object preparePaymentObject)
         {
             if (!_ExplorerProvider.IsAvailable(network))
                 throw new PaymentMethodUnavailableException($"Full node not available");
-            var getFeeRate = _FeeRateProviderFactory.CreateFeeProvider(network).GetFeeRateAsync();
-            var getAddress = _WalletProvider.GetWallet(network).ReserveAddressAsync(supportedPaymentMethod.DerivationStrategyBase);
+            var prepare = (Prepare)preparePaymentObject;
             Payments.Bitcoin.BitcoinLikeOnChainPaymentMethod onchainMethod = new Payments.Bitcoin.BitcoinLikeOnChainPaymentMethod();
-            onchainMethod.FeeRate = await getFeeRate;
+            onchainMethod.FeeRate = await prepare.GetFeeRate;
             onchainMethod.TxFee = onchainMethod.FeeRate.GetFee(100); // assume price for 100 bytes
-            onchainMethod.DepositAddress = (await getAddress).ToString();
+            onchainMethod.DepositAddress = (await prepare.ReserveAddress).ToString();
             return onchainMethod;
         }
     }

BTCPayServer/Payments/IPaymentMethodHandler.cs

@@ -20,23 +20,46 @@ namespace BTCPayServer.Payments
         /// <param name="store"></param>
         /// <param name="network"></param>
         /// <returns></returns>
-        Task<IPaymentMethodDetails> CreatePaymentMethodDetails(ISupportedPaymentMethod supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network);
+        Task<IPaymentMethodDetails> CreatePaymentMethodDetails(ISupportedPaymentMethod supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network, object preparePaymentObject);
+
+        /// <summary>
+        /// This method called before the rate have been fetched
+        /// </summary>
+        /// <param name="supportedPaymentMethod"></param>
+        /// <param name="store"></param>
+        /// <param name="network"></param>
+        /// <returns></returns>
+        object PreparePayment(ISupportedPaymentMethod supportedPaymentMethod, StoreData store, BTCPayNetwork network);
     }
 
     public interface IPaymentMethodHandler<T> : IPaymentMethodHandler where T : ISupportedPaymentMethod
     {
-        Task<IPaymentMethodDetails> CreatePaymentMethodDetails(T supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network);
+        Task<IPaymentMethodDetails> CreatePaymentMethodDetails(T supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network, object preparePaymentObject);
     }
 
     public abstract class PaymentMethodHandlerBase<T> : IPaymentMethodHandler<T> where T : ISupportedPaymentMethod
     {
-        public abstract Task<IPaymentMethodDetails> CreatePaymentMethodDetails(T supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network);
+        
+        public abstract Task<IPaymentMethodDetails> CreatePaymentMethodDetails(T supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network, object preparePaymentObject);
+        public virtual object PreparePayment(T supportedPaymentMethod, StoreData store, BTCPayNetwork network)
+        {
+            return null;
+        }
 
-        Task<IPaymentMethodDetails> IPaymentMethodHandler.CreatePaymentMethodDetails(ISupportedPaymentMethod supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network)
+        object IPaymentMethodHandler.PreparePayment(ISupportedPaymentMethod supportedPaymentMethod, StoreData store, BTCPayNetwork network)
         {
             if (supportedPaymentMethod is T method)
             {
-                return CreatePaymentMethodDetails(method, paymentMethod, store, network);
+                return PreparePayment(method, store, network);
+            }
+            throw new NotSupportedException("Invalid supportedPaymentMethod");
+        }
+
+        Task<IPaymentMethodDetails> IPaymentMethodHandler.CreatePaymentMethodDetails(ISupportedPaymentMethod supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network, object preparePaymentObject)
+        {
+            if (supportedPaymentMethod is T method)
+            {
+                return CreatePaymentMethodDetails(method, paymentMethod, store, network, preparePaymentObject);
             }
             throw new NotSupportedException("Invalid supportedPaymentMethod");
         }

BTCPayServer/Payments/Lightning/LightningLikePaymentHandler.cs

@@ -26,7 +26,7 @@ namespace BTCPayServer.Payments.Lightning
             _LightningClientFactory = lightningClientFactory;
             _Dashboard = dashboard;
         }
-        public override async Task<IPaymentMethodDetails> CreatePaymentMethodDetails(LightningSupportedPaymentMethod supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network)
+        public override async Task<IPaymentMethodDetails> CreatePaymentMethodDetails(LightningSupportedPaymentMethod supportedPaymentMethod, PaymentMethod paymentMethod, StoreData store, BTCPayNetwork network, object preparePaymentObject)
         {
             var storeBlob = store.GetStoreBlob();
             var test = Test(supportedPaymentMethod, network);

BTCPayServer/Rating/ExchangeRates.cs

@@ -221,6 +221,16 @@ namespace BTCPayServer.Rating
     }
     public class ExchangeRate
     {
+        public ExchangeRate()
+        {
+
+        }
+        public ExchangeRate(string exchange, CurrencyPair currencyPair, BidAsk bidAsk)
+        {
+            this.Exchange = exchange;
+            this.CurrencyPair = currencyPair;
+            this.BidAsk = bidAsk;
+        }
         public string Exchange { get; set; }
         public CurrencyPair CurrencyPair { get; set; }
         public BidAsk BidAsk { get; set; }

