Allow single withdrawer in CC swaps

channel/adjudicator.go

@@ -1,4 +1,4 @@
-// Copyright 2024 PolyCrypt GmbH
+// Copyright 2025 PolyCrypt GmbH
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -19,9 +19,11 @@ import (
 	"errors"
 	"fmt"
 	"github.com/stellar/go/xdr"
+	"math/big"
 	pchannel "perun.network/go-perun/channel"
 	"perun.network/go-perun/log"
 	pwallet "perun.network/go-perun/wallet"
+	"perun.network/perun-stellar-backend/channel/types"
 	"perun.network/perun-stellar-backend/client"
 	"perun.network/perun-stellar-backend/wallet"
 	"time"
@@ -89,6 +91,12 @@ func (a *Adjudicator) Withdraw(ctx context.Context, req pchannel.AdjudicatorReq,
 	}
 	if req.Tx.State.IsFinal {
 		log.Println("Channel is final, closing now")
+		withdrawSelf := needWithdraw([]pchannel.Bal{req.Tx.State.Balances[0][req.Idx], req.Tx.State.Balances[1][req.Idx]}, req.Tx.State.Assets)
+		withdrawOther := needWithdraw([]pchannel.Bal{req.Tx.State.Balances[0][1-req.Idx], req.Tx.State.Balances[1][1-req.Idx]}, req.Tx.State.Assets)
+		if req.Idx == 0 && a.oneWithdrawer && (!withdrawSelf || !withdrawOther) { // If one participant does not need to withdraw, the swap is cross-chain which means A does not need to close
+			log.Println("A only closes when A & B have to withdraw")
+			return nil
+		}
 		err := a.Close(ctx, req.Tx.State, req.Tx.Sigs)
 		if err != nil {
 			chanControl, errChanState = a.CB.GetChannelInfo(ctx, a.perunAddr, req.Tx.State.ID)
@@ -119,12 +127,19 @@ func (a *Adjudicator) Withdraw(ctx context.Context, req pchannel.AdjudicatorReq,
 }
 
 func (a *Adjudicator) handleWithdrawal(ctx context.Context, req pchannel.AdjudicatorReq) error {
-	if a.oneWithdrawer {
+	withdrawOther := needWithdraw([]pchannel.Bal{req.Tx.State.Balances[0][1-req.Idx], req.Tx.State.Balances[1][1-req.Idx]}, req.Tx.State.Assets)
+	if a.oneWithdrawer && withdrawOther {
+		log.Println("Withdrawing other", req.Idx)
 		if err := a.withdrawOther(ctx, req); err != nil {
 			return err
 		}
 	}
-	return a.withdraw(ctx, req)
+	withdrawSelf := needWithdraw([]pchannel.Bal{req.Tx.State.Balances[0][req.Idx], req.Tx.State.Balances[1][req.Idx]}, req.Tx.State.Assets)
+	if withdrawSelf {
+		log.Println("Withdrawing self", req.Idx)
+		return a.withdraw(ctx, req)
+	}
+	return nil
 }
 
 func (a *Adjudicator) withdraw(ctx context.Context, req pchannel.AdjudicatorReq) error {
@@ -173,3 +188,13 @@ func (a Adjudicator) Progress(ctx context.Context, req pchannel.ProgressReq) err
 	// only relevant for AppChannels
 	return nil
 }
+
+func needWithdraw(balances []pchannel.Bal, assets []pchannel.Asset) bool {
+	for i, bal := range balances {
+		_, ok := assets[i].(*types.StellarAsset)
+		if bal.Cmp(big.NewInt(0)) != 0 && ok { // if balance is 0 or asset is not stellar asset, participant does not need to withdraw
+			return true
+		}
+	}
+	return false
+}

channel/ethbackend.go

@@ -99,7 +99,7 @@ func assetToEthAsset(asset channel.Asset) ChannelAsset {
 		log.Panicf("expected asset of type MultiLedgerAsset, but got wrong asset type: %T", asset)
 	}
 	id := new(big.Int)
-	_, ok = id.SetString(string(multiAsset.AssetID().LedgerID().MapKey()), 10) // base 10 for decimal numbers
+	_, ok = id.SetString(string(multiAsset.LedgerBackendID().LedgerID().MapKey()), 10) // base 10 for decimal numbers
 	if !ok {
 		log.Panicf("Error: Failed to parse string into big.Int")
 	}

channel/funder.go

@@ -1,4 +1,4 @@
-// Copyright 2023 PolyCrypt GmbH
+// Copyright 2025 PolyCrypt GmbH
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -106,7 +106,7 @@ func (f *Funder) fundParty(ctx context.Context, req pchannel.FundingReq) error {
 			}
 
