Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Loader;
using System.Threading.Tasks;
using FreneticUtilities.FreneticDataSyntax;
using FreneticUtilities.FreneticExtensions;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.StaticFiles;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace DenizenMetaWebsite
{
    public class Startup(IConfiguration configuration)
    {
        public IConfiguration Configuration { get; } = configuration;

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IHostApplicationLifetime lifetime)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error/Any");
            }
            MetaSiteCore.Init();
            FileExtensionContentTypeProvider provider = new();
            provider.Mappings[".fds"] = "text/plain";
            app.UseStaticFiles(new StaticFileOptions() { ContentTypeProvider = provider });
            app.Use(async (context, next) =>
            {
                string path = context.Request.Path.Value;
                if (path.CountCharacter('/') > 3)
                {
                    int thirdSlash = path.IndexOf('/', path.IndexOf('/', path.IndexOf('/') + 1) + 1) + 1;
                    context.Request.Path = path[..thirdSlash] + path[thirdSlash..].Replace("/", "%252f");
                }
                await next();
            });
            app.Use(async (context, next) =>
            {
                await next();
                if (context.Response.StatusCode == 404)
                {
                    string path = context.Request.Path.Value.ToLowerFast();
                    if (!path.StartsWith("/error/"))
                    {
                        context.Request.Path = "/Error/Error404";
                        await next();
                    }
                }
            });
            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Docs}/{action=Index}/{id?}");
            });
        }
    }
}