using System.Security.Cryptography.X509Certificates;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Management;
using ZB.MOM.WW.ScadaBridge.Commons.Types.DataConnections;
using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;

namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests.Adapters;

/// <summary>
/// Gitea #121: the real <see cref="RealOpcUaClient"/> against a real, strictly-trusting
/// in-process server. Before the fix every Sign / SignAndEncrypt session failed before
/// activation with <c>ApplicationCertificate … cannot be found</c> (BadConfigurationError)
/// because the client never configured an application certificate. These tests run the actual
/// adapter through both <see cref="RealOpcUaClient.ConnectAsync"/> and
/// <see cref="RealOpcUaClient.VerifyEndpointAsync"/>, with AutoAccept OFF on both sides.
/// </summary>
public sealed class RealOpcUaSecureConnectTests : IDisposable
{
    // Server_ServerStatus_State — present on every server, readable anonymously.
    private const string ServerStateNode = "i=2259";

    private readonly string _clientPki =
        Path.Combine(Path.GetTempPath(), "sb121-client", Guid.NewGuid().ToString("N"));

    /// <inheritdoc />
    public void Dispose()
    {
        try { Directory.Delete(_clientPki, recursive: true); } catch { /* best-effort */ }
    }

    private OpcUaGlobalOptions ClientOptions(string? applicationUri = null, bool autoCreate = true) => new()
    {
        ApplicationName = "SB121Client",
        ApplicationUri = applicationUri ?? "urn:localhost:SB121Client",
        OwnCertificateStorePath = Path.Combine(_clientPki, "own"),
        TrustedPeerStorePath = Path.Combine(_clientPki, "trusted"),
        TrustedIssuerStorePath = Path.Combine(_clientPki, "issuers"),
        RejectedCertificateStorePath = Path.Combine(_clientPki, "rejected"),
        AutoCreateApplicationCertificate = autoCreate,
    };

    private string OwnCertsDir => Path.Combine(_clientPki, "own", "certs");

    /// <summary>Trusts the server on the client side exactly as the site CertStoreActor does.</summary>
    private void ClientTrusts(X509Certificate2 server)
    {
        var dir = Path.Combine(_clientPki, "trusted", "certs");
        Directory.CreateDirectory(dir);
        File.WriteAllBytes(Path.Combine(dir, $"{server.Thumbprint}.der"), server.RawData);
    }

    private static OpcUaConnectionOptions Secured(string mode) => new(SecurityMode: mode, AutoAcceptUntrustedCerts: false);

    private static OpcUaEndpointConfig ProbeConfig(string url, OpcUaSecurityMode mode) => new()
    {
        EndpointUrl = url,
        SecurityMode = mode,
        AutoAcceptUntrustedCerts = false,
    };

    private async Task<X509Certificate2> ProvisionClientAsync(OpcUaGlobalOptions? options = null) =>
        await OpcUaApplicationIdentity.EnsureApplicationCertificateAsync(options ?? ClientOptions(), NullLogger.Instance);

    /// <summary>Mutual trust: connects, reads, reconnects and restarts on ONE persisted identity.</summary>
    [Theory]
    [InlineData("Sign")]
    [InlineData("SignAndEncrypt")]
    public async Task Connect_WithMutualTrust_ReadsAndReconnectsOnTheSameIdentity(string mode)
    {
        using var clientCert = await ProvisionClientAsync();
        await using var server = await SecureOpcUaTestServer.StartAsync(clientCert);
        ClientTrusts(server.Certificate);

        var client = new RealOpcUaClient(ClientOptions());
        await client.ConnectAsync(server.Url, Secured(mode));
        Assert.True(client.IsConnected);
        Assert.Equal(0u, (await client.ReadValueAsync(ServerStateNode)).StatusCode);

        // Reconnect on the same instance.
        await client.DisconnectAsync();
        Assert.False(client.IsConnected);
        await client.ConnectAsync(server.Url, Secured(mode));
        Assert.Equal(0u, (await client.ReadValueAsync(ServerStateNode)).StatusCode);
        await client.DisposeAsync();

        // A fresh instance (process restart) loads the persisted identity.
        await using var restarted = new RealOpcUaClient(ClientOptions());
        await restarted.ConnectAsync(server.Url, Secured(mode));
        Assert.Equal(0u, (await restarted.ReadValueAsync(ServerStateNode)).StatusCode);

        var der = Assert.Single(Directory.GetFiles(OwnCertsDir, "*.der"));
        using var onDisk = X509CertificateLoader.LoadCertificate(await File.ReadAllBytesAsync(der));
        Assert.Equal(clientCert.Thumbprint, onDisk.Thumbprint);
    }