BTCPayServer/Services/Rates/BTCPayRateProviderFactory.cs

@@ -1,215 +0,0 @@
-using System;
-using System.Collections.Concurrent;
-using System.Collections.Generic;
-using System.Linq;
-using System.Net.Http;
-using System.Threading.Tasks;
-using BTCPayServer.Rating;
-using ExchangeSharp;
-using Microsoft.Extensions.Caching.Memory;
-using Microsoft.Extensions.Options;
-
-namespace BTCPayServer.Services.Rates
-{
-    public class ExchangeException
-    {
-        public Exception Exception { get; set; }
-        public string ExchangeName { get; set; }
-    }
-    public class RateResult
-    {
-        public List<ExchangeException> ExchangeExceptions { get; set; } = new List<ExchangeException>();
-        public string Rule { get; set; }
-        public string EvaluatedRule { get; set; }
-        public HashSet<RateRulesErrors> Errors { get; set; }
-        public BidAsk BidAsk { get; set; }
-        public bool Cached { get; internal set; }
-    }
-
-    public class BTCPayRateProviderFactory
-    {
-        class QueryRateResult
-        {
-            public bool CachedResult { get; set; }
-            public List<ExchangeException> Exceptions { get; set; }
-            public ExchangeRates ExchangeRates { get; set; }
-        }
-        IMemoryCache _Cache;
-        private IOptions<MemoryCacheOptions> _CacheOptions;
-        public IMemoryCache Cache
-        {
-            get
-            {
-                return _Cache;
-            }
-        }
-        CoinAverageSettings _CoinAverageSettings;
-        public BTCPayRateProviderFactory(IOptions<MemoryCacheOptions> cacheOptions,
-                                         BTCPayNetworkProvider btcpayNetworkProvider,
-                                         CoinAverageSettings coinAverageSettings)
-        {
-            if (cacheOptions == null)
-                throw new ArgumentNullException(nameof(cacheOptions));
-            _CoinAverageSettings = coinAverageSettings;
-            _Cache = new MemoryCache(cacheOptions);
-            _CacheOptions = cacheOptions;
-            // We use 15 min because of limits with free version of bitcoinaverage
-            CacheSpan = TimeSpan.FromMinutes(15.0);
-            this.btcpayNetworkProvider = btcpayNetworkProvider;
-            InitExchanges();
-        }
-
-        public bool UseCoinAverageAsFallback { get; set; } = true;
-
-        private void InitExchanges()
-        {
-            // We need to be careful to only add exchanges which OnGetTickers implementation make only 1 request
-            DirectProviders.Add("binance", new ExchangeSharpRateProvider("binance", new ExchangeBinanceAPI(), true));
-            DirectProviders.Add("bittrex", new ExchangeSharpRateProvider("bittrex", new ExchangeBittrexAPI(), true));
-            DirectProviders.Add("poloniex", new ExchangeSharpRateProvider("poloniex", new ExchangePoloniexAPI(), false));
-            DirectProviders.Add("hitbtc", new ExchangeSharpRateProvider("hitbtc", new ExchangeHitbtcAPI(), false));
-            DirectProviders.Add("cryptopia", new ExchangeSharpRateProvider("cryptopia", new ExchangeCryptopiaAPI(), false));
-
-            // Handmade providers
-            DirectProviders.Add("bitpay", new BitpayRateProvider(new NBitpayClient.Bitpay(new NBitcoin.Key(), new Uri("https://bitpay.com/"))));
-            DirectProviders.Add(QuadrigacxRateProvider.QuadrigacxName, new QuadrigacxRateProvider());
-            DirectProviders.Add(CoinAverageRateProvider.CoinAverageName, new CoinAverageRateProvider() { Exchange = CoinAverageRateProvider.CoinAverageName, Authenticator = _CoinAverageSettings });
-
-            // Those exchanges make multiple requests when calling GetTickers so we remove them
-            //DirectProviders.Add("kraken", new ExchangeSharpRateProvider("kraken", new ExchangeKrakenAPI(), true));
-            //DirectProviders.Add("gdax", new ExchangeSharpRateProvider("gdax", new ExchangeGdaxAPI()));
-            //DirectProviders.Add("gemini", new ExchangeSharpRateProvider("gemini", new ExchangeGeminiAPI()));
-            //DirectProviders.Add("bitfinex", new ExchangeSharpRateProvider("bitfinex", new ExchangeBitfinexAPI()));
-            //DirectProviders.Add("okex", new ExchangeSharpRateProvider("okex", new ExchangeOkexAPI()));
-            //DirectProviders.Add("bitstamp", new ExchangeSharpRateProvider("bitstamp", new ExchangeBitstampAPI()));
-        }
-
-        public CoinAverageExchanges GetSupportedExchanges()
-        {
-            CoinAverageExchanges exchanges = new CoinAverageExchanges();
-            foreach (var exchange in _CoinAverageSettings.AvailableExchanges)
-            {
-                exchanges.Add(exchange.Value);
-            }
-
-            // Add other exchanges supported here
-            exchanges.Add(new CoinAverageExchange(CoinAverageRateProvider.CoinAverageName, "Coin Average"));
-            exchanges.Add(new CoinAverageExchange("cryptopia", "Cryptopia"));
-
-            return exchanges;
-        }
-
-        private readonly Dictionary<string, IRateProvider> _DirectProviders = new Dictionary<string, IRateProvider>();
-        public Dictionary<string, IRateProvider> DirectProviders
-        {
-            get
-            {
-                return _DirectProviders;
-            }
-        }
-
-
-        BTCPayNetworkProvider btcpayNetworkProvider;
-        TimeSpan _CacheSpan;
-        public TimeSpan CacheSpan
-        {
-            get
-            {
-                return _CacheSpan;
-            }
-            set
-            {
-                _CacheSpan = value;
-                InvalidateCache();
-            }
-        }
-
-        public void InvalidateCache()
-        {
-            _Cache = new MemoryCache(_CacheOptions);
-        }
-
-        public async Task<RateResult> FetchRate(CurrencyPair pair, RateRules rules)
-        {
-            return await FetchRates(new HashSet<CurrencyPair>(new[] { pair }), rules).First().Value;
-        }
-
-        public Dictionary<CurrencyPair, Task<RateResult>> FetchRates(HashSet<CurrencyPair> pairs, RateRules rules)
-        {
-            if (rules == null)
-                throw new ArgumentNullException(nameof(rules));
-
-            var fetchingRates = new Dictionary<CurrencyPair, Task<RateResult>>();
-            var fetchingExchanges = new Dictionary<string, Task<QueryRateResult>>();
-            var consolidatedRates = new ExchangeRates();
-
-            foreach (var i in pairs.Select(p => (Pair: p, RateRule: rules.GetRuleFor(p))))
-            {
-                var dependentQueries = new List<Task<QueryRateResult>>();
-                foreach (var requiredExchange in i.RateRule.ExchangeRates)
-                {
-                    if (!fetchingExchanges.TryGetValue(requiredExchange.Exchange, out var fetching))
-                    {
-                        fetching = QueryRates(requiredExchange.Exchange);
-                        fetchingExchanges.Add(requiredExchange.Exchange, fetching);
-                    }
-                    dependentQueries.Add(fetching);
-                }
-                fetchingRates.Add(i.Pair, GetRuleValue(dependentQueries, i.RateRule));
-            }
-            return fetchingRates;
-        }
-
-        private async Task<RateResult> GetRuleValue(List<Task<QueryRateResult>> dependentQueries, RateRule rateRule)
-        {
-            var result = new RateResult();
-            result.Cached = true;
-            foreach (var queryAsync in dependentQueries)
-            {
-                var query = await queryAsync;
-                if (!query.CachedResult)
-                    result.Cached = false;
-                result.ExchangeExceptions.AddRange(query.Exceptions);
-                foreach (var rule in query.ExchangeRates)
-                {
-                    rateRule.ExchangeRates.SetRate(rule.Exchange, rule.CurrencyPair, rule.BidAsk);
-                }
-            }
-            rateRule.Reevaluate();
-            result.BidAsk = rateRule.BidAsk;
-            result.Errors = rateRule.Errors;
-            result.EvaluatedRule = rateRule.ToString(true);
-            result.Rule = rateRule.ToString(false);
-            return result;
-        }
-
-
-        private async Task<QueryRateResult> QueryRates(string exchangeName)
-        {
-            List<IRateProvider> providers = new List<IRateProvider>();
-            if (DirectProviders.TryGetValue(exchangeName, out var directProvider))
-                providers.Add(directProvider);
-            if (_CoinAverageSettings.AvailableExchanges.ContainsKey(exchangeName))
-            {
-                providers.Add(new CoinAverageRateProvider()
-                {
-                    Exchange = exchangeName,
-                    Authenticator = _CoinAverageSettings
-                });
-            }
-            var fallback = new FallbackRateProvider(providers.ToArray());
-            var cached = new CachedRateProvider(exchangeName, fallback, _Cache)
-            {
-                CacheSpan = CacheSpan
-            };
-            var value = await cached.GetRatesAsync();
-            return new QueryRateResult()
-            {
-                CachedResult = !fallback.Used,
-                ExchangeRates = value,
-                Exceptions = fallback.Exceptions
-                .Select(c => new ExchangeException() { Exception = c, ExchangeName = exchangeName }).ToList()
-            };
-        }
-    }
-}

