Make rate calculation scriptable

BTCPayServer.Tests/TestAccount.cs

@@ -79,7 +79,7 @@ namespace BTCPayServer.Tests
             var store = parent.PayTester.GetController<StoresController>(UserId, StoreId);
             ExtKey = new ExtKey().GetWif(SupportedNetwork.NBitcoinNetwork);
             DerivationScheme = new DerivationStrategyFactory(SupportedNetwork.NBitcoinNetwork).Parse(ExtKey.Neuter().ToString() + "-[legacy]");
-            var vm = (StoreViewModel)((ViewResult)store.UpdateStore(StoreId)).Model;
+            var vm = (StoreViewModel)((ViewResult)store.UpdateStore()).Model;
             vm.SpeedPolicy = SpeedPolicy.MediumSpeed;
             await store.UpdateStore(vm);
 

BTCPayServer.Tests/UnitTest1.cs

@@ -297,7 +297,7 @@ namespace BTCPayServer.Tests
                 var user = tester.NewAccount();
                 user.GrantAccess();
                 var storeController = user.GetController<StoresController>();
-                Assert.IsType<ViewResult>(storeController.UpdateStore(user.StoreId));
+                Assert.IsType<ViewResult>(storeController.UpdateStore());
                 Assert.IsType<ViewResult>(storeController.AddLightningNode(user.StoreId, "BTC"));
 
                 var testResult = storeController.AddLightningNode(user.StoreId, new LightningNodeViewModel()
@@ -312,7 +312,7 @@ namespace BTCPayServer.Tests
                     Url = tester.MerchantCharge.Client.Uri.AbsoluteUri
                 }, "save", "BTC").GetAwaiter().GetResult());
 
-                var storeVm = Assert.IsType<Models.StoreViewModels.StoreViewModel>(Assert.IsType<ViewResult>(storeController.UpdateStore(user.StoreId)).Model);
+                var storeVm = Assert.IsType<Models.StoreViewModels.StoreViewModel>(Assert.IsType<ViewResult>(storeController.UpdateStore()).Model);
                 Assert.Single(storeVm.LightningNodes.Where(l => !string.IsNullOrEmpty(l.Address)));
             }
         }
@@ -678,9 +678,9 @@ namespace BTCPayServer.Tests
         private static decimal CreateInvoice(ServerTester tester, TestAccount user, string exchange)
         {
             var storeController = user.GetController<StoresController>();
-            var vm = (StoreViewModel)((ViewResult)storeController.UpdateStore(user.StoreId)).Model;
+            var vm = (RatesViewModel)((ViewResult)storeController.Rates()).Model;
             vm.PreferredExchange = exchange;
-            storeController.UpdateStore(vm).Wait();
+            storeController.Rates(vm).Wait();
             var invoice2 = user.BitPay.CreateInvoice(new Invoice()
             {
                 Price = 5000.0,
@@ -717,10 +717,10 @@ namespace BTCPayServer.Tests
 
 
                 var storeController = user.GetController<StoresController>();
-                var vm = (StoreViewModel)((ViewResult)storeController.UpdateStore(user.StoreId)).Model;
+                var vm = (RatesViewModel)((ViewResult)storeController.Rates()).Model;
                 Assert.Equal(1.0, vm.RateMultiplier);
                 vm.RateMultiplier = 0.5;
-                storeController.UpdateStore(vm).Wait();
+                storeController.Rates(vm).Wait();
 
 
                 var invoice2 = user.BitPay.CreateInvoice(new Invoice()
@@ -796,6 +796,66 @@ namespace BTCPayServer.Tests
             }
         }
 