 			if req.Idx == pchannel.Index(0) && !chanState.Control.FundedA {
-				shouldFund := need_funding(req.State.Balances[0], req.State.Assets)
+				shouldFund := needFunding(req.State.Balances[0], req.State.Assets)
 				if !shouldFund {
 					log.Println("Party A does not need to fund")
 					return nil
@@ -148,9 +148,9 @@ func (f *Funder) fundParty(ctx context.Context, req pchannel.FundingReq) error {
 				log.Println("Balance A: ", bal0, bal1, " after funding amount: ", req.State.Balances, req.State.Assets)
 				continue
 			}
-			if req.Idx == pchannel.Index(1) && !chanState.Control.FundedB && (chanState.Control.FundedA || !need_funding(req.State.Balances[0], req.State.Assets)) { // If party A has funded or does not need to fund, party B funds
+			if req.Idx == pchannel.Index(1) && !chanState.Control.FundedB && (chanState.Control.FundedA || !needFunding(req.State.Balances[0], req.State.Assets)) { // If party A has funded or does not need to fund, party B funds
 				log.Println("Funding party B")
-				shouldFund := need_funding(req.State.Balances[1], req.State.Assets)
+				shouldFund := needFunding(req.State.Balances[1], req.State.Assets)
 				if !shouldFund {
 					log.Println("Party B does not need to fund", req.State.Balances[1], req.State.Assets)
 					return nil
@@ -269,7 +269,7 @@ func assetSliceToSet(assets []xdr.ScVal) map[string]struct{} {
 	return assetSet
 }
 
-func need_funding(balances []pchannel.Bal, assets []pchannel.Asset) bool {
+func needFunding(balances []pchannel.Bal, assets []pchannel.Asset) bool {
 	for i, bal := range balances {
 		_, ok := assets[i].(*types.StellarAsset)
 		if bal.Cmp(big.NewInt(0)) != 0 && ok { // if balance is 0 or asset is not stellar asset, participant does not need to fund

channel/test/setup.go

@@ -1,4 +1,4 @@
-// Copyright 2024 PolyCrypt GmbH
+// Copyright 2025 PolyCrypt GmbH
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -114,8 +114,6 @@ func NewTestSetup(t *testing.T, options ...bool) *Setup {
 	}
 
 	_, kpsToFund, _ := MakeRandPerunAccsWallets(5)
-	// kpsToFund[2], _ = keypair.ParseFull("SD4XPDWFDY25V7NRMF47QE4WT6WOFWUJIZGFRMMCRHGVINJ3RMMDG6WS")
-	// kpsToFund[3], _ = keypair.ParseFull("SDHDGJMVERIXSN5LQ5KDLW3F2QIVM2D6CLP3BDHSKWBAYX53YDEY3FND")
 	require.NoError(t, CreateFundStellarAccounts(kpsToFund, initLumensBalance))
 
 	depTokenOneKp := kpsToFund[2]
@@ -142,8 +140,6 @@ func NewTestSetup(t *testing.T, options ...bool) *Setup {
 	require.NoError(t, InitTokenContract(depTokenOneKp, tokenAddressOne, HorizonURL))
 	require.NoError(t, InitTokenContract(depTokenTwoKp, tokenAddressTwo, HorizonURL))
 
-	// acc0 := wallet.NewAccount("5de4111afa1a4b94908f83103eb1f1706367c2e68ca870fc3fb9a804cdab365a", *kpsToFund[0].FromAddress(), [20]byte([]byte{86, 253, 40, 156, 238, 113, 74, 94, 71, 28, 65, 132, 54, 239, 166, 62, 120, 13, 122, 135}))
-	// acc1 := wallet.NewAccount("7c852118294e51e653712a81e05800f419141751be58f605c371e15141b007a6", *kpsToFund[0].FromAddress(), [20]byte([]byte{101, 54, 66, 91, 233, 90, 102, 97, 246, 198, 246, 141, 112, 155, 107, 225, 82, 120, 93, 246}))
 	acc0, err := wallet.NewRandomAccountWithAddress(mathrand.New(mathrand.NewSource(0)), kpsToFund[0].FromAddress())
 	acc1, err := wallet.NewRandomAccountWithAddress(mathrand.New(mathrand.NewSource(0)), kpsToFund[1].FromAddress())
 	w0 := wallet.NewEphemeralWallet()

channel/types/asset.go

@@ -153,8 +153,8 @@ func (a Asset) Address() []byte {
 
 }
 
-// AssetID returns the asset ID of the Stellar asset.
-func (s StellarAsset) AssetID() multi.AssetID {
+// LedgerBackendID returns the asset ID of the Stellar asset.
+func (s StellarAsset) LedgerBackendID() multi.LedgerBackendID {
 	return s.id
 }
 

channel/types/ethasset.go

@@ -123,11 +123,11 @@ func (id ChainID) MapKey() multi.LedgerIDMapKey {
 type (
 	// Asset is an Ethereum asset.
 	EthAsset struct {
-		assetID     AssetID
+		assetID     LedgerBackendID
 		AssetHolder wallet.Address
 	}
-
-	AssetID struct {
+	// LedherBackendID holds the ChainID and BackendID of an Asset.
+	LedgerBackendID struct {
 		backendID uint32
 		ledgerID  ChainID
 	}
@@ -137,23 +137,23 @@ type (
 )
 
 func MakeEthAsset(id *big.Int, holder wallet.Address) EthAsset {
-	return EthAsset{assetID: AssetID{backendID: 1, ledgerID: MakeChainID(id)}, AssetHolder: holder}
+	return EthAsset{assetID: LedgerBackendID{backendID: 1, ledgerID: MakeChainID(id)}, AssetHolder: holder}
 }
 
