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

internal/infrastructure/mailer/transport.go

@@ -0,0 +1,116 @@
+package mailer
+
+import (
+	"RenewCMS/internal/infrastructure/config"
+	"crypto/tls"
+	"errors"
+	"net"
+	"net/smtp"
+	"strconv"
+	"time"
+)
+
+const (
+	implicitTLSPort = 465
+	dialTimeout     = 10 * time.Second
+	sessionTimeout  = 30 * time.Second
+)
+
+type transport struct {
+	settings  config.SmtpSettings
+	tlsConfig *tls.Config
+}
+
+func newTransport(settings config.SmtpSettings, tlsConfig *tls.Config) transport {
+	if tlsConfig == nil {
+		tlsConfig = &tls.Config{}
+	}
+	tlsConfig = tlsConfig.Clone()
+	if tlsConfig.ServerName == "" {
+		tlsConfig.ServerName = settings.Host
+	}
+	if tlsConfig.MinVersion == 0 {
+		tlsConfig.MinVersion = tls.VersionTLS12
+	}
+	return transport{settings: settings, tlsConfig: tlsConfig}
+}
+
+func (t transport) deliver(sender string, receiver string, payload []byte) error {
+	client, err := t.connect()
+	if err != nil {
+		return err
+	}
+	defer func() { _ = client.Close() }()
+
+	if err := t.negotiate(client); err != nil {
+		return err
+	}
+	if err := client.Mail(sender); err != nil {
+		return err
+	}
+	if err := client.Rcpt(receiver); err != nil {
+		return err
+	}
+	if err := writeData(client, payload); err != nil {
+		return err
+	}
+	return client.Quit()
+}
+
+func (t transport) connect() (*smtp.Client, error) {
+	address := net.JoinHostPort(t.settings.Host, strconv.Itoa(t.settings.Port))
+	dialer := &net.Dialer{Timeout: dialTimeout}
+
+	connection, err := dialer.Dial("tcp", address)
+	if err != nil {
+		return nil, err
+	}
+	if err := connection.SetDeadline(time.Now().Add(sessionTimeout)); err != nil {
+		_ = connection.Close()
+		return nil, err
+	}
+	if t.settings.Port == implicitTLSPort {
+		connection = tls.Client(connection, t.tlsConfig)
+	}
+
+	client, err := smtp.NewClient(connection, t.settings.Host)
+	if err != nil {
+		_ = connection.Close()
+		return nil, err
+	}
+	return client, nil
+}
+
+func (t transport) negotiate(client *smtp.Client) error {
+	if t.settings.Port != implicitTLSPort {
+		if supported, _ := client.Extension("STARTTLS"); supported {
+			if err := client.StartTLS(t.tlsConfig); err != nil {
+				return err
+			}
+		}
+	}
+	return t.authenticate(client)
+}
+
+func (t transport) authenticate(client *smtp.Client) error {
+	if t.settings.Login == "" {
+		return nil
+	}
+	advertised, mechanisms := client.Extension("AUTH")
+	if !advertised {
+		return errors.New("smtp server does not support authentication")
+	}
+	return client.Auth(selectAuth(mechanisms, t.settings))
+}
+
+func writeData(client *smtp.Client, payload []byte) error {
+	writer, err := client.Data()
+	if err != nil {
+		return err
+	}
+	if _, err := writer.Write(payload); err != nil {
+		_ = writer.Close()
+		return err
+	}
+	return writer.Close()
+}