error hint

errors.go

@@ -0,0 +1,11 @@
+package tunnel
+
+import "fmt"
+
+type WrongDataFrameTypeError struct {
+	ShouldBe Type
+}
+
+func (w WrongDataFrameTypeError) Error() string {
+	return fmt.Sprintf("wrong dataframe type, should be %s(%d)", w.ShouldBe, w.ShouldBe)
+}

manager.go

@@ -1,7 +1,6 @@
 package tunnel
 
 import (
-	"errors"
 	"io"
 )
 
@@ -84,8 +83,7 @@ func (m *Manager) Connect() (*Connection, error) {
 
 	df = <-connection.RX
 	if df.Type != TypeConnected {
-
-		return nil, errors.New("failed to connect")
+		return nil, WrongDataFrameTypeError{ShouldBe: TypeConnected}
 	}
 	return connection, nil
 }
@@ -93,7 +91,7 @@ func (m *Manager) Connect() (*Connection, error) {
 func (m *Manager) Accept() (*Connection, error) {
 	df := <-m.accept
 	if df.Type != TypeRequest {
-		return nil, errors.New("failed to accept")
+		return nil, WrongDataFrameTypeError{ShouldBe: TypeRequest}
 	}
 	connection := &Connection{
 		ID: df.ID,

types.go

@@ -9,3 +9,17 @@ func NewID() ID {
 }
 
 type Type uint8
+
+func (t Type) String() string {
+	switch t {
+	case TypeNormal:
+		return "normal"
+	case TypeRequest:
+		return "request"
+	case TypeConnected:
+		return "connected"
+	case TypeClosed:
+		return "closed"
+	}
+	return "invalid"
+}