refac: removed 7 direct and 12 indirect go modules for custom code instead

internal/infrastructure/mailer/auth.go

@@ -0,0 +1,47 @@
+package mailer
+
+import (
+	"RenewCMS/internal/infrastructure/config"
+	"errors"
+	"net/smtp"
+	"strings"
+)
+
+type loginAuth struct {
+	username string
+	password string
+}
+
+func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
+	if !server.TLS && !isLoopback(server.Name) {
+		return "", nil, errors.New("refusing to send credentials over an unencrypted connection")
+	}
+	return "LOGIN", nil, nil
+}
+
+func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if !more {
+		return nil, nil
+	}
+	switch strings.ToLower(strings.TrimSpace(string(fromServer))) {
+	case "username:":
+		return []byte(a.username), nil
+	case "password:":
+		return []byte(a.password), nil
+	}
+	return nil, errors.New("unexpected server challenge")
+}
+
+func isLoopback(host string) bool {
+	return host == "localhost" || host == "127.0.0.1" || host == "::1"
+}
+
+func selectAuth(mechanisms string, settings config.SmtpSettings) smtp.Auth {
+	advertised := strings.Fields(strings.ToUpper(mechanisms))
+	for _, mechanism := range advertised {
+		if mechanism == "PLAIN" {
+			return smtp.PlainAuth("", settings.Login, settings.Password, settings.Host)
+		}
+	}
+	return &loginAuth{username: settings.Login, password: settings.Password}
+}