package common

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

type CustomError struct {
	Message string
}

func (e *CustomError) Error() string {
	return e.Message
}

// RandomString generates a string with the given length using crypt/rand
func RandomString(length int) (string, error) {
	if length < 0 {
		err := &CustomError{Message: "Length has to be bigger than 0"}
		return "", err
	}
	if length > math.MaxInt32 {
		err := &CustomError{Message: fmt.Sprintf("Length has to be bigger than %d", math.MaxInt32)}
		return "", err
	}
	const characters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"
	byteSlice := make([]byte, length)
	for i := 0; i < length; i++ {
		randomInt, err := rand.Int(rand.Reader, big.NewInt(int64(len(characters))))
		if err != nil {
			return "", err
		}
		byteSlice[i] = characters[randomInt.Int64()]
	}
	return string(byteSlice), nil
}