implement txs.Visitor in X chain wallet

wallet/chain/x/backend.go

@@ -4,8 +4,6 @@
 package x
 
 import (
-	"fmt"
-
 	stdcontext "context"
 
 	"github.com/ava-labs/avalanchego/ids"
@@ -48,38 +46,14 @@ func NewBackend(ctx Context, chainID ids.ID, utxos ChainUTXOs) Backend {
 	}
 }
 
-// TODO: implement txs.Visitor here
 func (b *backend) AcceptTx(ctx stdcontext.Context, tx *txs.Tx) error {
-	switch utx := tx.Unsigned.(type) {
-	case *txs.BaseTx, *txs.CreateAssetTx, *txs.OperationTx:
-	case *txs.ImportTx:
-		for _, input := range utx.ImportedIns {
-			utxoID := input.UTXOID.InputID()
-			if err := b.RemoveUTXO(ctx, utx.SourceChain, utxoID); err != nil {
-				return err
-			}
-		}
-	case *txs.ExportTx:
-		txID := tx.ID()
-		for i, out := range utx.ExportedOuts {
-			err := b.AddUTXO(
-				ctx,
-				utx.DestinationChain,
-				&avax.UTXO{
-					UTXOID: avax.UTXOID{
-						TxID:        txID,
-						OutputIndex: uint32(len(utx.Outs) + i),
-					},
-					Asset: avax.Asset{ID: out.AssetID()},
-					Out:   out.Out,
-				},
-			)
-			if err != nil {
-				return err
-			}
-		}
-	default:
-		return fmt.Errorf("%w: %T", errUnknownTxType, tx.Unsigned)
+	err := tx.Unsigned.Visit(&backendVisitor{
+		b:    b,
+		ctx:  ctx,
+		txID: tx.ID(),
+	})
+	if err != nil {
+		return err
 	}
 
 	inputUTXOs := tx.Unsigned.InputUTXOs()

wallet/chain/x/backend_visitor.go

@@ -0,0 +1,64 @@
+// Copyright (C) 2019-2023, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package x
+
+import (
+	stdcontext "context"
+
+	"github.com/ava-labs/avalanchego/ids"
+	"github.com/ava-labs/avalanchego/vms/avm/txs"
+	"github.com/ava-labs/avalanchego/vms/components/avax"
+)
+
+var _ txs.Visitor = (*backendVisitor)(nil)
+
+// backendVisitor handles accepting of transactions for the backend
+type backendVisitor struct {
+	b    *backend
+	ctx  stdcontext.Context
+	txID ids.ID
+}
+
+func (*backendVisitor) BaseTx(*txs.BaseTx) error {
+	return nil
+}
+
+func (*backendVisitor) CreateAssetTx(*txs.CreateAssetTx) error {
+	return nil
+}
+
+func (*backendVisitor) OperationTx(*txs.OperationTx) error {
+	return nil
+}
+
+func (b *backendVisitor) ImportTx(tx *txs.ImportTx) error {
+	for _, in := range tx.ImportedIns {
+		utxoID := in.UTXOID.InputID()
+		if err := b.b.RemoveUTXO(b.ctx, tx.SourceChain, utxoID); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (b *backendVisitor) ExportTx(tx *txs.ExportTx) error {
+	for i, out := range tx.ExportedOuts {
+		err := b.b.AddUTXO(
+			b.ctx,
+			tx.DestinationChain,
+			&avax.UTXO{
+				UTXOID: avax.UTXOID{
+					TxID:        b.txID,
+					OutputIndex: uint32(len(tx.Outs) + i),
+				},
+				Asset: avax.Asset{ID: out.AssetID()},
+				Out:   out.Out,
+			},
+		)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}