Auto detect authentication type

Signed-off-by: utkarshm <utkarshm@jfrog.com>

email.go

@@ -38,7 +38,6 @@ SMTPServer represents a SMTP Server
 If authentication is CRAM-MD5 then the Password is the Secret
 */
 type SMTPServer struct {
-	Authentication AuthType
 	Encryption     Encryption
 	Username       string
 	Password       string
@@ -123,19 +122,21 @@ func (contentType ContentType) string() string {
 	return contentTypes[contentType]
 }
 
-type AuthType int
+type AuthType string
 
 const (
 	// AuthPlain implements the PLAIN authentication
-	AuthPlain AuthType = iota
+	AuthPlain AuthType = "PLAIN"
 	// AuthLogin implements the LOGIN authentication
-	AuthLogin
+	AuthLogin AuthType = "LOGIN"
 	// AuthCRAMMD5 implements the CRAM-MD5 authentication
-	AuthCRAMMD5
-	// AuthNone for SMTP servers without authentication
-	AuthNone
+	AuthCRAMMD5 AuthType = "CRAM-MD5"
 )
 
+func (at AuthType) String() string {
+	return string(at)
+}
+
 // NewMSG creates a new email. It uses UTF-8 by default. All charsets: http://webcheatsheet.com/HTML/character_sets_list.php
 func NewMSG() *Email {
 	email := &Email{
@@ -152,7 +153,6 @@ func NewMSG() *Email {
 // NewSMTPClient returns the client for send email
 func NewSMTPClient() *SMTPServer {
 	server := &SMTPServer{
-		Authentication: AuthPlain,
 		Encryption:     EncryptionNone,
 		ConnectTimeout: 10 * time.Second,
 		SendTimeout:    10 * time.Second,
@@ -717,7 +717,7 @@ func dial(host string, port string, encryption Encryption, config *tls.Config) (
 
 // smtpConnect connects to the smtp server and starts TLS and passes auth
 // if necessary
-func smtpConnect(host, port, helo string, a auth, at AuthType, encryption Encryption, config *tls.Config) (*smtpClient, error) {
+func smtpConnect(host, port, helo string, encryption Encryption, config *tls.Config) (*smtpClient, error) {
 	// connect to the mail server
 	c, err := dial(host, port, encryption, config)
 
@@ -746,42 +746,32 @@ func smtpConnect(host, port, helo string, a auth, at AuthType, encryption Encryp
 		}
 	}
 
-	// only pass authentication if defined
-	if at != AuthNone {
-		// pass the authentication if necessary
-		if a != nil {
-			if ok, _ := c.extension("AUTH"); ok {
-				if err = c.authenticate(a); err != nil {
-					c.close()
-					return nil, fmt.Errorf("Mail Error on Auth: %w", err)
-				}
-			}
-		}
-	}
-
 	return c, nil
 }
 
-// Connect returns the smtp client
-func (server *SMTPServer) Connect() (*SMTPClient, error) {
-
-	var a auth
-
-	switch server.Authentication {
-	case AuthPlain:
+func (server *SMTPServer) getAuth(a string) (auth, error) {
+	var afn auth
+	switch a {
+	case AuthPlain.String():
 		if server.Username != "" || server.Password != "" {
-			a = plainAuthfn("", server.Username, server.Password, server.Host)
+			afn = plainAuthfn("", server.Username, server.Password, server.Host)
 		}
-	case AuthLogin:
+	case AuthLogin.String():
 		if server.Username != "" || server.Password != "" {
-			a = loginAuthfn("", server.Username, server.Password, server.Host)
+			afn = loginAuthfn("", server.Username, server.Password, server.Host)
 		}
-	case AuthCRAMMD5:
+	case AuthCRAMMD5.String():
 		if server.Username != "" || server.Password != "" {
-			a = cramMD5Authfn(server.Username, server.Password)
+			afn = cramMD5Authfn(server.Username, server.Password)
 		}
+	default:
+		return nil, fmt.Errorf("Mail Error on determining auth type, %s is not supported", a)
 	}
+	return afn, nil
+}
 
+// Connect returns the smtp client
+func (server *SMTPServer) Connect() (*SMTPClient, error) {
 	var smtpConnectChannel chan error
 	var c *smtpClient
 	var err error
@@ -795,7 +785,7 @@ func (server *SMTPServer) Connect() (*SMTPClient, error) {
 	if server.ConnectTimeout != 0 {
 		smtpConnectChannel = make(chan error, 2)
 		go func() {
-			c, err = smtpConnect(server.Host, fmt.Sprintf("%d", server.Port), server.Helo, a, server.Authentication, server.Encryption, tlsConfig)
+			c, err = smtpConnect(server.Host, fmt.Sprintf("%d", server.Port), server.Helo, server.Encryption, tlsConfig)
 			// send the result
 			smtpConnectChannel <- err
 		}()
@@ -810,12 +800,25 @@ func (server *SMTPServer) Connect() (*SMTPClient, error) {
 		}
 	} else {
 		// no ConnectTimeout, just fire the connect
-		c, err = smtpConnect(server.Host, fmt.Sprintf("%d", server.Port), server.Helo, a, server.Authentication, server.Encryption, tlsConfig)
+		c, err = smtpConnect(server.Host, fmt.Sprintf("%d", server.Port), server.Helo, server.Encryption, tlsConfig)
 		if err != nil {
 			return nil, err
 		}
 	}
-
+	// only pass authentication if defined
+	if server.Username != "" {
+		// pass the authentication if necessary
+		if ok, a := c.extension("AUTH"); ok {
+			afn, err := server.getAuth(a)
+			if err != nil {
+				return nil, err
+			}
+			if err = c.authenticate(afn); err != nil {
+				c.close()
+				return nil, fmt.Errorf("Mail Error on Auth: %w", err)
+			}
+		}
+	}
 	return &SMTPClient{
 		Client:      c,
 		KeepAlive:   server.KeepAlive,

example/example_test.go

@@ -120,9 +120,6 @@ func TestSendMultipleEmails(t *testing.T) {
 	client.ConnectTimeout = connectTimeout
 	client.SendTimeout = sendTimeout
 
-	//For authentication you can use AuthPlain, AuthLogin or AuthCRAMMD5
-	client.Authentication = mail.AuthPlain
-
 	//KeepAlive true because the connection need to be open for multiple emails
 	//For avoid inactivity timeout, every 30 second you can send a NO OPERATION command to smtp client
 	//use smtpClient.Client.Noop() after 30 second of inactivity in this example