using Microsoft.Extensions.Logging.Abstractions;
using Opc.Ua.Server;
using Shouldly;
using Xunit;

namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;

/// <summary>
/// Verifies the F13a cert auto-creation slice of <see cref="OpcUaApplicationHost"/>: the SDK
/// self-signs a certificate into <c>{PkiStoreRoot}/own/certs/</c> on first boot against a
/// fresh PKI tree, and the file persists for reuse on the next boot.
/// </summary>
public sealed class OpcUaApplicationHostTests : IDisposable
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    private readonly string _pkiRoot = Path.Combine(
        Path.GetTempPath(),
        $"otopcua-pki-{Guid.NewGuid():N}");

    /// <summary>Verifies StartAsync creates a self-signed certificate in the PKI own store.</summary>
    [Fact]
    public async Task StartAsync_creates_application_certificate_in_pki_own()
    {
        await using var host = new OpcUaApplicationHost(
            new OpcUaApplicationHostOptions
            {
                ApplicationName = "OtOpcUa.Test",
                ApplicationUri = $"urn:OtOpcUa.Test:{Guid.NewGuid():N}",
                OpcUaPort = AllocateFreePort(),
                PublicHostname = "localhost",
                PkiStoreRoot = _pkiRoot,
            },
            NullLogger<OpcUaApplicationHost>.Instance);

        await host.StartAsync(new StandardServer(), Ct);

        var ownCerts = Path.Combine(_pkiRoot, "own", "certs");
        Directory.Exists(ownCerts).ShouldBeTrue($"expected SDK to create {ownCerts}");
        Directory.EnumerateFiles(ownCerts).ShouldNotBeEmpty("expected a self-signed cert file in the own store");
    }

    /// <summary>Verifies StartAsync reuses an existing certificate on the second boot.</summary>
    [Fact]
    public async Task StartAsync_reuses_existing_certificate_on_second_boot()
    {
        var port1 = AllocateFreePort();
        await using (var first = new OpcUaApplicationHost(
            new OpcUaApplicationHostOptions
            {
                ApplicationName = "OtOpcUa.Reuse",
                ApplicationUri = "urn:OtOpcUa.Reuse",
                OpcUaPort = port1,
                PublicHostname = "localhost",
                PkiStoreRoot = _pkiRoot,
            },
            NullLogger<OpcUaApplicationHost>.Instance))
        {
            await first.StartAsync(new StandardServer(), Ct);
        }

        var ownCerts = Path.Combine(_pkiRoot, "own", "certs");
        var firstFiles = Directory.GetFiles(ownCerts).OrderBy(f => f).ToArray();
        firstFiles.ShouldNotBeEmpty();

        var port2 = AllocateFreePort();
        await using (var second = new OpcUaApplicationHost(
            new OpcUaApplicationHostOptions
            {
                ApplicationName = "OtOpcUa.Reuse",
                ApplicationUri = "urn:OtOpcUa.Reuse",
                OpcUaPort = port2,
                PublicHostname = "localhost",
                PkiStoreRoot = _pkiRoot,
            },
            NullLogger<OpcUaApplicationHost>.Instance))
        {
            await second.StartAsync(new StandardServer(), Ct);
        }

        var secondFiles = Directory.GetFiles(ownCerts).OrderBy(f => f).ToArray();
        secondFiles.ShouldBe(firstFiles, "expected the second boot to reuse the cert from the first, not create a new one");
    }

    private static int AllocateFreePort()
    {
        using var listener = new System.Net.Sockets.TcpListener(System.Net.IPAddress.Loopback, 0);
        listener.Start();
        var port = ((System.Net.IPEndPoint)listener.LocalEndpoint).Port;
        listener.Stop();
        return port;
    }

    /// <summary>Cleans up the temporary PKI directory.</summary>
    public void Dispose()
    {
        if (Directory.Exists(_pkiRoot))
        {
            try { Directory.Delete(_pkiRoot, recursive: true); }
            catch { /* best-effort cleanup */ }
        }
    }
}
