package accessToken

import (
	"errors"
	"fmt"
	"regexp"
)

func Generate(prefix string, secret string) (string, error) {

	if len(prefix) != 3 {
		return "", errors.New("prefix is not 3 characters long")
	}

	randomString, err := randomBase62String(30)
	if err != nil {
		return "", err
	}

	firstPart := fmt.Sprintf("%s_%s", prefix, randomString)

	checksum, err := getChecksum(firstPart + secret)
	if err != nil {
		return "", err
	}

	return firstPart + checksum, nil
}

func Validate(token string, secret string) (bool, error) {

	exp := regexp.MustCompile("([abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ]{3})_([0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ]{30})([0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ]{6})")

	if !exp.Match([]byte(token)) {
		return false, errors.New("wrong token format")
	}

	checksum, err := getChecksum(token[:len(token)-6] + secret)
	if err != nil {
		return false, err
	}

	return token[len(token)-6:] == checksum, nil
}