+        [Fact]
+        public void CanModifyRates()
+        {
+            using (var tester = ServerTester.Create())
+            {
+                tester.Start();
+                var user = tester.NewAccount();
+                user.GrantAccess();
+                user.RegisterDerivationScheme("BTC");
+
+                var store = user.GetController<StoresController>();
+                var rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates()).Model);
+                Assert.False(rateVm.ShowScripting);
+                Assert.Equal("coinaverage", rateVm.PreferredExchange);
+                Assert.Equal(1.0, rateVm.RateMultiplier);
+                Assert.Null(rateVm.TestRateRules);
+
+                rateVm.PreferredExchange = "bitflyer";
+                Assert.IsType<RedirectToActionResult>(store.Rates(rateVm, "Save").Result);
+                rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates()).Model);
+                Assert.Equal("bitflyer", rateVm.PreferredExchange);
+
+                rateVm.ScriptTest = "BTC_JPY,BTC_CAD";
+                rateVm.RateMultiplier = 1.1;
+                store = user.GetController<StoresController>();
+                rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates(rateVm, "Test").Result).Model);
+                Assert.NotNull(rateVm.TestRateRules);
+                Assert.Equal(2, rateVm.TestRateRules.Count);
+                Assert.False(rateVm.TestRateRules[0].Error);
+                Assert.StartsWith("(bitflyer(BTC_JPY)) * 1.10 =", rateVm.TestRateRules[0].Rule, StringComparison.OrdinalIgnoreCase);
+                Assert.True(rateVm.TestRateRules[1].Error);
+                Assert.IsType<RedirectToActionResult>(store.Rates(rateVm, "Save").Result);
+
+                Assert.IsType<RedirectToActionResult>(store.ShowRateRulesPost(true).Result);
+                Assert.IsType<RedirectToActionResult>(store.Rates(rateVm, "Save").Result);
+                store = user.GetController<StoresController>();
+                rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates()).Model);
+                Assert.Equal(rateVm.DefaultScript, rateVm.Script);
+                Assert.True(rateVm.ShowScripting);
+                rateVm.ScriptTest = "BTC_JPY";
+                rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates(rateVm, "Test").Result).Model);
+                Assert.True(rateVm.ShowScripting);
+                Assert.Contains("(bitflyer(BTC_JPY)) * 1.10 = ", rateVm.TestRateRules[0].Rule, StringComparison.OrdinalIgnoreCase);
+
+                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);";
+                rateVm.RateMultiplier = 0.5;
+                rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates(rateVm, "Test").Result).Model);
+                Assert.True(rateVm.TestRateRules.All(t => !t.Error));
+                Assert.IsType<RedirectToActionResult>(store.Rates(rateVm, "Save").Result);
+                store = user.GetController<StoresController>();
+                rateVm = Assert.IsType<RatesViewModel>(Assert.IsType<ViewResult>(store.Rates()).Model);
+                Assert.Equal(0.5, rateVm.RateMultiplier);
+                Assert.True(rateVm.ShowScripting);
+                Assert.Contains("DOGE_X", rateVm.Script, StringComparison.OrdinalIgnoreCase);
+            }
+        }
+
         [Fact]
         public void CanPayWithTwoCurrencies()
         {
@@ -1255,7 +1315,7 @@ namespace BTCPayServer.Tests
         public void CheckRatesProvider()
         {
             var provider = new BTCPayNetworkProvider(NetworkType.Mainnet);
-            var coinAverage = new CoinAverageRateProvider(provider);
+            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();

BTCPayServer/Controllers/InvoiceController.UI.cs

@@ -460,9 +460,9 @@ namespace BTCPayServer.Controllers
                 StatusMessage = $"Invoice {result.Data.Id} just created!";
                 return RedirectToAction(nameof(ListInvoices));
             }
-            catch (BitpayHttpException)
+            catch (BitpayHttpException ex)
             {
-                ModelState.TryAddModelError(nameof(model.Currency), "Unsupported currency");
+                ModelState.TryAddModelError(nameof(model.Currency), $"Error: {ex.Message}");
                 return View(model);
             }
         }

BTCPayServer/Controllers/StoresController.cs

@@ -4,6 +4,7 @@ using BTCPayServer.Data;
 using BTCPayServer.HostedServices;
 using BTCPayServer.Models;
 using BTCPayServer.Models.StoreViewModels;
+using BTCPayServer.Rating;
 using BTCPayServer.Security;
 using BTCPayServer.Services;
 using BTCPayServer.Services.Rates;
@@ -20,6 +21,7 @@ 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;
@@ -33,6 +35,7 @@ namespace BTCPayServer.Controllers
     [AutoValidateAntiforgeryToken]
     public partial class StoresController : Controller
     {
+        BTCPayRateProviderFactory _RateFactory;
         public string CreatedStoreId { get; set; }
         public StoresController(
             NBXplorerDashboard dashboard,
@@ -46,12 +49,14 @@ namespace BTCPayServer.Controllers
             AccessTokenController tokenController,
             BTCPayWalletProvider walletProvider,
             BTCPayNetworkProvider networkProvider,
+            BTCPayRateProviderFactory rateFactory,
             ExplorerClientProvider explorerProvider,
             IFeeProviderFactory feeRateProvider,
             LanguageService langService,
             IHostingEnvironment env,
             CoinAverageSettings coinAverage)
         {
+            _RateFactory = rateFactory;
             _Dashboard = dashboard;
             _Repo = repo;
             _TokenRepository = tokenRepo;
@@ -191,6 +196,143 @@ namespace BTCPayServer.Controllers
             return RedirectToAction(nameof(StoreUsers), new { storeId = storeId, userId = userId });
         }
 
