/**
 * @Author: koulei
 * @Description:
 * @File: uuid
 * @Version: 1.0.0
 * @Date: 2021/9/17 17:53
 */

package gf

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
)

var Uuid = uuid{}

type uuid struct {
}

// New Simple call
func (u *uuid) New() string {
	uuid, _ := u.GenerateUUID()
	return uuid
}

// GenerateRandomBytes is used to generate random bytes of given size.
func (u *uuid) GenerateRandomBytes(size int) ([]byte, error) {
	buf := make([]byte, size)
	if _, err := rand.Read(buf); err != nil {
		return nil, fmt.Errorf("failed to read random bytes: %v", err)
	}
	return buf, nil
}

const uuidLen = 16

// GenerateUUID is used to generate a random UUID
func (u *uuid) GenerateUUID() (string, error) {
	buf, err := u.GenerateRandomBytes(uuidLen)
	if err != nil {
		return "", err
	}
	return u.FormatUUID(buf)
}

func (u *uuid) FormatUUID(buf []byte) (string, error) {
	if buffLength := len(buf); buffLength != uuidLen {
		return "", fmt.Errorf("wrong length byte slice (%d)", buffLength)
	}

	return fmt.Sprintf("%x-%x-%x-%x-%x",
		buf[0:4],
		buf[4:6],
		buf[6:8],
		buf[8:10],
		buf[10:16]), nil
}

func (u *uuid) ParseUUID(uuid string) ([]byte, error) {
	if len(uuid) != 2*uuidLen+4 {
		return nil, fmt.Errorf("uuid string is wrong length")
	}

	if uuid[8] != '-' ||
		uuid[13] != '-' ||
		uuid[18] != '-' ||
		uuid[23] != '-' {
		return nil, fmt.Errorf("uuid is improperly formatted")
	}

	hexStr := uuid[0:8] + uuid[9:13] + uuid[14:18] + uuid[19:23] + uuid[24:36]

	ret, err := hex.DecodeString(hexStr)
	if err != nil {
		return nil, err
	}
	if len(ret) != uuidLen {
		return nil, fmt.Errorf("decoded hex is the wrong length")
	}

	return ret, nil
}