Fix accounting calculation when multi crypto

BTCPayServer.Tests/UnitTest1.cs

@@ -23,6 +23,7 @@ using Microsoft.EntityFrameworkCore;
 using BTCPayServer.Services.Rates;
 using Microsoft.Extensions.Caching.Memory;
 using BTCPayServer.Eclair;
+using System.Collections.Generic;
 
 namespace BTCPayServer.Tests
 {
@@ -75,6 +76,88 @@ namespace BTCPayServer.Tests
             accounting = cryptoData.Calculate();
             Assert.Equal(Money.Zero, accounting.Due);
             Assert.Equal(Money.Coins(1.3m), accounting.TotalDue);
+
+            entity = new InvoiceEntity();
+            entity.ProductInformation = new ProductInformation() { Price = 5000 };
+            entity.SetCryptoData(new System.Collections.Generic.Dictionary<string, CryptoData>(new KeyValuePair<string, CryptoData>[] {
+                new KeyValuePair<string,CryptoData>("BTC", new CryptoData()
+                                                           {
+                                                                Rate = 1000,
+                                                                TxFee = Money.Coins(0.1m)
+                                                           }),
+                new KeyValuePair<string,CryptoData>("LTC", new CryptoData()
+                                                           {
+                                                                Rate = 500,
+                                                                TxFee = Money.Coins(0.01m)
+                                                           })
+            }));
+            entity.Payments = new List<PaymentEntity>();
+            cryptoData = entity.GetCryptoData("BTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Coins(5.1m), accounting.Due);
+
+            cryptoData = entity.GetCryptoData("LTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Coins(10.01m), accounting.TotalDue);
+
+            entity.Payments.Add(new PaymentEntity() { CryptoCode = "BTC", Output = new TxOut(Money.Coins(1.0m), new Key()), Accounted = true });
+
+            cryptoData = entity.GetCryptoData("BTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Coins(4.2m), accounting.Due);
+            Assert.Equal(Money.Coins(1.0m), accounting.CryptoPaid);
+            Assert.Equal(Money.Coins(1.0m), accounting.Paid);
+            Assert.Equal(Money.Coins(5.2m), accounting.TotalDue);
+            Assert.Equal(2, accounting.TxCount);
+
+            cryptoData = entity.GetCryptoData("LTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Coins(10.01m + 0.1m * 2 - 2.0m /* 8.21m */), accounting.Due);
+            Assert.Equal(Money.Coins(0.0m), accounting.CryptoPaid);
+            Assert.Equal(Money.Coins(2.0m), accounting.Paid);
+            Assert.Equal(Money.Coins(10.01m + 0.1m * 2), accounting.TotalDue);
+
+            entity.Payments.Add(new PaymentEntity() { CryptoCode = "LTC", Output = new TxOut(Money.Coins(1.0m), new Key()), Accounted = true });
+
+
+            cryptoData = entity.GetCryptoData("BTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Coins(4.2m - 0.5m + 0.01m / 2), accounting.Due);
+            Assert.Equal(Money.Coins(1.0m), accounting.CryptoPaid);
+            Assert.Equal(Money.Coins(1.5m), accounting.Paid);
+            Assert.Equal(Money.Coins(5.2m + 0.01m / 2), accounting.TotalDue); // The fee for LTC added
+            Assert.Equal(2, accounting.TxCount);
+
+            cryptoData = entity.GetCryptoData("LTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Coins(8.21m - 1.0m + 0.01m), accounting.Due);
+            Assert.Equal(Money.Coins(1.0m), accounting.CryptoPaid);
+            Assert.Equal(Money.Coins(3.0m), accounting.Paid);
+            Assert.Equal(Money.Coins(10.01m + 0.1m * 2 + 0.01m), accounting.TotalDue);
+            Assert.Equal(2, accounting.TxCount);
+
+            var remaining = Money.Coins(4.2m - 0.5m + 0.01m / 2);
+            entity.Payments.Add(new PaymentEntity() { CryptoCode = "BTC", Output = new TxOut(remaining, new Key()), Accounted = true });
+
+            cryptoData = entity.GetCryptoData("BTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Zero, accounting.Due);
+            Assert.Equal(Money.Coins(1.0m) + remaining, accounting.CryptoPaid);
+            Assert.Equal(Money.Coins(1.5m) + remaining, accounting.Paid);
+            Assert.Equal(Money.Coins(5.2m + 0.01m / 2), accounting.TotalDue);
+            Assert.Equal(accounting.Paid, accounting.TotalDue);
+            Assert.Equal(2, accounting.TxCount);
+
+            cryptoData = entity.GetCryptoData("LTC");
+            accounting = cryptoData.Calculate();
+            Assert.Equal(Money.Zero, accounting.Due);
+            Assert.Equal(Money.Coins(1.0m), accounting.CryptoPaid);
+            Assert.Equal(Money.Coins(3.0m) + remaining * 2, accounting.Paid);
+            // Paying 2 BTC fee, LTC fee removed because fully paid
+            Assert.Equal(Money.Coins(10.01m + 0.1m * 2 + 0.1m * 2 /* + 0.01m no need to pay this fee anymore */), accounting.TotalDue);
+            Assert.Equal(1, accounting.TxCount);
+            Assert.Equal(accounting.Paid, accounting.TotalDue);
+
 #pragma warning restore CS0618
         }
 

