Can tweak the rate at store level

BTCPayServer.Tests/TestAccount.cs

@@ -61,10 +61,9 @@ namespace BTCPayServer.Tests
             await store.CreateStore(new CreateStoreViewModel() { Name = "Test Store" });
             StoreId = store.CreatedStoreId;
             DerivationScheme = new DerivationStrategyFactory(SupportedNetwork.NBitcoinNetwork).Parse(ExtKey.Neuter().ToString() + "-[legacy]");
-            await store.UpdateStore(StoreId, new StoreViewModel()
+            var vm = (StoreViewModel)((ViewResult)await store.UpdateStore(StoreId)).Model;
-            {
+            vm.SpeedPolicy = SpeedPolicy.MediumSpeed;
-                SpeedPolicy = SpeedPolicy.MediumSpeed
+            await store.UpdateStore(StoreId, vm);
-            });
 
             await store.AddDerivationScheme(StoreId, new DerivationSchemeViewModel()
             {

BTCPayServer.Tests/UnitTest1.cs

@@ -24,6 +24,7 @@ using BTCPayServer.Services.Rates;
 using Microsoft.Extensions.Caching.Memory;
 using BTCPayServer.Eclair;
 using System.Collections.Generic;
+using BTCPayServer.Models.StoreViewModels;
 
 namespace BTCPayServer.Tests
 {
@@ -392,6 +393,50 @@ namespace BTCPayServer.Tests
             }
         }
 
+
+        [Fact]
+        public void CanTweakRate()
+        {
+            using (var tester = ServerTester.Create())
+            {
+                tester.Start();
+                var user = tester.NewAccount();
+                user.GrantAccess();
+
+
+                // First we try payment with a merchant having only BTC
+                var invoice1 = user.BitPay.CreateInvoice(new Invoice()
+                {
+                    Price = 5000.0,
+                    Currency = "USD",
+                    PosData = "posData",
+                    OrderId = "orderId",
+                    ItemDesc = "Some description",
+                    FullNotifications = true
+                }, Facade.Merchant);
+
+
+                var storeController = tester.PayTester.GetController<StoresController>(user.UserId);
+                var vm = (StoreViewModel)((ViewResult)storeController.UpdateStore(user.StoreId).Result).Model;
+                Assert.Equal(1.0, vm.RateMultiplier);
+                vm.RateMultiplier = 0.5;
+                storeController.UpdateStore(user.StoreId, vm).Wait();
+
+
+                var invoice2 = user.BitPay.CreateInvoice(new Invoice()
+                {
+                    Price = 5000.0,
+                    Currency = "USD",
+                    PosData = "posData",
+                    OrderId = "orderId",
+                    ItemDesc = "Some description",
+                    FullNotifications = true
+                }, Facade.Merchant);
+
+                Assert.True(invoice2.BtcPrice.Almost(invoice1.BtcPrice * 2, 0.00001m));
+            }
+        }
+
         [Fact]
         public void CanHaveLTCOnlyStore()
         {

BTCPayServer/Controllers/InvoiceController.cs

@@ -130,7 +130,7 @@ namespace BTCPayServer.Controllers
                         {
                             network = _.Network,
                             getFeeRate = _.FeeRateProvider.GetFeeRateAsync(),
-                            getRate = _.RateProvider.GetRateAsync(invoice.Currency),
+                            getRate = storeBlob.ApplyRateRules(_.Network, _.RateProvider).GetRateAsync(invoice.Currency),
                             getAddress = _.Wallet.ReserveAddressAsync(_.DerivationStrategy)
                         };
                     });
@@ -164,7 +164,7 @@ namespace BTCPayServer.Controllers
 #pragma warning disable CS0618
                 var btc = _NetworkProvider.BTC;
                 var feeProvider = _FeeProviderFactory.CreateFeeProvider(btc);
-                var rateProvider = _RateProviders.GetRateProvider(btc);
+                var rateProvider = storeBlob.ApplyRateRules(btc, _RateProviders.GetRateProvider(btc));
                 if (feeProvider != null && rateProvider != null)
                 {
                     var gettingFee = feeProvider.GetFeeRateAsync();

BTCPayServer/Controllers/StoresController.cs

@@ -164,6 +164,7 @@ namespace BTCPayServer.Controllers
             vm.StatusMessage = StatusMessage;
             vm.MonitoringExpiration = storeBlob.MonitoringExpiration;
             vm.InvoiceExpiration = storeBlob.InvoiceExpiration;
+            vm.RateMultiplier = (double)storeBlob.GetRateMultiplier();
             return View(vm);
         }
 
