[MM-8497] Ability to set Do Not Disturb for a specified period of time (#17680)

* Revert "Revert "[MM-8497] Ability to set Do Not Disturb for a specified period of time (#16067)" (#17657)"

This reverts commit ff383990f8.

* add debug log for recurring function

* add feature flag for dnd timed status

* refactoring changes

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/server.go

@@ -209,6 +209,9 @@ type Server struct {
 
 	imgDecoder *imaging.Decoder
 	imgEncoder *imaging.Encoder
+
+	dndTaskMut sync.Mutex
+	dndTask    *model.ScheduledTask
 }
 
 func NewServer(options ...Option) (*Server, error) {
@@ -673,6 +676,7 @@ func NewServer(options ...Option) (*Server, error) {
 			s.runLicenseExpirationCheckJob()
 			runCheckAdminSupportStatusJob(app, c)
 			runCheckWarnMetricStatusJob(app, c)
+			runDNDStatusExpireJob(app)
 		})
 		s.runJobs()
 	}
@@ -689,6 +693,14 @@ func NewServer(options ...Option) (*Server, error) {
 			s.ShutDownPlugins()
 		}
 	})
+	s.AddConfigListener(func(oldCfg, newCfg *model.Config) {
+		if !oldCfg.FeatureFlags.TimedDND && newCfg.FeatureFlags.TimedDND {
+			runDNDStatusExpireJob(app)
+		}
+		if oldCfg.FeatureFlags.TimedDND && !newCfg.FeatureFlags.TimedDND {
+			stopDNDStatusExpireJob(app)
+		}
+	})
 
 	return s, nil
 }
@@ -1051,6 +1063,12 @@ func (s *Server) Shutdown() {
 		mlog.Warn("Error flushing logs", mlog.Err(err))
 	}
 
+	s.dndTaskMut.Lock()
+	if s.dndTask != nil {
+		s.dndTask.Cancel()
+	}
+	s.dndTaskMut.Unlock()
+
 	mlog.Info("Server stopped")
 
 	// this should just write the "server stopped" record, the rest are already flushed.
@@ -2284,3 +2302,41 @@ func (s *Server) ReadFile(path string) ([]byte, *model.AppError) {
 // 	}
 // 	return result, nil
 // }
+
+func createDNDStatusExpirationRecurringTask(a *App) {
+	a.srv.dndTaskMut.Lock()
+	a.srv.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, 5*time.Minute)
+	a.srv.dndTaskMut.Unlock()
+}
+
+func cancelDNDStatusExpirationRecurringTask(a *App) {
+	a.srv.dndTaskMut.Lock()
+	if a.srv.dndTask != nil {
+		a.srv.dndTask.Cancel()
+		a.srv.dndTask = nil
+	}
+	a.srv.dndTaskMut.Unlock()
+}
+
+func runDNDStatusExpireJob(a *App) {
+	if !a.Config().FeatureFlags.TimedDND {
+		return
+	}
+	if a.IsLeader() {
+		createDNDStatusExpirationRecurringTask(a)
+	}
+	a.srv.AddClusterLeaderChangedListener(func() {
+		mlog.Info("Cluster leader changed. Determining if unset DNS status task should be running", mlog.Bool("isLeader", a.IsLeader()))
+		if a.IsLeader() {
+			createDNDStatusExpirationRecurringTask(a)
+		} else {
+			cancelDNDStatusExpirationRecurringTask(a)
+		}
+	})
+}
+
+func stopDNDStatusExpireJob(a *App) {
+	if a.IsLeader() {
+		cancelDNDStatusExpirationRecurringTask(a)
+	}
+}