BTCPayServer/Services/Rates/BackgroundFetcherRateProvider.cs

@@ -0,0 +1,116 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.ExceptionServices;
+using System.Threading.Tasks;
+using BTCPayServer.Data;
+using BTCPayServer.Rating;
+
+namespace BTCPayServer.Services.Rates
+{
+    public class BackgroundFetcherRateProvider : IRateProvider
+    {
+        public class LatestFetch
+        {
+            public ExchangeRates Latest;
+            public DateTimeOffset Timestamp;
+            public DateTimeOffset Expiration;
+            public Exception Exception;
+
+            internal ExchangeRates GetResult()
+            {
+                if(Expiration < DateTimeOffset.UtcNow)
+                {
+                    if(Exception != null)
+                    {
+                        ExceptionDispatchInfo.Capture(Exception).Throw();
+                    }
+                    else
+                    {
+                        throw new InvalidOperationException("The rate has expired");
+                    }
+                }
+                return Latest;
+            }
+
+            internal void CopyFrom(LatestFetch previous)
+            {
+                Latest = previous.Latest;
+                Timestamp = previous.Timestamp;
+                Expiration = previous.Expiration;
+                Exception = previous.Exception;
+            }
+        }
+
+        IRateProvider _Inner;
+        public BackgroundFetcherRateProvider(IRateProvider inner)
+        {
+            if (inner == null)
+                throw new ArgumentNullException(nameof(inner));
+            _Inner = inner;
+        }
+
+        public TimeSpan RefreshRate { get; set; } = TimeSpan.FromSeconds(30);
+        public TimeSpan ValidatyTime { get; set; } = TimeSpan.FromMinutes(10);
+
+        public DateTimeOffset NextUpdate
+        {
+            get
+            {
+                var latest = _Latest;
+                if (latest == null || latest.Exception != null)
+                    return DateTimeOffset.UtcNow;
+                return latest.Timestamp + RefreshRate;
+            }
+        }
+
+        public async Task<LatestFetch> UpdateIfNecessary()
+        {
+            if (NextUpdate <= DateTimeOffset.UtcNow)
+            {
+                try
+                {
+                    await Fetch();
+                }
+                catch { } // Exception is inside _Latest
+                return _Latest;
+            }
+            return _Latest;
+        }
+
+        LatestFetch _Latest;
+        public async Task<ExchangeRates> GetRatesAsync()
+        {
+            return (_Latest ?? (await Fetch())).GetResult();
+        }
+
+        private async Task<LatestFetch> Fetch()
+        {
+            var previous = _Latest;
+            var fetch = new LatestFetch();
+            try
+            {
+                var rates = await _Inner.GetRatesAsync();
+                fetch.Latest = rates;
+                fetch.Expiration = DateTimeOffset.UtcNow + ValidatyTime;
+            }
+            catch (Exception ex)
+            {
+                if(previous != null)
+                {
+                    fetch.CopyFrom(previous);
+                }
+                fetch.Exception = ex;
+            }
+            fetch.Timestamp = DateTimeOffset.UtcNow;
+            _Latest = fetch;
+            fetch.GetResult(); // Will throw if not valid
+            return fetch;
+        }
+
+        public void InvalidateCache()
+        {
+            _Latest = null;
+        }
+    }
+}

BTCPayServer/Services/Rates/CachedRateProvider.cs

@@ -38,7 +38,7 @@ namespace BTCPayServer.Services.Rates
             get;
             set;
         } = TimeSpan.FromMinutes(1.0);
-        public IMemoryCache MemoryCache { get => _MemoryCache; private set => _MemoryCache = value; }
+        public IMemoryCache MemoryCache { get => _MemoryCache; set => _MemoryCache = value; }
         
         public Task<ExchangeRates> GetRatesAsync()
         {

BTCPayServer/Services/Rates/CoinAverageRateProvider.cs

@@ -56,6 +56,19 @@ namespace BTCPayServer.Services.Rates
         {
 
         }
+
+        public HttpClient HttpClient
+        {
+            get
+            {
+                return _LocalClient ?? _Client;
+            }
+            set
+            {
+                _LocalClient = null;
+            }
+        }
+        HttpClient _LocalClient;
         static HttpClient _Client = new HttpClient();
 
         public string Exchange { get; set; } = CoinAverageName;
@@ -107,7 +120,7 @@ namespace BTCPayServer.Services.Rates
             {
                 await auth.AddHeader(request);
             }
-            var resp = await _Client.SendAsync(request);
+            var resp = await HttpClient.SendAsync(request);
             using (resp)
             {
 
@@ -150,7 +163,7 @@ namespace BTCPayServer.Services.Rates
             {
                 await auth.AddHeader(request);
             }
-            var resp = await _Client.SendAsync(request);
+            var resp = await HttpClient.SendAsync(request);
             resp.EnsureSuccessStatusCode();
         }
 
@@ -162,7 +175,7 @@ namespace BTCPayServer.Services.Rates
             {
                 await auth.AddHeader(request);
             }
-            var resp = await _Client.SendAsync(request);
+            var resp = await HttpClient.SendAsync(request);
             resp.EnsureSuccessStatusCode();
             var jobj = JObject.Parse(await resp.Content.ReadAsStringAsync());
             var response = new GetRateLimitsResponse();
@@ -193,7 +206,7 @@ namespace BTCPayServer.Services.Rates
             {
                 await auth.AddHeader(request);
             }
-            var resp = await _Client.SendAsync(request);
+            var resp = await HttpClient.SendAsync(request);
             resp.EnsureSuccessStatusCode();
             var jobj = JObject.Parse(await resp.Content.ReadAsStringAsync());
             var response = new GetExchangeTickersResponse();

BTCPayServer/Services/Rates/ExchangeSharpRateProvider.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -43,17 +44,17 @@ namespace BTCPayServer.Services.Rates
         }
 
         // ExchangeSymbolToGlobalSymbol throws exception which would kill perf
-        HashSet<string> notFoundSymbols = new HashSet<string>();
+        ConcurrentDictionary<string, string> notFoundSymbols = new ConcurrentDictionary<string, string>();
         private ExchangeRate CreateExchangeRate(KeyValuePair<string, ExchangeTicker> ticker)
         {
-            if (notFoundSymbols.Contains(ticker.Key))
+            if (notFoundSymbols.ContainsKey(ticker.Key))
                 return null;
             try
             {
                 var tickerName = _ExchangeAPI.ExchangeSymbolToGlobalSymbol(ticker.Key);
                 if (!CurrencyPair.TryParse(tickerName, out var pair))
                 {
-                    notFoundSymbols.Add(ticker.Key);
+                    notFoundSymbols.TryAdd(ticker.Key, ticker.Key);
                     return null;
                 }
                 if(ReverseCurrencyPair)
@@ -66,7 +67,7 @@ namespace BTCPayServer.Services.Rates
             }
             catch (ArgumentException)
             {
-                notFoundSymbols.Add(ticker.Key);
+                notFoundSymbols.TryAdd(ticker.Key, ticker.Key);
                 return null;
             }
         }

BTCPayServer/Services/Rates/FallbackRateProvider.cs

@@ -9,7 +9,6 @@ namespace BTCPayServer.Services.Rates
     public class FallbackRateProvider : IRateProvider
     {
         IRateProvider[] _Providers;
-        public bool Used { get; set; }
         public FallbackRateProvider(IRateProvider[] providers)
         {
             if (providers == null)
@@ -19,7 +18,6 @@ namespace BTCPayServer.Services.Rates
 
         public async Task<ExchangeRates> GetRatesAsync()
         {
-            Used = true;
             foreach (var p in _Providers)
             {
                 try

