// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package collection

import (
	"encoding/binary"
	"encoding/hex"
)

// UUIDHashCode is a hash function for hashing string uuid
// if the uuid is malformed, then the hash function always
// returns 0 as the hash value
func UUIDHashCode(input interface{}) uint32 {
	key, ok := input.(string)
	if !ok {
		return 0
	}
	if len(key) != UUIDStringLength {
		return 0
	}
	// Use the first 4 bytes of the uuid as the hash
	b, err := hex.DecodeString(key[:8])
	if err != nil {
		return 0
	}
	return binary.BigEndian.Uint32(b)
}
