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

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

/// <summary>
/// #81 residual — verifies <see cref="SdkServiceLevelPublisher"/> locates the standard
/// <c>VariableIds.Server_ServiceLevel</c> node through the SDK's DiagnosticsNodeManager and
/// writes the byte value. Boots a real <see cref="StandardServer"/> on a free port so the
/// SDK populates its predefined diagnostics nodes — that's what production sees.
/// </summary>
public sealed class SdkServiceLevelPublisherTests : IDisposable
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

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

    [Fact]
    public void Missing_ServiceLevel_is_reported_as_failure()
    {
        var server = System.Reflection.DispatchProxy.Create<IServerInternal, FaultingServer>();
        var publisher = new SdkServiceLevelPublisher(server, NullLogger<SdkServiceLevelPublisher>.Instance);
        Should.Throw<InvalidOperationException>(() => publisher.Publish(0));
    }

    [Fact]
    public void Sdk_write_failure_propagates_the_original_exception()
    {
        var server = System.Reflection.DispatchProxy.Create<IServerInternal, FaultingServer>();
        var proxy = (FaultingServer)(object)server;
        proxy.Node = new Opc.Ua.ServerObjectState(null)
        {
            ServiceLevel = new Opc.Ua.PropertyState<byte>(null),
        };
        proxy.Fault = new InvalidOperationException("controlled diagnostics failure");
        var publisher = new SdkServiceLevelPublisher(server, NullLogger<SdkServiceLevelPublisher>.Instance);
        Should.Throw<InvalidOperationException>(() => publisher.Publish(0)).ShouldBeSameAs(proxy.Fault);
    }

    public class FaultingServer : System.Reflection.DispatchProxy
    {
        public Opc.Ua.ServerObjectState? Node { get; set; }
        public Exception? Fault { get; set; }
        protected override object? Invoke(System.Reflection.MethodInfo? method, object?[]? args)
        {
            if (method?.Name == "get_ServerObject") return Node;
            if (method?.Name == "get_DiagnosticsLock") throw Fault!;
            throw new NotSupportedException(method?.Name);
        }
    }

    /// <summary>Verifies that the publisher writes values to the standard Server.ServiceLevel variable.</summary>
    [Fact]
    public async Task Publish_writes_value_to_Server_ServiceLevel_variable()
    {
        var applicationUri = $"urn:OtOpcUa.SvcLevel:{Guid.NewGuid():N}";
        var started = await OpcUaHostStart.StartAsync(
            port => new OpcUaApplicationHost(
                new OpcUaApplicationHostOptions
                {
                    ApplicationName = "OtOpcUa.SvcLevel",
                    ApplicationUri = applicationUri,
                    OpcUaPort = port,
                    PublicHostname = "localhost",
                    PkiStoreRoot = _pkiRoot,
                },
                NullLogger<OpcUaApplicationHost>.Instance),
            () => new StandardServer(), Ct);
        await using var host = started.Host;
        var server = started.Server;

        var publisher = new SdkServiceLevelPublisher(
            server.CurrentInstance,
            NullLogger<SdkServiceLevelPublisher>.Instance);

        publisher.Publish(200);

        var variable = server.CurrentInstance.ServerObject.ServiceLevel;
        variable.ShouldNotBeNull("Server.ServiceLevel must be present in the address space");
        variable.Value.ShouldBe((byte)200);
    }

    /// <summary>Verifies that publishing service level values is idempotent when called multiple times.</summary>
    [Fact]
    public async Task Publish_is_idempotent_when_called_multiple_times()
    {
        var applicationUri = $"urn:OtOpcUa.SvcLevel.Idem:{Guid.NewGuid():N}";
        var started = await OpcUaHostStart.StartAsync(
            port => new OpcUaApplicationHost(
                new OpcUaApplicationHostOptions
                {
                    ApplicationName = "OtOpcUa.SvcLevel.Idem",
                    ApplicationUri = applicationUri,
                    OpcUaPort = port,
                    PublicHostname = "localhost",
                    PkiStoreRoot = _pkiRoot,
                },
                NullLogger<OpcUaApplicationHost>.Instance),
            () => new StandardServer(), Ct);
        await using var host = started.Host;
        var server = started.Server;
        var publisher = new SdkServiceLevelPublisher(
            server.CurrentInstance,
            NullLogger<SdkServiceLevelPublisher>.Instance);

        publisher.Publish(100);
        publisher.Publish(150);
        publisher.Publish(240);

        server.CurrentInstance.ServerObject.ServiceLevel.Value.ShouldBe((byte)240);
    }

    /// <summary>Disposes and cleans up the test resources.</summary>
    public void Dispose()
    {
        if (Directory.Exists(_pkiRoot))
        {
            try { Directory.Delete(_pkiRoot, recursive: true); }
            catch { /* best-effort */ }
        }
    }
}