From 4c57405945229194b992dffe1f4cfeed153a8663 Mon Sep 17 00:00:00 2001
From: Nicolas Dorier <nicolas.dorier@gmail.com>
Date: Fri, 30 Jul 2021 18:46:49 +0900
Subject: [PATCH] Properly clip taxIncluded and invoice's amount (#2724)

---
 BTCPayServer.Tests/UnitTest1.cs               | 16 ++++++++++
 BTCPayServer/Controllers/InvoiceController.cs | 31 ++++++++++++-------
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/BTCPayServer.Tests/UnitTest1.cs b/BTCPayServer.Tests/UnitTest1.cs
index 6c6a4fe01..eac4c83e3 100644
--- a/BTCPayServer.Tests/UnitTest1.cs
+++ b/BTCPayServer.Tests/UnitTest1.cs
@@ -2803,6 +2803,22 @@ namespace BTCPayServer.Tests
                 var invoice = user.BitPay.CreateInvoice(
                     new Invoice() { Price = -0.1m, Currency = "BTC", FullNotifications = true }, Facade.Merchant);
                 Assert.Equal(0.0m, invoice.Price);
+
+                // Should round down to 50.51, taxIncluded should be also clipped to this value because taxIncluded can't be higher than the price.
+                var invoice5 = user.BitPay.CreateInvoice(
+                    new Invoice() { Price = 50.513m, Currency = "USD", FullNotifications = true, TaxIncluded = 50.516m }, Facade.Merchant);
+                Assert.Equal(50.51m, invoice5.Price);
+                Assert.Equal(50.51m, invoice5.TaxIncluded);
+
+                var greenfield = await user.CreateClient();
+                var invoice5g = await greenfield.CreateInvoice(user.StoreId, new CreateInvoiceRequest()
+                {
+                    Amount = 50.513m,
+                    Currency = "USD",
+                    Metadata = new JObject() { new JProperty("taxIncluded", 50.516m) }
+                });
+                Assert.Equal(50.51m, invoice5g.Amount);
+                Assert.Equal(50.51m, (decimal)invoice5g.Metadata["taxIncluded"]);
             }
         }
 
diff --git a/BTCPayServer/Controllers/InvoiceController.cs b/BTCPayServer/Controllers/InvoiceController.cs
index d5c971ef3..21f01e3ff 100644
--- a/BTCPayServer/Controllers/InvoiceController.cs
+++ b/BTCPayServer/Controllers/InvoiceController.cs
@@ -112,24 +112,14 @@ namespace BTCPayServer.Controllers
             FillBuyerInfo(invoice, entity);
 
             var taxIncluded = invoice.TaxIncluded.HasValue ? invoice.TaxIncluded.Value : 0m;
+            var price = invoice.Price;
 
-            var currencyInfo = _CurrencyNameTable.GetNumberFormatInfo(invoice.Currency, false);
-            if (currencyInfo != null)
-            {
-                int divisibility = currencyInfo.CurrencyDecimalDigits;
-                invoice.Price = invoice.Price.RoundToSignificant(ref divisibility);
-                divisibility = currencyInfo.CurrencyDecimalDigits;
-                invoice.TaxIncluded = taxIncluded.RoundToSignificant(ref divisibility);
-            }
-            invoice.Price = Math.Max(0.0m, invoice.Price);
-            invoice.TaxIncluded = Math.Max(0.0m, taxIncluded);
-            invoice.TaxIncluded = Math.Min(taxIncluded, invoice.Price);
             entity.Metadata.ItemCode = invoice.ItemCode;
             entity.Metadata.ItemDesc = invoice.ItemDesc;
             entity.Metadata.Physical = invoice.Physical;
             entity.Metadata.TaxIncluded = invoice.TaxIncluded;
             entity.Currency = invoice.Currency;
-            entity.Price = invoice.Price;
+            entity.Price = price;
 
             entity.RedirectURLTemplate = invoice.RedirectURL ?? store.StoreWebsite;
             entity.RedirectAutomatically =
@@ -195,6 +185,23 @@ namespace BTCPayServer.Controllers
             InvoiceLogs logs = new InvoiceLogs();
             logs.Write("Creation of invoice starting", InvoiceEventData.EventSeverity.Info);
 
+            entity.Price = Math.Max(0.0m, entity.Price);
+            var currencyInfo = _CurrencyNameTable.GetNumberFormatInfo(entity.Currency, false);
+            if (currencyInfo != null)
+            {
+                entity.Price = entity.Price.RoundToSignificant(currencyInfo.CurrencyDecimalDigits);
+            }
+            if (entity.Metadata.TaxIncluded is decimal taxIncluded)
+            {
+                if (currencyInfo != null)
+                {
+                    taxIncluded = taxIncluded.RoundToSignificant(currencyInfo.CurrencyDecimalDigits);
+                }
+                taxIncluded = Math.Max(0.0m, taxIncluded);
+                taxIncluded = Math.Min(taxIncluded, entity.Price);
+                entity.Metadata.TaxIncluded = taxIncluded;
+            }
+
             var getAppsTaggingStore = _InvoiceRepository.GetAppsTaggingStore(store.Id);
             var storeBlob = store.GetStoreBlob();