package common

import (
	"crypto/rand"
	"fmt"
	"io"
	"os"
	"time"

	"github.com/golang/protobuf/ptypes/timestamp"
)

// GenerateBytesUUID 生成一个byte数组的UUID
func GenerateBytesUUID() []byte {
	uuid := make([]byte, 16)
	_, err := io.ReadFull(rand.Reader, uuid)
	if err != nil {
		panic(fmt.Sprintf("Error generating UUID: %s", err))
	}

	// variant bits; see section 4.1.1
	uuid[8] = uuid[8]&^0xc0 | 0x80

	// version 4 (pseudo-random); see section 4.1.3
	uuid[6] = uuid[6]&^0xf0 | 0x40

	return uuid
}

// GenerateUUID 生成一个string类型的生成UUID
func GenerateUUID() string {
	uuid := GenerateBytesUUID()
	return idBytesToStr(uuid)
}

// CreateUtcTimestamp 创建时间戳
func CreateUtcTimestamp() *timestamp.Timestamp {
	now := time.Now().UTC()
	secs := now.Unix()
	nanos := int32(now.UnixNano() - (secs * 1000000000))
	return &(timestamp.Timestamp{Seconds: secs, Nanos: nanos})
}

// idBytesToStr 将byte数组转为字符串
// 函数返回一个格式为 "xxxx-xx-xx-xx-xxxxxxxxxxxx" 的字符串，其中 "x" 表示一个十六进制数字
func idBytesToStr(id []byte) string {
	return fmt.Sprintf("%x-%x-%x-%x-%x", id[0:4], id[4:6], id[6:8], id[8:10], id[10:])
}

// ConcatenateBytes 连接byte数组
func ConcatenateBytes(data ...[]byte) []byte {
	finalLength := 0
	for _, slice := range data {
		finalLength += len(slice)
	}
	result := make([]byte, finalLength)
	last := 0
	for _, slice := range data {
		for i := range slice {
			result[i+last] = slice[i]
		}
		last += len(slice)
	}
	return result
}

// dirExists 判断一个路径是否存在
func dirExists(path string) bool {
	fi, err := os.Stat(path)
	if err != nil {
		return false
	}
	return fi.IsDir()
}