vm: refactor stack dump commands

pkg/vm/cli/cli.go

@@ -301,7 +301,17 @@ func handleBreak(c *ishell.Context) {
 
 func handleXStack(c *ishell.Context) {
 	v := getVMFromContext(c)
-	c.Println(v.Stack(c.Cmd.Name))
+	var stackDump string
+	switch c.Cmd.Name {
+	case "estack":
+		stackDump = v.DumpEStack()
+	case "istack":
+		stackDump = v.DumpIStack()
+	default:
+		c.Err(errors.New("unknown stack"))
+		return
+	}
+	c.Println(stackDump)
 }
 
 func handleSlots(c *ishell.Context) {
@@ -470,7 +480,7 @@ func runVMWithHandling(c *ishell.Context, v *vm.VM) {
 	case v.HasFailed():
 		message = "" // the error will be printed on return
 	case v.HasHalted():
-		message = v.Stack("estack")
+		message = v.DumpEStack()
 	case v.AtBreakpoint():
 		ctx := v.Context()
 		if ctx.NextIP() < ctx.LenInstr() {

pkg/vm/vm.go

@@ -334,15 +334,18 @@ func (v *VM) PopResult() interface{} {
 	return v.estack.Pop().Value()
 }
 
-// Stack returns json formatted representation of the given stack.
-func (v *VM) Stack(n string) string {
-	var s *Stack
-	if n == "istack" {
-		s = &v.istack
-	}
-	if n == "estack" {
-		s = v.estack
-	}
+// DumpIStack returns json formatted representation of the invocation stack.
+func (v *VM) DumpIStack() string {
+	return dumpStack(&v.istack)
+}
+
+// DumpEStack returns json formatted representation of the execution stack.
+func (v *VM) DumpEStack() string {
+	return dumpStack(v.estack)
+}
+
+// dumpStack returns json formatted representation of the given stack.
+func dumpStack(s *Stack) string {
 	b, _ := json.MarshalIndent(s, "", "    ")
 	return string(b)
 }