package util

import (
	"math/rand"
	"time"
	"unicode/utf8"
	"unsafe"
)

// StrLen utf8 string length
func StrLen(s string) int {
	return utf8.RuneCountInString(s)
}

// StrMax verify string's max lenth
func StrMax(s string, max int) bool {
	n := utf8.RuneCountInString(s)
	return n <= max
}

// StrMin verify string's min lenth
func StrMin(s string, min int) bool {
	n := utf8.RuneCountInString(s)
	return n >= min
}

// StrRange verify string's Range lenth
func StrRange(s string, min, max int) bool {
	n := utf8.RuneCountInString(s)
	if n <= max && n >= min {
		return true
	}
	return false
}

// Random 指定长度的随机字符串(字母或数字)
func Random(n int) string {
	str := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	bytes := []byte(str)
	result := []byte{}

	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	n1 := len(bytes)
	for i := 0; i < n; i++ {
		result = append(result, bytes[r.Intn(n1)])
	}
	return string(result)
}

// StringToBytes converts string to byte slice without a memory allocation.
func StringToBytes(s string) []byte {
	return *(*[]byte)(unsafe.Pointer(
		&struct {
			string
			Cap int
		}{s, len(s)},
	))
}

// BytesToString converts byte slice to string without a memory allocation.
func BytesToString(b []byte) string {
	return *(*string)(unsafe.Pointer(&b))
}