op-node: JSON Marshaling for span batch

op-node/rollup/derive/span_batch.go

@@ -3,6 +3,7 @@ package derive
 import (
 	"bytes"
 	"encoding/binary"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -452,6 +453,22 @@ type SpanBatch struct {
 	Batches       []*SpanBatchElement // List of block input in derived form
 }
 
+// spanBatchMarshaling is a helper type used for JSON marshaling.
+type spanBatchMarshaling struct {
+	ParentCheck   []hexutil.Bytes     `json:"parent_check"`
+	L1OriginCheck []hexutil.Bytes     `json:"l1_origin_check"`
+	Batches       []*SpanBatchElement `json:"span_batch_elements"`
+}
+
+func (b *SpanBatch) MarshalJSON() ([]byte, error) {
+	spanBatch := spanBatchMarshaling{
+		ParentCheck:   []hexutil.Bytes{b.ParentCheck[:]},
+		L1OriginCheck: []hexutil.Bytes{b.L1OriginCheck[:]},
+		Batches:       b.Batches,
+	}
+	return json.Marshal(spanBatch)
+}
+
 // GetBatchType returns its batch type (batch_version)
 func (b *SpanBatch) GetBatchType() int {
 	return SpanBatchType