BTCPayServer/Services/Rates/KrakenExchangeRateProvider.cs

@@ -0,0 +1,135 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Text;
+using System.Threading.Tasks;
+using BTCPayServer.Rating;
+using ExchangeSharp;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace BTCPayServer.Services.Rates
+{
+    // Make sure that only one request is sent to kraken in general
+    public class KrakenExchangeRateProvider : IRateProvider
+    {
+        public KrakenExchangeRateProvider()
+        {
+            _Helper = new ExchangeKrakenAPI();
+        }
+        ExchangeKrakenAPI _Helper;
+        public HttpClient HttpClient
+        {
+            get
+            {
+                return _LocalClient ?? _Client;
+            }
+            set
+            {
+                _LocalClient = null;
+            }
+        }
+        HttpClient _LocalClient;
+        static HttpClient _Client = new HttpClient();
+
+        // ExchangeSymbolToGlobalSymbol throws exception which would kill perf
+        ConcurrentDictionary<string, string> notFoundSymbols = new ConcurrentDictionary<string, string>();
+        string[] _Symbols = Array.Empty<string>();
+        DateTimeOffset? _LastSymbolUpdate = null;
+
+        public async Task<ExchangeRates> GetRatesAsync()
+        {
+            var result = new ExchangeRates();
+            var symbols = await GetSymbolsAsync();
+            var normalizedPairsList = symbols.Where(s => !notFoundSymbols.ContainsKey(s)).Select(s => _Helper.NormalizeSymbol(s)).ToList();
+            var csvPairsList = string.Join(",", normalizedPairsList);
+            JToken apiTickers = await MakeJsonRequestAsync<JToken>("/0/public/Ticker", null, new Dictionary<string, object> { { "pair", csvPairsList } });
+            var tickers = new List<KeyValuePair<string, ExchangeTicker>>();
+            foreach (string symbol in symbols)
+            {
+                var ticker = ConvertToExchangeTicker(symbol, apiTickers[symbol]);
+                if (ticker != null)
+                {
+                    try
+                    {
+                        var global = _Helper.ExchangeSymbolToGlobalSymbol(symbol);
+                        if (CurrencyPair.TryParse(global, out var pair))
+                            result.Add(new ExchangeRate("kraken", pair.Inverse(), new BidAsk(ticker.Bid, ticker.Ask)));
+                        else
+                            notFoundSymbols.TryAdd(symbol, symbol);
+                    }
+                    catch (ArgumentException)
+                    {
+                        notFoundSymbols.TryAdd(symbol, symbol);
+                    }
+                }
+            }
+            return result;
+        }
+
+        private static ExchangeTicker ConvertToExchangeTicker(string symbol, JToken ticker)
+        {
+            if (ticker == null)
+                return null;
+            decimal last = ticker["c"][0].ConvertInvariant<decimal>();
+            return new ExchangeTicker
+            {
+                Ask = ticker["a"][0].ConvertInvariant<decimal>(),
+                Bid = ticker["b"][0].ConvertInvariant<decimal>(),
+                Last = last,
+                Volume = new ExchangeVolume
+                {
+                    BaseVolume = ticker["v"][1].ConvertInvariant<decimal>(),
+                    BaseSymbol = symbol,
+                    ConvertedVolume = ticker["v"][1].ConvertInvariant<decimal>() * last,
+                    ConvertedSymbol = symbol,
+                    Timestamp = DateTime.UtcNow
+                }
+            };
+        }
+
+        private async Task<string[]> GetSymbolsAsync()
+        {
+            if (_LastSymbolUpdate != null && DateTimeOffset.UtcNow - _LastSymbolUpdate.Value < TimeSpan.FromDays(0.5))
+            {
+                return _Symbols;
+            }
+            else
+            {
+                JToken json = await MakeJsonRequestAsync<JToken>("/0/public/AssetPairs");
+                var symbols = (from prop in json.Children<JProperty>() where !prop.Name.Contains(".d", StringComparison.OrdinalIgnoreCase) select prop.Name).ToArray();
+                _Symbols = symbols;
+                _LastSymbolUpdate = DateTimeOffset.UtcNow;
+                return symbols;
+            }
+        }
+
+        private async Task<T> MakeJsonRequestAsync<T>(string url, string baseUrl = null, Dictionary<string, object> payload = null, string requestMethod = null)
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append("https://api.kraken.com");
+            ;
+            sb.Append(url);
+            if (payload != null)
+            {
+                sb.Append("?");
+                sb.Append(String.Join('&', payload.Select(kv => $"{kv.Key}={kv.Value}").OfType<object>().ToArray()));
+            }
+            var request = new HttpRequestMessage(HttpMethod.Get, sb.ToString());
+            var response = await HttpClient.SendAsync(request);
+            string stringResult = await response.Content.ReadAsStringAsync();
+            var result = JsonConvert.DeserializeObject<T>(stringResult);
+            if (result is JToken json)
+            {
+                if (!(json is JArray) && json["error"] is JArray error && error.Count != 0)
+                {
+                    throw new APIException(error[0].ToStringInvariant());
+                }
+                result = (T)(object)(json["result"] ?? json);
+            }
+            return result;
+        }
+    }
+}

BTCPayServer/Services/Rates/NullRateProvider.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Rating;
+
+namespace BTCPayServer.Services.Rates
+{
+    public class NullRateProvider : IRateProvider
+    {
+        private NullRateProvider()
+        {
+
+        }
+        private static readonly NullRateProvider _Instance = new NullRateProvider();
+        public static NullRateProvider Instance
+        {
+            get
+            {
+                return _Instance;
+            }
+        }
+        public Task<ExchangeRates> GetRatesAsync()
+        {
+            return Task.FromResult(new ExchangeRates());
+        }
+    }
+}

BTCPayServer/Services/Rates/RateFetcher.cs

@@ -0,0 +1,94 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Threading.Tasks;
+using BTCPayServer.Rating;
+using ExchangeSharp;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Options;
+using static BTCPayServer.Services.Rates.RateProviderFactory;
+
+namespace BTCPayServer.Services.Rates
+{
+    public class ExchangeException
+    {
+        public Exception Exception { get; set; }
+        public string ExchangeName { get; set; }
+    }
+    public class RateResult
+    {
+        public List<ExchangeException> ExchangeExceptions { get; set; } = new List<ExchangeException>();
+        public string Rule { get; set; }
+        public string EvaluatedRule { get; set; }
+        public HashSet<RateRulesErrors> Errors { get; set; }
+        public BidAsk BidAsk { get; set; }
+        public TimeSpan Latency { get; internal set; }
+    }
+
+    public class RateFetcher
+    {
+        private readonly RateProviderFactory _rateProviderFactory;
+
+        public RateFetcher(RateProviderFactory rateProviderFactory)
+        {
+            _rateProviderFactory = rateProviderFactory;
+        }
+
+        public RateProviderFactory RateProviderFactory => _rateProviderFactory;
+
+        public async Task<RateResult> FetchRate(CurrencyPair pair, RateRules rules)
+        {
+            return await FetchRates(new HashSet<CurrencyPair>(new[] { pair }), rules).First().Value;
+        }
+
+        public Dictionary<CurrencyPair, Task<RateResult>> FetchRates(HashSet<CurrencyPair> pairs, RateRules rules)
+        {
+            if (rules == null)
+                throw new ArgumentNullException(nameof(rules));
+
+            var fetchingRates = new Dictionary<CurrencyPair, Task<RateResult>>();
+            var fetchingExchanges = new Dictionary<string, Task<QueryRateResult>>();
+            var consolidatedRates = new ExchangeRates();
+
+            foreach (var i in pairs.Select(p => (Pair: p, RateRule: rules.GetRuleFor(p))))
+            {
+                var dependentQueries = new List<Task<QueryRateResult>>();
+                foreach (var requiredExchange in i.RateRule.ExchangeRates)
+                {
+                    if (!fetchingExchanges.TryGetValue(requiredExchange.Exchange, out var fetching))
+                    {
+                        fetching = _rateProviderFactory.QueryRates(requiredExchange.Exchange);
+                        fetchingExchanges.Add(requiredExchange.Exchange, fetching);
+                    }
+                    dependentQueries.Add(fetching);
+                }
+                fetchingRates.Add(i.Pair, GetRuleValue(dependentQueries, i.RateRule));
+            }
+            return fetchingRates;
+        }
+
+        private async Task<RateResult> GetRuleValue(List<Task<QueryRateResult>> dependentQueries, RateRule rateRule)
+        {
+            var result = new RateResult();
+            foreach (var queryAsync in dependentQueries)
+            {
+                var query = await queryAsync;
+                result.Latency = query.Latency;
+                if (query.Exception != null)
+                    result.ExchangeExceptions.Add(query.Exception);
+                foreach (var rule in query.ExchangeRates)
+                {
+                    rateRule.ExchangeRates.SetRate(rule.Exchange, rule.CurrencyPair, rule.BidAsk);
+                }
+            }
+            rateRule.Reevaluate();
+            result.BidAsk = rateRule.BidAsk;
+            result.Errors = rateRule.Errors;
+            result.EvaluatedRule = rateRule.ToString(true);
+            result.Rule = rateRule.ToString(false);
+            return result;
+        }
+    }
+}

