using System.Reflection;
using Microsoft.Extensions.Logging.Abstractions;
using Opc.Ua;
using Opc.Ua.Server;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Server.Redundancy;
using ConfigRedundancyMode = ZB.MOM.WW.OtOpcUa.Configuration.Enums.RedundancyMode;

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

/// <summary>
///     Unit coverage for <see cref="ServerRedundancyNodeWriter"/>. Uses a <see cref="DispatchProxy"/>
///     stand-in for <see cref="IServerInternal"/> — the writer only needs <c>ServerObject</c> +
///     <c>DefaultSystemContext</c>, so we stub just those and let every other member return
///     null (the writer never touches anything else).
/// </summary>
public sealed class ServerRedundancyNodeWriterTests
{
    [Fact]
    public void ApplyServiceLevel_sets_node_value_and_dedupes_unchanged()
    {
        var env = BuildEnv();

        env.Writer.ApplyServiceLevel(200);
        env.ServerObject.ServiceLevel.Value.ShouldBe((byte)200);

        var timestampAfterFirst = env.ServerObject.ServiceLevel.Timestamp;

        // Same value — writer should early-out without touching Timestamp.
        Thread.Sleep(5);
        env.Writer.ApplyServiceLevel(200);
        env.ServerObject.ServiceLevel.Timestamp.ShouldBe(timestampAfterFirst);

        env.Writer.ApplyServiceLevel(150);
        env.ServerObject.ServiceLevel.Value.ShouldBe((byte)150);
        env.ServerObject.ServiceLevel.Timestamp.ShouldBeGreaterThan(timestampAfterFirst);
    }

    [Fact]
    public void ApplyRedundancySupport_maps_config_enum()
    {
        var env = BuildEnv();

        env.Writer.ApplyRedundancySupport(ConfigRedundancyMode.Warm);
        env.ServerObject.ServerRedundancy.RedundancySupport.Value.ShouldBe(RedundancySupport.Warm);

        env.Writer.ApplyRedundancySupport(ConfigRedundancyMode.Hot);
        env.ServerObject.ServerRedundancy.RedundancySupport.Value.ShouldBe(RedundancySupport.Hot);

        env.Writer.ApplyRedundancySupport(ConfigRedundancyMode.None);
        env.ServerObject.ServerRedundancy.RedundancySupport.Value.ShouldBe(RedundancySupport.None);
    }

    [Fact]
    public void ApplyServerUriArray_writes_when_non_transparent_state_present()
    {
        var env = BuildEnv(nonTransparent: true);

        env.Writer.ApplyServerUriArray(["urn:self", "urn:peer"]);
        var ntr = (NonTransparentRedundancyState)env.ServerObject.ServerRedundancy;
        ntr.ServerUriArray.Value.ShouldBe(new[] { "urn:self", "urn:peer" });

        var ts = ntr.ServerUriArray.Timestamp;
        Thread.Sleep(5);
        env.Writer.ApplyServerUriArray(["urn:self", "urn:peer"]); // dedupe
        ntr.ServerUriArray.Timestamp.ShouldBe(ts);

        env.Writer.ApplyServerUriArray(["urn:self", "urn:peer", "urn:peer2"]);
        ntr.ServerUriArray.Value.Length.ShouldBe(3);
    }

    [Fact]
    public void ApplyServerUriArray_skips_silently_on_base_redundancy_type()
    {
        var env = BuildEnv(nonTransparent: false);
        Should.NotThrow(() => env.Writer.ApplyServerUriArray(["urn:self"]));
        env.ServerObject.ServerRedundancy.ShouldBeOfType<ServerRedundancyState>();
    }

    private static Env BuildEnv(bool nonTransparent = false)
    {
        var serverObject = new ServerObjectState(parent: null)
        {
            ServiceLevel = new PropertyState<byte>(null),
        };
        serverObject.ServerRedundancy = nonTransparent
            ? new NonTransparentRedundancyState(serverObject)
            {
                RedundancySupport = new PropertyState<RedundancySupport>(null),
                ServerUriArray = new PropertyState<string[]>(null),
            }
            : new ServerRedundancyState(serverObject)
            {
                RedundancySupport = new PropertyState<RedundancySupport>(null),
            };

        var proxy = DispatchProxy.Create<IServerInternal, FakeServerInternalProxy>();
        var fake = (FakeServerInternalProxy)(object)proxy;
        fake.ServerObjectValue = serverObject;
        fake.DefaultSystemContextValue = new ServerSystemContext(proxy);

        var writer = new ServerRedundancyNodeWriter(proxy, NullLogger<ServerRedundancyNodeWriter>.Instance);
        return new Env(proxy, serverObject, writer);
    }

    private sealed record Env(
        IServerInternal Server,
        ServerObjectState ServerObject,
        ServerRedundancyNodeWriter Writer);

    public class FakeServerInternalProxy : DispatchProxy
    {
        public ServerObjectState? ServerObjectValue;
        public ISystemContext? DefaultSystemContextValue;

        protected override object? Invoke(MethodInfo? targetMethod, object?[]? args) =>
            targetMethod?.Name switch
            {
                "get_ServerObject" => ServerObjectValue,
                "get_DefaultSystemContext" => DefaultSystemContextValue,
                _ => null,
            };
    }
}