+        [HttpGet]
+        [Route("{storeId}/rates")]
+        public IActionResult Rates()
+        {
+            var storeBlob = StoreData.GetStoreBlob();
+            var vm = new RatesViewModel();
+            vm.SetExchangeRates(GetSupportedExchanges(), storeBlob.PreferredExchange ?? CoinAverageRateProvider.CoinAverageName);
+            vm.RateMultiplier = (double)storeBlob.GetRateMultiplier();
+            vm.Script = storeBlob.GetRateRules(_NetworkProvider).ToString();
+            vm.DefaultScript = storeBlob.GetDefaultRateRules(_NetworkProvider).ToString();
+            vm.AvailableExchanges = GetSupportedExchanges();
+            vm.ShowScripting = storeBlob.RateScripting;
+            return View(vm);
+        }
+
+        [HttpPost]
+        [Route("{storeId}/rates")]
+        public async Task<IActionResult> Rates(RatesViewModel model, string command = null)
+        {
+            model.SetExchangeRates(GetSupportedExchanges(), model.PreferredExchange);
+            if (!ModelState.IsValid)
+            {
+                return View(model);
+            }
+            if (model.PreferredExchange != null)
+                model.PreferredExchange = model.PreferredExchange.Trim().ToLowerInvariant();
+
+            var blob = StoreData.GetStoreBlob();
+            model.DefaultScript = blob.GetDefaultRateRules(_NetworkProvider).ToString();
+            model.AvailableExchanges = GetSupportedExchanges();
+
+            blob.PreferredExchange = model.PreferredExchange;
+            blob.SetRateMultiplier(model.RateMultiplier);
+
+            if (!model.ShowScripting)
+            {
+                if (!GetSupportedExchanges().Select(c => c.Name).Contains(blob.PreferredExchange, StringComparer.OrdinalIgnoreCase))
+                {
+                    ModelState.AddModelError(nameof(model.PreferredExchange), $"Unsupported exchange ({model.RateSource})");
+                    return View(model);
+                }
+            }
+            RateRules rules = null;
+            if (model.ShowScripting)
+            {
+                if (!RateRules.TryParse(model.Script, out rules, out var errors))
+                {
+                    errors = errors ?? new List<RateRulesErrors>();
+                    var errorString = String.Join(", ", errors.ToArray());
+                    ModelState.AddModelError(nameof(model.Script), $"Parsing error ({errorString})");
+                    return View(model);
+                }
+                else
+                {
+                    blob.RateScript = rules.ToString();
+                }
+            }
+            rules = blob.GetRateRules(_NetworkProvider);
+
+            if (command == "Test")
+            {
+                if (string.IsNullOrWhiteSpace(model.ScriptTest))
+                {
+                    ModelState.AddModelError(nameof(model.ScriptTest), "Fill out currency pair to test for (like BTC_USD,BTC_CAD)");
+                    return View(model);
+                }
+                var splitted = model.ScriptTest.Split(',', StringSplitOptions.RemoveEmptyEntries);
+
+                var pairs = new List<CurrencyPair>();
+                foreach (var pair in splitted)
+                {
+                    if (!CurrencyPair.TryParse(pair, out var currencyPair))
+                    {
+                        ModelState.AddModelError(nameof(model.ScriptTest), $"Invalid currency pair '{pair}' (it should be formatted like BTC_USD,BTC_CAD)");
+                        return View(model);
+                    }
+                    pairs.Add(currencyPair);
+                }
+
+                var fetchs = _RateFactory.FetchRates(pairs.ToHashSet(), rules);
+                var testResults = new List<RatesViewModel.TestResultViewModel>();
+                foreach (var fetch in fetchs)
+                {
+                    var testResult = await (fetch.Value);
+                    testResults.Add(new RatesViewModel.TestResultViewModel()
+                    {
+                        CurrencyPair = fetch.Key.ToString(),
+                        Error = testResult.Errors.Count != 0,
+                        Rule = testResult.Errors.Count == 0 ? testResult.Rule + " = " + testResult.Value.Value.ToString(CultureInfo.InvariantCulture) 
+                                                            : testResult.EvaluatedRule
+                    });
+                }
+                model.TestRateRules = testResults;
+                return View(model);
+            }
+            else // command == Save
+            {
+                if (StoreData.SetStoreBlob(blob))
+                {
+                    await _Repo.UpdateStore(StoreData);
+                    StatusMessage = "Rate settings updated";
+                }
+                return RedirectToAction(nameof(Rates), new
+                {
+                    storeId = StoreData.Id
+                });
+            }
+        }
+
+        [HttpGet]
+        [Route("{storeId}/rates/confirm")]
+        public IActionResult ShowRateRules(bool scripting)
+        {
+            return View("Confirm", new ConfirmModel()
+            {
+                Action = nameof(ShowRateRulesPost),
+                Title = "Rate rule scripting",
+                Description = scripting ?
+                                "This action will mofify your current rate sources. Are you sure to turn on rate rules scripting? (Advanced users)"
+                                : "This action will delete your rate script. Are you sure to turn off rate rules scripting?",
+                ButtonClass = "btn-primary"
+            });
+        }
+
+        [HttpPost]
+        [Route("{storeId}/rates/confirm")]
+        public async Task<IActionResult> ShowRateRulesPost(bool scripting)
+        {
+            var blob = StoreData.GetStoreBlob();
+            blob.RateScripting = scripting;
+            blob.RateScript = blob.GetDefaultRateRules(_NetworkProvider).ToString();
+            StoreData.SetStoreBlob(blob);
+            await _Repo.UpdateStore(StoreData);
+            StatusMessage = "Rate rules scripting activated";
+            return RedirectToAction(nameof(Rates), new { storeId = StoreData.Id });
+        }
+
         [HttpGet]
         [Route("{storeId}/checkout")]
         public IActionResult CheckoutExperience()
@@ -268,7 +410,7 @@ namespace BTCPayServer.Controllers
 
