using System.Reflection;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.OpcUa;

/// <summary>
///     Arch-review <b>03/U2</b> — a mechanical, reflection-driven guard that <b>every</b> method of
///     <b>every</b> forwarding interface the deferred wrappers implement actually reaches the inner
///     sink/publisher. The per-member hand-written tests in <c>DeferredAddressSpaceSinkTests</c> cover
///     the members that exist today; this test closes the class of bug where a <i>newly-added</i> sink
///     capability is implemented on <c>DeferredAddressSpaceSink</c> as a silent no-op (never forwarded),
///     so the optimization ships <b>inert on every driver-role host</b> — the F10b / PR#423 failure mode,
///     because actors inject the deferred <i>wrapper</i>, not the inner <c>SdkAddressSpaceSink</c>.
///
///     A <see cref="DispatchProxy"/> recording inner auto-implements any future interface member with
///     zero maintenance, so adding a method to <see cref="IOpcUaAddressSpaceSink"/> or
///     <see cref="ISurgicalAddressSpaceSink"/> is covered automatically — if the wrapper forgets to
///     forward it, <see cref="Every_forwarding_interface_method_reaches_the_inner_sink"/> fails. Adding a
///     brand-new capability <i>interface</i> to the wrapper is caught by
///     <see cref="DeferredAddressSpaceSink_implements_exactly_the_known_forwarding_interfaces"/>.
/// </summary>
public class DeferredSinkForwardingReflectionTests
{
    /// <summary>The interfaces whose members <see cref="DeferredAddressSpaceSink"/> is contractually
    /// required to forward to its inner sink. Kept in sync with reality by
    /// <see cref="DeferredAddressSpaceSink_implements_exactly_the_known_forwarding_interfaces"/>.</summary>
    private static readonly Type[] ForwardingInterfaces =
    {
        typeof(IOpcUaAddressSpaceSink),
        typeof(ISurgicalAddressSpaceSink),
    };

    [Fact]
    public void DeferredAddressSpaceSink_implements_exactly_the_known_forwarding_interfaces()
    {
        // Guard-of-the-guard: if a new capability interface is added to (or removed from)
        // DeferredAddressSpaceSink, this trips — forcing whoever added it to (1) list it in
        // ForwardingInterfaces and (2) extend IRecordingSink so the exhaustive forwarding test
        // below actually covers its members. Without this, a new interface could ship with an
        // un-forwarded member and no test would notice (the F10b / PR#423 trap class).
        var actual = typeof(DeferredAddressSpaceSink).GetInterfaces()
            .Where(i => i.Namespace == typeof(IOpcUaAddressSpaceSink).Namespace)
            .ToHashSet();

        actual.ShouldBe(
            ForwardingInterfaces.ToHashSet(),
            ignoreOrder: true,
            customMessage:
            "A forwarding interface was added to / removed from DeferredAddressSpaceSink without updating " +
            "this exhaustive forwarding guard. Update ForwardingInterfaces + IRecordingSink, then re-run.");
    }

    [Fact]
    public void Every_forwarding_interface_method_reaches_the_inner_sink()
    {
        foreach (var method in ForwardingInterfaces.SelectMany(i => i.GetMethods()))
        {
            // Fresh wrapper + recorder per member so Invoked reflects exactly this call.
            var proxy = DispatchProxy.Create<IRecordingSink, RecordingProxy>();
            var recorder = (RecordingProxy)(object)proxy;

            var deferred = new DeferredAddressSpaceSink();
            deferred.SetSink(proxy);

            var args = method.GetParameters().Select(p => DummyArg(p.ParameterType)).ToArray();
            method.Invoke(deferred, args);

            recorder.Invoked.ShouldContain(
                method.Name,
                $"DeferredAddressSpaceSink.{method.Name} did NOT forward to its inner sink — it ships inert " +
                "on every driver-role host (F10b / PR#423 class). Forward it in DeferredAddressSpaceSink.cs.");
        }
    }

