Add content_type parsing

msg/content_type.go

@@ -0,0 +1,48 @@
+package msg
+
+import (
+	"fmt"
+	"mime"
+)
+
+var (
+	ErrInvalidContentType = fmt.Errorf("invalid Message ContentType")
+	ErrMissingContentType = fmt.Errorf("empty ContentType")
+)
+
+// Returns the message type as defined in the contenttype, not the message as such
+func (m *Message) MessageType() (string, error) {
+
+	_, params, err := m.ParseContentType()
+	if err != nil {
+		return "", ErrInvalidContentType
+	}
+
+	for k, v := range params {
+		if k == "type" {
+			return v, nil
+		}
+	}
+
+	return "", ErrInvalidContentType
+}
+
+// A parser which add a little specific functionality to the standard mime.ParseMediaType
+// Use this instead.
+func (m *Message) ParseContentType() (string, map[string]string, error) {
+
+	contentType, params, err := mime.ParseMediaType(m.ContentType)
+	if err != nil {
+		return contentType, params, fmt.Errorf("msg_parse_content_type: %w", err)
+	}
+
+	if contentType == "" {
+		return contentType, params, ErrMissingContentType
+	}
+
+	if contentType != MESSAGE_CONTENT_TYPE {
+		return contentType, params, fmt.Errorf("%s: %w", contentType, ErrInvalidContentType)
+	}
+
+	return contentType, params, nil
+}

msg/errors.go

@@ -14,8 +14,7 @@ var (
 	ErrFetchDoc              = fmt.Errorf("failed to fetch entity document")
 	ErrInvalidMessageType    = fmt.Errorf("invalid Message type")
 	ErrInvalidRecipient      = fmt.Errorf("invalid recipient")
-	ErrMissingContentType    = fmt.Errorf("empty ContentType")
-	ErrMissingContent        = fmt.Errorf("empty ContentType")
+	ErrMissingContent        = fmt.Errorf("empty Content")
 	ErrMissingFrom           = fmt.Errorf("mmissing From sender")
 	ErrMissinSignature       = fmt.Errorf("mmissing signature")
 	ErrNilMessage            = fmt.Errorf("nil Message provided")