Add liquidity ads to the channel opening flow

We previously only used liquidity ads with splicing: we now support it
during the initial channel opening flow as well. This lets us add more
unit tests, including tests for the case where the node receiving the
`open_channel` message is responsible for paying the commitment fees.

We also update liquidity ads to use the latest version of the spec from
lightning/bolts#1153. This introduces more ways
of paying the liquidity fees, to support on-the-fly funding without
existing channel balance (not implemented in this commit).

Note that we need some backwards-compatibility with the previous
liquidity ads types in our state serialization code: when we're in the
middle of signing a splice transaction, we may have a legacy liquidity
lease in our splice status. We ignore it when finalizing the splice: the
only consequence is that we won't store an entry in our DB for that
lease, but the channel will otherwise work correctly.

src/commonMain/kotlin/fr/acinq/lightning/NodeParams.kt

@@ -70,14 +70,15 @@ object DefaultSwapInParams {
  * @param trampolineFees ordered list of trampoline fees to try when making an outgoing payment.
  * @param invoiceDefaultRoutingFees default routing fees set in invoices when we don't have any channel.
  * @param swapInParams parameters for swap-in transactions.
- * @param leaseRate rate at which our peer sells their liquidity.
+ * @param remoteFundingRates rates at which our peer sells their liquidity.
  */
 data class WalletParams(
     val trampolineNode: NodeUri,
     val trampolineFees: List<TrampolineFees>,
     val invoiceDefaultRoutingFees: InvoiceDefaultRoutingFees,
     val swapInParams: SwapInParams,
-    val leaseRate: LiquidityAds.LeaseRate,
+    // TODO: once standardized, we should get this data from our peer's init message.
+    val remoteFundingRates: LiquidityAds.WillFundRates,
 )
 
 /**

src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelAction.kt

@@ -87,7 +87,7 @@ sealed class ChannelAction {
             abstract val txId: TxId
             data class ViaSpliceOut(val amount: Satoshi, override val miningFees: Satoshi, val address: String, override val txId: TxId) : StoreOutgoingPayment()
             data class ViaSpliceCpfp(override val miningFees: Satoshi, override val txId: TxId) : StoreOutgoingPayment()
-            data class ViaInboundLiquidityRequest(override val txId: TxId, override val miningFees: Satoshi, val lease: LiquidityAds.Lease) : StoreOutgoingPayment()
+            data class ViaInboundLiquidityRequest(override val txId: TxId, override val miningFees: Satoshi, val purchase: LiquidityAds.Purchase) : StoreOutgoingPayment()
             data class ViaClose(val amount: Satoshi, override val miningFees: Satoshi, val address: String, override val txId: TxId, val isSentToDefaultAddress: Boolean, val closingType: ChannelClosingType) : StoreOutgoingPayment()
         }
         data class SetLocked(val txId: TxId) : Storage()

src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelCommand.kt

@@ -35,7 +35,7 @@ sealed class ChannelCommand {
             val channelFlags: ChannelFlags,
             val channelConfig: ChannelConfig,
             val channelType: ChannelType.SupportedChannelType,
-            val requestRemoteFunding: LiquidityAds.RequestRemoteFunding?,
+            val requestRemoteFunding: LiquidityAds.RequestFunding?,
             val channelOrigin: Origin?,
         ) : Init() {
             fun temporaryChannelId(keyManager: KeyManager): ByteVector32 = keyManager.channelKeys(localParams.fundingKeyPath).temporaryChannelId
@@ -48,7 +48,8 @@ sealed class ChannelCommand {
             val walletInputs: List<WalletState.Utxo>,
             val localParams: LocalParams,
             val channelConfig: ChannelConfig,
-            val remoteInit: InitMessage
+            val remoteInit: InitMessage,
+            val fundingRates: LiquidityAds.WillFundRates?
         ) : Init()
 
         data class Restore(val state: PersistedChannelState) : Init()
@@ -86,7 +87,7 @@ sealed class ChannelCommand {
         data class UpdateFee(val feerate: FeeratePerKw, val commit: Boolean = false) : Commitment(), ForbiddenDuringSplice, ForbiddenDuringQuiescence
         data object CheckHtlcTimeout : Commitment()
         sealed class Splice : Commitment() {
-            data class Request(val replyTo: CompletableDeferred<Response>, val spliceIn: SpliceIn?, val spliceOut: SpliceOut?, val requestRemoteFunding: LiquidityAds.RequestRemoteFunding?, val feerate: FeeratePerKw, val origins: List<Origin>) : Splice() {
+            data class Request(val replyTo: CompletableDeferred<Response>, val spliceIn: SpliceIn?, val spliceOut: SpliceOut?, val requestRemoteFunding: LiquidityAds.RequestFunding?, val feerate: FeeratePerKw, val origins: List<Origin>) : Splice() {
                 val pushAmount: MilliSatoshi = spliceIn?.pushAmount ?: 0.msat
                 val spliceOutputs: List<TxOut> = spliceOut?.let { listOf(TxOut(it.amount, it.scriptPubKey)) } ?: emptyList()
 