BTCPayServer/Services/Rates/RateProviderFactory.cs

@@ -0,0 +1,174 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Threading.Tasks;
+using BTCPayServer.Rating;
+using ExchangeSharp;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Options;
+
+namespace BTCPayServer.Services.Rates
+{
+    public class RateProviderFactory
+    {
+        class WrapperRateProvider : IRateProvider
+        {
+            private readonly IRateProvider _inner;
+            public Exception Exception { get; private set; }
+            public TimeSpan Latency { get; set; }
+            public WrapperRateProvider(IRateProvider inner)
+            {
+                _inner = inner;
+            }
+            public Task<ExchangeRates> GetRatesAsync()
+            {
+                DateTimeOffset now = DateTimeOffset.UtcNow;
+                try
+                {
+                    return _inner.GetRatesAsync();
+                }
+                catch (Exception ex)
+                {
+                    Exception = ex;
+                    return Task.FromResult(new ExchangeRates());
+                }
+                finally
+                {
+                    Latency = DateTimeOffset.UtcNow - now;
+                }
+            }
+        }
+        public class QueryRateResult
+        {
+            public TimeSpan Latency { get; set; }
+            public ExchangeRates ExchangeRates { get; set; }
+            public ExchangeException Exception { get; internal set; }
+        }
+        public RateProviderFactory(IOptions<MemoryCacheOptions> cacheOptions,
+                                   IHttpClientFactory httpClientFactory,
+                                   CoinAverageSettings coinAverageSettings)
+        {
+            _httpClientFactory = httpClientFactory;
+            _CoinAverageSettings = coinAverageSettings;
+            _CacheOptions = cacheOptions;
+            // We use 15 min because of limits with free version of bitcoinaverage
+            CacheSpan = TimeSpan.FromMinutes(15.0);
+            InitExchanges();
+        }
+        private IOptions<MemoryCacheOptions> _CacheOptions;
+        TimeSpan _CacheSpan;
+        public TimeSpan CacheSpan
+        {
+            get
+            {
+                return _CacheSpan;
+            }
+            set
+            {
+                _CacheSpan = value;
+                InvalidateCache();
+            }
+        }
+        public void InvalidateCache()
+        {
+            var cache = new MemoryCache(_CacheOptions);
+            foreach (var provider in Providers.Select(p => p.Value as CachedRateProvider).Where(p => p != null))
+            {
+                provider.CacheSpan = CacheSpan;
+                provider.MemoryCache = cache;
+            }
+            if (Providers.TryGetValue(CoinAverageRateProvider.CoinAverageName, out var coinAverage) && coinAverage is BackgroundFetcherRateProvider c)
+                c.RefreshRate = CacheSpan;
+        }
+        CoinAverageSettings _CoinAverageSettings;
+        private readonly IHttpClientFactory _httpClientFactory;
+        private readonly Dictionary<string, IRateProvider> _DirectProviders = new Dictionary<string, IRateProvider>();
+        public Dictionary<string, IRateProvider> Providers
+        {
+            get
+            {
+                return _DirectProviders;
+            }
+        }
+
+        private void InitExchanges()
+        {
+            // We need to be careful to only add exchanges which OnGetTickers implementation make only 1 request
+            Providers.Add("binance", new ExchangeSharpRateProvider("binance", new ExchangeBinanceAPI(), true));
+            Providers.Add("bittrex", new ExchangeSharpRateProvider("bittrex", new ExchangeBittrexAPI(), true));
+            Providers.Add("poloniex", new ExchangeSharpRateProvider("poloniex", new ExchangePoloniexAPI(), true));
+            Providers.Add("hitbtc", new ExchangeSharpRateProvider("hitbtc", new ExchangeHitbtcAPI(), false));
+            Providers.Add("cryptopia", new ExchangeSharpRateProvider("cryptopia", new ExchangeCryptopiaAPI(), false));
+
+            // Handmade providers
+            Providers.Add("bitpay", new BitpayRateProvider(new NBitpayClient.Bitpay(new NBitcoin.Key(), new Uri("https://bitpay.com/"))));
+            Providers.Add(QuadrigacxRateProvider.QuadrigacxName, new QuadrigacxRateProvider());
+            Providers.Add(CoinAverageRateProvider.CoinAverageName, new CoinAverageRateProvider() { Exchange = CoinAverageRateProvider.CoinAverageName, HttpClient = _httpClientFactory?.CreateClient(), Authenticator = _CoinAverageSettings });
+            Providers.Add("kraken", new KrakenExchangeRateProvider() { HttpClient = _httpClientFactory?.CreateClient() });
+
+            // Those exchanges make multiple requests when calling GetTickers so we remove them
+            //DirectProviders.Add("gdax", new ExchangeSharpRateProvider("gdax", new ExchangeGdaxAPI()));
+            //DirectProviders.Add("gemini", new ExchangeSharpRateProvider("gemini", new ExchangeGeminiAPI()));
+            //DirectProviders.Add("bitfinex", new ExchangeSharpRateProvider("bitfinex", new ExchangeBitfinexAPI()));
+            //DirectProviders.Add("okex", new ExchangeSharpRateProvider("okex", new ExchangeOkexAPI()));
+            //DirectProviders.Add("bitstamp", new ExchangeSharpRateProvider("bitstamp", new ExchangeBitstampAPI()));
+
+            foreach (var provider in Providers.ToArray())
+            {
+                var prov = new BackgroundFetcherRateProvider(Providers[provider.Key]);
+                prov.RefreshRate = provider.Key == CoinAverageRateProvider.CoinAverageName ? CacheSpan : TimeSpan.FromMinutes(1.0);
+                Providers[provider.Key] = prov;
+            }
+
+            var cache = new MemoryCache(_CacheOptions);
+            foreach (var supportedExchange in GetSupportedExchanges())
+            {
+                if (!Providers.ContainsKey(supportedExchange.Key))
+                {
+                    var coinAverage = new CoinAverageRateProvider()
+                    {
+                        Exchange = supportedExchange.Key,
+                        HttpClient = _httpClientFactory?.CreateClient(),
+                        Authenticator = _CoinAverageSettings
+                    };
+                    var cached = new CachedRateProvider(supportedExchange.Key, coinAverage, cache)
+                    {
+                        CacheSpan = CacheSpan
+                    };
+                    Providers.Add(supportedExchange.Key, cached);
+                }
+            }
+        }
+
+        public CoinAverageExchanges GetSupportedExchanges()
+        {
+            CoinAverageExchanges exchanges = new CoinAverageExchanges();
+            foreach (var exchange in _CoinAverageSettings.AvailableExchanges)
+            {
+                exchanges.Add(exchange.Value);
+            }
+
+            // Add other exchanges supported here
+            exchanges.Add(new CoinAverageExchange(CoinAverageRateProvider.CoinAverageName, "Coin Average"));
+            exchanges.Add(new CoinAverageExchange("cryptopia", "Cryptopia"));
+
+            return exchanges;
+        }
+
+        public async Task<QueryRateResult> QueryRates(string exchangeName)
+        {
+            Providers.TryGetValue(exchangeName, out var directProvider);
+            directProvider = directProvider ?? NullRateProvider.Instance;
+
+            var wrapper = new WrapperRateProvider(directProvider);
+            var value = await wrapper.GetRatesAsync();
+            return new QueryRateResult()
+            {
+                Latency = wrapper.Latency,
+                ExchangeRates = value,
+                Exception = wrapper.Exception != null ? new ExchangeException() { Exception = wrapper.Exception, ExchangeName = exchangeName } : null
+            };
+        }
+    }
+}

