parse multipart emails

main.go

@@ -1,11 +1,15 @@
 package main
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"log/slog"
+	"mime"
+	"mime/multipart"
 	"net/mail"
 	"net/url"
 	"os"
@@ -27,22 +31,55 @@ type ReceivedEmail struct {
 	body       string
 }
 
-func (re *ReceivedEmail) String() string {
-	return fmt.Sprintf(`FROM: %s
-	TO: %s,
-	BODY: %s`, re.Msg.Header.Get("From"), re.Recipients, re.Body())
-}
-
-func (re *ReceivedEmail) Body() string {
+func (re *ReceivedEmail) Body() (string, error) {
 	if re.body == "" {
-		body, err := io.ReadAll(re.Msg.Body)
-		if err != nil {
-			slog.Error("failed to read email body", slog.String("err", err.Error()))
+		// 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
+					}
+				}
+			}
 		}
-		re.body = string(body)
 	}
 
-	return re.body
+	return re.body, nil
 }
 
 type Config struct {
@@ -138,7 +175,13 @@ func (bkd *Backend) forwardEmail(email ReceivedEmail) error {
 				destinationURL := r.GetTargetURL()
 				destinationURL.RawQuery = urlParams.Encode()
 
-				if err := shoutrrr.Send(destinationURL.String(), email.Body()); err != nil {
+				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
 				}