APIv4 POST /reactions (#6092)

* APIv4 POST /reactions

* update corresponding V3 endpoint

app/reaction.go

@@ -7,6 +7,25 @@ import (
 	"github.com/mattermost/platform/model"
 )
 
+func SaveReactionForPost(reaction *model.Reaction) (*model.Reaction, *model.AppError) {
+	post, err := GetSinglePost(reaction.PostId)
+	if err != nil {
+		return nil, err
+	}
+
+	if result := <-Srv.Store.Reaction().Save(reaction); result.Err != nil {
+		return nil, result.Err
+	} else {
+		reaction = result.Data.(*model.Reaction)
+
+		go sendReactionEvent(model.WEBSOCKET_EVENT_REACTION_ADDED, reaction, post)
+
+		InvalidateCacheForReactions(reaction.PostId)
+
+		return reaction, nil
+	}
+}
+
 func GetReactionsForPost(postId string) ([]*model.Reaction, *model.AppError) {
 	if result := <-Srv.Store.Reaction().GetForPost(postId, true); result.Err != nil {
 		return nil, result.Err
@@ -14,3 +33,18 @@ func GetReactionsForPost(postId string) ([]*model.Reaction, *model.AppError) {
 		return result.Data.([]*model.Reaction), nil
 	}
 }
+
+func sendReactionEvent(event string, reaction *model.Reaction, post *model.Post) {
+	// send out that a reaction has been added/removed
+	message := model.NewWebSocketEvent(event, "", post.ChannelId, "", nil)
+	message.Add("reaction", reaction.ToJson())
+	Publish(message)
+
+	// The post is always modified since the UpdateAt always changes
+	InvalidateCacheForChannelPosts(post.ChannelId)
+	post.HasReactions = true
+	post.UpdateAt = model.GetMillis()
+	umessage := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POST_EDITED, "", post.ChannelId, "", nil)
+	umessage.Add("post", post.ToJson())
+	Publish(umessage)
+}