allow engine copy to perform safe state mutations

server/mscalendar/availability.go

@@ -117,14 +117,14 @@ func (m *mscalendar) retrieveUsersToSync(userIndex store.UserIndex, syncJobSumma
 		users = append(users, user)
 
 		if fetchIndividually {
-			err = m.Filter(withActingUser(user.MattermostUserID))
+			engine, err := m.FilterCopy(withActingUser(user.MattermostUserID))
 			if err != nil {
 				m.Logger.Warnf("Not able to enable active user %s from user index. err=%v", user.MattermostUserID, err)
 				continue
 			}
 
 			calendarUser := newUserFromStoredUser(user)
-			calendarEvents, err := m.GetCalendarEvents(calendarUser, start, end)
+			calendarEvents, err := engine.GetCalendarEvents(calendarUser, start, end)
 			if err != nil {
 				syncJobSummary.NumberOfUsersFailedStatusChanged++
 				m.Logger.With(bot.LogContext{

server/mscalendar/daily_summary.go

@@ -145,17 +145,21 @@ func (m *mscalendar) ProcessAllDailySummary(now time.Time) error {
 				continue
 			}
 
-			m.Filter(withActingUser(storeUser.MattermostUserID))
+			engine, err := m.FilterCopy(withActingUser(storeUser.MattermostUserID))
+			if err != nil {
+				m.Logger.Errorf("Error creating user engine %s. err=%v", storeUser.MattermostUserID, err)
+				continue
+			}
 
-			tz, err := m.GetTimezone(u)
+			tz, err := engine.GetTimezone(u)
 			if err != nil {
-				m.Logger.Errorf("Error posting daily summary for user %s. err=%v", storeUser.MattermostUserID, shouldPostErr)
+				m.Logger.Errorf("Error posting daily summary for user %s. err=%v", storeUser.MattermostUserID, err)
 				continue
 			}
 
-			events, err := m.getTodayCalendarEvents(u, now, tz)
+			events, err := engine.getTodayCalendarEvents(u, now, tz)
 			if err != nil {
-				m.Logger.Errorf("Error posting daily summary for user %s. err=%v", storeUser.MattermostUserID, shouldPostErr)
+				m.Logger.Errorf("Error posting daily summary for user %s. err=%v", storeUser.MattermostUserID, err)
 				continue
 			}
 

server/mscalendar/filters.go

@@ -3,6 +3,8 @@
 
 package mscalendar
 
+import "github.com/pkg/errors"
+
 type filterf func(*mscalendar) error
 
 func (m *mscalendar) Filter(filters ...filterf) error {
@@ -15,6 +17,16 @@ func (m *mscalendar) Filter(filters ...filterf) error {
 	return nil
 }
 
+// FilterCopy creates a copy of the calendar engine and applies filters to it
+func (m *mscalendar) FilterCopy(filters ...filterf) (*mscalendar, error) {
+	engine := m.copy()
+	if err := engine.Filter(filters...); err != nil {
+		return nil, errors.Wrap(err, "error filtering engine copy")
+	}
+
+	return engine, nil
+}
+
 func withActingUserExpanded(m *mscalendar) error {
 	return m.ExpandUser(m.actingUser)
 }

server/mscalendar/mscalendar.go

@@ -60,6 +60,17 @@ type mscalendar struct {
 	client     remote.Client
 }
 
+// copy returns a copy of the calendar engine
+func (m mscalendar) copy() *mscalendar {
+	user := *m.actingUser
+	client := m.client
+	return &mscalendar{
+		Env:        m.Env,
+		actingUser: &user,
+		client:     client,
+	}
+}
+
 func New(env Env, actingMattermostUserID string) MSCalendar {
 	return &mscalendar{
 		Env:        env,

server/mscalendar/mscalendar_test.go

@@ -0,0 +1,23 @@
+package mscalendar
+
+import (
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCopy(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	user := newTestUserNumbered(1)
+	env, _ := makeStatusSyncTestEnv(ctrl)
+
+	engine := New(env, user.MattermostUserID)
+
+	engineCopy := engine.(*mscalendar).copy()
+
+	assert.NotSame(t, engine, engineCopy)
+	assert.NotSame(t, engine.(*mscalendar).actingUser, engineCopy.actingUser)
+	assert.NotSame(t, engine.(*mscalendar).client, engineCopy.client)
+}