using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.AspNetCore.Hosting.Server.Features;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Logging;

namespace XWorld.Server.Gateway
{
    // 独立内网 CDN：Kestrel 静态文件服务，HTTP 根 = root（发布产物 client/ 目录）。
    // 仿 GameServerHost 的 Start/Stop 形态；缺失文件返回 404，无目录浏览。
    public sealed class StaticFileServer
    {
        private readonly string _root;
        private readonly int _port;
        private readonly bool _bindAll;
        private WebApplication _app;

        public string HttpBaseUrl { get; private set; } // 例如 http://127.0.0.1:15081

        public StaticFileServer(string root, int port = 15081, bool bindAllInterfaces = false)
        {
            if (string.IsNullOrWhiteSpace(root)) throw new ArgumentException("root 不能为空", nameof(root));
            _root = Path.GetFullPath(root);
            _port = port;
            _bindAll = bindAllInterfaces;
        }

        public async Task StartAsync()
        {
            Directory.CreateDirectory(_root); // 根目录不存在则建空目录（GET 全 404，而非启动崩溃）

            var builder = WebApplication.CreateBuilder();
            builder.Logging.ClearProviders();
            builder.WebHost.ConfigureKestrel(o =>
                o.Listen(_bindAll ? System.Net.IPAddress.Any : System.Net.IPAddress.Loopback, _port)); // 0 = 临时端口

            var app = builder.Build();

            var provider = new PhysicalFileProvider(_root);
            var opts = new StaticFileOptions
            {
                FileProvider = provider,
                ServeUnknownFileTypes = true, // .bytes/.unity3d/.sig 等无标准 MIME 也要发
                DefaultContentType = "application/octet-stream",
            };
            app.UseStaticFiles(opts); // 仅静态文件，不开目录浏览；未命中落到下面的 404

            await app.StartAsync();
            _app = app;

            string http = app.Services.GetRequiredService<IServer>()
                .Features.Get<IServerAddressesFeature>().Addresses.FirstOrDefault()
                ?? throw new InvalidOperationException("Kestrel 已启动但未注册任何监听地址");
            HttpBaseUrl = http;
        }

        public async Task StopAsync()
        {
            if (_app == null) return;
            await _app.StopAsync();
            await _app.DisposeAsync();
            _app = null;
        }
    }
}