/*
 * Copyright 2019 Dgraph Labs, Inc. and Contributors
 *
 * 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 z

import (
	"github.com/cespare/xxhash"
)

// TODO: Figure out a way to re-use memhash for the second uint64 hash, we
//       already know that appending bytes isn't reliable for generating a
//       second hash (see Ristretto PR #88).
//
//       We also know that while the Go runtime has a runtime memhash128
//       function, it's not possible to use it to generate [2]uint64 or
//       anything resembling a 128bit hash, even though that's exactly what
//       we need in this situation.
func KeyToHash(key interface{}) (uint64, uint64) {
	if key == nil {
		return 0, 0
	}
	switch k := key.(type) {
	case uint64:
		return k, 0
	case string:
		return MemHashString(k), xxhash.Sum64String(k)
	case []byte:
		return MemHash(k), xxhash.Sum64(k)
	case byte:
		return uint64(k), 0
	case int:
		return uint64(k), 0
	case int32:
		return uint64(k), 0
	case uint32:
		return uint64(k), 0
	case int64:
		return uint64(k), 0
	default:
		panic("Key type not supported")
	}
}