[GH-6798] added a new api endpoint to get the bulk reactions for posts (#10049)

* 6798 added a new api to get the bulk reactions for posts

* 6798 added the permsission check before getting the reactions

* GH-6798 added a new app function for the new endpoint

* 6798 added a store method to get reactions for multiple posts

* 6798 connected the app function with the new store function

* 6798 fixed the review comments

api4/reaction.go

@@ -13,6 +13,7 @@ func (api *API) InitReaction() {
 	api.BaseRoutes.Reactions.Handle("", api.ApiSessionRequired(saveReaction)).Methods("POST")
 	api.BaseRoutes.Post.Handle("/reactions", api.ApiSessionRequired(getReactions)).Methods("GET")
 	api.BaseRoutes.ReactionByNameForPostForUser.Handle("", api.ApiSessionRequired(deleteReaction)).Methods("DELETE")
+	api.BaseRoutes.Posts.Handle("/ids/reactions", api.ApiSessionRequired(getBulkReactions)).Methods("POST")
 }
 
 func saveReaction(c *Context, w http.ResponseWriter, r *http.Request) {
@@ -106,3 +107,20 @@ func deleteReaction(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	ReturnStatusOK(w)
 }
+
+func getBulkReactions(c *Context, w http.ResponseWriter, r *http.Request) {
+	postIds := model.ArrayFromJson(r.Body)
+	for _, postId := range postIds {
+		if !c.App.SessionHasPermissionToChannelByPost(c.App.Session, postId, model.PERMISSION_READ_CHANNEL) {
+			c.SetPermissionError(model.PERMISSION_READ_CHANNEL)
+			return
+		}
+	}
+	reactions, err := c.App.GetBulkReactionsForPosts(postIds)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	w.Write([]byte(model.MapPostIdToReactionsToJson(reactions)))
+}