QrRapido/Middleware/LanguageRedirectionMiddleware.cs

using System.Globalization;
using System.Linq;

namespace QRRapidoApp.Middleware
{
    /// <summary>
    /// Middleware de redirecionamento de idioma otimizado para SEO.
    ///
    /// Comportamento:
    /// - "/" → Retorna 200 OK em Português (canonical)
    /// - "/pt-BR" ou "/pt-BR/*" → Redireciona 301 para "/" ou "/*" (sem prefixo)
    /// - "/es-PY" ou "/es-PY/*" → Retorna 200 OK em Espanhol (mantém URL)
    /// - "/pix", "/wifi", etc. → Retorna 200 OK em Português (sem redirect)
    /// </summary>
    public class LanguageRedirectionMiddleware
    {
        private readonly RequestDelegate _next;
        private readonly ILogger<LanguageRedirectionMiddleware> _logger;
        private readonly string[] _supportedCultures = { "pt-BR", "es-PY" };
        private const string DefaultCulture = "pt-BR";
        private const string CookieName = ".AspNetCore.Culture";

        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 special routes (static files, API, auth callbacks, etc.)
            if (IsSpecialRoute(path))
            {
                await _next(context);
                return;
            }

            var segments = path.Split('/', StringSplitOptions.RemoveEmptyEntries);
            var firstSegment = segments.Length > 0 ? segments[0] : "";

            // Check if URL starts with a culture prefix
            if (IsCultureSegment(firstSegment))
            {
                // /pt-BR/* → Redirect 301 to /* (remove pt-BR prefix, it's the default)
                if (string.Equals(firstSegment, "pt-BR", StringComparison.OrdinalIgnoreCase))
                {
                    var remainingPath = segments.Length > 1
                        ? "/" + string.Join('/', segments.Skip(1))
                        : "/";

                    if (context.Request.QueryString.HasValue)
                    {
                        remainingPath += context.Request.QueryString.Value;
                    }

                    _logger.LogInformation("Redirecting /pt-BR{Path} to {RedirectUrl} (canonical)",
                        remainingPath == "/" ? "" : remainingPath, remainingPath);

                    context.Response.Redirect(remainingPath, permanent: true);
                    return;
                }

                // /es-PY/* → Continue normally (Spanish has its own URLs)
                if (string.Equals(firstSegment, "es-PY", StringComparison.OrdinalIgnoreCase))
                {
                    // Set culture for the request
                    SetCulture(context, "es-PY");
                    await _next(context);
                    return;
                }

                // Handle lowercase aliases: /pt-br → /pt-BR, /es-py → /es-PY
                if (TryHandleCultureAlias(context, firstSegment, segments))
                {
                    return;
                }
            }

            // No culture prefix → Serve in Portuguese (default)
            // URLs like /, /pix, /wifi, /vcard etc.
            SetCulture(context, DefaultCulture);
            await _next(context);
        }

        private bool IsCultureSegment(string segment)
        {
            if (string.IsNullOrEmpty(segment)) return false;

            // Check exact matches and aliases
            return string.Equals(segment, "pt-BR", StringComparison.OrdinalIgnoreCase) ||
                   string.Equals(segment, "es-PY", StringComparison.OrdinalIgnoreCase) ||
                   string.Equals(segment, "pt", StringComparison.OrdinalIgnoreCase) ||
                   string.Equals(segment, "es", StringComparison.OrdinalIgnoreCase);
        }

        private bool TryHandleCultureAlias(HttpContext context, string firstSegment, string[] segments)
        {
            string? targetCulture = null;
            string? targetPrefix = null;

            // Map aliases to canonical forms
            if (string.Equals(firstSegment, "pt", StringComparison.OrdinalIgnoreCase) ||
                (string.Equals(firstSegment, "pt-br", StringComparison.Ordinal) && firstSegment != "pt-BR"))
            {
                // /pt/* or /pt-br/* → Redirect to /* (Portuguese is canonical without prefix)
                targetCulture = "pt-BR";
                targetPrefix = ""; // No prefix for Portuguese
            }
            else if (string.Equals(firstSegment, "es", StringComparison.OrdinalIgnoreCase) ||
                     (string.Equals(firstSegment, "es-py", StringComparison.OrdinalIgnoreCase) && firstSegment != "es-PY"))
            {
                // /es/* or /es-py/* → Redirect to /es-PY/*
                targetCulture = "es-PY";
                targetPrefix = "/es-PY";
            }

            if (targetCulture != null)
            {
                var remainingPath = segments.Length > 1
                    ? "/" + string.Join('/', segments.Skip(1))
                    : "";

                var redirectUrl = targetPrefix + remainingPath;
                if (string.IsNullOrEmpty(redirectUrl)) redirectUrl = "/";

                if (context.Request.QueryString.HasValue)
                {
                    redirectUrl += context.Request.QueryString.Value;
                }

                _logger.LogInformation("Redirecting alias '{Alias}' to canonical URL: {RedirectUrl}",
                    firstSegment, redirectUrl);

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

            return false;
        }

        private void SetCulture(HttpContext context, string culture)
        {
            var cultureInfo = new CultureInfo(culture);
            CultureInfo.CurrentCulture = cultureInfo;
            CultureInfo.CurrentUICulture = cultureInfo;

            // Store in HttpContext for downstream use
            context.Items["Culture"] = culture;
        }

        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", "Pagamento/CreateCheckout",
                "Pagamento/StripeWebhook", "api/QR", "Home/Error", "ads.txt"
            };

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