// Copyright 2025 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package txn

import (
	"context"

	"go.uber.org/zap"

	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
	"go.etcd.io/etcd/api/v3/mvccpb"
	"go.etcd.io/etcd/pkg/v3/traceutil"
	"go.etcd.io/etcd/server/v3/storage/mvcc"
)

func DeleteRange(ctx context.Context, lg *zap.Logger, kv mvcc.KV, dr *pb.DeleteRangeRequest) (resp *pb.DeleteRangeResponse, trace *traceutil.Trace, err error) {
	ctx, trace = traceutil.EnsureTrace(ctx, lg, "delete_range",
		traceutil.Field{Key: "key", Value: string(dr.Key)},
		traceutil.Field{Key: "range_end", Value: string(dr.RangeEnd)},
	)
	txnWrite := kv.Write(trace)
	defer txnWrite.End()
	resp, err = deleteRange(ctx, txnWrite, dr)
	return resp, trace, err
}

func deleteRange(ctx context.Context, txnWrite mvcc.TxnWrite, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
	resp := &pb.DeleteRangeResponse{}
	resp.Header = &pb.ResponseHeader{}
	end := mkGteRange(dr.RangeEnd)

	if dr.PrevKv {
		rr, err := txnWrite.Range(ctx, dr.Key, end, mvcc.RangeOptions{})
		if err != nil {
			return nil, err
		}
		if rr != nil {
			resp.PrevKvs = make([]*mvccpb.KeyValue, len(rr.KVs))
			for i := range rr.KVs {
				resp.PrevKvs[i] = &rr.KVs[i]
			}
		}
	}

	resp.Deleted, resp.Header.Revision = txnWrite.DeleteRange(dr.Key, end)
	return resp, nil
}

// mkGteRange determines if the range end is a >= range. This works around grpc
// sending empty byte strings as nil; >= is encoded in the range end as '\0'.
// If it is a GTE range, then []byte{} is returned to indicate the empty byte
// string (vs nil being no byte string).
func mkGteRange(rangeEnd []byte) []byte {
	if len(rangeEnd) == 1 && rangeEnd[0] == 0 {
		return []byte{}
	}
	return rangeEnd
}