package auth

import (
	"errors"
	"regexp"
	"unicode/utf8"

	"golang.org/x/crypto/bcrypt"
)

var (
	ErrPasswordTooShort = errors.New("password must be at least 8 characters")
	ErrInvalidEmail     = errors.New("invalid email")
	ErrInvalidUsername  = errors.New("username must be 3-64 characters: letters, digits, underscore")
)

var (
	emailRegex    = regexp.MustCompile(`^[^\s@]+@[^\s@]+\.[^\s@]+$`)
	usernameRegex = regexp.MustCompile(`^[a-zA-Z0-9_]{3,64}$`)
)

func HashPassword(password string) (string, error) {
	if utf8.RuneCountInString(password) < 8 {
		return "", ErrPasswordTooShort
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return "", err
	}
	return string(hash), nil
}

func ValidateEmail(email string) error {
	if !emailRegex.MatchString(email) {
		return ErrInvalidEmail
	}
	return nil
}

func ValidateUsername(username string) error {
	if !usernameRegex.MatchString(username) {
		return ErrInvalidUsername
	}
	return nil
}