rpc: allow to marshal Iterators for invoke* results

pkg/rpc/response/result/invoke.go

@@ -2,20 +2,35 @@ package result
 
 import (
 	"encoding/json"
+	"fmt"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 )
 
 // Invoke represents code invocation result and is used by several RPC calls
 // that invoke functions, scripts and generic bytecode.
 type Invoke struct {
-	State          string
-	GasConsumed    int64
-	Script         []byte
-	Stack          []stackitem.Item
-	FaultException string
-	Transaction    *transaction.Transaction
+	State                  string
+	GasConsumed            int64
+	Script                 []byte
+	Stack                  []stackitem.Item
+	FaultException         string
+	Transaction            *transaction.Transaction
+	maxIteratorResultItems int
+}
+
+// NewInvoke returns new Invoke structure with the given fields set.
+func NewInvoke(vm *vm.VM, script []byte, faultException string, maxIteratorResultItems int) *Invoke {
+	return &Invoke{
+		State:                  vm.State().String(),
+		GasConsumed:            vm.GasConsumed(),
+		Script:                 script,
+		Stack:                  vm.Estack().ToArray(),
+		FaultException:         faultException,
+		maxIteratorResultItems: maxIteratorResultItems,
+	}
 }
 
 type invokeAux struct {
@@ -27,15 +42,51 @@ type invokeAux struct {
 	Transaction    []byte          `json:"tx,omitempty"`
 }
 
+type iteratorAux struct {
+	Type      string            `json:"type"`
+	Value     []json.RawMessage `json:"iterator"`
+	Truncated bool              `json:"truncated"`
+}
+
+// Iterator represents deserialized VM iterator values with truncated flag.
+type Iterator struct {
+	Values    []stackitem.Item
+	Truncated bool
+}
+
 // MarshalJSON implements json.Marshaler.
 func (r Invoke) MarshalJSON() ([]byte, error) {
 	var st json.RawMessage
 	arr := make([]json.RawMessage, len(r.Stack))
 	for i := range arr {
-		data, err := stackitem.ToJSONWithTypes(r.Stack[i])
-		if err != nil {
-			st = []byte(`"error: recursive reference"`)
-			break
+		var (
+			data []byte
+			err  error
+		)
+		if (r.Stack[i].Type() == stackitem.InteropT) && vm.IsIterator(r.Stack[i]) {
+			iteratorValues, truncated := vm.IteratorValues(r.Stack[i], r.maxIteratorResultItems)
+			value := make([]json.RawMessage, len(iteratorValues))
+			for j := range iteratorValues {
+				value[j], err = stackitem.ToJSONWithTypes(iteratorValues[j])
+				if err != nil {
+					st = []byte(`"error: recursive reference"`)
+					break
+				}
+			}
+			data, err = json.Marshal(iteratorAux{
+				Type:      stackitem.InteropT.String(),
+				Value:     value,
+				Truncated: truncated,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to marshal iterator: %w", err)
+			}
+		} else {
+			data, err = stackitem.ToJSONWithTypes(r.Stack[i])
+			if err != nil {
+				st = []byte(`"error: recursive reference"`)
+				break
+			}
 		}
 		arr[i] = data
 	}
@@ -76,6 +127,26 @@ func (r *Invoke) UnmarshalJSON(data []byte) error {
 			if err != nil {
 				break
 			}
+			if st[i].Type() == stackitem.InteropT {
+				iteratorAux := new(iteratorAux)
+				if json.Unmarshal(arr[i], iteratorAux) == nil {
+					iteratorValues := make([]stackitem.Item, len(iteratorAux.Value))
+					for j := range iteratorValues {
+						iteratorValues[j], err = stackitem.FromJSONWithTypes(iteratorAux.Value[j])
+						if err != nil {
+							err = fmt.Errorf("failed to unmarshal iterator values: %w", err)
+							break
+						}
+					}
+
+					// it's impossible to restore initial iterator type; also iterator is almost
+					// useless outside of the VM, thus let's replace it with a special structure.
+					st[i] = stackitem.NewInterop(Iterator{
+						Values:    iteratorValues,
+						Truncated: iteratorAux.Truncated,
+					})
+				}
+			}
 		}
 		if err == nil {
 			r.Stack = st