-func (id AssetID) BackendID() uint32 {
+func (id LedgerBackendID) BackendID() uint32 {
 	return id.backendID
 }
 
-func (id AssetID) LedgerID() multi.LedgerID {
+func (id LedgerBackendID) LedgerID() multi.LedgerID {
 	return &id.ledgerID
 }
 
-// MakeAssetID makes a AssetID for the given id.
-func MakeAssetID(id *big.Int) multi.AssetID {
+// MakeAssetID makes a LedgerBackendID for the given id.
+func MakeLedgerBackendID(id *big.Int) multi.LedgerBackendID {
 	if id.Sign() < 0 {
 		panic("must not be smaller than zero")
 	}
-	return AssetID{backendID: 1, ledgerID: MakeChainID(id)}
+	return LedgerBackendID{backendID: 1, ledgerID: MakeChainID(id)}
 }
 
 // MapKey returns the asset's map key representation.
@@ -184,11 +184,11 @@ func (a *EthAsset) UnmarshalBinary(data []byte) error {
 
 // LedgerID returns the ledger ID the asset lives on.
 func (a EthAsset) LedgerID() multi.LedgerID {
-	return a.AssetID().LedgerID()
+	return a.LedgerBackendID().LedgerID()
 }
 
-// AssetID returns the ledger ID the asset lives on.
-func (a EthAsset) AssetID() multi.AssetID {
+// LedgerBackendID returns the ledger ID the asset lives on.
+func (a EthAsset) LedgerBackendID() multi.LedgerBackendID {
 	return a.assetID
 }
 

go.mod

@@ -14,7 +14,7 @@ require (
 	github.com/ethereum/go-ethereum v1.10.12
 	github.com/stellar/go-xdr v0.0.0-20231122183749-b53fb00bcac2
 	github.com/stretchr/testify v1.9.0
-	perun.network/go-perun v0.12.1-0.20250114072911-f46b0c55fe65
+	perun.network/go-perun v0.12.1-0.20250128081648-21d0af4e234b
 	polycry.pt/poly-go v0.0.0-20220301085937-fb9d71b45a37
 )
 

go.sum

@@ -658,8 +658,8 @@ honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWh
 honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.1-2019.2.3/go.mod h1:a3bituU0lyd329TUQxRnasdCoJDkEUEAqEt0JzvZhAg=
 honnef.co/go/tools v0.1.3/go.mod h1:NgwopIslSNH47DimFoV78dnkksY2EFtX0ajyb3K/las=
-perun.network/go-perun v0.12.1-0.20250114072911-f46b0c55fe65 h1:kJ3AS374fe23a/9puoaOwCr9Bx2L/WJ5p2npDql3m4A=
-perun.network/go-perun v0.12.1-0.20250114072911-f46b0c55fe65/go.mod h1:uH8iwi75alXDizxxDzH0A+6uqXPbagCpKfl8ECMv/cA=
+perun.network/go-perun v0.12.1-0.20250128081648-21d0af4e234b h1:6FeodthJZB10aWGk/DgtV2VicacyUnLaUoT8OUcwSms=
+perun.network/go-perun v0.12.1-0.20250128081648-21d0af4e234b/go.mod h1:uH8iwi75alXDizxxDzH0A+6uqXPbagCpKfl8ECMv/cA=
 polycry.pt/poly-go v0.0.0-20220301085937-fb9d71b45a37 h1:iA5GzEa/hHfVlQpimEjPV09NATwHXxSjWNB0VVodtew=
 polycry.pt/poly-go v0.0.0-20220301085937-fb9d71b45a37/go.mod h1:XUBrNtqgEhN3EEOP/5gh7IBd3xVHKidCjXDZfl9+kMU=
 rsc.io/binaryregexp v0.2.0/go.mod h1:qTv7/COck+e2FymRvadv62gMdZztPaShugOCi3I+8D8=

wire/balances.go

@@ -256,7 +256,7 @@ func extractAndConvertLedgerID(asset channel.Asset) (uint64, error) {
 	if !ok {
 		return 0, errors.New("invalid Asset format")
 	}
-	id := multiAsset.AssetID().LedgerID()
+	id := multiAsset.LedgerBackendID().LedgerID()
 	if id == nil {
 		return 0, errors.New("invalid LedgerID")
 	}