add Selector interface

conn.go

@@ -8,19 +8,18 @@ import (
 	"time"
 )
 
-type Config struct {
-	Methods        []uint8
-	SelectMethod   func(methods ...uint8) uint8
-	MethodSelected func(method uint8, conn net.Conn) (net.Conn, error)
-}
-
-func defaultConfig() *Config {
-	return &Config{}
+type Selector interface {
+	// return supported methods
+	Methods() []uint8
+	// select method
+	Select(methods ...uint8) (method uint8)
+	// on method selected
+	OnSelected(method uint8, conn net.Conn) (net.Conn, error)
 }
 
 type Conn struct {
 	c              net.Conn
-	config         *Config
+	selector       Selector
 	method         uint8
 	isClient       bool
 	handshaked     bool
@@ -28,18 +27,18 @@ type Conn struct {
 	handshakeErr   error
 }
 
-func ClientConn(conn net.Conn, config *Config) *Conn {
+func ClientConn(conn net.Conn, selector Selector) *Conn {
 	return &Conn{
 		c:        conn,
-		config:   config,
+		selector: selector,
 		isClient: true,
 	}
 }
 
-func ServerConn(conn net.Conn, config *Config) *Conn {
+func ServerConn(conn net.Conn, selector Selector) *Conn {
 	return &Conn{
-		c:      conn,
-		config: config,
+		c:        conn,
+		selector: selector,
 	}
 }
 
@@ -64,11 +63,13 @@ func (conn *Conn) Handleshake() error {
 }
 
 func (conn *Conn) clientHandshake() error {
-	if conn.config == nil {
-		conn.config = defaultConfig()
-	}
+	var methods []uint8
+	var nm int
 
-	nm := len(conn.config.Methods)
+	if conn.selector != nil {
+		methods = conn.selector.Methods()
+	}
+	nm = len(methods)
 	if nm == 0 {
 		nm = 1
 	}
@@ -76,7 +77,7 @@ func (conn *Conn) clientHandshake() error {
 	b := make([]byte, 2+nm)
 	b[0] = Ver5
 	b[1] = uint8(nm)
-	copy(b[2:], conn.config.Methods)
+	copy(b[2:], methods)
 
 	if _, err := conn.c.Write(b); err != nil {
 		return err
@@ -90,8 +91,8 @@ func (conn *Conn) clientHandshake() error {
 		return ErrBadVersion
 	}
 
-	if conn.config.MethodSelected != nil {
-		c, err := conn.config.MethodSelected(b[1], conn.c)
+	if conn.selector != nil {
+		c, err := conn.selector.OnSelected(b[1], conn.c)
 		if err != nil {
 			return err
 		}
@@ -104,26 +105,22 @@ func (conn *Conn) clientHandshake() error {
 }
 
 func (conn *Conn) serverHandshake() error {
-	if conn.config == nil {
-		conn.config = defaultConfig()
-	}
-
 	methods, err := ReadMethods(conn.c)
 	if err != nil {
 		return err
 	}
 
 	method := MethodNoAuth
-	if conn.config.SelectMethod != nil {
-		method = conn.config.SelectMethod(methods...)
+	if conn.selector != nil {
+		method = conn.selector.Select(methods...)
 	}
 
 	if _, err := conn.c.Write([]byte{Ver5, method}); err != nil {
 		return err
 	}
 
-	if conn.config.MethodSelected != nil {
-		c, err := conn.config.MethodSelected(method, conn.c)
+	if conn.selector != nil {
+		c, err := conn.selector.OnSelected(method, conn.c)
 		if err != nil {
 			return err
 		}