    /// <summary>Strict server trust: a server the client has not trusted is refused, and quarantined in rejected/.</summary>
    [Theory]
    [InlineData("Sign")]
    [InlineData("SignAndEncrypt")]
    public async Task Connect_ServerNotTrustedByClient_IsRefused(string mode)
    {
        using var clientCert = await ProvisionClientAsync();
        await using var server = await SecureOpcUaTestServer.StartAsync(clientCert);

        await using var client = new RealOpcUaClient(ClientOptions());
        var ex = await Assert.ThrowsAsync<Opc.Ua.ServiceResultException>(() => client.ConnectAsync(server.Url, Secured(mode)));
        // A trust refusal — not the pre-#121 BadConfigurationError ("ApplicationCertificate … cannot be found").
        Assert.Equal(Opc.Ua.StatusCodes.BadCertificateUntrusted, ex.StatusCode);
        Assert.False(client.IsConnected);
    }

    /// <summary>Strict mutual trust: a server that has not trusted the client refuses the channel.</summary>
    [Theory]
    [InlineData("Sign")]
    [InlineData("SignAndEncrypt")]
    public async Task Connect_ClientNotTrustedByServer_IsRefused(string mode)
    {
        await using var server = await SecureOpcUaTestServer.StartAsync();
        ClientTrusts(server.Certificate);

        await using var client = new RealOpcUaClient(ClientOptions());
        var ex = await Assert.ThrowsAsync<Opc.Ua.ServiceResultException>(() => client.ConnectAsync(server.Url, Secured(mode)));
        // The server's refusal of an untrusted client channel — proves a client certificate WAS presented.
        Assert.Equal(Opc.Ua.StatusCodes.BadSecurityChecksFailed, ex.StatusCode);
        Assert.False(client.IsConnected);
    }

    /// <summary>The verify probe presents the same identity: success under mutual trust.</summary>
    [Theory]
    [InlineData(OpcUaSecurityMode.Sign)]
    [InlineData(OpcUaSecurityMode.SignAndEncrypt)]
    public async Task Verify_WithMutualTrust_Succeeds(OpcUaSecurityMode mode)
    {
        using var clientCert = await ProvisionClientAsync();
        await using var server = await SecureOpcUaTestServer.StartAsync(clientCert);
        ClientTrusts(server.Certificate);

        var result = await RealOpcUaClient.VerifyEndpointAsync(
            ProbeConfig(server.Url, mode), ClientOptions(), NullLogger.Instance, TimeSpan.FromSeconds(30), CancellationToken.None);

        Assert.True(result.Success, $"{result.FailureKind}: {result.Error}");
        Assert.Single(Directory.GetFiles(OwnCertsDir, "*.der"));
    }

    /// <summary>The probe captures — and never trusts — an untrusted server certificate.</summary>
    [Theory]
    [InlineData(OpcUaSecurityMode.Sign)]
    [InlineData(OpcUaSecurityMode.SignAndEncrypt)]
    public async Task Verify_ServerNotTrusted_ReturnsUntrustedCertificate(OpcUaSecurityMode mode)
    {
        using var clientCert = await ProvisionClientAsync();
        await using var server = await SecureOpcUaTestServer.StartAsync(clientCert);

        var result = await RealOpcUaClient.VerifyEndpointAsync(
            ProbeConfig(server.Url, mode), ClientOptions(), NullLogger.Instance, TimeSpan.FromSeconds(30), CancellationToken.None);

        Assert.False(result.Success);
        Assert.Equal(VerifyFailureKind.UntrustedCertificate, result.FailureKind);
        Assert.Equal(server.Certificate.Thumbprint, result.Cert?.Thumbprint);
        Assert.False(Directory.Exists(Path.Combine(_clientPki, "trusted", "certs"))
                     && Directory.GetFiles(Path.Combine(_clientPki, "trusted", "certs")).Length > 0,
            "the probe must never trust the server certificate");
    }

    /// <summary>The probe fails when the server has not trusted the client.</summary>
    [Theory]
    [InlineData(OpcUaSecurityMode.Sign)]
    [InlineData(OpcUaSecurityMode.SignAndEncrypt)]
    public async Task Verify_ClientNotTrustedByServer_Fails(OpcUaSecurityMode mode)
    {
        await using var server = await SecureOpcUaTestServer.StartAsync();
        ClientTrusts(server.Certificate);

        var result = await RealOpcUaClient.VerifyEndpointAsync(
            ProbeConfig(server.Url, mode), ClientOptions(), NullLogger.Instance, TimeSpan.FromSeconds(30), CancellationToken.None);

        Assert.False(result.Success);
        Assert.NotNull(result.FailureKind);
        Assert.Contains("80130000", result.Error); // BadSecurityChecksFailed, not BadConfigurationError
    }

