automation

cmd/smtp2shoutrrr/main.go

@@ -0,0 +1,297 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"log/slog"
+	"mime"
+	"mime/multipart"
+	"net/mail"
+	"net/url"
+	"os"
+	"slices"
+	"strings"
+	"time"
+
+	"git.nakama.town/fmartingr/gotoolkit/encoding"
+	"git.nakama.town/fmartingr/gotoolkit/model"
+	"git.nakama.town/fmartingr/gotoolkit/service"
+	"github.com/containrrr/shoutrrr"
+	"github.com/emersion/go-sasl"
+	"github.com/emersion/go-smtp"
+)
+
+type ReceivedEmail struct {
+	Recipients []string
+	Msg        *mail.Message
+	body       string
+}
+
+func (re *ReceivedEmail) Body() (string, error) {
+	if re.body == "" {
+		// Get the Content-Type header
+		contentType := re.Msg.Header.Get("Content-Type")
+
+		if contentType == "" {
+			body, err := io.ReadAll(re.Msg.Body)
+			if err != nil {
+				return "", fmt.Errorf("failed to read email body: %w", err)
+			}
+			re.body = string(body)
+		} else {
+			mediaType, params, err := mime.ParseMediaType(contentType)
+			if err != nil {
+				log.Fatalf("Failed to parse Content-Type: %v", err)
+			}
+
+			if strings.HasPrefix(mediaType, "multipart/alternative") {
+				// Parse the multipart message
+				mr := multipart.NewReader(re.Msg.Body, params["boundary"])
+				for {
+					part, err := mr.NextPart()
+					if err != nil {
+						break // End of parts
+					}
+					defer part.Close()
+
+					// Print part headers
+					fmt.Printf("Part Content-Type: %s\n", part.Header.Get("Content-Type"))
+
+					// Set body if this is the text/plain part
+					if strings.HasPrefix(part.Header.Get("Content-Type"), "text/plain") {
+						// Read the part's body
+						body := new(bytes.Buffer)
+						_, err = body.ReadFrom(part)
+						if err != nil {
+							slog.Error("Failed to read part body", slog.String("err", err.Error()))
+							return "", fmt.Errorf("failed to read part body: %w", err)
+						}
+
+						re.body = body.String()
+						break
+					}
+				}
+			}
+		}
+	}
+
+	return re.body, nil
+}
+
+type Config struct {
+	Port       int
+	Recipients []ConfigRecipient
+}
+
+func (c *Config) SetDefaults() {
+	if c.Port == 0 {
+		c.Port = 11125
+	}
+}
+
+type ConfigRecipient struct {
+	Addresses []string // email addresses
+	Target    string   // shoutrrr address
+	targetURL *url.URL
+}
+
+func (cr ConfigRecipient) GetTargetURL() *url.URL {
+	if cr.targetURL == nil {
+		var err error
+		cr.targetURL, err = url.Parse(cr.Target)
+		if err != nil {
+			slog.Error("failed to parse shoutrrr target URL", slog.String("target", cr.Target), slog.String("err", err.Error()))
+		}
+	}
+	return cr.targetURL
+}
+
+var _ model.Server = (*smtpServer)(nil)
+
+type smtpServer struct {
+	backend *smtp.Server
+	config  Config
+}
+
+func (s *smtpServer) IsEnabled() bool {
+	return true
+}
+
+func (s *smtpServer) Start(_ context.Context) error {
+	slog.Info("Started SMTP server", slog.String("addr", s.backend.Addr))
+	return s.backend.ListenAndServe()
+}
+
+func (s *smtpServer) Stop(ctx context.Context) error {
+	slog.Info("Stopping SMTP server")
+	return s.backend.Shutdown(ctx)
+}
+
+func NewSMTPServer(config *Config) model.Server {
+	be := &Backend{
+		config: config,
+	}
+
+	smtpBackend := smtp.NewServer(be)
+	smtpBackend.Addr = fmt.Sprintf(":%d", config.Port)
+	// smtpBackend.Domain = "localhost"
+	smtpBackend.WriteTimeout = 10 * time.Second
+	smtpBackend.ReadTimeout = 10 * time.Second
+	smtpBackend.MaxMessageBytes = 1024 * 1024
+	smtpBackend.MaxRecipients = 50
+	smtpBackend.AllowInsecureAuth = true
+
+	return &smtpServer{
+		backend: smtpBackend,
+	}
+}
+
+// The Backend implements SMTP server methods.
