Implement simple taproot channels

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

@@ -270,6 +270,12 @@ sealed class Feature {
         override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
+    @Serializable
+    object SimpleTaprootStaging : Feature() {
+        override val rfcName get() = "option_simple_taproot_staging"
+        override val mandatory get() = 180
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
+    }
 }
 
 @Serializable
@@ -353,7 +359,8 @@ data class Features(val activated: Map<Feature, FeatureSupport>, val unknown: Se
             Feature.ChannelBackupProvider,
             Feature.ExperimentalSplice,
             Feature.OnTheFlyFunding,
-            Feature.FundingFeeCredit
+            Feature.FundingFeeCredit,
+            Feature.SimpleTaprootStaging
         )
 
         operator fun invoke(bytes: ByteVector): Features = invoke(bytes.toByteArray())
@@ -387,7 +394,8 @@ data class Features(val activated: Map<Feature, FeatureSupport>, val unknown: Se
             Feature.TrampolinePayment to listOf(Feature.PaymentSecret),
             Feature.ExperimentalTrampolinePayment to listOf(Feature.PaymentSecret),
             Feature.OnTheFlyFunding to listOf(Feature.ExperimentalSplice),
-            Feature.FundingFeeCredit to listOf(Feature.OnTheFlyFunding)
+            Feature.FundingFeeCredit to listOf(Feature.OnTheFlyFunding),
+            Feature.SimpleTaprootStaging to listOf(Feature.AnchorOutputs, Feature.StaticRemoteKey)
         )
 
         class FeatureException(message: String) : IllegalArgumentException(message)

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

@@ -211,6 +211,7 @@ data class NodeParams(
             Feature.ExperimentalSplice to FeatureSupport.Optional,
             Feature.OnTheFlyFunding to FeatureSupport.Optional,
             Feature.FundingFeeCredit to FeatureSupport.Optional,
+            Feature.SimpleTaprootStaging to FeatureSupport.Optional
         ),
         dustLimit = 546.sat,
         maxRemoteDustLimit = 600.sat,

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

@@ -22,6 +22,7 @@ data class InvalidPushAmount                       (override val channelId: Byte
 data class InvalidMaxAcceptedHtlcs                 (override val channelId: ByteVector32, val maxAcceptedHtlcs: Int, val max: Int) : ChannelException(channelId, "invalid max_accepted_htlcs=$maxAcceptedHtlcs (max=$max)")
 data class InvalidChannelType                      (override val channelId: ByteVector32, val ourChannelType: ChannelType, val theirChannelType: ChannelType) : ChannelException(channelId, "invalid channel_type=${theirChannelType.name}, expected channel_type=${ourChannelType.name}")
 data class MissingChannelType                      (override val channelId: ByteVector32) : ChannelException(channelId, "option_channel_type was negotiated but channel_type is missing")
+data class MissingNextLocalNonces                  (override val channelId: ByteVector32) : ChannelException(channelId, "missing next local nonces")
 data class DustLimitTooSmall                       (override val channelId: ByteVector32, val dustLimit: Satoshi, val min: Satoshi) : ChannelException(channelId, "dustLimit=$dustLimit is too small (min=$min)")
 data class DustLimitTooLarge                       (override val channelId: ByteVector32, val dustLimit: Satoshi, val max: Satoshi) : ChannelException(channelId, "dustLimit=$dustLimit is too large (max=$max)")
 data class ToSelfDelayTooHigh                      (override val channelId: ByteVector32, val toSelfDelay: CltvExpiryDelta, val max: CltvExpiryDelta) : ChannelException(channelId, "unreasonable to_self_delay=$toSelfDelay (max=$max)")

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

@@ -59,6 +59,15 @@ sealed class ChannelType {
             override val features: Set<Feature> get() = setOf(Feature.StaticRemoteKey, Feature.AnchorOutputs, Feature.ZeroReserveChannels)
         }
 
+        object SimpleTaprootStaging : SupportedChannelType() {
+            override val name: String get() = "simple_taproot_staging"
+            override val features: Set<Feature> get() = setOf(Feature.SimpleTaprootStaging, Feature.StaticRemoteKey, Feature.AnchorOutputs)
+        }
+
+        object SimpleTaprootStagingZeroReserve : SupportedChannelType() {
+            override val name: String get() = "simple_taproot_staging_zero_reserve"
+            override val features: Set<Feature> get() = setOf(Feature.SimpleTaprootStaging, Feature.StaticRemoteKey, Feature.AnchorOutputs, Feature.ZeroReserveChannels)
+        }
     }
 
     data class UnsupportedChannelType(val featureBits: Features) : ChannelType() {
@@ -71,6 +80,8 @@ sealed class ChannelType {
         // NB: Bolt 2: features must exactly match in order to identify a channel type.
         fun fromFeatures(features: Features): ChannelType = when (features) {
             // @formatter:off
+            Features(Feature.StaticRemoteKey to FeatureSupport.Mandatory, Feature.AnchorOutputs to FeatureSupport.Mandatory, Feature.ZeroReserveChannels to FeatureSupport.Mandatory, Feature.SimpleTaprootStaging to FeatureSupport.Mandatory) -> SupportedChannelType.SimpleTaprootStagingZeroReserve
+            Features(Feature.StaticRemoteKey to FeatureSupport.Mandatory, Feature.AnchorOutputs to FeatureSupport.Mandatory, Feature.SimpleTaprootStaging to FeatureSupport.Mandatory) -> SupportedChannelType.SimpleTaprootStaging
             Features(Feature.StaticRemoteKey to FeatureSupport.Mandatory, Feature.AnchorOutputs to FeatureSupport.Mandatory, Feature.ZeroReserveChannels to FeatureSupport.Mandatory) -> SupportedChannelType.AnchorOutputsZeroReserve
             Features(Feature.StaticRemoteKey to FeatureSupport.Mandatory, Feature.AnchorOutputs to FeatureSupport.Mandatory) -> SupportedChannelType.AnchorOutputs
             else -> UnsupportedChannelType(features)