         [HttpGet]
         [Route("{storeId}")]
-        public IActionResult UpdateStore(string storeId)
+        public IActionResult UpdateStore()
         {
             var store = HttpContext.GetStoreData();
             if (store == null)
@@ -276,7 +418,6 @@ namespace BTCPayServer.Controllers
 
             var storeBlob = store.GetStoreBlob();
             var vm = new StoreViewModel();
-            vm.SetExchangeRates(GetSupportedExchanges(), storeBlob.PreferredExchange ?? CoinAverageRateProvider.CoinAverageName);
             vm.Id = store.Id;
             vm.StoreName = store.StoreName;
             vm.StoreWebsite = store.StoreWebsite;
@@ -285,7 +426,6 @@ namespace BTCPayServer.Controllers
             AddPaymentMethods(store, vm);
             vm.MonitoringExpiration = storeBlob.MonitoringExpiration;
             vm.InvoiceExpiration = storeBlob.InvoiceExpiration;
-            vm.RateMultiplier = (double)storeBlob.GetRateMultiplier();
             vm.LightningDescriptionTemplate = storeBlob.LightningDescriptionTemplate;
             return View(vm);
         }
@@ -328,13 +468,6 @@ namespace BTCPayServer.Controllers
         [Route("{storeId}")]
         public async Task<IActionResult> UpdateStore(StoreViewModel model)
         {
-            model.SetExchangeRates(GetSupportedExchanges(), model.PreferredExchange);
-            if (!ModelState.IsValid)
-            {
-                return View(model);
-            }
-            if (model.PreferredExchange != null)
-                model.PreferredExchange = model.PreferredExchange.Trim().ToLowerInvariant();
             AddPaymentMethods(StoreData, model);
 
             bool needUpdate = false;
@@ -360,26 +493,11 @@ namespace BTCPayServer.Controllers
             blob.InvoiceExpiration = model.InvoiceExpiration;
             blob.LightningDescriptionTemplate = model.LightningDescriptionTemplate ?? string.Empty;
 
-            bool newExchange = blob.PreferredExchange != model.PreferredExchange;
-            blob.PreferredExchange = model.PreferredExchange;
-
-            blob.SetRateMultiplier(model.RateMultiplier);
-
             if (StoreData.SetStoreBlob(blob))
             {
                 needUpdate = true;
             }
 
-            if (newExchange)
-            {
-
-                if (!GetSupportedExchanges().Select(c => c.Name).Contains(blob.PreferredExchange, StringComparer.OrdinalIgnoreCase))
-                {
-                    ModelState.AddModelError(nameof(model.PreferredExchange), $"Unsupported exchange ({model.RateSource})");
-                    return View(model);
-                }
-            }
-
             if (needUpdate)
             {
                 await _Repo.UpdateStore(StoreData);

BTCPayServer/Extensions.cs

@@ -200,13 +200,5 @@ namespace BTCPayServer
             var res = JsonConvert.SerializeObject(o, Formatting.None, jsonSettings);
             return res;
         }
-
-        public static HtmlString ToJSVariableModel(this object o, string variableName)
-        {
-            var encodedJson = JavaScriptEncoder.Default.Encode(o.ToJson());
-            return new HtmlString($"var {variableName} = JSON.parse('" + encodedJson + "');");
-        }
-
-
     }
 }

BTCPayServer/Models/ConfirmModel.cs

@@ -19,5 +19,6 @@ namespace BTCPayServer.Models
         {
             get; set;
         }
+        public string ButtonClass { get; set; } = "btn-danger";
     }
 }

