using Microsoft.Extensions.Logging.Abstractions;
using Opc.Ua;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

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

/// <summary>
///     Review 01 L3 / H5 / H4 — the device-write dispatch behind <see cref="OtOpcUaNodeManager.OnEquipmentTagWrite"/>
///     and the manager's clock: a gateway that throws synchronously is refused inline (the handler runs under
///     the SDK <c>Lock</c>, and the throw used to escape it), a faulted dispatch task is observed and still
///     reverts the optimistic value, and the timestamps the manager stamps come from the injected
///     <see cref="OtOpcUaNodeManager.Clock"/>.
/// </summary>
public sealed class NodeManagerWriteDispatchTests : IDisposable
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

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

    /// <summary>H5 — a synchronous throw out of the gateway is a Bad result, never an escaped exception.</summary>
    [Fact]
    public async Task A_gateway_that_throws_synchronously_is_refused_inline()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            nm.EnsureVariable("eq-1/sp", null, "Sp", "Int32", writable: true, realm: AddressSpaceRealm.Uns);
            nm.WriteValue("eq-1/sp", 7, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Uns);

            var result = nm.DispatchDeviceWrite(
                new ThrowingGateway(), "ns=2;s=eq-1/sp", "eq-1/sp", AddressSpaceRealm.Uns,
                optimisticValue: 42, priorValue: 7, priorStatus: StatusCodes.Good, clientUserId: "op");

            ServiceResult.IsBad(result).ShouldBeTrue();
            result.StatusCode.ShouldBe((StatusCode)StatusCodes.BadDeviceFailure);
            result.ToString().ShouldContain("boom");
            nm.TryGetVariable("eq-1/sp")!.Value.ShouldBe(7, "nothing was applied, so nothing needs reverting");
        }
        finally { await host.DisposeAsync(); }
    }

    /// <summary>L3 — a faulted dispatch task is observed and the optimistic value is reverted with its reason.</summary>
    [Fact]
    public async Task A_faulted_dispatch_is_observed_and_reverts_the_optimistic_value()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            nm.EnsureVariable("eq-1/sp", null, "Sp", "Int32", writable: true, realm: AddressSpaceRealm.Uns);
            nm.WriteValue("eq-1/sp", 7, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Uns);
            var node = nm.TryGetVariable("eq-1/sp")!;

            var result = nm.DispatchDeviceWrite(
                new FaultingGateway(), "ns=2;s=eq-1/sp", "eq-1/sp", AddressSpaceRealm.Uns,
                optimisticValue: 42, priorValue: 7, priorStatus: StatusCodes.Good, clientUserId: "op");
            ServiceResult.IsGood(result).ShouldBeTrue("the dispatch itself started; the SDK applies the value optimistically");
            node.Value = 42; // what the SDK does on Good

            var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(5);
            while (DateTime.UtcNow < deadline && !Equals(node.Value, 7)) await Task.Delay(20, Ct);
            node.Value.ShouldBe(7, "the faulted dispatch must revert the optimistic value");
            node.StatusCode.ShouldBe((StatusCode)StatusCodes.Good);
        }
        finally { await host.DisposeAsync(); }
    }

    /// <summary>Positive control for the two above: a gateway that succeeds leaves the optimistic value standing.</summary>
    [Fact]
    public async Task A_successful_dispatch_leaves_the_optimistic_value()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            nm.EnsureVariable("eq-1/sp", null, "Sp", "Int32", writable: true, realm: AddressSpaceRealm.Uns);
            nm.WriteValue("eq-1/sp", 7, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Uns);
            var node = nm.TryGetVariable("eq-1/sp")!;

            nm.DispatchDeviceWrite(
                new SucceedingGateway(), "ns=2;s=eq-1/sp", "eq-1/sp", AddressSpaceRealm.Uns,
                optimisticValue: 42, priorValue: 7, priorStatus: StatusCodes.Good, clientUserId: "op");
            node.Value = 42;

            await Task.Delay(200, Ct);
            node.Value.ShouldBe(42);
        }
        finally { await host.DisposeAsync(); }
    }

    /// <summary>H4 — the revert stamps the manager's clock, not the wall clock.</summary>
    [Fact]
    public async Task The_revert_timestamps_come_from_the_injected_clock()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            var fixedNow = new DateTime(2030, 1, 2, 3, 4, 5, DateTimeKind.Utc);
            nm.Clock = new FixedClock(fixedNow);
            nm.EnsureVariable("eq-1/sp", null, "Sp", "Int32", writable: true, realm: AddressSpaceRealm.Uns);
            nm.WriteValue("eq-1/sp", 7, OpcUaStatus.Good, new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc), AddressSpaceRealm.Uns);
            var node = nm.TryGetVariable("eq-1/sp")!;
            node.Value = 42;

            nm.RevertOptimisticWriteIfNeeded(
                "eq-1/sp", new NodeWriteOutcome(false, "rejected"), optimisticValue: 42, priorValue: 7,
                priorStatus: StatusCodes.Good, clientUserId: "op", realm: AddressSpaceRealm.Uns);

            node.Timestamp.ShouldBe(fixedNow);
            OtOpcUaNodeManager.RemainingShelveMs(fixedNow.AddSeconds(30), fixedNow).ShouldBe(30_000);
        }
        finally { await host.DisposeAsync(); }
    }

    private async Task<(OpcUaApplicationHost Host, OtOpcUaSdkServer Server)> BootAsync() =>
        await OpcUaHostStart.StartAsync(
            port => new OpcUaApplicationHost(
                new OpcUaApplicationHostOptions
                {
                    ApplicationName = "OtOpcUa.DispatchTest",
                    ApplicationUri = $"urn:OtOpcUa.DispatchTest:{Guid.NewGuid():N}",
                    OpcUaPort = port,
                    PublicHostname = "localhost",
                    PkiStoreRoot = _pkiRoot,
                },
                NullLogger<OpcUaApplicationHost>.Instance),
            () => new OtOpcUaSdkServer(), Ct);

    public void Dispose()
    {
        if (Directory.Exists(_pkiRoot)) Directory.Delete(_pkiRoot, recursive: true);
    }

    private sealed class ThrowingGateway : IOpcUaNodeWriteGateway
    {
        public Task<NodeWriteOutcome> WriteAsync(string nodeId, object? value, AddressSpaceRealm realm, CancellationToken ct) =>
            throw new InvalidOperationException("boom");
    }

    private sealed class FaultingGateway : IOpcUaNodeWriteGateway
    {
        public Task<NodeWriteOutcome> WriteAsync(string nodeId, object? value, AddressSpaceRealm realm, CancellationToken ct) =>
            Task.FromException<NodeWriteOutcome>(new TimeoutException("gateway ask timed out"));
    }

    private sealed class SucceedingGateway : IOpcUaNodeWriteGateway
    {
        public Task<NodeWriteOutcome> WriteAsync(string nodeId, object? value, AddressSpaceRealm realm, CancellationToken ct) =>
            Task.FromResult(new NodeWriteOutcome(true, null));
    }

    private sealed class FixedClock(DateTime utcNow) : TimeProvider
    {
        public override DateTimeOffset GetUtcNow() => new(utcNow, TimeSpan.Zero);
    }
}