    [Fact]
    public void Every_IServiceLevelPublisher_method_reaches_the_inner_publisher()
    {
        // DeferredServiceLevelPublisher is the sibling late-binding adapter with the same trap;
        // the plan (03/U2) calls for the same treatment.
        foreach (var method in typeof(IServiceLevelPublisher).GetMethods())
        {
            var proxy = DispatchProxy.Create<IServiceLevelPublisher, RecordingProxy>();
            var recorder = (RecordingProxy)(object)proxy;

            var deferred = new DeferredServiceLevelPublisher();
            deferred.SetInner(proxy);

            var args = method.GetParameters().Select(p => DummyArg(p.ParameterType)).ToArray();
            method.Invoke(deferred, args);

            recorder.Invoked.ShouldContain(
                method.Name,
                $"DeferredServiceLevelPublisher.{method.Name} did NOT forward to its inner publisher.");
        }
    }

    /// <summary>Combined interface so a single <see cref="DispatchProxy"/> recorder implements every
    /// forwarding member of <see cref="IOpcUaAddressSpaceSink"/> + <see cref="ISurgicalAddressSpaceSink"/>
    /// (the wrapper requires an inner that is BOTH for surgical forwarding to engage). New members on
    /// either base interface are implemented by the proxy automatically.</summary>
    public interface IRecordingSink : IOpcUaAddressSpaceSink, ISurgicalAddressSpaceSink;

    /// <summary>Records the name of every interface member the wrapper forwards to it. Returns
    /// <c>true</c> for <see cref="bool"/>-returning members so the wrapper's capability-sniffing
    /// <c>_inner is ISurgicalAddressSpaceSink surgical &amp;&amp; surgical.X(...)</c> short-circuit
    /// still invokes (and thus records) the member.</summary>
    public class RecordingProxy : DispatchProxy
    {
        /// <summary>Gets the names of the interface members invoked on this proxy.</summary>
        public List<string> Invoked { get; } = new();

        /// <inheritdoc />
        protected override object? Invoke(MethodInfo? targetMethod, object?[]? args)
        {
            Invoked.Add(targetMethod!.Name);
            var rt = targetMethod.ReturnType;
            if (rt == typeof(void)) return null;
            if (rt == typeof(bool)) return true;
            return rt.IsValueType ? Activator.CreateInstance(rt) : null;
        }
    }

    /// <summary>Builds a non-null dummy argument for any parameter type in the sink interfaces so the
    /// reflective invoke can't throw on a null value type. Fidelity of the forwarded args is asserted
    /// by the hand-written per-member tests; here we only need the call to arrive.</summary>
    private static object? DummyArg(Type t)
    {
        if (t == typeof(string)) return "n";
        if (t == typeof(object)) return 0;

        var underlying = Nullable.GetUnderlyingType(t);
        if (underlying != null) return DummyArg(underlying);

        if (t.IsEnum) return Enum.GetValues(t).GetValue(0);
        if (t == typeof(DateTime)) return DateTime.UtcNow;

        if (t.IsValueType)
        {
            if (t.IsPrimitive || t == typeof(decimal)) return Activator.CreateInstance(t);
            var vctor = GreediestCtor(t);
            return vctor is null
                ? Activator.CreateInstance(t)
                : vctor.Invoke(vctor.GetParameters().Select(p => DummyArg(p.ParameterType)).ToArray());
        }

        // Reference type with a greedy constructor (e.g. the AlarmConditionSnapshot record).
        var ctor = GreediestCtor(t);
        return ctor?.Invoke(ctor.GetParameters().Select(p => DummyArg(p.ParameterType)).ToArray());
    }

    private static ConstructorInfo? GreediestCtor(Type t) =>
        t.GetConstructors().OrderByDescending(c => c.GetParameters().Length).FirstOrDefault();
}