smtp wrapper

smtp/smtp.go

@@ -0,0 +1,116 @@
+package smtp
+
+import (
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"net/mail"
+	"net/smtp"
+)
+
+var (
+	ErrSMTPInvalidConfig    = errors.New("invalid smtp configuration")
+	ErrSMTPConnectionFailed = errors.New("connection to smtp server failed")
+	ErrSendMessageFailed    = errors.New("could not send message")
+)
+
+type SSLSMTPConfig struct {
+	URL      string
+	Username string
+	Password string
+}
+
+func (ssc *SSLSMTPConfig) Valid() bool {
+	if _, _, err := net.SplitHostPort(ssc.URL); err != nil {
+		return false
+	}
+
+	return ssc.Username != "" && ssc.Password != ""
+}
+
+type SSLSMTP struct {
+	config    *SSLSMTPConfig
+	client    *smtp.Client
+	connected bool
+}
+
+func NewSSLSMTP(config *SSLSMTPConfig) *SSLSMTP {
+	return &SSLSMTP{
+		config: config,
+	}
+}
+
+func (s *SSLSMTP) Connect() error {
+	if !s.config.Valid() {
+		return ErrSMTPInvalidConfig
+	}
+
+	host, _, _ := net.SplitHostPort(s.config.URL)
+	auth := smtp.PlainAuth("", s.config.Username, s.config.Password, host)
+	conn, err := tls.Dial("tcp", s.config.URL, &tls.Config{ServerName: host})
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrSMTPConnectionFailed, err)
+	}
+	client, err := smtp.NewClient(conn, host)
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrSMTPConnectionFailed, err)
+	}
+	if err := client.Auth(auth); err != nil {
+		return fmt.Errorf("%w: %v", ErrSMTPConnectionFailed, err)
+	}
+	s.client = client
+	s.connected = true
+
+	return nil
+}
+
+func (s *SSLSMTP) Close() error {
+	if !s.connected {
+		return nil
+	}
+
+	if err := s.client.Quit(); err != nil {
+		return fmt.Errorf("%w: %v", ErrSMTPConnectionFailed, err)
+	}
+	s.connected = false
+
+	return nil
+}
+
+func (s *SSLSMTP) Send(from, to mail.Address, subject, body string) error {
+	if err := s.Connect(); err != nil {
+		return err
+	}
+	defer s.Close()
+
+	headers := make(map[string]string)
+	headers["From"] = from.String()
+	headers["To"] = to.String()
+	headers["Subject"] = subject
+
+	message := ""
+	for k, v := range headers {
+		message += fmt.Sprintf("%s: %s\r\n", k, v)
+	}
+	message += fmt.Sprintf("\r\n%s", body)
+
+	if err := s.client.Mail(from.Address); err != nil {
+		return fmt.Errorf("%w: %v", ErrSendMessageFailed, err)
+	}
+	if err := s.client.Rcpt(to.Address); err != nil {
+		return fmt.Errorf("%w: %v", ErrSendMessageFailed, err)
+	}
+	wc, err := s.client.Data()
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrSendMessageFailed, err)
+	}
+	if _, err := wc.Write([]byte(message)); err != nil {
+		return fmt.Errorf("%w: %v", ErrSendMessageFailed, err)
+	}
+	if err := wc.Close(); err != nil {
+		return fmt.Errorf("%w: %v", ErrSendMessageFailed, err)
+	}
+
+	return nil
+}