offchain/BuildTxs: remove checkpoint tapscript field

internal/core/application/service.go

@@ -554,17 +554,11 @@ func (s *service) SubmitOffchainTx(
 			)
 		}
 
-		tapleafScript := ptx.Inputs[inputIndex].TaprootLeafScript[0]
-		checkpointTapscript := &waddrmgr.Tapscript{
-			RevealedScript: tapleafScript.Script,
-		}
-
 		ins = append(ins, offchain.VtxoInput{
-			Outpoint:            &checkpointPsbt.UnsignedTx.TxIn[0].PreviousOutPoint,
-			Tapscript:           tapscript,
-			CheckpointTapscript: checkpointTapscript,
-			RevealedTapscripts:  tapscripts,
-			Amount:              int64(vtxo.Amount),
+			Outpoint:           &checkpointPsbt.UnsignedTx.TxIn[0].PreviousOutPoint,
+			Tapscript:          tapscript,
+			RevealedTapscripts: tapscripts,
+			Amount:             int64(vtxo.Amount),
 		})
 	}
 

pkg/ark-lib/offchain/tx.go

@@ -22,11 +22,9 @@ type VtxoInput struct {
 	Amount   int64
 	// Tapscript is the path used to spend the vtxo
 	Tapscript *waddrmgr.Tapscript
-	// CheckpointTapscript is the path used to craft checkpoint output script
-	// it is combined with the signer's unroll script to creaft a new "checkpoint" output script
-	// it can be nil, defaulting to Tapscript if not set
-	CheckpointTapscript *waddrmgr.Tapscript
-	RevealedTapscripts  []string
+	// RevealedTapscripts is the whole taproot tree of the vtxo
+	// it must be revealed to the ark operator in order to verify the spent paths are valid
+	RevealedTapscripts []string
 }
 
 // BuildTxs builds the ark and checkpoint txs for the given inputs and outputs.
@@ -167,15 +165,7 @@ func buildArkTx(vtxos []VtxoInput, outputs []*wire.TxOut) (*psbt.Packet, error)
 func buildCheckpointTx(
 	vtxo VtxoInput, signerUnrollScript *script.CSVMultisigClosure,
 ) (*psbt.Packet, *VtxoInput, error) {
-	// create the checkpoint vtxo script from collaborative closure
-	checkpointCollaborativeTapscript := vtxo.Tapscript
-	if vtxo.CheckpointTapscript != nil {
-		checkpointCollaborativeTapscript = vtxo.CheckpointTapscript
-	}
-
-	collaborativeClosure, err := script.DecodeClosure(
-		checkpointCollaborativeTapscript.RevealedScript,
-	)
+	collaborativeClosure, err := script.DecodeClosure(vtxo.Tapscript.RevealedScript)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -205,7 +195,7 @@ func buildCheckpointTx(
 	// Now that we have the checkpoint tx, we need to return the corresponding output that will be
 	// used as input for the ark tx.
 	tapLeafHash := txscript.NewBaseTapLeaf(
-		checkpointCollaborativeTapscript.RevealedScript,
+		vtxo.Tapscript.RevealedScript,
 	).TapHash()
 	collaborativeLeafProof, err := tapTree.GetTaprootMerkleProof(tapLeafHash)
 	if err != nil {

test/e2e/e2e_test.go

@@ -1556,7 +1556,6 @@ func TestSendToConditionMultisigClosure(t *testing.T) {
 	require.NoError(t, err)
 
 	closure := vtxoScript.ForfeitClosures()[0]
-	checkpointClosure := vtxoScript.ForfeitClosures()[1]
 
 	bobAddr := arklib.Address{
 		HRP:        "tark",
@@ -1567,9 +1566,6 @@ func TestSendToConditionMultisigClosure(t *testing.T) {
 	scriptBytes, err := closure.Script()
 	require.NoError(t, err)
 
-	checkpointScript, err := checkpointClosure.Script()
-	require.NoError(t, err)
-
 	merkleProof, err := vtxoTapTree.GetTaprootMerkleProof(
 		txscript.NewBaseTapLeaf(scriptBytes).TapHash(),
 	)
@@ -1578,24 +1574,11 @@ func TestSendToConditionMultisigClosure(t *testing.T) {
 	ctrlBlock, err := txscript.ParseControlBlock(merkleProof.ControlBlock)
 	require.NoError(t, err)
 
-	checkpointMerkleProof, err := vtxoTapTree.GetTaprootMerkleProof(
-		txscript.NewBaseTapLeaf(checkpointScript).TapHash(),
-	)
-	require.NoError(t, err)
-
-	checkpointCtrlBlock, err := txscript.ParseControlBlock(checkpointMerkleProof.ControlBlock)
-	require.NoError(t, err)
-
 	tapscript := &waddrmgr.Tapscript{
 		ControlBlock:   ctrlBlock,
 		RevealedScript: merkleProof.Script,
 	}
 
-	checkpointTapscript := &waddrmgr.Tapscript{
-		ControlBlock:   checkpointCtrlBlock,
-		RevealedScript: checkpointMerkleProof.Script,
-	}
-
 	bobAddrStr, err := bobAddr.EncodeV0()
 	require.NoError(t, err)
 
@@ -1666,17 +1649,16 @@ func TestSendToConditionMultisigClosure(t *testing.T) {
 		unilateralExitDelayType = arklib.LocktimeTypeBlock
 	}
 
-	ptx, checkpointsPtx, err := offchain.BuildTxs(
+	arkPtx, checkpointsPtx, err := offchain.BuildTxs(
 		[]offchain.VtxoInput{
 			{
 				Outpoint: &wire.OutPoint{
 					Hash:  virtualPtx.UnsignedTx.TxHash(),
 					Index: bobOutputIndex,
 				},
-				Amount:              bobOutput.Value,
-				Tapscript:           tapscript,
-				CheckpointTapscript: checkpointTapscript,
-				RevealedTapscripts:  tapscripts,
+				Amount:             bobOutput.Value,
+				Tapscript:          tapscript,
+				RevealedTapscripts: tapscripts,
 			},
 		},
 		[]*wire.TxOut{
@@ -1699,7 +1681,11 @@ func TestSendToConditionMultisigClosure(t *testing.T) {
 
 	explorer := explorer.NewExplorer("http://localhost:3000", arklib.BitcoinRegTest)
 
-	encodedVirtualTx, err := ptx.B64Encode()
+	// add condition witness to the ark ptx
+	err = txutils.AddConditionWitness(0, arkPtx, wire.TxWitness{preimage[:]})
+	require.NoError(t, err)
+
+	encodedVirtualTx, err := arkPtx.B64Encode()
 	require.NoError(t, err)
 
 	signedTx, err := bobWallet.SignTransaction(
@@ -1724,6 +1710,7 @@ func TestSendToConditionMultisigClosure(t *testing.T) {
 		ptx, err := psbt.NewFromRawBytes(strings.NewReader(checkpoint), true)
 		require.NoError(t, err)
 
+		// add condition witness to the checkpoint ptx
 		err = txutils.AddConditionWitness(0, ptx, wire.TxWitness{preimage[:]})
 		require.NoError(t, err)