// raftTruncatedStateLocked returns metadata about the log that preceded the
// first current entry. This includes both entries that have been compacted away
// and the dummy entries that make up the starting point of an empty log.
// raftTruncatedStateLocked requires that the replica lock be held.
func (r *Replica) raftTruncatedStateLocked() (roachpb.RaftTruncatedState, error) {
	if r.mu.truncatedState != nil {
		return *r.mu.truncatedState, nil
	}
	ts := roachpb.RaftTruncatedState{}
	ok, err := engine.MVCCGetProto(r.store.Engine(), keys.RaftTruncatedStateKey(r.RangeID),
		roachpb.ZeroTimestamp, true, nil, &ts)
	if err != nil {
		return ts, err
	}
	if !ok {
		if r.isInitializedLocked() {
			// If we created this range, set the initial log index/term.
			ts.Index = raftInitialLogIndex
			ts.Term = raftInitialLogTerm
		} else {
			// This is a new range we are receiving from another node. Start
			// from zero so we will receive a snapshot.
			ts.Index = 0
			ts.Term = 0
		}
	}

	if ts.Index != 0 {
		r.mu.truncatedState = &ts
	}
	return ts, nil
}

func raftTruncatedState(eng engine.Engine, rangeID roachpb.RangeID, isInitialized bool) (roachpb.RaftTruncatedState, error) {
	ts := roachpb.RaftTruncatedState{}
	ok, err := engine.MVCCGetProto(context.Background(), eng, keys.RaftTruncatedStateKey(rangeID),
		roachpb.ZeroTimestamp, true, nil, &ts)
	if err != nil {
		return ts, err
	}
	if !ok {
		if isInitialized {
			// If we created this range, set the initial log index/term.
			ts.Index = raftInitialLogIndex
			ts.Term = raftInitialLogTerm
		} else {
			// This is a new range we are receiving from another node. Start
			// from zero so we will receive a snapshot.
			ts.Index = 0
			ts.Term = 0
		}
	}
	return ts, nil
}