+type Backend struct {
+	config *Config
+}
+
+// NewSession is called after client greeting (EHLO, HELO).
+func (bkd *Backend) NewSession(c *smtp.Conn) (smtp.Session, error) {
+	return &Session{
+		forwarderFunc: bkd.forwardEmail,
+	}, nil
+}
+
+func (bkd *Backend) forwardEmail(email ReceivedEmail) error {
+	slog.Info("forwading message", slog.String("to", strings.Join(email.Recipients, ",")))
+
+	for _, r := range bkd.config.Recipients {
+		for _, a := range email.Recipients {
+			if slices.Contains(r.Addresses, a) {
+				urlParams := url.Values{
+					"title": {email.Msg.Header.Get("Subject")},
+				}
+
+				destinationURL := r.GetTargetURL()
+				destinationURL.RawQuery = urlParams.Encode()
+
+				body, err := email.Body()
+				if err != nil {
+					slog.Error("Error getting email body", slog.String("err", err.Error()))
+					continue
+				}
+
+				if err := shoutrrr.Send(destinationURL.String(), body); err != nil {
+					slog.Error("Error sending message", slog.String("err", err.Error()))
+					continue
+				}
+
+				// Already sent via this configuration, go to the next
+				break
+			}
+		}
+	}
+
+	return nil
+}
+
+// A Session is returned after successful login.
+type Session struct {
+	addresses []string
+	body      string
+
+	forwarderFunc func(ReceivedEmail) error
+}
+
+// AuthMechanisms returns a slice of available auth mechanisms; only PLAIN is
+// supported in this example.
+func (s *Session) AuthMechanisms() []string {
+	return []string{sasl.Plain}
+}
+
+// Auth is the handler for supported authenticators.
+func (s *Session) Auth(mech string) (sasl.Server, error) {
+	return sasl.NewPlainServer(func(identity, username, password string) error {
+		if username != "username" || password != "password" {
+			return errors.New("Invalid username or password")
+		}
+		return nil
+	}), nil
+}
+
+func (s *Session) Mail(from string, opts *smtp.MailOptions) error {
+	slog.Debug("Mail from", slog.String("from", from))
+	return nil
+}
+
+func (s *Session) Rcpt(to string, opts *smtp.RcptOptions) error {
+	slog.Debug("Rcpt to", slog.String("to", to))
+	s.addresses = append(s.addresses, to)
+	return nil
+}
+
+func (s *Session) Data(r io.Reader) error {
+	msg, err := mail.ReadMessage(r)
+	if err != nil {
+		slog.Error("Error reading data", slog.String("err", err.Error()))
+		return fmt.Errorf("Error reading data: %w", err)
+	}
+
+	slog.Info("Received email", slog.String("destination", strings.Join(s.addresses, ",")))
+
+	if err := s.forwarderFunc(ReceivedEmail{
+		Recipients: s.addresses,
+		Msg:        msg,
+	}); err != nil {
+		slog.Error("Error forwarding email", slog.String("err", err.Error()))
+	}
+
+	return nil
+}
+
+func (s *Session) Reset() {}
+
+func (s *Session) Logout() error {
+	return nil
+}
+
+func main() {
+	var config *Config
+	configPath := "config.toml"
+
+	f, err := os.Open(configPath)
+	if err != nil {
+		slog.Error("Error opening config file", slog.String("err", err.Error()), slog.String("path", configPath))
+		return
+	}
+
+	enc := encoding.NewTOMLEncoding()
+	if err := enc.DecodeReader(f, &config); err != nil {
+		slog.Error("Error decoding config file", slog.String("err", err.Error()), slog.String("path", configPath))
+		return
+	}
+
+	config.SetDefaults()
+
+	slog.Info("config loaded", slog.Int("recipients", len(config.Recipients)))
+
+	ctx := context.Background()
+	smtpServer := NewSMTPServer(config)
+
+	svc, err := service.NewService([]model.Server{
+		smtpServer,
+	})
+	if err != nil {
+		slog.Error("Error creating service:", slog.String("err", err.Error()))
+		return
+	}
+
+	if err := svc.Start(ctx); err != nil {
+		slog.Error("Error starting service:", slog.String("err", err.Error()))
+		return
+	}
+
+	if err := svc.WaitStop(ctx); err != nil {
+		slog.Error("Error waiting for service interruption:", slog.String("err", err.Error()))
+	}
+}