Hackathon: Post Reminders (#20555)

This PR adds the post reminder backend work.

We add a new API endpoint via which a user can set a reminder for a post. An ephemeral message will be sent down the line to let the user know about the action. And then after the time is over, the system admin bot will send a DM message to the user about the reminder post.

api4/post.go

@@ -34,6 +34,8 @@ func (api *API) InitPost() {
 	api.BaseRoutes.Post.Handle("", api.APISessionRequired(updatePost)).Methods("PUT")
 	api.BaseRoutes.Post.Handle("/patch", api.APISessionRequired(patchPost)).Methods("PUT")
 	api.BaseRoutes.PostForUser.Handle("/set_unread", api.APISessionRequired(setPostUnread)).Methods("POST")
+	api.BaseRoutes.PostForUser.Handle("/reminder", api.APISessionRequired(setPostReminder)).Methods("POST")
+
 	api.BaseRoutes.Post.Handle("/pin", api.APISessionRequired(pinPost)).Methods("POST")
 	api.BaseRoutes.Post.Handle("/unpin", api.APISessionRequired(unpinPost)).Methods("POST")
 }
@@ -842,6 +844,36 @@ func setPostUnread(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func setPostReminder(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequirePostId().RequireUserId()
+	if c.Err != nil {
+		return
+	}
+
+	if c.AppContext.Session().UserId != c.Params.UserId && !c.App.SessionHasPermissionToUser(*c.AppContext.Session(), c.Params.UserId) {
+		c.SetPermissionError(model.PermissionEditOtherUsers)
+		return
+	}
+	if !c.App.SessionHasPermissionToChannelByPost(*c.AppContext.Session(), c.Params.PostId, model.PermissionReadChannel) {
+		c.SetPermissionError(model.PermissionReadChannel)
+		return
+	}
+
+	var reminder model.PostReminder
+	if jsonErr := json.NewDecoder(r.Body).Decode(&reminder); jsonErr != nil {
+		c.SetInvalidParam("target_time")
+		return
+	}
+
+	appErr := c.App.SetPostReminder(c.Params.PostId, c.Params.UserId, reminder.TargetTime)
+	if appErr != nil {
+		c.Err = appErr
+		return
+	}
+
+	ReturnStatusOK(w)
+}
+
 func saveIsPinnedPost(c *Context, w http.ResponseWriter, isPinned bool) {
 	c.RequirePostId()
 	if c.Err != nil {

api4/post_test.go

@@ -3164,3 +3164,63 @@ func TestGetPostStripActionIntegrations(t *testing.T) {
 	// integration must be omitted
 	require.Nil(t, action["integration"])
 }
+
+func TestPostReminder(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	client := th.Client
+	userWSClient, err := th.CreateWebSocketClient()
+	require.NoError(t, err)
+	defer userWSClient.Close()
+	userWSClient.Listen()
+
+	targetTime := time.Now().UTC().Unix()
+	resp, err := client.SetPostReminder(&model.PostReminder{
+		TargetTime: targetTime,
+		PostId:     th.BasicPost.Id,
+		UserId:     th.BasicUser.Id,
+	})
+	require.NoError(t, err)
+	CheckOKStatus(t, resp)
+
+	post, _, err := client.GetPost(th.BasicPost.Id, "")
+	require.NoError(t, err)
+
+	user, _, err := client.GetUser(post.UserId, "")
+	require.NoError(t, err)
+
+	var caught bool
+	func() {
+		for {
+			select {
+			case ev := <-userWSClient.EventChannel:
+				if ev.EventType() == model.WebsocketEventEphemeralMessage {
+					caught = true
+					data := ev.GetData()
+
+					post, ok := data["post"].(string)
+					require.True(t, ok)
+
+					var parsedPost model.Post
+					err := json.Unmarshal([]byte(post), &parsedPost)
+					require.NoError(t, err)
+
+					assert.Equal(t, model.PostTypeEphemeral, parsedPost.Type)
+					assert.Equal(t, th.BasicUser.Id, parsedPost.UserId)
+					assert.Equal(t, th.BasicPost.Id, parsedPost.RootId)
+
+					require.Equal(t, float64(targetTime), parsedPost.GetProp("target_time").(float64))
+					require.Equal(t, th.BasicPost.Id, parsedPost.GetProp("post_id").(string))
+					require.Equal(t, user.Username, parsedPost.GetProp("username").(string))
+					require.Equal(t, th.BasicTeam.Name, parsedPost.GetProp("team_name").(string))
+					return
+				}
+			case <-time.After(1 * time.Second):
+				return
+			}
+		}
+	}()
+
+	require.Truef(t, caught, "User should have received %s event", model.WebsocketEventEphemeralMessage)
+}