using System.Net;
using System.Net.Http;
using System.Net.Sockets;
using System.Reflection;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Server.Kestrel.Core;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Xunit;

namespace ZB.MOM.WW.ScadaBridge.Host.Tests;

/// <summary>
/// ScadaBridge#108 (F1): central re-binds its HTTP surface from ASPNETCORE_URLS. It used to keep only
/// the port, so <c>https://+:443</c> served plaintext. https must now get TLS from the configured node
/// certificate or refuse to boot; http must bind exactly as before.
/// </summary>
public sealed class CentralHttpsBindingTests : IDisposable
{
    private readonly string _dir = Directory.CreateTempSubdirectory("sb108").FullName;

    /// <summary>Removes the generated certificate files.</summary>
    public void Dispose() => Directory.Delete(_dir, recursive: true);

    private (string pfx, X509Certificate2 cert) MakePfx(string password)
    {
        using var rsa = RSA.Create(2048);
        var req = new CertificateRequest("CN=localhost", rsa, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
        var san = new SubjectAlternativeNameBuilder();
        san.AddDnsName("localhost");
        req.CertificateExtensions.Add(san.Build());
        using var ephemeral = req.CreateSelfSigned(DateTimeOffset.UtcNow.AddMinutes(-5), DateTimeOffset.UtcNow.AddDays(1));
        var bytes = ephemeral.Export(X509ContentType.Pfx, password);
        var path = Path.Combine(_dir, "node.pfx");
        File.WriteAllBytes(path, bytes);
        return (path, X509CertificateLoader.LoadPkcs12(bytes, password));
    }

    /// <summary>The scheme survives parsing.</summary>
    [Theory]
    [InlineData("http://+:5000", 5000, false)]
    [InlineData("https://+:443", 443, true)]
    [InlineData("HTTPS://*:8443", 8443, true)]
    [InlineData("https://localhost", 443, true)]
    public void Scheme_is_kept(string url, int port, bool https)
    {
        Assert.Equal(new HttpBindEndpoint(port, https), Assert.Single(Program.ParseHttpBindEndpoints(url)));
    }

    /// <summary>One port with two schemes is a config error.</summary>
    [Fact]
    public void Same_port_with_two_schemes_throws() =>
        Assert.Throws<InvalidOperationException>(() => Program.ParseHttpBindEndpoints("http://+:5000;https://+:5000"));

    /// <summary>https without a certificate refuses to boot (the F1 downgrade is closed).</summary>
    [Fact]
    public void Https_without_certificate_refuses_to_boot()
    {
        var eps = Program.ParseHttpBindEndpoints("https://+:443");
        var ex = Assert.Throws<InvalidOperationException>(() => CentralHttpBinding.LoadCertificateIfNeeded(eps, new NodeTlsOptions()));
        Assert.Contains("Refusing to boot", ex.Message);
    }

    /// <summary>Both a path and a thumbprint is ambiguous.</summary>
    [Fact]
    public void Path_and_thumbprint_together_throw()
    {
        var eps = Program.ParseHttpBindEndpoints("https://+:443");
        Assert.Throws<InvalidOperationException>(() => CentralHttpBinding.LoadCertificateIfNeeded(
            eps, new NodeTlsOptions { CertificatePath = "x.pfx", CertificateThumbprint = "ABCD" }));
    }

    /// <summary>http-only URLs ignore the certificate settings and load nothing.</summary>
    [Fact]
    public void Http_only_loads_no_certificate()
    {
        var eps = Program.ParseHttpBindEndpoints("http://+:5000");
        Assert.Null(CentralHttpBinding.LoadCertificateIfNeeded(eps, new NodeTlsOptions { CertificatePath = "missing.pfx" }));
    }

    private static List<(string endpoint, HttpProtocols protocols, bool tls)> Effective(Action<KestrelServerOptions> configure)
    {
        var options = new KestrelServerOptions
        {
            ApplicationServices = new ServiceCollection().AddLogging().BuildServiceProvider(),
        };
        configure(options);
        var prop = typeof(KestrelServerOptions).GetProperty("CodeBackedListenOptions", BindingFlags.Instance | BindingFlags.NonPublic)!;
        var isTls = typeof(ListenOptions).GetProperty("IsTls", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)!;
        return ((System.Collections.IEnumerable)prop.GetValue(options)!).Cast<ListenOptions>()
            .Select(l => (l.IPEndPoint!.ToString(), l.Protocols, (bool)isTls.GetValue(l)!)).ToList();
    }

