QrRapido/Middleware/LanguageRedirectionMiddleware.cs

using System.Globalization;

namespace QRRapidoApp.Middleware
{
    public class LanguageRedirectionMiddleware
    {
        private readonly RequestDelegate _next;
        private readonly ILogger<LanguageRedirectionMiddleware> _logger;
        private readonly string[] _supportedCultures = { "pt-BR", "es", "en" };
        private const string DefaultCulture = "pt-BR";

        public LanguageRedirectionMiddleware(RequestDelegate next, ILogger<LanguageRedirectionMiddleware> logger)
        {
            _next = next;
            _logger = logger;
        }

        public async Task InvokeAsync(HttpContext context)
        {
            var path = context.Request.Path.Value?.TrimStart('/') ?? "";
            
            // Skip if already has culture in path, or if it's an API, static file, or special route
            if (HasCultureInPath(path) || IsSpecialRoute(path))
            {
                await _next(context);
                return;
            }

            // Detect browser language
            var detectedCulture = DetectBrowserLanguage(context);
            
            // Build redirect URL with culture
            var redirectUrl = $"/{detectedCulture}";
            if (!string.IsNullOrEmpty(path))
            {
                redirectUrl += $"/{path}";
            }
            
            // Add query string if present
            if (context.Request.QueryString.HasValue)
            {
                redirectUrl += context.Request.QueryString.Value;
            }

            _logger.LogInformation("Redirecting to localized URL: {RedirectUrl} (detected culture: {Culture})", 
                redirectUrl, detectedCulture);

            context.Response.Redirect(redirectUrl, permanent: false);
        }

        private bool HasCultureInPath(string path)
        {
            if (string.IsNullOrEmpty(path))
                return false;

            var segments = path.Split('/', StringSplitOptions.RemoveEmptyEntries);
            if (segments.Length == 0)
                return false;

            return _supportedCultures.Contains(segments[0]);
        }

        private bool IsSpecialRoute(string path)
        {
            var specialRoutes = new[]
            {
                "api/", "health", "_framework/", "lib/", "css/", "js/", "images/", 
                "favicon.ico", "robots.txt", "sitemap.xml",
                "signin-microsoft", "signin-google", "signout-callback-oidc",
                "Account/ExternalLoginCallback", "Account/Logout"
            };

            return specialRoutes.Any(route => path.StartsWith(route, StringComparison.OrdinalIgnoreCase));
        }

        private string DetectBrowserLanguage(HttpContext context)
        {
            var acceptLanguage = context.Request.GetTypedHeaders().AcceptLanguage;

            if (acceptLanguage != null && acceptLanguage.Any())
            {
                // Check for exact matches first
                foreach (var lang in acceptLanguage.OrderByDescending(x => x.Quality ?? 1.0))
                {
                    var langCode = lang.Value.Value;

                    // Special case: es-PY should redirect to pt-BR
                    if (string.Equals(langCode, "es-PY", StringComparison.OrdinalIgnoreCase))
                    {
                        return DefaultCulture;
                    }

                    // Check exact match
                    if (_supportedCultures.Contains(langCode))
                    {
                        return langCode;
                    }

                    // Check language part only (e.g., 'es' from 'es-AR')
                    var languagePart = langCode.Split('-')[0];
                    var matchingCulture = _supportedCultures.FirstOrDefault(c => c.StartsWith(languagePart + "-") || c == languagePart);
                    if (matchingCulture != null)
                    {
                        return matchingCulture;
                    }
                }
            }

            // Default fallback
            return DefaultCulture;
        }
    }
}