package utils

import (
	"math"
	"math/rand"
	"strconv"
	"strings"
	"time"
)

var tenToAny = strings.Split("abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ", "")

//创建短的SN
func MakeShortSN(n int64) string {
	sn := decimalToAny(int(n), 62)
	rand.Seed(time.Now().Unix())
	return sn + tenToAny[rand.Intn(len(tenToAny))]
}

// 10进制转任意进制
func decimalToAny(num, n int) string {
	new_num_str := ""
	var remainder int
	var remainder_string string
	for num != 0 {
		remainder = num % n
		if 76 > remainder && remainder > 9 {
			remainder_string = tenToAny[remainder]
		} else {
			remainder_string = strconv.Itoa(remainder)
		}
		new_num_str = remainder_string + new_num_str
		num = num / n
	}
	return new_num_str
}

// map根据value找key
func findKey(in string) int {
	result := -1
	for k, v := range tenToAny {
		if in == v {
			result = k
		}
	}
	return result
}

// 任意进制转10进制
func anyToDecimal(num string, n int) int {
	var new_num float64
	new_num = 0.0
	nNum := len(strings.Split(num, "")) - 1
	for _, value := range strings.Split(num, "") {
		tmp := float64(findKey(value))
		if tmp != -1 {
			new_num = new_num + tmp*math.Pow(float64(n), float64(nNum))
			nNum = nNum - 1
		} else {
			break
		}
	}
	return int(new_num)
}