// 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
}

// InternalTruncateLog discards a prefix of the raft log.
func (r *Range) InternalTruncateLog(batch engine.Engine, ms *engine.MVCCStats, args *proto.InternalTruncateLogRequest, reply *proto.InternalTruncateLogResponse) {
	// args.Index is the first index to keep.
	term, err := r.Term(args.Index - 1)
	if err != nil {
		reply.SetGoError(err)
		return
	}
	start := keys.RaftLogKey(r.Desc().RaftID, 0)
	end := keys.RaftLogKey(r.Desc().RaftID, args.Index)
	err = batch.Iterate(engine.MVCCEncodeKey(start), engine.MVCCEncodeKey(end),
		func(kv proto.RawKeyValue) (bool, error) {
			err := batch.Clear(kv.Key)
			return false, err
		})
	if err != nil {
		reply.SetGoError(err)
		return
	}
	ts := proto.RaftTruncatedState{
		Index: args.Index - 1,
		Term:  term,
	}
	err = engine.MVCCPutProto(batch, ms, keys.RaftTruncatedStateKey(r.Desc().RaftID),
		proto.ZeroTimestamp, nil, &ts)
	reply.SetGoError(err)
}

// raftTruncatedState 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.
func (r *Replica) raftTruncatedState() (proto.RaftTruncatedState, error) {
	if ts := r.getCachedTruncatedState(); ts != nil {
		return *ts, nil
	}
	ts := proto.RaftTruncatedState{}
	ok, err := engine.MVCCGetProto(r.rm.Engine(), keys.RaftTruncatedStateKey(r.Desc().RangeID),
		proto.ZeroTimestamp, true, nil, &ts)
	if err != nil {
		return ts, err
	}
	if !ok {
		if r.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
		}
	}

	if ts.Index != 0 {
		r.setCachedTruncatedState(&ts)
	}
	return ts, nil
}

func raftTruncatedState(
	eng engine.Reader, rangeID roachpb.RangeID,
) (roachpb.RaftTruncatedState, error) {
	ts := roachpb.RaftTruncatedState{}
	_, err := engine.MVCCGetProto(context.Background(), eng, keys.RaftTruncatedStateKey(rangeID),
		hlc.ZeroTimestamp, true, nil, &ts)
	return ts /* zero if not found */, err
}

func setTruncatedState(
	eng engine.ReadWriter,
	ms *enginepb.MVCCStats,
	rangeID roachpb.RangeID,
	truncState roachpb.RaftTruncatedState,
) error {
	return engine.MVCCPutProto(context.Background(), eng, ms,
		keys.RaftTruncatedStateKey(rangeID), hlc.ZeroTimestamp, nil, &truncState)
}

func loadTruncatedState(
	ctx context.Context, reader engine.Reader, rangeID roachpb.RangeID,
) (roachpb.RaftTruncatedState, error) {
	var truncState roachpb.RaftTruncatedState
	if _, err := engine.MVCCGetProto(ctx, reader,
		keys.RaftTruncatedStateKey(rangeID), hlc.ZeroTimestamp, true,
		nil, &truncState); err != nil {
		return roachpb.RaftTruncatedState{}, err
	}
	return truncState, nil
}

// createRangeData creates sample range data in all possible areas of
// the key space. Returns a slice of the encoded keys of all created
// data.
func createRangeData(t *testing.T, r *Replica) []engine.MVCCKey {
	ts0 := hlc.ZeroTimestamp
	ts := hlc.Timestamp{WallTime: 1}
	desc := r.Desc()
	keyTSs := []struct {
		key roachpb.Key
		ts  hlc.Timestamp
	}{
		{keys.AbortCacheKey(r.RangeID, testTxnID), ts0},
		{keys.AbortCacheKey(r.RangeID, testTxnID2), ts0},
		{keys.RangeFrozenStatusKey(r.RangeID), ts0},
		{keys.RangeLastGCKey(r.RangeID), ts0},
		{keys.RaftAppliedIndexKey(r.RangeID), ts0},
		{keys.RaftTruncatedStateKey(r.RangeID), ts0},
		{keys.LeaseAppliedIndexKey(r.RangeID), ts0},
		{keys.RangeStatsKey(r.RangeID), ts0},
		{keys.RaftHardStateKey(r.RangeID), ts0},
		{keys.RaftLastIndexKey(r.RangeID), ts0},
		{keys.RaftLogKey(r.RangeID, 1), ts0},
		{keys.RaftLogKey(r.RangeID, 2), ts0},
		{keys.RangeLastReplicaGCTimestampKey(r.RangeID), ts0},
		{keys.RangeLastVerificationTimestampKey(r.RangeID), ts0},
		{keys.RangeDescriptorKey(desc.StartKey), ts},
		{keys.TransactionKey(roachpb.Key(desc.StartKey), uuid.NewV4()), ts0},
		{keys.TransactionKey(roachpb.Key(desc.StartKey.Next()), uuid.NewV4()), ts0},
		{keys.TransactionKey(fakePrevKey(desc.EndKey), uuid.NewV4()), ts0},
		// TODO(bdarnell): KeyMin.Next() results in a key in the reserved system-local space.
		// Once we have resolved https://github.com/cockroachdb/cockroach/issues/437,
		// replace this with something that reliably generates the first valid key in the range.
		//{r.Desc().StartKey.Next(), ts},
		// The following line is similar to StartKey.Next() but adds more to the key to
		// avoid falling into the system-local space.
		{append(append([]byte{}, desc.StartKey...), '\x02'), ts},
		{fakePrevKey(r.Desc().EndKey), ts},
	}

	keys := []engine.MVCCKey{}
	for _, keyTS := range keyTSs {
		if err := engine.MVCCPut(context.Background(), r.store.Engine(), nil, keyTS.key, keyTS.ts, roachpb.MakeValueFromString("value"), nil); err != nil {
			t.Fatal(err)
		}
		keys = append(keys, engine.MVCCKey{Key: keyTS.key, Timestamp: keyTS.ts})
	}
	return keys
}

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
}