1 files changed, 12 insertions, 3 deletions

diff --git a/model/post.go b/model/post.go
index 5578514b5..2c90d8b7b 100644
--- a/model/post.go
+++ b/model/post.go
@@ -10,9 +10,10 @@ import (
 )
 
 const (
-	POST_DEFAULT          = ""
-	POST_SLACK_ATTACHMENT = "slack_attachment"
-	POST_JOIN_LEAVE       = "join_leave"
+	POST_SYSTEM_MESSAGE_PREFIX = "system_"
+	POST_DEFAULT               = ""
+	POST_SLACK_ATTACHMENT      = "slack_attachment"
+	POST_JOIN_LEAVE            = "system_join_leave"
 )
 
 type Post struct {
@@ -112,6 +113,10 @@ func (o *Post) IsValid() *AppError {
 		return NewAppError("Post.IsValid", "Invalid filenames", "id="+o.Id)
 	}
 
+	if utf8.RuneCountInString(StringInterfaceToJson(o.Props)) > 8000 {
+		return NewAppError("Post.IsValid", "Invalid props", "id="+o.Id)
+	}
+
 	return nil
 }
 
@@ -155,3 +160,7 @@ func (o *Post) AddProp(key string, value interface{}) {
 
 func (o *Post) PreExport() {
 }
+
+func (o *Post) IsSystemMessage() bool {
+	return len(o.Type) >= len(POST_SYSTEM_MESSAGE_PREFIX) && o.Type[:len(POST_SYSTEM_MESSAGE_PREFIX)] == POST_SYSTEM_MESSAGE_PREFIX
+}