From 0d361f3df158ed2aa31d5c9f90215f626ca4b054 Mon Sep 17 00:00:00 2001
From: Darko Draskovic <darko.draskovic@gmail.com>
Date: Wed, 22 Jan 2020 15:58:24 +0100
Subject: [PATCH] Fix twins update revision counter (#1011)

Signed-off-by: Darko Draskovic <darko.draskovic@gmail.com>
---
 twins/api/http/endpoint_test.go |  7 +++++--
 twins/service.go                | 17 ++++++++++++++---
 twins/service_test.go           |  2 ++
 twins/twins.go                  | 12 ++++++------
 4 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/twins/api/http/endpoint_test.go b/twins/api/http/endpoint_test.go
index 57bc9e40..9d36a7ee 100644
--- a/twins/api/http/endpoint_test.go
+++ b/twins/api/http/endpoint_test.go
@@ -28,6 +28,7 @@ import (
 )
 
 const (
+	twinName    = "name"
 	contentType = "application/json"
 	email       = "user@example.com"
 	token       = "token"
@@ -201,9 +202,11 @@ func TestUpdateTwin(t *testing.T) {
 
 	twin := twins.Twin{ThingID: thingID}
 	def := twins.Definition{}
-	data := toJSON(twin)
 	stw, _ := svc.AddTwin(context.Background(), token, twin, def)
 
+	twin.Name = twinName
+	data := toJSON(twin)
+
 	tw := twin
 	tw.Name = invalidName
 	invalidData := toJSON(tw)
@@ -230,7 +233,7 @@ func TestUpdateTwin(t *testing.T) {
 			id:          stw.ID,
 			contentType: contentType,
 			auth:        token,
-			status:      http.StatusOK,
+			status:      http.StatusBadRequest,
 		},
 		{
 			desc:        "update non-existent twin",
diff --git a/twins/service.go b/twins/service.go
index 0f574b74..a48eb6af 100644
--- a/twins/service.go
+++ b/twins/service.go
@@ -154,27 +154,38 @@ func (ts *twinsService) UpdateTwin(ctx context.Context, token string, twin Twin,
 	if err != nil {
 		return err
 	}
-	tw.Updated = time.Now()
-	tw.Revision++
+
+	revision := false
 
 	if twin.Name != "" {
+		revision = true
 		tw.Name = twin.Name
 	}
 
 	if twin.ThingID != "" {
+		revision = true
 		tw.ThingID = twin.ThingID
 	}
 
 	if len(def.Attributes) > 0 {
+		revision = true
 		def.Created = time.Now()
 		def.ID = tw.Definitions[len(tw.Definitions)-1].ID + 1
 		tw.Definitions = append(tw.Definitions, def)
 	}
 
-	if len(twin.Metadata) == 0 {
+	if len(twin.Metadata) > 0 {
+		revision = true
 		tw.Metadata = twin.Metadata
 	}
 
+	if !revision {
+		return ErrMalformedEntity
+	}
+
+	tw.Updated = time.Now()
+	tw.Revision++
+
 	if err := ts.twins.Update(ctx, tw); err != nil {
 		return err
 	}
diff --git a/twins/service_test.go b/twins/service_test.go
index 7a1f6aa4..2311df9f 100644
--- a/twins/service_test.go
+++ b/twins/service_test.go
@@ -86,6 +86,8 @@ func TestUpdateTwin(t *testing.T) {
 	saved, err := svc.AddTwin(context.Background(), token, twin, def)
 	require.Nil(t, err, fmt.Sprintf("unexpected error: %s\n", err))
 
+	saved.Name = twinName
+
 	cases := []struct {
 		desc  string
 		twin  twins.Twin
diff --git a/twins/twins.go b/twins/twins.go
index a7f01a9b..fa2c57e8 100644
--- a/twins/twins.go
+++ b/twins/twins.go
@@ -13,16 +13,16 @@ type Metadata map[string]interface{}
 
 // Attribute stores individual attribute data
 type Attribute struct {
-	Channel      string
-	Subtopic     string
-	PersistState bool
+	Channel      string `json:"channel"`
+	Subtopic     string `json:"subtopic"`
+	PersistState bool   `json:"persist_state"`
 }
 
 // Definition stores entity's attributes
 type Definition struct {
-	ID         int
-	Created    time.Time
-	Attributes map[string]Attribute
+	ID         int                  `json:"id"`
+	Created    time.Time            `json:"created"`
+	Attributes map[string]Attribute `json:"attributes"`
 }
 
 // Twin represents a Mainflux thing digital twin. Each twin is owned by one thing, and