BTCPayServer/Models/StoreViewModels/RatesViewModel.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Rating;
+using BTCPayServer.Services.Rates;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace BTCPayServer.Models.StoreViewModels
+{
+    public class RatesViewModel
+    {
+        public class TestResultViewModel
+        {
+            public string CurrencyPair { get; set; }
+            public string Rule { get; set; }
+            public bool Error { get; set; }
+        }
+        class Format
+        {
+            public string Name { get; set; }
+            public string Value { get; set; }
+        }
+        public void SetExchangeRates(CoinAverageExchange[] supportedList, string preferredExchange)
+        {
+            var defaultStore = preferredExchange ?? CoinAverageRateProvider.CoinAverageName;
+            var choices = supportedList.Select(o => new Format() { Name = o.Display, Value = o.Name }).ToArray();
+            var chosen = choices.FirstOrDefault(f => f.Value == defaultStore) ?? choices.FirstOrDefault();
+            Exchanges = new SelectList(choices, nameof(chosen.Value), nameof(chosen.Name), chosen);
+            PreferredExchange = chosen.Value;
+        }
+
+        public List<TestResultViewModel> TestRateRules { get; set; }
+
+        public SelectList Exchanges { get; set; }
+
+        public bool ShowScripting { get; set; }
+
+        [Display(Name = "Rate rules")]
+        [MaxLength(2000)]
+        public string Script { get; set; }
+        public string DefaultScript { get; set; }
+        public string ScriptTest { get; set; }
+        public CoinAverageExchange[] AvailableExchanges { get; set; }
+
+        [Display(Name = "Multiply the original rate by ...")]
+        [Range(0.01, 10.0)]
+        public double RateMultiplier
+        {
+            get;
+            set;
+        }
+
+        [Display(Name = "Preferred price source (eg. bitfinex, bitstamp...)")]
+        public string PreferredExchange { get; set; }
+
+        public string RateSource
+        {
+            get
+            {
+                return PreferredExchange == CoinAverageRateProvider.CoinAverageName ? "https://apiv2.bitcoinaverage.com/indices/global/ticker/short" : $"https://apiv2.bitcoinaverage.com/exchanges/{PreferredExchange}";
+            }
+        }
+    }
+}

BTCPayServer/Models/StoreViewModels/StoreViewModel.cs

@@ -13,11 +13,6 @@ namespace BTCPayServer.Models.StoreViewModels
 {
     public class StoreViewModel
     {
-        class Format
-        {
-            public string Name { get; set; }
-            public string Value { get; set; }
-        }
         public class DerivationScheme
         {
             public string Crypto { get; set; }
@@ -50,36 +45,6 @@ namespace BTCPayServer.Models.StoreViewModels
 
         public List<StoreViewModel.DerivationScheme> DerivationSchemes { get; set; } = new List<StoreViewModel.DerivationScheme>();
 
-        public void SetExchangeRates(CoinAverageExchange[] supportedList, string preferredExchange)
-        {
-            var defaultStore = preferredExchange ?? CoinAverageRateProvider.CoinAverageName;
-            var choices = supportedList.Select(o => new Format() { Name = o.Display, Value = o.Name }).ToArray();
-            var chosen = choices.FirstOrDefault(f => f.Value == defaultStore) ?? choices.FirstOrDefault();
-            Exchanges = new SelectList(choices, nameof(chosen.Value), nameof(chosen.Name), chosen);
-            PreferredExchange = chosen.Value;
-        }
-
-        public SelectList Exchanges { get; set; }
-
-        [Display(Name = "Preferred price source (eg. bitfinex, bitstamp...)")]
-        public string PreferredExchange { get; set; }
-
-        public string RateSource
-        {
-            get
-            {
-                return PreferredExchange == CoinAverageRateProvider.CoinAverageName ? "https://apiv2.bitcoinaverage.com/indices/global/ticker/short" : $"https://apiv2.bitcoinaverage.com/exchanges/{PreferredExchange}";
-            }
-        }
-
-        [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 * 24)]
         public int InvoiceExpiration

BTCPayServer/Rating/CurrencyPair.cs

@@ -30,6 +30,7 @@ namespace BTCPayServer.Rating
             if (str == null)
                 throw new ArgumentNullException(nameof(str));
             value = null;
+            str = str.Trim();
             var splitted = str.Split('_');
             if (splitted.Length != 2)
                 return false;

BTCPayServer/Rating/RateRules.cs

@@ -20,6 +20,7 @@ namespace BTCPayServer.Rating
         DivideByZero,
         PreprocessError,
         RateUnavailable,
+        InvalidExchangeName,
     }
     public class RateRules
     {
@@ -28,13 +29,6 @@ namespace BTCPayServer.Rating
             public List<RateRulesErrors> Errors = new List<RateRulesErrors>();
 
