package utils

import (
	crand "crypto/rand"
	"fmt"
	"math/big"
	"math/rand"
	"time"
)

func RandString(l int, c ...string) string {
	var (
		chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
		str   string
		num   *big.Int
	)
	if len(c) > 0 {
		chars = c[0]
	}
	chrLen := int64(len(chars))
	for len(str) < l {
		num, _ = crand.Int(crand.Reader, big.NewInt(chrLen))
		str += string(chars[num.Int64()])
	}
	return str
}

func RandNum() string {
	seed := time.Now().UnixNano() + rand.Int63()
	return fmt.Sprintf("%05v", rand.New(rand.NewSource(seed)).Int31n(1000000))
}

//x的y次方
func RandPow(l int) string {
	var i = "1"
	for j := 0; j < l; j++ {
		i += "0"
	}
	k := StrToInt64(i)
	n := rand.New(rand.NewSource(time.Now().UnixNano())).Int63n(k)
	ls := "%0" + IntToStr(l) + "v"
	str := fmt.Sprintf(ls, n)
	//min := int(math.Pow10(l - 1))
	//max := int(math.Pow10(l) - 1)
	return str
}