    /// <summary>
    /// The probe is usually what first creates a node's identity, so creation must reach the
    /// supplied logger as a Warning carrying the thumbprint servers must trust — once, not on reuse.
    /// </summary>
    [Fact]
    public async Task Verify_FirstSecuredProbe_LogsCertificateCreationOnce()
    {
        await using var server = await SecureOpcUaTestServer.StartAsync();
        var log = new CapturingLogger();

        for (var i = 0; i < 2; i++)
            await RealOpcUaClient.VerifyEndpointAsync(
                ProbeConfig(server.Url, OpcUaSecurityMode.SignAndEncrypt), ClientOptions(), log,
                TimeSpan.FromSeconds(30), CancellationToken.None);

        var der = Assert.Single(Directory.GetFiles(OwnCertsDir, "*.der"));
        using var cert = X509CertificateLoader.LoadCertificate(await File.ReadAllBytesAsync(der));
        var created = Assert.Single(log.Entries, e => e.Level == LogLevel.Warning && e.Message.Contains("CREATED"));
        Assert.Contains(cert.Thumbprint, created.Message);
    }

    private sealed class CapturingLogger : ILogger
    {
        public List<(LogLevel Level, string Message)> Entries { get; } = new();

        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;

        public bool IsEnabled(LogLevel logLevel) => true;

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception,
            Func<TState, Exception?, string> formatter)
        {
            lock (Entries) Entries.Add((logLevel, formatter(state, exception)));
        }
    }

    /// <summary>None is unchanged: it connects without reading or creating the own store.</summary>
    [Fact]
    public async Task Connect_None_DoesNotTouchTheOwnStore()
    {
        await using var server = await SecureOpcUaTestServer.StartAsync();

        await using var client = new RealOpcUaClient(ClientOptions());
        await client.ConnectAsync(server.Url, new OpcUaConnectionOptions());
        Assert.Equal(0u, (await client.ReadValueAsync(ServerStateNode)).StatusCode);

        var probe = await RealOpcUaClient.VerifyEndpointAsync(
            ProbeConfig(server.Url, OpcUaSecurityMode.None), ClientOptions(), NullLogger.Instance,
            TimeSpan.FromSeconds(30), CancellationToken.None);
        Assert.True(probe.Success, $"{probe.FailureKind}: {probe.Error}");

        Assert.False(Directory.Exists(Path.Combine(_clientPki, "own")));
    }

    /// <summary>A persisted identity is reused, never rotated — including when concurrent connects race on an empty store.</summary>
    [Fact]
    public async Task Provisioning_ReusesThePersistedCertificate_AndCreatesOnlyOneUnderConcurrency()
    {
        var certs = await Task.WhenAll(Enumerable.Range(0, 8).Select(_ => ProvisionClientAsync()));
        try
        {
            Assert.Single(certs.Select(c => c.Thumbprint).Distinct());
            using var again = await ProvisionClientAsync();
            Assert.Equal(certs[0].Thumbprint, again.Thumbprint);
            Assert.Single(Directory.GetFiles(OwnCertsDir, "*.der"));
            Assert.True(Opc.Ua.X509Utils.CompareApplicationUriWithCertificate(again, "urn:localhost:SB121Client", out _),
                "the certificate carries the configured ApplicationUri");
        }
        finally
        {
            foreach (var c in certs) c.Dispose();
        }
    }

    /// <summary>A persisted certificate that no longer matches the ApplicationUri fails closed instead of being replaced.</summary>
    [Fact]
    public async Task Provisioning_ApplicationUriMismatch_FailsWithoutRotating()
    {
        using var original = await ProvisionClientAsync();

        await Assert.ThrowsAsync<InvalidOperationException>(
            () => ProvisionClientAsync(ClientOptions(applicationUri: "urn:elsewhere:SB121Client")));

        var der = Assert.Single(Directory.GetFiles(OwnCertsDir, "*.der"));
        using var onDisk = X509CertificateLoader.LoadCertificate(await File.ReadAllBytesAsync(der));
        Assert.Equal(original.Thumbprint, onDisk.Thumbprint);
    }

    /// <summary>With auto-create off, a missing certificate fails the secured connect rather than inventing one.</summary>
    [Fact]
    public async Task Provisioning_AutoCreateDisabled_MissingCertificateFails()
    {
        await Assert.ThrowsAsync<InvalidOperationException>(() => ProvisionClientAsync(ClientOptions(autoCreate: false)));
        Assert.False(Directory.Exists(OwnCertsDir) && Directory.GetFiles(OwnCertsDir).Length > 0);
    }
}