package domain

import (
	"errors"
	"strings"
	"unicode"
	"unicode/utf8"

	"golang.org/x/text/cases"
	"golang.org/x/text/unicode/norm"
)

const (
	MinimumPasswordRunes = 12
	MaximumPasswordBytes = 1024
	MaximumIdentityRunes = 128
)

var (
	ErrInvalidUsername    = errors.New("invalid username")
	ErrInvalidDisplayName = errors.New("invalid display name")
	ErrInvalidPassword    = errors.New("invalid password")
)

type OwnerIdentity struct {
	Username    string
	UsernameKey string
	DisplayName string
}

func NewOwnerIdentity(username, displayName string) (OwnerIdentity, error) {
	username, usernameKey, err := NormalizeUsername(username)
	if err != nil {
		return OwnerIdentity{}, err
	}
	displayName = norm.NFC.String(strings.TrimSpace(displayName))
	if !validIdentityText(displayName) {
		return OwnerIdentity{}, ErrInvalidDisplayName
	}
	return OwnerIdentity{
		Username:    username,
		UsernameKey: usernameKey,
		DisplayName: displayName,
	}, nil
}

func NormalizeUsername(username string) (string, string, error) {
	username = norm.NFC.String(strings.TrimSpace(username))
	if !validIdentityText(username) {
		return "", "", ErrInvalidUsername
	}
	return username, cases.Fold().String(username), nil
}

func ValidatePassword(password string) error {
	if !utf8.ValidString(password) || len(password) > MaximumPasswordBytes || utf8.RuneCountInString(password) < MinimumPasswordRunes {
		return ErrInvalidPassword
	}
	return nil
}

func validIdentityText(value string) bool {
	count := utf8.RuneCountInString(value)
	if count == 0 || count > MaximumIdentityRunes {
		return false
	}
	for _, character := range value {
		if unicode.IsControl(character) {
			return false
		}
	}
	return true
}