@@ -105,7 +106,7 @@ sealed class ChannelCommand {
                     val fundingTxId: TxId,
                     val capacity: Satoshi,
                     val balance: MilliSatoshi,
-                    val liquidityLease: LiquidityAds.Lease?,
+                    val liquidityPurchase: LiquidityAds.Purchase?,
                 ) : Response()
 
                 sealed class Failure : Response() {

src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelException.kt

@@ -28,7 +28,9 @@ data class ToSelfDelayTooHigh                      (override val channelId: Byte
 data class MissingLiquidityAds                     (override val channelId: ByteVector32) : ChannelException(channelId, "liquidity ads field is missing")
 data class InvalidLiquidityAdsSig                  (override val channelId: ByteVector32) : ChannelException(channelId, "liquidity ads signature is invalid")
 data class InvalidLiquidityAdsAmount               (override val channelId: ByteVector32, val proposed: Satoshi, val min: Satoshi) : ChannelException(channelId, "liquidity ads funding amount is too low (expected at least $min, got $proposed)")
-data class InvalidLiquidityRates                   (override val channelId: ByteVector32) : ChannelException(channelId, "rejecting liquidity ads proposed rates")
+data class InvalidLiquidityAdsRate                 (override val channelId: ByteVector32) : ChannelException(channelId, "liquidity ads funding rate does not match the rate we selected")
+data class UnexpectedLiquidityAdsFundingFee        (override val channelId: ByteVector32, val fundingTxId: TxId) : ChannelException(channelId, "unexpected liquidity ads funding fee for txId=$fundingTxId (transaction not found)")
+data class InvalidLiquidityAdsFundingFee           (override val channelId: ByteVector32, val fundingTxId: TxId, val paymentHash: ByteVector32, val expected: Satoshi, val proposed: MilliSatoshi) : ChannelException(channelId, "invalid liquidity ads funding fee for txId=$fundingTxId and paymentHash=$paymentHash (expected $expected, got $proposed)")
 data class ChannelFundingError                     (override val channelId: ByteVector32) : ChannelException(channelId, "channel funding error")
 data class RbfAttemptAborted                       (override val channelId: ByteVector32) : ChannelException(channelId, "rbf attempt aborted")
 data class SpliceAborted                           (override val channelId: ByteVector32) : ChannelException(channelId, "splice aborted")

src/commonMain/kotlin/fr/acinq/lightning/channel/InteractiveTx.kt

@@ -673,8 +673,7 @@ data class InteractiveTxSession(
     val isComplete: Boolean = txCompleteSent != null && txCompleteReceived != null
 
