2 files changed, 25 insertions, 4 deletions
diff --git a/model/post.go b/model/post.go
index e66009dd6..5c86ce70d 100644
--- a/model/post.go
+++ b/model/post.go
@@ -10,9 +10,11 @@ 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"
+	POST_HEADER_CHANGE         = "system_header_change"
 )
 
 type Post struct {
@@ -104,7 +106,7 @@ func (o *Post) IsValid() *AppError {
 	}
 
 	// should be removed once more message types are supported
-	if !(o.Type == POST_DEFAULT || o.Type == POST_JOIN_LEAVE || o.Type == POST_SLACK_ATTACHMENT) {
+	if !(o.Type == POST_DEFAULT || o.Type == POST_JOIN_LEAVE || o.Type == POST_SLACK_ATTACHMENT || o.Type == POST_HEADER_CHANGE) {
 		return NewAppError("Post.IsValid", "Invalid type", "id="+o.Type)
 	}
 
@@ -159,3 +161,7 @@ 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
+}
diff --git a/model/post_test.go b/model/post_test.go
index f498c83e6..cbd323fab 100644
--- a/model/post_test.go
+++ b/model/post_test.go
@@ -98,3 +98,18 @@ func TestPostPreSave(t *testing.T) {
 
 	o.Etag()
 }
+
+func TestPostIsSystemMessage(t *testing.T) {
+	post1 := Post{Message: "test_1"}
+	post1.PreSave()
+
+	if post1.IsSystemMessage() {
+		t.Fatalf("TestPostIsSystemMessage failed, expected post1.IsSystemMessage() to be false")
+	}
+
+	post2 := Post{Message: "test_2", Type: POST_JOIN_LEAVE}
+	post2.PreSave()
+	if !post2.IsSystemMessage() {
+		t.Fatalf("TestPostIsSystemMessage failed, expected post2.IsSystemMessage() to be true")
+	}
+}