             bool IsInvocation;
-            public override SyntaxNode VisitArgumentList(ArgumentListSyntax node)
-            {
-                IsInvocation = false;
-                var result = base.VisitArgumentList(node);
-                IsInvocation = true;
-                return result;
-            }
             public override SyntaxNode VisitInvocationExpression(InvocationExpressionSyntax node)
             {
                 if (IsInvocation)
@@ -42,17 +36,22 @@ namespace BTCPayServer.Rating
                     Errors.Add(RateRulesErrors.NestedInvocation);
                     return base.VisitInvocationExpression(node);
                 }
+                if (node.Expression is IdentifierNameSyntax id)
+                {
                     IsInvocation = true;
-                var result = base.VisitInvocationExpression(node);
+                    var arglist = (ArgumentListSyntax)this.Visit(node.ArgumentList);
                     IsInvocation = false;
-                return result;
+                    return SyntaxFactory.InvocationExpression(SyntaxFactory.IdentifierName(id.Identifier.ValueText.ToLowerInvariant()), arglist)
+                                        .WithTriviaFrom(id);
+                }
+                else
+                {
+                    Errors.Add(RateRulesErrors.InvalidExchangeName);
+                    return node;
+                }
             }
             public override SyntaxNode VisitIdentifierName(IdentifierNameSyntax node)
             {
-                if (IsInvocation)
-                {
-                    return SyntaxFactory.IdentifierName(node.Identifier.ValueText.ToLowerInvariant());
-                }
                 if (CurrencyPair.TryParse(node.Identifier.ValueText, out var currencyPair))
                 {
                     return SyntaxFactory.IdentifierName(currencyPair.ToString())
@@ -109,14 +108,22 @@ namespace BTCPayServer.Rating
             this.root = ruleList.GetSyntaxNode();
         }
         public static bool TryParse(string str, out RateRules rules)
+        {
+            return TryParse(str, out rules, out var unused);
+        }
+        public static bool TryParse(string str, out RateRules rules, out List<RateRulesErrors> errors)
         {
             rules = null;
+            errors = null;
             var expression = CSharpSyntaxTree.ParseText(str, new CSharpParseOptions(LanguageVersion.Default).WithKind(SourceCodeKind.Script));
             var rewriter = new NormalizeCurrencyPairsRewritter();
             // Rename BTC_usd to BTC_USD and verify structure
             var root = rewriter.Visit(expression.GetRoot());
             if (rewriter.Errors.Count > 0)
+            {
+                errors = rewriter.Errors;
                 return false;
+            }
             rules = new RateRules(root);
             return true;
         }
@@ -154,7 +161,7 @@ namespace BTCPayServer.Rating
                 return CreateExpression($"ERR_NO_RULE_MATCH({p})");
             var best = candidates
                     .OrderBy(c => c.Prioriy)
-                    .ThenBy(c => c.Expression.Span)
+                    .ThenBy(c => c.Expression.Span.Start)
                     .First();
 
             return best.Expression;

BTCPayServer/Services/Rates/BTCPayRateProviderFactory.cs

@@ -158,7 +158,7 @@ namespace BTCPayServer.Services.Rates
                 providers.Add(directProvider);
             if (_CoinAverageSettings.AvailableExchanges.ContainsKey(exchangeName))
             {
-                providers.Add(new CoinAverageRateProvider(btcpayNetworkProvider)
+                providers.Add(new CoinAverageRateProvider()
                 {
                     Exchange = exchangeName,
                     Authenticator = _CoinAverageSettings

BTCPayServer/Services/Rates/CoinAverageRateProvider.cs

@@ -55,13 +55,7 @@ namespace BTCPayServer.Services.Rates
         BTCPayNetworkProvider _NetworkProvider;
         public CoinAverageRateProvider()
         {
-
+            _NetworkProvider = new BTCPayNetworkProvider(NBitcoin.NetworkType.Mainnet);
-        }
-        public CoinAverageRateProvider(BTCPayNetworkProvider networkProvider)
-        {
-            if (networkProvider == null)
-                throw new ArgumentNullException(nameof(networkProvider));
-            _NetworkProvider = networkProvider;
         }
         static HttpClient _Client = new HttpClient();
 

BTCPayServer/Services/Rates/CoinAverageSettings.cs

@@ -30,6 +30,14 @@ namespace BTCPayServer.Services.Rates
         }
         public string Name { get; set; }
         public string Display { get; set; }
+        public string Url
+        {
+            get
+            {
+                return Name == CoinAverageRateProvider.CoinAverageName ? $"https://apiv2.bitcoinaverage.com/indices/global/ticker/short"
+                                     : $"https://apiv2.bitcoinaverage.com/exchanges/{Name}";
+            }
+        }
     }
     public class CoinAverageExchanges : Dictionary<string, CoinAverageExchange>
     {

BTCPayServer/Views/Invoice/Checkout.cshtml

@@ -16,7 +16,7 @@
     <bundle name="wwwroot/bundles/checkout-bundle.min.css" />
 
     <script type="text/javascript">
-		@Model.ToJSVariableModel("srvModel")
+        var srvModel = @Html.Raw(Json.Serialize(Model));
     </script>
 
     <bundle name="wwwroot/bundles/checkout-bundle.min.js" />

BTCPayServer/Views/Invoice/ListInvoices.cshtml

@@ -19,7 +19,7 @@
                 <p>Create, search or pay an invoice. (<a href="#help" data-toggle="collapse">Help</a>)</p>
                 <div id="help" class="collapse text-left">
                     <p>
-                        You can search for invoice Id, deposit address, price, order id, store id, any buyer information and any product information.</br>
+                        You can search for invoice Id, deposit address, price, order id, store id, any buyer information and any product information.<br />
                         You can also apply filters to your search by searching for `filtername:value`, here is a list of supported filters
                     </p>
                     <ul>

