package domain

import (
	"fmt"
	"strings"
	"unicode/utf8"
)

// NormalizeSessionID applies the shared session identifier rule.
func NormalizeSessionID(raw string) (string, error) {
	normalized := strings.TrimSpace(raw)
	if normalized == "" {
		return "", nil
	}
	if length := utf8.RuneCountInString(normalized); length > SessionIDMaxLength {
		return "", fmt.Errorf("session_id length %d exceeds maximum %d", length, SessionIDMaxLength)
	}
	return normalized, nil
}