     fun send(): Pair<InteractiveTxSession, InteractiveTxSessionAction> {
-        val msg = toSend.firstOrNull()
-        return when (msg) {
+        return when (val msg = toSend.firstOrNull()) {
             null -> {
                 val localSwapIns = localInputs.filterIsInstance<InteractiveTxInput.LocalSwapIn>()
                 val remoteSwapIns = remoteInputs.filterIsInstance<InteractiveTxInput.RemoteSwapIn>()
@@ -987,7 +986,6 @@ data class InteractiveTxSigningSession(
     val fundingParams: InteractiveTxParams,
     val fundingTxIndex: Long,
     val fundingTx: PartiallySignedSharedTransaction,
-    val liquidityLease: LiquidityAds.Lease?,
     val localCommit: Either<UnsignedLocalCommit, LocalCommit>,
     val remoteCommit: RemoteCommit,
 ) {
@@ -1065,7 +1063,7 @@ data class InteractiveTxSigningSession(
             sharedTx: SharedTransaction,
             localPushAmount: MilliSatoshi,
             remotePushAmount: MilliSatoshi,
-            liquidityLease: LiquidityAds.Lease?,
+            liquidityPurchase: LiquidityAds.Purchase?,
             localCommitmentIndex: Long,
             remoteCommitmentIndex: Long,
             commitTxFeerate: FeeratePerKw,
@@ -1075,7 +1073,16 @@ data class InteractiveTxSigningSession(
             val channelKeys = channelParams.localParams.channelKeys(keyManager)
             val unsignedTx = sharedTx.buildUnsignedTx()
             val sharedOutputIndex = unsignedTx.txOut.indexOfFirst { it.publicKeyScript == fundingParams.fundingPubkeyScript(channelKeys) }
-            val liquidityFees = liquidityLease?.fees?.total?.toMilliSatoshi() ?: 0.msat
+            val liquidityFees = liquidityPurchase?.let { l ->
+                val fees = l.fees.total.toMilliSatoshi()
+                when (l.paymentDetails) {
+                    is LiquidityAds.PaymentDetails.FromChannelBalance -> if (fundingParams.isInitiator) fees else -fees
+                    is LiquidityAds.PaymentDetails.FromChannelBalanceForFutureHtlc -> if (fundingParams.isInitiator) fees else -fees
+                    // Fees will be paid later, from relayed HTLCs.
+                    is LiquidityAds.PaymentDetails.FromFutureHtlc -> 0.msat
+                    is LiquidityAds.PaymentDetails.FromFutureHtlcWithPreimage -> 0.msat
+                }
+            } ?: 0.msat
             return Helpers.Funding.makeCommitTxs(
                 channelKeys,
                 channelParams.channelId,
@@ -1120,7 +1127,7 @@ data class InteractiveTxSigningSession(
                 val unsignedLocalCommit = UnsignedLocalCommit(localCommitmentIndex, firstCommitTx.localSpec, firstCommitTx.localCommitTx, listOf())
                 val remoteCommit = RemoteCommit(remoteCommitmentIndex, firstCommitTx.remoteSpec, firstCommitTx.remoteCommitTx.tx.txid, remotePerCommitmentPoint)
                 val signedFundingTx = sharedTx.sign(session, keyManager, fundingParams, channelParams.localParams, channelParams.remoteParams.nodeId)
-                Pair(InteractiveTxSigningSession(fundingParams, fundingTxIndex, signedFundingTx, liquidityLease, Either.Left(unsignedLocalCommit), remoteCommit), commitSig)
+                Pair(InteractiveTxSigningSession(fundingParams, fundingTxIndex, signedFundingTx, Either.Left(unsignedLocalCommit), remoteCommit), commitSig)
             }
         }
 
@@ -1168,7 +1175,7 @@ sealed class SpliceStatus {
     /** Our peer has asked us to stop sending new updates and wait for our updates to be added to the local and remote commitments. */
     data class ReceivedStfu(val stfu: Stfu) : QuiescenceNegotiation.NonInitiator()
     /** Our updates have been added to the local and remote commitments, we wait for our peer to use the now quiescent channel. */
-    object NonInitiatorQuiescent : QuiescentSpliceStatus()
+    data object NonInitiatorQuiescent : QuiescentSpliceStatus()
     /** We told our peer we want to splice funds in the channel. */
     data class Requested(val command: ChannelCommand.Commitment.Splice.Request, val spliceInit: SpliceInit) : QuiescentSpliceStatus()
     /** We both agreed to splice and are building the splice transaction. */
@@ -1177,11 +1184,11 @@ sealed class SpliceStatus {
         val spliceSession: InteractiveTxSession,
         val localPushAmount: MilliSatoshi,
         val remotePushAmount: MilliSatoshi,
-        val liquidityLease: LiquidityAds.Lease?,
+        val liquidityPurchase: LiquidityAds.Purchase?,
         val origins: List<Origin>
     ) : QuiescentSpliceStatus()
     /** The splice transaction has been negotiated, we're exchanging signatures. */
-    data class WaitingForSigs(val session: InteractiveTxSigningSession, val origins: List<Origin>) : QuiescentSpliceStatus()
+    data class WaitingForSigs(val session: InteractiveTxSigningSession, val liquidityPurchase: LiquidityAds.Purchase?, val origins: List<Origin>) : QuiescentSpliceStatus()
     /** The splice attempt was aborted by us, we're waiting for our peer to ack. */
     data object Aborted : QuiescentSpliceStatus()
 }

src/commonMain/kotlin/fr/acinq/lightning/channel/states/LegacyWaitForFundingLocked.kt

@@ -48,7 +48,6 @@ data class LegacyWaitForFundingLocked(
                         null,
                         null,
                         SpliceStatus.None,
-                        listOf(),
                     )
                     val actions = listOf(
                         ChannelAction.Storage.StoreState(nextState),