BTCPayServer/Views/Shared/Confirm.cshtml

@@ -15,7 +15,7 @@
         <div class="row">
             <div class="col-lg-12 text-center">
                 <form method="post">
-                    <button type="submit" class="btn btn-secondary btn-danger" title="Continue">@Model.Action</button>
+                    <button type="submit" class="btn btn-secondary @Model.ButtonClass" title="Continue">@Model.Action</button>
                 </form>
             </div>
         </div>

BTCPayServer/Views/Stores/AddDerivationScheme.cshtml

@@ -125,7 +125,7 @@
 @section Scripts {
     @await Html.PartialAsync("_ValidationScriptsPartial")
     <script type="text/javascript">
-		@Model.ServerUrl.ToJSVariableModel("srvModel");
+		var srvModel = @Html.Raw(Json.Serialize(Model.ServerUrl));
     </script>
     <script src="~/js/ledgerwebsocket.js" type="text/javascript" defer="defer"></script>
     <script src="~/js/StoreAddDerivationScheme.js" type="text/javascript" defer="defer"></script>

BTCPayServer/Views/Stores/Rates.cshtml

@@ -0,0 +1,149 @@
+@model RatesViewModel
+@{
+    Layout = "../Shared/_NavLayout.cshtml";
+    ViewData["Title"] = "Rates";
+    ViewData.AddActivePage(BTCPayServer.Views.Stores.StoreNavPages.Rates);
+}
+
+<h4>@ViewData["Title"]</h4>
+@Html.Partial("_StatusMessage", TempData["TempDataProperty-StatusMessage"])
+
+<div class="row">
+    <div class="col-md-8">
+        <div asp-validation-summary="All" class="text-danger"></div>
+    </div>
+</div>
+<div class="row">
+    <div class="col-md-8">
+        <form method="post">
+            @if(Model.ShowScripting)
+            {
+                <div class="form-group">
+                    <h5>Scripting</h5>
+                    <span>Rate script allows you to express precisely how you want to calculate rates for currency pairs.</span>
+                    <p class="text-muted">
+                        <b>Supported exchanges are</b>:
+                        @for(int i = 0; i < Model.AvailableExchanges.Length; i++)
+                        {
+                            <a href="@Model.AvailableExchanges[i].Url">@Model.AvailableExchanges[i].Name</a><span>@(i == Model.AvailableExchanges.Length - 1 ? "" : ",")</span>
+                        }
+                    </p>
+                    <p><a href="#help" data-toggle="collapse"><b>Click here for more information</b></a></p>
+                </div>
+            }
+            @if(Model.TestRateRules != null)
+            {
+                <div class="form-group">
+                    <h5>Test results:</h5>
+                    <table class="table table-sm table-responsive-md">
+                        <tbody>
+                            @foreach(var result in Model.TestRateRules)
+                            {
+                                <tr>
+                                    @if(result.Error)
+                                    {
+                                        <th class="small"><span class="fa fa-times" style="color:red;"></span> @result.CurrencyPair</th>
+                                    }
+                                    else
+                                    {
+                                        <th class="small"><span class="fa fa-check" style="color:green;"></span> @result.CurrencyPair</th>
+                                    }
+                                    <td>@result.Rule</td>
+                                </tr>
+                            }
+                        </tbody>
+                    </table>
+                </div>
+            }
+            @if(Model.ShowScripting)
+            {
+                <div id="help" class="collapse text-left">
+                    <p>
+                        The script language is composed of several rules composed of a currency pair and a mathematic expression.
+                        The example below will use <code>gdax</code> for both <code>LTC_USD</code> and <code>BTC_USD</code> pairs.
+                    </p>
+                    <pre>
+                    <code>
+                            LTC_USD = gdax(LTC_USD);
+                            BTC_USD = gdax(BTC_USD);
+                        </code>
+                    </pre>
+                    <p>However, explicitely setting specific pairs like this can be a bit difficult. Instead, you can define a rule <code>X_X</code> which will match any currency pair. The following example will use <code>gdax</code> for getting the rate of any currency pair.</p>
+                    <pre>
+                    <code>
+                            X_X = gdax(X_X);
+                        </code>
+                    </pre>
+                    <p>However, <code>gdax</code> does not support the <code>BTC_CAD</code> pair. For this reason you can add a rule mapping all <code>X_CAD</code> to <code>quadrigacx</code>, a Canadian exchange.</p>
+                    <pre>
+                    <code>
+                            X_CAD = quadrigacx(X_CAD);
+                            X_X = gdax(X_X);
+                        </code>
+                    </pre>
+                    <p>A given currency pair match the most specific rule. If two rules are matching and are as specific, the first rule will be chosen.</p>
+                    <p>
+                        But now, what if you want to support <code>DOGE</code>? The problem with <code>DOGE</code> is that most exchange do not have any pair for it. But <code>bittrex</code> has a <code>DOGE_BTC</code> pair. <br />
+                        Luckily, the rule engine allow you to reference rules:
+                    </p>
+                    <pre>
+                    <code>
+                            DOGE_X = bittrex(DOGE_BTC) * BTC_X
+                            X_CAD = quadrigacx(X_CAD);
+                            X_X = gdax(X_X);
+                        </code>
+                    </pre>
+                    <p>With <code>DOGE_USD</code> will be expanded to <code>bittrex(DOGE_BTC) * gdax(BTC_USD)</code>. And <code>DOGE_CAD</code> will be expanded to <code>bittrex(DOGE_BTC) * quadrigacx(BTC_CAD)</code></p>
+                </div>
+                <div class="form-group">
+                    <label asp-for="Script"></label>
+                    <textarea asp-for="Script" rows="20" cols="80" class="form-control"></textarea>
+                    <span asp-validation-for="Script" class="text-danger"></span>
+                    <a href="#" onclick="$('#Script').val(defaultScript); return false;">Set to default settings</a>
+                </div>
+                <div class="form-group">
+                    <a asp-action="ShowRateRules" asp-route-scripting="false">Turn off advanced rate rule scripting</a>
+                </div>
+            }
+            else
+            {
+                <div class="form-group">
+                    <label asp-for="PreferredExchange"></label>
+                    <select asp-for="PreferredExchange" asp-items="Model.Exchanges" class="form-control"></select>
+                    <span asp-validation-for="PreferredExchange" class="text-danger"></span>
+                    <p id="PreferredExchangeHelpBlock" class="form-text text-muted">
+                        Current price source is <a href="@Model.RateSource" target="_blank">@Model.PreferredExchange</a>.
+                    </p>
+                </div>
+                <div class="form-group">
+                    <a asp-action="ShowRateRules" asp-route-scripting="true">Turn on advanced rate rule scripting</a>
+                </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">
+                <h5>Testing</h5>
+                <span>Enter currency pairs which you want to test against your rule (eg. <code>DOGE_USD,DOGE_CAD,BTC_CAD,BTC_USD</code>)</span>
+                <div class="input-group">
+                    <input placeholder="BTC_USD, BTC_CAD" asp-for="ScriptTest" class="form-control" />
+                    <span class="input-group-btn">
+                        <button name="command" value="Test" type="submit" class="btn btn-primary" title="Test">
+                            <span class="fa fa-vial"></span> Test
+                        </button>
+                    </span>
+                </div>
+                <span asp-validation-for="ScriptTest" class="text-danger"></span>
+            </div>
+            <button name="command" type="submit" class="btn btn-primary" value="Save">Save</button>
+            <input type="hidden" asp-for="ShowScripting" />
+        </form>
+    </div>
+</div>
+
+@section Scripts {
+    <script type="text/javascript">var defaultScript = @Html.Raw(Json.Serialize(Model.DefaultScript));</script>
+    @await Html.PartialAsync("_ValidationScriptsPartial")
+}

