Support accepting 0 amount bolt 11 invoices for payouts (#4014)

* Support accepting 0 amount bolt 11 invoices for payouts

* add test

* handle validation better

* fix case when we just want pp to provide amt

* Update BTCPayServer/HostedServices/PullPaymentHostedService.cs

* Update BTCPayServer/HostedServices/PullPaymentHostedService.cs

* Update BTCPayServer/Data/Payouts/LightningLike/UILightningLikePayoutController.cs

* Update UILightningLikePayoutController.cs

* fix null

* fix payments of payouts on cln

* add comment

* bump lightning lib

---------

Co-authored-by: Nicolas Dorier <nicolas.dorier@gmail.com>

BTCPayServer.Tests/GreenfieldAPITests.cs

@@ -3586,7 +3586,17 @@ namespace BTCPayServer.Tests
                 sourceLink = "https://chocolate.com"
             }).ToString());
             
-            
+            customerInvoice = await tester.CustomerLightningD.CreateInvoice(LightMoney.FromUnit(10, LightMoneyUnit.Satoshi),
+                Guid.NewGuid().ToString(), TimeSpan.FromDays(40));
+            var payout2 = await adminClient.CreatePayout(admin.StoreId,
+                new CreatePayoutThroughStoreRequest()
+                {
+                    Approved = true,
+                    Amount = new Money(100, MoneyUnit.Satoshi).ToDecimal(MoneyUnit.BTC),
+                    PaymentMethod = "BTC_LightningNetwork",
+                    Destination = customerInvoice.BOLT11
+                });
+            Assert.Equal(payout2.Amount, new Money(100, MoneyUnit.Satoshi).ToDecimal(MoneyUnit.BTC));
         }
 
         [Fact(Timeout = 60 * 2 * 1000)]

BTCPayServer/BTCPayServer.csproj

@@ -48,7 +48,7 @@
     <PackageReference Include="YamlDotNet" Version="8.0.0" />
     <PackageReference Include="BIP78.Sender" Version="0.2.2" />
     <PackageReference Include="BTCPayServer.Hwi" Version="2.0.2" />
-    <PackageReference Include="BTCPayServer.Lightning.All" Version="1.4.28" />
+    <PackageReference Include="BTCPayServer.Lightning.All" Version="1.4.29" />
     <PackageReference Include="CsvHelper" Version="15.0.5" />
     <PackageReference Include="Dapper" Version="2.0.123" />
     <PackageReference Include="Fido2" Version="2.0.2" />

BTCPayServer/Controllers/GreenField/GreenfieldPullPaymentController.cs

@@ -324,20 +324,13 @@ namespace BTCPayServer.Controllers.Greenfield
                 return this.CreateValidationError(ModelState);
             }
             
-            if (request.Amount is null && destination.destination.Amount != null)
+            var amtError = ClaimRequest.IsPayoutAmountOk(destination.destination, request.Amount, paymentMethodId.CryptoCode, ppBlob.Currency);
+            if (amtError.error is not null)
             {
-                request.Amount = destination.destination.Amount;
+                ModelState.AddModelError(nameof(request.Amount), amtError.error );
-            }
-            else if (request.Amount != null && destination.destination.Amount != null && request.Amount != destination.destination.Amount)
-            {
-                ModelState.AddModelError(nameof(request.Amount), $"Amount is implied in destination ({destination.destination.Amount}) that does not match the payout amount provided {request.Amount})");
-                return this.CreateValidationError(ModelState);
-            }
-            if (request.Amount is { } v && (v < ppBlob.MinimumClaim || v == 0.0m))
-            {
-                ModelState.AddModelError(nameof(request.Amount), $"Amount too small (should be at least {ppBlob.MinimumClaim})");
                 return this.CreateValidationError(ModelState);
             }
+            request.Amount = amtError.amount;
             var result = await _pullPaymentService.Claim(new ClaimRequest()
             {
                 Destination = destination.destination,
@@ -395,15 +388,13 @@ namespace BTCPayServer.Controllers.Greenfield
                 return this.CreateValidationError(ModelState);
             }
 
-            if (request.Amount is null && destination.destination.Amount != null)
+            var amtError = ClaimRequest.IsPayoutAmountOk(destination.destination, request.Amount);
+            if (amtError.error is not null)
             {
-                request.Amount = destination.destination.Amount;
+                ModelState.AddModelError(nameof(request.Amount), amtError.error );
-            }
-            else if (request.Amount != null && destination.destination.Amount != null && request.Amount != destination.destination.Amount)
-            {
-                ModelState.AddModelError(nameof(request.Amount), $"Amount is implied in destination ({destination.destination.Amount}) that does not match the payout amount provided {request.Amount})");
                 return this.CreateValidationError(ModelState);
             }
+            request.Amount = amtError.amount;
             if (request.Amount is { } v && (v < ppBlob?.MinimumClaim || v == 0.0m))
             {
                 var minimumClaim = ppBlob?.MinimumClaim is decimal val ? val : 0.0m;

BTCPayServer/Controllers/UIPullPaymentController.cs

@@ -200,20 +200,14 @@ namespace BTCPayServer.Controllers
                 return await ViewPullPayment(pullPaymentId);
             }
             