BTCPayServer/Services/SettingsRepository.cs

@@ -83,7 +83,7 @@ namespace BTCPayServer.Services
         MultiValueDictionary<Type, TaskCompletionSource<bool>> _Subscriptions = new MultiValueDictionary<Type, TaskCompletionSource<bool>>();
         public async Task WaitSettingsChanged<T>(CancellationToken cancellation)
         {
-            var tcs = new TaskCompletionSource<bool>();
+            var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
             using (cancellation.Register(() =>
              {
                  try

BTCPayServer/Views/Apps/ListApps.cshtml

@@ -1,4 +1,5 @@
-@model ListAppsViewModel
+@using BTCPayServer.Services.Apps
+@model ListAppsViewModel
 @{
     ViewData["Title"] = "Stores";
 }

BTCPayServer/Views/Server/Services.cshtml

@@ -13,49 +13,46 @@
 </div>
 
 <div class="row">
-    @if(Model.LNDServices.Count != 0)
-    {
-        <div class="col-md-8">
-            <div class="form-group">
-                <h5>LND nodes</h5>
-                <span>You can get access to internal LND services here. For gRPC, only BTC is supported.</span>
-            </div>
 
-            <div class="form-group">
-                <table class="table table-sm table-responsive-md">
-                    <thead>
-                        <tr>
-                            <th>Crypto</th>
-                            <th>Access Type</th>
-                            <th style="text-align:right">Actions</th>
-                        </tr>
-                    </thead>
-                    <tbody>
-                        @foreach(var lnd in Model.LNDServices)
-                        {
-                            <tr>
-                                <td>@lnd.Crypto</td>
-                                <td>@lnd.Type</td>
-                                <td style="text-align:right">
-                                    <a asp-action="LNDGRPCServices" asp-route-cryptoCode="@lnd.Crypto" asp-route-index="@lnd.Index">See information</a>
-                                </td>
-                            </tr>
-                        }
-                        @if(Model.HasSSH)
-                        {
-                            <tr>
-                                <td>None</td>
-                                <td>SSH</td>
-                                <td style="text-align:right">
-                                    <a asp-action="SSHService">See information</a>
-                                </td>
-                            </tr>
-                        }
-                    </tbody>
-                </table>
-            </div>
+    <div class="col-md-8">
+        <div class="form-group">
+            <span>You can get access here to LND-gRPC or SSH services exposed by your server</span>
         </div>
-    }
+
+        <div class="form-group">
+            <table class="table table-sm table-responsive-md">
+                <thead>
+                    <tr>
+                        <th>Crypto</th>
+                        <th>Access Type</th>
+                        <th style="text-align:right">Actions</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    @foreach(var lnd in Model.LNDServices)
+                    {
+                        <tr>
+                            <td>@lnd.Crypto</td>
+                            <td>@lnd.Type</td>
+                            <td style="text-align:right">
+                                <a asp-action="LNDGRPCServices" asp-route-cryptoCode="@lnd.Crypto" asp-route-index="@lnd.Index">See information</a>
+                            </td>
+                        </tr>
+                    }
+                    @if(Model.HasSSH)
+                    {
+                        <tr>
+                            <td>None</td>
+                            <td>SSH</td>
+                            <td style="text-align:right">
+                                <a asp-action="SSHService">See information</a>
+                            </td>
+                        </tr>
+                    }
+                </tbody>
+            </table>
+        </div>
+    </div>
 </div>
 
 @section Scripts {

BTCPayServer/Views/Shared/_Layout.cshtml

@@ -26,6 +26,8 @@
 
     @* JS *@
     <bundle name="wwwroot/bundles/main-bundle.min.js" />
+
+    @RenderSection("HeadScripts", required: false)
 </head>
 
 <body id="page-top">

BTCPayServer/Views/Shared/_NavLayout.cshtml

@@ -3,7 +3,6 @@
     ViewBag.ShowMenu = ViewBag.ShowMenu ?? true;
 }
 
-
 <section>
     <div class="container">
         <div class="row">
@@ -16,7 +15,7 @@
         <div>
             <div class="row">
                 <div class="col-md-3">
-                    @if(ViewBag.ShowMenu)
+                    @if (ViewBag.ShowMenu)
                     {
                         @await Html.PartialAsync("_Nav")
                     }
@@ -28,6 +27,10 @@
         </div>
     </div>
 </section>
+@section HeadScripts {
+    @RenderSection("HeadScripts", required: false)
+}
+
 @section Scripts {
     @RenderSection("Scripts", required: false)
 }

BTCPayServer/Views/Stores/AddDerivationScheme.cshtml

@@ -1,8 +1,7 @@
 @model DerivationSchemeViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = $"{Model.CryptoCode} Derivation scheme";
-    ViewData.AddActivePage(BTCPayServer.Views.Stores.StoreNavPages.Index);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Index, $"{Model.CryptoCode} Derivation scheme");
 }
 
 <partial name="_StatusMessage" for="StatusMessage" />

BTCPayServer/Views/Stores/AddLightningNode.cshtml

@@ -1,8 +1,7 @@
 @model LightningNodeViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Add lightning node (Experimental)";
-    ViewData.AddActivePage(BTCPayServer.Views.Stores.StoreNavPages.Index);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Index, "Add lightning node (Experimental)");
 }
 
 <h4>@ViewData["Title"]</h4>

BTCPayServer/Views/Stores/CheckoutExperience.cshtml

@@ -1,8 +1,7 @@
 @model CheckoutExperienceViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Checkout experience";
-    ViewData.AddActivePage(BTCPayServer.Views.Stores.StoreNavPages.Checkout);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Checkout, "Checkout experience");
 }
 
 <h4>@ViewData["Title"]</h4>

BTCPayServer/Views/Stores/CreateToken.cshtml

@@ -1,8 +1,7 @@
 @model CreateTokenViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Create a new token";
-    ViewData.AddActivePage(StoreNavPages.Tokens);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Tokens, "Create a new token");
     ViewBag.HidePublicKey = ViewBag.HidePublicKey ?? false;
     ViewBag.ShowStores = ViewBag.ShowStores ?? false;
 }

BTCPayServer/Views/Stores/ListTokens.cshtml

@@ -1,8 +1,7 @@
 @model TokensViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Access Tokens";
-    ViewData.AddActivePage(StoreNavPages.Tokens);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Tokens, "Access Tokens");
 }
 