BTCPayServer/Views/Stores/StoreNavPages.cs

@@ -11,6 +11,7 @@ namespace BTCPayServer.Views.Stores
     {
         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";
@@ -20,6 +21,7 @@ namespace BTCPayServer.Views.Stores
 
         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)
         {

BTCPayServer/Views/Stores/UpdateStore.cshtml

@@ -34,19 +34,6 @@
                 <label asp-for="NetworkFee"></label>
                 <input asp-for="NetworkFee" type="checkbox" class="form-check" />
             </div>
-            <div class="form-group">
-                <label asp-for="PreferredExchange"></label>
-                <select asp-for="PreferredExchange" asp-items="Model.Exchanges" class="form-control"></select>
-                <span asp-validation-for="PreferredExchange" class="text-danger"></span>
-                <p id="PreferredExchangeHelpBlock" class="form-text text-muted">
-                    Current price source is <a href="@Model.RateSource" target="_blank">@Model.PreferredExchange</a>.
-                </p>
-            </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" />

BTCPayServer/Views/Stores/Wallet.cshtml

@@ -65,7 +65,7 @@
     @section Scripts
         {
         <script type="text/javascript">
-		@Model.ToJSVariableModel("srvModel")
+		    var srvModel = @Html.Raw(Json.Serialize(Model));
         </script>
         <script src="~/js/ledgerwebsocket.js" type="text/javascript" defer="defer"></script>
         <script src="~/js/StoreWallet.js" type="text/javascript" defer="defer"></script>

BTCPayServer/Views/Stores/_Nav.cshtml

@@ -3,6 +3,7 @@
 
 <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>