func (s *Service) Rewind(dt message.AbsoluteTick) error {
if dt > s.tick {
return errors.New(fmt.Sprintf("Cannot rewind by %d: negative tick", dt))
} else if dt < 0 {
return errors.New(fmt.Sprintf("Cannot rewind by %d: negative rewind", dt))
} else if dt == 0 {
return nil
}
target := s.tick - dt
// Browse deltas list backward (from newer to older)
for e := s.deltas.LastBefore(s.tick); e != nil; e = e.Prev() {
d := e.Value.(*Delta)
if d.tick <= target {
// Reached target, stop here
break
}
// Revert delta
if d.From != nil {
current := s.Get(d.EntityId)
if current != nil {
// The entity has been updated, revert update
diff := d.Diff
if diff == nil {
diff = message.NewFilledEntityDiff(true)
}
current.ApplyDiff(diff, d.From)
} else {
// The entity has been deleted, restore it
s.entities[d.EntityId] = d.From
}
} else {
// The entity has been created, delete it
delete(s.entities, d.EntityId)
}
if s.frontend != nil {
s.frontend.locker.Lock()
s.frontend.deltas.Insert(d.Inverse().(*Delta))
s.frontend.locker.Unlock()
}
}
s.tick = target
return nil
}
// Deep copy this entity.
func (e *Entity) Copy() *Entity {
copy := New()
copy.Id = e.Id
copy.ApplyDiff(message.NewFilledEntityDiff(true), e)
return copy
}