Add attachment download endpoint for DocSys integration

main.go

@@ -490,6 +490,12 @@ func handleMessages(w http.ResponseWriter, r *http.Request, accountName string,
 		return
 	}
 
+	// Check for /messages/{uid}/attachments
+	if len(pathParts) > 1 && pathParts[1] == "attachments" {
+		handleGetAttachments(w, r, client, folder, uid)
+		return
+	}
+
 	switch r.Method {
 	case "GET":
 		handleGetMessage(w, r, client, folder, uid)
@@ -849,3 +855,41 @@ func handleDeleteMessage(w http.ResponseWriter, r *http.Request, client *imapcli
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(map[string]string{"status": "deleted"})
 }
+
+func handleGetAttachments(w http.ResponseWriter, r *http.Request, client *imapclient.Client, folder string, uid uint32) {
+	uidSet := imap.UIDSetNum(imap.UID(uid))
+
+	options := &imap.FetchOptions{
+		UID:         true,
+		BodySection: []*imap.FetchItemBodySection{{}},
+	}
+
+	fetchCmd := client.Fetch(uidSet, options)
+
+	msgData := fetchCmd.Next()
+	if msgData == nil {
+		fetchCmd.Close()
+		http.Error(w, "Message not found", http.StatusNotFound)
+		return
+	}
+
+	buf, err := msgData.Collect()
+	if err != nil {
+		fetchCmd.Close()
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	fetchCmd.Close()
+
+	if len(buf.BodySection) == 0 {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode([]Attachment{})
+		return
+	}
+
+	raw := buf.BodySection[0].Bytes
+	attachments := ExtractAttachments(raw)
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(attachments)
+}

mime.go

@@ -120,6 +120,95 @@ func decodeBody(body []byte, encoding string) []byte {
 	}
 }
 
+// Attachment represents an email attachment with content
+type Attachment struct {
+	Filename    string `json:"filename"`
+	ContentType string `json:"content_type"`
+	Size        int    `json:"size"`
+	Content     string `json:"content"` // base64 encoded
+}
+
+// ExtractAttachments extracts all attachments from raw email bytes
+func ExtractAttachments(raw []byte) []Attachment {
+	attachments := make([]Attachment, 0) // Initialize to empty slice (not nil)
+
+	entity, err := message.Read(bytes.NewReader(raw))
+	if err != nil {
+		return attachments
+	}
+
+	extractAttachmentParts(entity, &attachments)
+	return attachments
+}
+
+func extractAttachmentParts(entity *message.Entity, attachments *[]Attachment) {
+	mediaType, params, err := mime.ParseMediaType(entity.Header.Get("Content-Type"))
+	if err != nil {
+		return
+	}
+
+	if strings.HasPrefix(mediaType, "multipart/") {
+		// Multipart message - recurse into parts
+		mr := entity.MultipartReader()
+		if mr == nil {
+			return
+		}
+
+		for {
+			part, err := mr.NextPart()
+			if err != nil {
+				break
+			}
+			extractAttachmentParts(part, attachments)
+		}
+	} else {
+		// Check if this is an attachment
+		disp := entity.Header.Get("Content-Disposition")
+		if disp == "" {
+			return
+		}
+
+		dispType, dispParams, err := mime.ParseMediaType(disp)
+		if err != nil {
+			return
+		}
+
+		if !strings.EqualFold(dispType, "attachment") && !strings.EqualFold(dispType, "inline") {
+			return
+		}
+
+		// Get filename
+		filename := dispParams["filename"]
+		if filename == "" {
+			filename = params["name"]
+		}
+		if filename == "" {
+			// Skip attachments without filename
+			return
+		}
+
+		// Read body
+		body, err := io.ReadAll(entity.Body)
+		if err != nil {
+			return
+		}
+
+		// Decode transfer encoding
+		encoding := strings.ToLower(entity.Header.Get("Content-Transfer-Encoding"))
+		decoded := decodeBody(body, encoding)
+
+		// Encode as base64 for JSON transport
+		content := base64.StdEncoding.EncodeToString(decoded)
+
+		*attachments = append(*attachments, Attachment{
+			Filename:    filename,
+			ContentType: mediaType,
+			Size:        len(decoded),
+			Content:     content,
+		})
+	}
+}
+
 // stripHTML removes HTML tags and returns plain text
 func stripHTML(html string) string {
 	var result strings.Builder