Store HTLC info in shutdown state (#226)

We need to keep track of pending HTLCs before we go to the negotiating phase.

Author: t-bast

src/commonMain/kotlin/fr/acinq/eclair/channel/Channel.kt

@@ -1786,7 +1786,7 @@ data class Normal(
                                     logger.info { "c:$channelId adding paymentHash=${it.paymentHash} cltvExpiry=${it.cltvExpiry} to htlcs db for commitNumber=$nextCommitNumber" }
                                     ChannelAction.Storage.HtlcInfo(channelId, nextCommitNumber, it.paymentHash, it.cltvExpiry)
                                 }
-                                val nextState = this.copy(commitments = result.value.first)
+                                val nextState = this.copy(commitments = commitments1)
                                 val actions = listOf(
                                     ChannelAction.Storage.StoreHtlcInfos(htlcInfos),
                                     ChannelAction.Storage.StoreState(nextState),
@@ -2195,8 +2195,21 @@ data class ShuttingDown(
                     is Either.Left -> handleCommandError(event.command, result.value)
                     is Either.Right -> {
                         val commitments1 = result.value.first
+                        val nextRemoteCommit = commitments1.remoteNextCommitInfo.left!!.nextRemoteCommit
+                        val nextCommitNumber = nextRemoteCommit.index
+                        // we persist htlc data in order to be able to claim htlc outputs in case a revoked tx is published by our
+                        // counterparty, so only htlcs above remote's dust_limit matter
+                        val trimmedHtlcs = Transactions.trimOfferedHtlcs(commitments.remoteParams.dustLimit, nextRemoteCommit.spec) + Transactions.trimReceivedHtlcs(commitments.remoteParams.dustLimit, nextRemoteCommit.spec)
+                        val htlcInfos = trimmedHtlcs.map { it.add }.map {
+                            logger.info { "c:$channelId adding paymentHash=${it.paymentHash} cltvExpiry=${it.cltvExpiry} to htlcs db for commitNumber=$nextCommitNumber" }
+                            ChannelAction.Storage.HtlcInfo(channelId, nextCommitNumber, it.paymentHash, it.cltvExpiry)
+                        }
                         val nextState = this.copy(commitments = commitments1)
-                        val actions = listOf(ChannelAction.Storage.StoreState(nextState), ChannelAction.Message.Send(result.value.second))
+                        val actions = listOf(
+                            ChannelAction.Storage.StoreHtlcInfos(htlcInfos),
+                            ChannelAction.Storage.StoreState(nextState),
+                            ChannelAction.Message.Send(result.value.second)
+                        )
                         Pair(nextState, actions)
                     }
                 }

src/commonTest/kotlin/fr/acinq/eclair/channel/states/ShutdownTestsCommon.kt

@@ -1,6 +1,7 @@
 package fr.acinq.eclair.channel.states
 
 import fr.acinq.bitcoin.*
+import fr.acinq.bitcoin.Crypto.sha256
 import fr.acinq.eclair.CltvExpiry
 import fr.acinq.eclair.Eclair.randomBytes32
 import fr.acinq.eclair.Eclair.randomKey
@@ -21,6 +22,7 @@ import fr.acinq.eclair.tests.utils.EclairTestSuite
 import fr.acinq.eclair.utils.Either
 import fr.acinq.eclair.utils.UUID
 import fr.acinq.eclair.utils.msat
+import fr.acinq.eclair.utils.toByteVector32
 import fr.acinq.eclair.wire.*
 import kotlin.test.*
 
@@ -186,8 +188,15 @@ class ShutdownTestsCommon : EclairTestSuite() {
         val fulfill = actions1.findOutgoingMessage<UpdateFulfillHtlc>()
         val (alice1, _) = alice.processEx(ChannelEvent.MessageReceived(fulfill))
         val (_, alice2) = signAndRevack(bob1, alice1)
-        val (alice3, _) = alice2.processEx(ChannelEvent.ExecuteCommand(CMD_SIGN))
-        assertTrue { alice3 is ShuttingDown && alice3.commitments.remoteNextCommitInfo.isLeft }
+        val (alice3, actions3) = alice2.processEx(ChannelEvent.ExecuteCommand(CMD_SIGN))
+        assertTrue(alice3 is ShuttingDown)
+        assertTrue(alice3.commitments.remoteNextCommitInfo.isLeft)
+        actions3.hasOutgoingMessage<CommitSig>()
+        actions3.has<ChannelAction.Storage.StoreState>()
+        // we still have 1 HTLC in the commit tx
+        val htlcInfos = actions3.find<ChannelAction.Storage.StoreHtlcInfos>()
+        assertEquals(htlcInfos.htlcs.size, 1)
+        assertEquals(htlcInfos.htlcs.first().paymentHash, r2.sha256())
     }
 
     @Test