 <partial name="_StatusMessage" for="StatusMessage" />

BTCPayServer/Views/Stores/PayButton.cshtml

@@ -0,0 +1,155 @@
+@model PayButtonViewModel
+@{
+    Layout = "../Shared/_NavLayout.cshtml";
+    ViewData.SetActivePageAndTitle(StoreNavPages.PayButton, "Pay Button");
+}
+
+<div class="container" id="payButtonCtrl">
+    <div class="row">
+        <div class="col-lg-7">
+            <div class="form-row">
+                <div class="form-group col-md-8">
+                    <label>Price</label>
+                    <input name="price" type="text" class="form-control"
+                           v-model="srvModel.price" v-on:change="inputChanges"
+                           v-validate="'required|decimal|min_value:0'" :class="{'is-invalid': errors.has('price') }">
+                    <small class="text-danger">{{ errors.first('price') }}</small>
+                </div>
+                <div class="form-group col-md-4">
+                    <label>&nbsp;</label>
+                    <input name="price" type="text" class="form-control"
+                           v-model="srvModel.currency" v-on:change="inputChanges"
+                           :class="{'is-invalid': errors.has('currency') }">
+                </div>
+            </div>
+            <div class="form-group">
+                <label>Checkout Description</label>
+                <input name="checkoutDesc" type="text" class="form-control" placeholder="(optional)"
+                       v-model="srvModel.checkoutDesc" v-on:change="inputChanges">
+            </div>
+            <div class="form-group">
+                <label>Order Id</label>
+                <input name="orderId" type="text" class="form-control" id="inputAddress" placeholder="(optional)"
+                       v-model="srvModel.orderId" v-on:change="inputChanges">
+            </div>
+            <div class="form-group">
+                <label>Pay Button Image Url</label>
+                <input name="payButtonImageUrl" type="text" class="form-control" id="inputAddress"
+                       v-model="srvModel.payButtonImageUrl" v-on:change="inputChanges"
+                       v-validate="'required|url'" :class="{'is-invalid': errors.has('payButtonImageUrl') }">
+                <small class="text-danger">{{ errors.first('payButtonImageUrl') }}</small>
+            </div>
+            <div class="form-group">
+                <label>Button Size</label>
+                <div style="vertical-align:top; font-size:12px; display:flex;">
+                    <button class="btn" style="width:95px;height:40px;margin-right:40px;"
+                            v-on:click="inputChanges($event, 0)" v-bind:class="{'btn-primary': (srvModel.buttonSize == 0) }">
+                        146 x 40 px
+                    </button>
+                    <button class="btn btn-default" style="width:126px;height:46px;margin-right:40px;"
+                            v-on:click="inputChanges($event, 1)" v-bind:class="{'btn-primary': (srvModel.buttonSize == 1) }">
+                        168 x 46 px
+                    </button>
+                    <button class="btn btn-default" style="width:146px;height:57px;"
+                            v-on:click="inputChanges($event, 2)" v-bind:class="{'btn-primary': (srvModel.buttonSize == 2) }">
+                        209 x 57 px
+                    </button>
+                </div>
+            </div>
+        </div>
+        <div class="col-lg-5">
+            <br />
+            Define parameters that define the purchase: price, currency and then optional description of purchase.
+            <br /><br />
+            Generated HTML will be displayed at the bottom of this page and all you need is to paste that HTML into your final page.
+            Clicking on the button will redirect customer to checkout.
+        </div>
+    </div>
+    <hr />
+    <h3>Payment Notifications</h3>
+    <br />
+    <div class="row">
+        <div class="col-lg-7">
+            <div class="form-group">
+                <label>Server IPN</label>
+                <input name="serverIpn" type="text" class="form-control" placeholder="(optional)"
+                       v-model="srvModel.serverIpn" v-on:change="inputChanges"
+                       v-validate="'url'" :class="{'is-invalid': errors.has('serverIpn') }">
+                <small class="text-danger">{{ errors.first('serverIpn') }}</small>
+            </div>
+            <div class="form-group">
+                <label>Send Email Notifications to</label>
+                <input name="notifyEmail" type="text" class="form-control" placeholder="(optional)"
+                       v-model="srvModel.notifyEmail" v-on:change="inputChanges"
+                       v-validate="'email'" :class="{'is-invalid': errors.has('notifyEmail') }">
+                <small class="text-danger">{{ errors.first('notifyEmail') }}</small>
+
+            </div>
+            <div class="form-group">
+                <label>Browser Redirect</label>
+                <input name="browserRedirect" type="text" class="form-control" placeholder="(optional)"
+                       v-model="srvModel.browserRedirect" v-on:change="inputChanges"
+                       v-validate="'url'" :class="{'is-invalid': errors.has('browserRedirect') }">
+                <small class="text-danger">{{ errors.first('browserRedirect') }}</small>
+            </div>
+        </div>
+        <div class="col-lg-5">
+            <br />
+            These parameters allow you to influence process after purchase. <i>Server IPN</i> is location we'll query with details.
+            We can also deliver email notification to specified addres.
+            <br /><br />
+            Finally <i>Browser Redirect</i> defines where BtcPayServer will redirect customer after puchase is completed.
+        </div>
+    </div>
+    <hr />
+    <h3>Generated code</h3>
+    <div class="row" v-show="!errors.any()">
+        <div class="col-lg-9">
+            <pre><code id="mainCode" class="html"></code></pre>
+            <button class="btn btn-primary" id="copyCode">
+                <i class="fa fa-copy"></i> Copy Code
+            </button>
+            <span class="copyLabelPopup" style="display:none;">Copied</span>
+        </div>
+        <div class="col-lg-3">
+            <div id="preview"></div>
+        </div>
+    </div>
+    <div class="row" v-show="errors.any()">
+        <div class="col-lg-12 text-danger">
+            Please fix errors shown in order for code generation to successfully execute.
+        </div>
+    </div>
+    <br />
+</div>
+
+
+@section HeadScripts {
+    <link rel="stylesheet" href="~/vendor/highlightjs/default.min.css">
+    <script src="~/vendor/highlightjs/highlight.min.js"></script>
+
+    <script src="~/vendor/vuejs/vue.js"></script>
+    <script src="~/vendor/vuejs-vee-validate/vee-validate.js"></script>
+
+    <script src="~/vendor/clipboard.js/clipboard.js"></script>
+
+    <script src="~/paybutton/paybutton.js"></script>
+}
+
+@section Scripts {
+    <script type="text/javascript">
+        var srvModel = @Html.Raw(Json.Serialize(Model));
+
+        var payButtonCtrl = new Vue({
+            el: '#payButtonCtrl',
+            data: {
+                srvModel: srvModel
+            },
+            methods: {
+                inputChanges: function (event, buttonSize) {
+                    inputChanges(event, buttonSize);
+                }
+            }
+        });
+    </script>
+}

BTCPayServer/Views/Stores/PayButtonHandle.cshtml

@@ -0,0 +1,20 @@
+@{ 
+    var allErrors = ViewData.ModelState.Values.SelectMany(v => v.Errors.Select(b => b.ErrorMessage));
+}
+
+<section>
+    <div class="container">
+        <div class="row">
+            <div class="col-lg-12">
+                <h2>Pay Button request failed</h2>
+                Please fix following errors:
+                <ul>
+                    @foreach (var error in allErrors)
+                    {
+                        <li>@error</li>
+                    }
+                </ul>
+            </div>
+        </div>
+    </div>
+</section>

BTCPayServer/Views/Stores/PayButtonTest.cshtml

@@ -0,0 +1,14 @@
+
+<section>
+    <div class="container" id="payButtonCtrl">
+        <div class="row">
+
+            <form method="POST" action="http://127.0.0.1:14142/stores/4b1AnMtMNuxwG7io2dUcB3TrT3yUbgajjGfJjVfdhBDu/pay">
+                <input type="hidden" name="price" value="10" />
+                <input type="hidden" name="currency" value="USD" />
+                <input type="image" src="http://127.0.0.1:14142/img/paybutton/pay.png" name="submit" style="width:209px" alt="Pay with BtcPay, Self-Hosted Bitcoin Payment Processor">
+            </form>
+
+        </div>
+    </div>
+</section>

BTCPayServer/Views/Stores/Rates.cshtml

@@ -1,8 +1,7 @@
 @model BTCPayServer.Models.StoreViewModels.RatesViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Rates";
-    ViewData.AddActivePage(BTCPayServer.Views.Stores.StoreNavPages.Rates);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Rates, "Rates");
 }
 