@@ -307,6 +308,8 @@ namespace BTCPayServer.Controllers
             var blob = store.GetStoreBlob();
             blob.NetworkFeeDisabled = !model.NetworkFee;
             blob.MonitoringExpiration = model.MonitoringExpiration;
+            blob.InvoiceExpiration = model.InvoiceExpiration;
+            blob.SetRateMultiplier(model.RateMultiplier);
 
             if (store.SetStoreBlob(blob))
             {

BTCPayServer/Data/StoreData.cs

@@ -11,6 +11,7 @@ using System.Threading.Tasks;
 using System.ComponentModel;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using BTCPayServer.Services.Rates;
 
 namespace BTCPayServer.Data
 {
@@ -99,10 +100,10 @@ namespace BTCPayServer.Data
 
             if (!existing && string.IsNullOrEmpty(derivationScheme))
             {
-                if(network.IsBTC)
+                if (network.IsBTC)
                     DerivationStrategy = null;
             }
-            else if(!existing)
+            else if (!existing)
                 strategies.Add(new JProperty(network.CryptoCode, new JValue(derivationScheme)));
             // This is deprecated so we don't have to set anymore
             //if (network.IsBTC)
@@ -173,6 +174,22 @@ namespace BTCPayServer.Data
         }
     }
 
+    public class RateRule
+    {
+        public RateRule()
+        {
+            RuleName = "Multiplier";
+        }
+        public string RuleName { get; set; }
+
+        public double Multiplier { get; set; }
+
+        public decimal Apply(BTCPayNetwork network, decimal rate)
+        {
+            return rate * (decimal)Multiplier;
+        }
+    }
+
     public class StoreBlob
     {
         public StoreBlob()
@@ -200,5 +217,30 @@ namespace BTCPayServer.Data
             set;
         }
 
+        public void SetRateMultiplier(double rate)
+        {
+            RateRules = new List<RateRule>();
+            RateRules.Add(new RateRule() { Multiplier = rate });
+        }
+        public decimal GetRateMultiplier()
+        {
+            decimal rate = 1.0m;
+            if (RateRules == null || RateRules.Count == 0)
+                return rate;
+            foreach (var rule in RateRules)
+            {
+                rate = rule.Apply(null, rate);
+            }
+            return rate;
+        }
+
+        public List<RateRule> RateRules { get; set; } = new List<RateRule>();
+
+        public IRateProvider ApplyRateRules(BTCPayNetwork network, IRateProvider rateProvider)
+        {
+            if (RateRules == null || RateRules.Count == 0)
+                return rateProvider;
+            return new TweakRateProvider(network, rateProvider, RateRules.ToList());
+        }
     }
 }

BTCPayServer/Models/StoreViewModels/StoreViewModel.cs

@@ -47,6 +47,14 @@ namespace BTCPayServer.Models.StoreViewModels
 
         public List<StoreViewModel.DerivationScheme> DerivationSchemes { get; set; } = new List<StoreViewModel.DerivationScheme>();
 
+        [Display(Name = "Multiply the original rate by ...")]
+        [Range(0.01, 10.0)]
+        public double RateMultiplier
+        {
+            get;
+            set;
+        }
+
         [Display(Name = "Invoice expires if the full amount has not been paid after ... minutes")]
         [Range(1, 60 * 24 * 31)]
         public int InvoiceExpiration

BTCPayServer/Services/Rates/TweakRateProvider.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Data;
+
+namespace BTCPayServer.Services.Rates
+{
+    public class TweakRateProvider : IRateProvider
+    {
+        private BTCPayNetwork network;
+        private IRateProvider rateProvider;
+        private List<RateRule> rateRules;
+
+        public TweakRateProvider(BTCPayNetwork network, IRateProvider rateProvider, List<RateRule> rateRules)
+        {
+            if (network == null)
+                throw new ArgumentNullException(nameof(network));
+            if (rateProvider == null)
+                throw new ArgumentNullException(nameof(rateProvider));
+            if (rateRules == null)
+                throw new ArgumentNullException(nameof(rateRules));
+            this.network = network;
+            this.rateProvider = rateProvider;
+            this.rateRules = rateRules;
+        }
+
+        public async Task<decimal> GetRateAsync(string currency)
+        {
+            var rate = await rateProvider.GetRateAsync(currency);
+            foreach(var rule in rateRules)
+            {
+                rate = rule.Apply(network, rate);
+            }
+            return rate;
+        }
+
+        public async Task<ICollection<Rate>> GetRatesAsync()
+        {
+            List<Rate> rates = new List<Rate>();
+            foreach (var rate in await rateProvider.GetRatesAsync())
+            {
+                var localRate = rate.Value;
+                foreach (var rule in rateRules)
+                {
+                    localRate = rule.Apply(network, localRate);
+                }
+                rates.Add(new Rate(rate.Currency, localRate));
+            }
+            return rates;
+        }
+    }
+}

BTCPayServer/Views/Stores/UpdateStore.cshtml

@@ -38,6 +38,11 @@
                 <label asp-for="NetworkFee"></label>
                 <input asp-for="NetworkFee" type="checkbox" class="form-check" />
             </div>
+            <div class="form-group">
+                <label asp-for="RateMultiplier"></label>
+                <input asp-for="RateMultiplier" class="form-control" />
+                <span asp-validation-for="RateMultiplier" class="text-danger"></span>
+            </div>
             <div class="form-group">
                 <label asp-for="InvoiceExpiration"></label>
                 <input asp-for="InvoiceExpiration" class="form-control" />