BTCPayServer/Services/Invoices/InvoiceEntity.cs

@@ -200,7 +200,7 @@ namespace BTCPayServer.Services.Invoices
         internal void SetDerivationStrategies(IEnumerable<DerivationStrategy> derivationStrategies)
         {
             JObject obj = new JObject();
-            foreach(var strat in derivationStrategies)
+            foreach (var strat in derivationStrategies)
             {
                 obj.Add(strat.Network.CryptoCode, new JValue(strat.DerivationStrategyBase.ToString()));
 #pragma warning disable CS0618
@@ -482,33 +482,38 @@ namespace BTCPayServer.Services.Invoices
         public CryptoDataAccounting Calculate()
         {
             var cryptoData = ParentEntity.GetCryptoData();
-            var totalDue = Money.Coins(ParentEntity.ProductInformation.Price / Rate) + TxFee;
+            var totalDue = Money.Coins(ParentEntity.ProductInformation.Price / Rate);
             var paid = Money.Zero;
             var cryptoPaid = Money.Zero;
-            int txCount = 1;
+
+            var paidTxFee = Money.Zero;
+            bool paidEnough = totalDue <= paid;
+            int txCount = 0;
             var payments =
                 ParentEntity.Payments
                 .Where(p => p.Accounted)
                 .OrderByDescending(p => p.ReceivedTime)
                 .Select(_ =>
                 {
+                    paidTxFee = _.GetValue(cryptoData, CryptoCode, cryptoData[_.GetCryptoCode()].TxFee);
                     paid += _.GetValue(cryptoData, CryptoCode);
+                    if(!paidEnough)
+                        totalDue += paidTxFee;
+                    paidEnough |= totalDue <= paid;
                     if (CryptoCode == _.GetCryptoCode())
-                        cryptoPaid += _.GetValue();
-                    return _;
-                })
-                .TakeWhile(_ =>
-                {
-                    var paidEnough = totalDue <= paid;
-                    if (!paidEnough && _.GetCryptoCode() == CryptoCode)
                     {
+                        cryptoPaid += _.GetValue();
                         txCount++;
-                        totalDue += TxFee;
                     }
-                    return !paidEnough;
+                    return _;
                 })
                 .ToArray();
 
+            if (!paidEnough)
+            {
+                txCount++;
+                totalDue += TxFee;
+            }
             var accounting = new CryptoDataAccounting();
             accounting.TotalDue = totalDue;
             accounting.Paid = paid;
@@ -573,20 +578,21 @@ namespace BTCPayServer.Services.Invoices
             return Output.Value;
 #pragma warning restore CS0618
         }
-        public Money GetValue(Dictionary<string, CryptoData> cryptoData, string cryptoCode)
+        public Money GetValue(Dictionary<string, CryptoData> cryptoData, string cryptoCode, Money value = null)
         {
 #pragma warning disable CS0618
+            value = value ?? Output.Value;
+#pragma warning restore CS0618
             var to = cryptoCode;
             var from = GetCryptoCode();
             if (to == from)
-                return Output.Value;
+                return value;
             var fromRate = cryptoData[from].Rate;
             var toRate = cryptoData[to].Rate;
 
-            var fiatValue = fromRate * Output.Value.ToDecimal(MoneyUnit.BTC);
+            var fiatValue = fromRate * value.ToDecimal(MoneyUnit.BTC);
             var otherCurrencyValue = toRate == 0 ? 0.0m : fiatValue / toRate;
             return Money.Coins(otherCurrencyValue);
-#pragma warning restore CS0618
         }
 
         public string GetCryptoCode()