 <h4>@ViewData["Title"]</h4>

BTCPayServer/Views/Stores/StoreNavPages.cs

@@ -7,28 +7,8 @@ using Microsoft.AspNetCore.Mvc.ViewFeatures;
 
 namespace BTCPayServer.Views.Stores
 {
-    public static class StoreNavPages
+    public enum StoreNavPages
     {
-        public static string ActivePageKey => "ActivePage";
-        public static string Index => "Index";
-        public static string Rates => "Rates";
-        public static string Checkout => "Checkout experience";
-
-        public static string Tokens => "Tokens";
-        public static string Users => "Users";
-        public static string UsersNavClass(ViewContext viewContext) => PageNavClass(viewContext, Users);
-        public static string TokensNavClass(ViewContext viewContext) => PageNavClass(viewContext, Tokens);
-
-        public static string CheckoutNavClass(ViewContext viewContext) => PageNavClass(viewContext, Checkout);
-        public static string IndexNavClass(ViewContext viewContext) => PageNavClass(viewContext, Index);
-        public static string RatesNavClass(ViewContext viewContext) => PageNavClass(viewContext, Rates);
-
-        public static string PageNavClass(ViewContext viewContext, string page)
-        {
-            var activePage = viewContext.ViewData["ActivePage"] as string;
-            return string.Equals(activePage, page, StringComparison.OrdinalIgnoreCase) ? "active" : null;
-        }
-
-        public static void AddActivePage(this ViewDataDictionary viewData, string activePage) => viewData[ActivePageKey] = activePage;
+        ActivePage, Index, Rates, Checkout, Tokens, Users, PayButton
     }
 }

BTCPayServer/Views/Stores/StoreUsers.cshtml

@@ -1,8 +1,7 @@
 @model StoreUsersViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Manage users";
-    ViewData.AddActivePage(StoreNavPages.Users);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Users, "Manage users");
 }
 
 <h4>@ViewData["Title"]</h4>

BTCPayServer/Views/Stores/UpdateStore.cshtml

@@ -1,12 +1,9 @@
 @model StoreViewModel
 @{
     Layout = "../Shared/_NavLayout.cshtml";
-    ViewData["Title"] = "Profile";
-    ViewData.AddActivePage(BTCPayServer.Views.Stores.StoreNavPages.Index);
+    ViewData.SetActivePageAndTitle(StoreNavPages.Index, "Profile");
 }
 
-
-
 <style type="text/css">
     .smMaxWidth {
         max-width: 150px;

BTCPayServer/Views/Stores/_Nav.cshtml

@@ -1,11 +1,9 @@
-@using BTCPayServer.Views.Stores
-@inject SignInManager<ApplicationUser> SignInManager
-
-<div class="nav flex-column nav-pills">
-    <a class="nav-link @StoreNavPages.IndexNavClass(ViewContext)" asp-action="UpdateStore">General settings</a>
-    <a class="nav-link @StoreNavPages.RatesNavClass(ViewContext)" asp-action="Rates">Rates</a>
-    <a class="nav-link @StoreNavPages.CheckoutNavClass(ViewContext)" asp-action="CheckoutExperience">Checkout experience</a>
-    <a class="nav-link @StoreNavPages.TokensNavClass(ViewContext)" asp-action="ListTokens">Access Tokens</a>
-    <a class="nav-link @StoreNavPages.UsersNavClass(ViewContext)" asp-action="StoreUsers">Users</a>
+<div class="nav flex-column nav-pills">
+    <a class="nav-link @ViewData.IsActivePage(StoreNavPages.Index)" asp-action="UpdateStore">General settings</a>
+    <a class="nav-link @ViewData.IsActivePage(StoreNavPages.Rates)" asp-action="Rates">Rates</a>
+    <a class="nav-link @ViewData.IsActivePage(StoreNavPages.Checkout)" asp-action="CheckoutExperience">Checkout experience</a>
+    <a class="nav-link @ViewData.IsActivePage(StoreNavPages.Tokens)" asp-action="ListTokens">Access Tokens</a>
+    <a class="nav-link @ViewData.IsActivePage(StoreNavPages.Users)" asp-action="StoreUsers">Users</a>
+    <a class="nav-link @ViewData.IsActivePage(StoreNavPages.PayButton)" asp-action="PayButton">Pay Button</a>
 </div>
 

BTCPayServer/Views/Stores/_ViewImports.cshtml

@@ -1 +1,2 @@
 @using BTCPayServer.Views.Stores
+@using BTCPayServer.Models.StoreViewModels

BTCPayServer/wwwroot/paybutton/paybutton.js

@@ -0,0 +1,94 @@
+$(function () {
+    inputChanges();
+
+    // Clipboard Copy
+    new Clipboard('#copyCode', {
+        text: function (trigger) {
+            $(".copyLabelPopup").show().delay(1000).fadeOut(500);
+            return inputChanges();
+        }
+    });
+});
+
+function esc(input) {
+    return ('' + input) /* Forces the conversion to string. */
+        .replace(/&/g, '&') /* This MUST be the 1st replacement. */
+        .replace(/'/g, ''') /* The 4 other predefined entities, required. */
+        .replace(/"/g, '"')
+        .replace(/</g, '&lt;')
+        .replace(/>/g, '&gt;')
+        /*
+        You may add other replacements here for HTML only 
+        (but it's not necessary).
+        Or for XML, only if the named entities are defined in its DTD.
+        */
+    ;
+}
+
+Vue.use(VeeValidate);
+const dictionary = {
+    en: {
+        attributes: {
+            price: 'Price', checkoutDesc: 'Checkout Description', orderId: 'Order Id',
+            serverIpn: 'Server IPN', notifyEmail: 'Send Email Notifications', browserRedirect: 'Browser Redirect',
+            payButtonImageUrl: "Pay Button Image Url"
+        }
+    }
+};
+VeeValidate.Validator.localize(dictionary);
+
+function inputChanges(event, buttonSize) {
+    if (buttonSize !== null && buttonSize !== undefined) {
+        srvModel.buttonSize = buttonSize;
+    }
+
+    var html = '<form method="POST" action="' + esc(srvModel.urlRoot + 'stores/'+ srvModel.storeId +  '/pay') + '">';
+    html += addinput("price", srvModel.price);
+    if (srvModel.currency) {
+        html += addinput("currency", srvModel.currency);
+    }
+    if (srvModel.checkoutDesc) {
+        html += addinput("checkoutDesc", srvModel.checkoutDesc);
+    }
+    if (srvModel.orderId) {
+        html += addinput("orderId", srvModel.orderId);
+    }
+
+    if (srvModel.serverIpn) {
+        html += addinput("serverIpn", srvModel.serverIpn);
+    }
+    if (srvModel.browserRedirect) {
+        html += addinput("browserRedirect", srvModel.browserRedirect);
+    }
+    if (srvModel.notifyEmail) {
+        html += addinput("notifyEmail", srvModel.notifyEmail);
+    }
+
+    var width = "209px";
+    if (srvModel.buttonSize === 0) {
+        width = "146px";
+    } else if (srvModel.buttonSize === 1) {
+        width = "168px";
+    } else if (srvModel.buttonSize === 2) {
+        width = "209px";
+    }
+    html += '\n    <input type="image" src="' + esc(srvModel.payButtonImageUrl) + '" name="submit" style="width:' + width +
+        '" alt="Pay with BtcPay, Self-Hosted Bitcoin Payment Processor">';
+
+    html += '\n</form>';
+
+    $("#mainCode").text(html).html();
+    $("#preview").html(html);
+
+    $('pre code').each(function (i, block) {
+        hljs.highlightBlock(block);
+    });
+
+    return html;
+}
+
+function addinput(name, value) {
+    var html = '\n    <input type="hidden" name="' + esc(name) + '" value="' + esc(value) + '" />';
+    return html;
+}
+