package characterdata

import (
	"errors"
	"fmt"
	"unicode"
	"unicode/utf8"

	"golang.org/x/text/encoding/simplifiedchinese"
)

const (
	CharacterNameMinBytes = 2
	CharacterNameMaxBytes = 30
)

var ErrCharacterNameInvalid = errors.New("character name is invalid")

// ValidateCharacterName owns the durable-name safety boundary shared by
// create, duplicate-check, and rename. It keeps the current client's GB18030
// byte limits while rejecting invisible/control data and punctuation already
// unsafe in the current NoPack UI/protocol paths.
func ValidateCharacterName(name string) error {
	if name == "" || !utf8.ValidString(name) {
		return fmt.Errorf("%w: name must be non-empty valid UTF-8", ErrCharacterNameInvalid)
	}
	encoded, err := simplifiedchinese.GB18030.NewEncoder().Bytes([]byte(name))
	if err != nil {
		return fmt.Errorf("%w: encode GB18030: %v", ErrCharacterNameInvalid, err)
	}
	if len(encoded) < CharacterNameMinBytes || len(encoded) > CharacterNameMaxBytes {
		return fmt.Errorf("%w: encoded length %d is outside %d..%d",
			ErrCharacterNameInvalid, len(encoded), CharacterNameMinBytes, CharacterNameMaxBytes)
	}
	for _, value := range name {
		if unicode.IsSpace(value) || unicode.IsControl(value) ||
			unicode.Is(unicode.Cf, value) || !unicode.IsGraphic(value) {
			return fmt.Errorf("%w: name contains whitespace, control, or invisible data", ErrCharacterNameInvalid)
		}
		switch value {
		case '\'', '\\', '%', '<', '>', '"', '|':
			return fmt.Errorf("%w: name contains forbidden character %q", ErrCharacterNameInvalid, value)
		}
	}
	return nil
}