package utils

import (
	"fmt"
	"github.com/w3liu/go-common/constant/timeformat"
	"math/rand"
	"os"
	"sync/atomic"
	"time"
)

var num int64

func PrefixGenerate(prefix string) string {
	return prefix + Generate(time.Now())
}

// Generate 生成24位订单号
// 前面17位代表时间精确到毫秒，中间3位代表进程id，最后4位代表序号
func Generate(t time.Time) string {
	s := t.Format(timeformat.Continuity)
	m := t.UnixNano()/1e6 - t.UnixNano()/1e9*1e3
	ms := sup(m, 3)
	p := os.Getpid() % 1000
	ps := sup(int64(p), 3)
	i := atomic.AddInt64(&num, 1)
	r := i % 10000
	rs := sup(r, 4)
	n := fmt.Sprintf("%s%s%s%s", s, ms, ps, rs)
	return n
}

// 对长度不足n的数字前面补0
func sup(i int64, n int) string {
	m := fmt.Sprintf("%d", i)
	for len(m) < n {
		m = fmt.Sprintf("0%s", m)
	}
	return m
}

// RandomString
// size 随机码的位数
// kind 0:纯数字 1:小写字母 2:大写字母 3:数字、大小写字母
func RandomString(size int, kind int) string {
	iKind, kinds, bytes := kind, [][]int{{10, 48}, {26, 97}, {26, 65}}, make([]byte, size)
	isAll := kind > 2 || kind < 0
	rand.Seed(time.Now().UnixNano())
	for i := 0; i < size; i++ {
		if isAll { // random iKind
			iKind = rand.Intn(3)
		}
		scope, base := kinds[iKind][0], kinds[iKind][1]
		bytes[i] = uint8(base + rand.Intn(scope))
	}
	return string(bytes)
}