-            if (vm.ClaimedAmount == 0)
+            var amtError = ClaimRequest.IsPayoutAmountOk(destination.destination, vm.ClaimedAmount == 0? null: vm.ClaimedAmount, paymentMethodId.CryptoCode, ppBlob.Currency);
+            if (amtError.error is not null)
             {
-                ModelState.AddModelError(nameof(vm.ClaimedAmount), "Amount is required");
+                ModelState.AddModelError(nameof(vm.ClaimedAmount), amtError.error );
             }
-            else
+            else if (amtError.amount is not null)
             {
-                var amount = ppBlob.Currency == "SATS" ? new Money(vm.ClaimedAmount, MoneyUnit.Satoshi).ToUnit(MoneyUnit.BTC) : vm.ClaimedAmount;
+                vm.ClaimedAmount = amtError.amount.Value;
-                if (destination.destination.Amount != null && amount != destination.destination.Amount)
-                {
-                    var implied = _displayFormatter.Currency(destination.destination.Amount.Value, paymentMethodId.CryptoCode, DisplayFormatter.CurrencyFormat.Symbol);
-                    var provided = _displayFormatter.Currency(vm.ClaimedAmount, ppBlob.Currency, DisplayFormatter.CurrencyFormat.Symbol);
-                    ModelState.AddModelError(nameof(vm.ClaimedAmount),
-                        $"Amount implied in destination ({implied}) does not match the payout amount provided ({provided}).");
-                }
             }
 
             if (!ModelState.IsValid)

BTCPayServer/Data/Payouts/IClaimDestination.cs

@@ -6,5 +6,6 @@ namespace BTCPayServer.Data
     {
         public string? Id { get; }
         decimal? Amount { get; }
+        bool IsExplicitAmountMinimum => false;
     }
 }

BTCPayServer/Data/Payouts/LightningLike/BoltInvoiceClaimDestination.cs

@@ -23,5 +23,6 @@ namespace BTCPayServer.Data.Payouts.LightningLike
         public uint256 PaymentHash { get; }
         public string Id => PaymentHash.ToString();
         public decimal? Amount { get; }
+        public bool IsExplicitAmountMinimum => true;
     }
 }

BTCPayServer/Data/Payouts/LightningLike/UILightningLikePayoutController.cs

@@ -264,7 +264,7 @@ namespace BTCPayServer.Data.Payouts.LightningLike
             PaymentMethodId pmi, CancellationToken cancellationToken)
         {
             var boltAmount = bolt11PaymentRequest.MinimumAmount.ToDecimal(LightMoneyUnit.BTC);
-            if (boltAmount != payoutBlob.CryptoAmount)
+            if (boltAmount > payoutBlob.CryptoAmount)
             {
 
                 payoutData.State = PayoutState.Cancelled;
@@ -295,9 +295,8 @@ namespace BTCPayServer.Data.Payouts.LightningLike
                 var result = await lightningClient.Pay(bolt11PaymentRequest.ToString(),
                     new PayInvoiceParams()
                     {
-                        Amount = bolt11PaymentRequest.MinimumAmount == LightMoney.Zero
+                        // CLN does not support explicit amount param if it is the same as the invoice amount
-                            ? new LightMoney((decimal)payoutBlob.CryptoAmount, LightMoneyUnit.BTC)
+                        Amount = payoutBlob.CryptoAmount == bolt11PaymentRequest.MinimumAmount.ToDecimal(LightMoneyUnit.BTC)? null: new LightMoney((decimal)payoutBlob.CryptoAmount, LightMoneyUnit.BTC)
-                            : null
                     }, cancellationToken);
                 string message = null;
                 if (result.Result == PayResult.Ok)

BTCPayServer/HostedServices/PullPaymentHostedService.cs

@@ -834,6 +834,31 @@ namespace BTCPayServer.HostedServices
 
     public class ClaimRequest
     {
+        public static (string error, decimal? amount) IsPayoutAmountOk(IClaimDestination destination, decimal? amount, string payoutCurrency = null, string ppCurrency = null)
+        {
+            return amount switch
+            {
+                null when destination.Amount is null && ppCurrency is null => ("Amount is not specified in destination or payout request", null),
+                null when destination.Amount is null => (null, null),
+                null when destination.Amount != null => (null,destination.Amount),
+                not null when destination.Amount is null => (null,amount),
+                not null when destination.Amount != null && amount != destination.Amount &&
+                              destination.IsExplicitAmountMinimum &&
+                              payoutCurrency == "BTC" && ppCurrency == "SATS" &&
+                              new Money(amount.Value, MoneyUnit.Satoshi).ToUnit(MoneyUnit.BTC) < destination.Amount =>
+                    ($"Amount is implied in both destination ({destination.Amount}) and payout request ({amount}), but the payout request amount is less than the destination amount",null),
+                not null when destination.Amount != null && amount != destination.Amount &&
+                              destination.IsExplicitAmountMinimum &&
+                              !(payoutCurrency == "BTC" && ppCurrency == "SATS") &&
+                              amount < destination.Amount =>
+                    ($"Amount is implied in both destination ({destination.Amount}) and payout request ({amount}), but the payout request amount is less than the destination amount",null),
+                not null when destination.Amount != null && amount != destination.Amount &&
+                              !destination.IsExplicitAmountMinimum =>
+                    ($"Amount is implied in destination ({destination.Amount}) that does not match the payout amount provided {amount})", null),
+                _ => (null, amount)
+            };
+        }
+        
         public static string GetErrorMessage(ClaimResult result)
         {
             switch (result)

btcpayserver.sln.DotSettings

@@ -0,0 +1,2 @@
+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/Abbreviations/=LNURL/@EntryIndexedValue">LNURL</s:String></wpf:ResourceDictionary>