package utl

import (
	"math/rand"
	"time"
)

var (
	s = rand.NewSource(time.Now().UnixNano())
	r = rand.New(s)
)

func RandNumString(sz int) string {
	b := make([]byte, sz)
	for i := 0; i < sz; i++ {
		b[i] = byte(0x30 + r.Intn(10))
	}
	return string(b)
}

func RandAlphaStr(sz int) string {
	starts := []int{0x30, 0x41, 0x61}
	lens := []int{10, 26, 26}
	b := make([]byte, sz)
	for i := 0; i < sz; i++ {
		idx := r.Intn(len(starts))
		b[i] = byte(starts[idx] + r.Intn(lens[idx]))
	}
	return string(b)
}

func RandInt(m, n int) int {
	if m > n {
		return RandInt(n, m)
	}
	return r.Intn(n-m) + m
}

var RandIntn = r.Intn

func RandChoice(sarr []string) string {
	return sarr[r.Intn(len(sarr))]
}