    /// <summary>
    /// http URLs produce the same effective Kestrel endpoint configuration as the pre-#108 inline
    /// loop (ListenAnyIP + Http1AndHttp2, no TLS).
    /// </summary>
    [Fact]
    public void Http_endpoints_are_identical_to_the_legacy_binding()
    {
        const string urls = "http://+:5000;http://*:8085";
        var legacy = Effective(o =>
        {
            foreach (var port in Program.ParseHttpBindPorts(urls))
            {
                o.ListenAnyIP(port, l => l.Protocols = HttpProtocols.Http1AndHttp2);
            }
        });
        var current = Effective(o => CentralHttpBinding.BindHttpSurface(o, Program.ParseHttpBindEndpoints(urls), null));

        Assert.Equal(2, current.Count);
        Assert.Equal(legacy, current);
        Assert.All(current, c => Assert.False(c.tls));
    }

    private static int FreePort()
    {
        var l = new TcpListener(IPAddress.Loopback, 0);
        l.Start();
        var p = ((IPEndPoint)l.LocalEndpoint).Port;
        l.Stop();
        return p;
    }

    /// <summary>
    /// A real Kestrel listener bound through the production path (certificate loaded from a .pfx +
    /// password) serves TLS on the https port with HTTP/1.1 and h2 by ALPN, and a plaintext client
    /// cannot talk to it; the http port still serves plaintext.
    /// </summary>
    [Fact]
    public async Task Real_https_listener_serves_tls_and_http_stays_plaintext()
    {
        var (pfx, expected) = MakePfx("pw");
        int httpsPort = FreePort(), httpPort = FreePort();
        var eps = Program.ParseHttpBindEndpoints($"https://+:{httpsPort};http://+:{httpPort}");
        var loaded = CentralHttpBinding.LoadCertificateIfNeeded(eps, new NodeTlsOptions { CertificatePath = pfx, CertificatePassword = "pw" });
        Assert.Equal(expected.Thumbprint, loaded!.Thumbprint);

        using var host = await new HostBuilder()
            .ConfigureWebHost(web => web
                .UseKestrel(k => CentralHttpBinding.BindHttpSurface(k, eps, loaded))
                .Configure(app => app.Run(ctx => ctx.Response.WriteAsync($"{ctx.Request.Scheme}/{ctx.Request.Protocol}"))))
            .StartAsync();
        try
        {
            using var handler = new SocketsHttpHandler
            {
                SslOptions = { RemoteCertificateValidationCallback = (_, c, _, _) => c?.GetCertHashString() == expected.Thumbprint },
            };
            using var client = new HttpClient(handler);

            using var h2 = new HttpRequestMessage(HttpMethod.Get, $"https://localhost:{httpsPort}/") { Version = HttpVersion.Version20, VersionPolicy = HttpVersionPolicy.RequestVersionExact };
            Assert.Equal("https/HTTP/2", await (await client.SendAsync(h2)).Content.ReadAsStringAsync()); // ALPN h2

            using var h11 = new HttpRequestMessage(HttpMethod.Get, $"https://localhost:{httpsPort}/") { Version = HttpVersion.Version11, VersionPolicy = HttpVersionPolicy.RequestVersionExact };
            Assert.Equal("https/HTTP/1.1", await (await client.SendAsync(h11)).Content.ReadAsStringAsync());

            // Plaintext to the TLS port must fail (it is not silently plain HTTP any more).
            await Assert.ThrowsAnyAsync<HttpRequestException>(() => client.GetStringAsync($"http://localhost:{httpsPort}/"));

            Assert.Equal("http/HTTP/1.1", await client.GetStringAsync($"http://localhost:{httpPort}/"));
        }
        finally
        {
            await host.StopAsync();
        }
    }
}