using Akka.Hosting;
using Akka.TestKit.Xunit2;
using Grpc.Core;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.AdminUI.Grpc;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Deploy;
using ZB.MOM.WW.OtOpcUa.Commons.Protos.MeshTransport.V1;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.ControlPlane;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Grpc;

/// <summary>
///     The central-side gRPC ingress for a node's deployment ack (mesh gRPC command plane
///     Phase 1B). It decodes the wire message and hands it to the registered
///     <c>CentralCommunicationActor</c> — the same actor the DistributedPubSub leg delivers to,
///     whose forward-to-the-coordinator path is untouched.
/// </summary>
/// <remarks>
///     Both failure modes matter more than the happy path. An ack that cannot be decoded must be
///     refused rather than guessed at (a wrong outcome seals a deployment nobody applied), and an ack
///     arriving before the actor exists must say <see cref="StatusCode.Unavailable"/> so the caller
///     retries instead of recording a permanent failure against a node that is fine.
/// </remarks>
public sealed class CentralCommandGrpcServiceTests : TestKit
{
    private static ApplyAckMessage WellFormed() => new()
    {
        DeploymentId = Guid.NewGuid().ToString("N"),
        NodeId = "site-a-1",
        Outcome = ApplyOutcome.Applied,
        CorrelationId = Guid.NewGuid().ToString("N"),
    };

    private static CentralCommandGrpcService Service(ActorRegistry registry) =>
        new(registry, NullLogger<CentralCommandGrpcService>.Instance);

    [Fact]
    public async Task A_well_formed_ack_is_decoded_and_told_to_the_registered_actor()
    {
        var probe = CreateTestProbe("central-comm");
        var registry = new ActorRegistry();
        registry.Register<CentralCommunicationActorKey>(probe.Ref);

        var request = WellFormed();
        request.FailureReason = "disk full";
        request.Outcome = ApplyOutcome.Failed;

        var response = await Service(registry).ReportApply(request, new FakeServerCallContext());

        response.ShouldNotBeNull();

        var received = probe.ExpectMsg<ApplyAck>(TimeSpan.FromSeconds(3));
        received.DeploymentId.ShouldBe(DeploymentId.Parse(request.DeploymentId));
        received.NodeId.Value.ShouldBe("site-a-1");
        received.Outcome.ShouldBe(ApplyAckOutcome.Failed);
        received.FailureReason.ShouldBe("disk full");
        received.CorrelationId.ToString().ShouldBe(request.CorrelationId);
    }

    [Fact]
    public async Task An_absent_failure_reason_arrives_as_null_and_an_empty_one_as_empty()
    {
        // Presence, not emptiness — the mapper's contract, asserted at the seam that actually feeds
        // the coordinator. Collapsing the two would report an operator-visible blank reason as "no
        // reason recorded".
        var probe = CreateTestProbe("central-comm");
        var registry = new ActorRegistry();
        registry.Register<CentralCommunicationActorKey>(probe.Ref);
        var service = Service(registry);

        await service.ReportApply(WellFormed(), new FakeServerCallContext());
        probe.ExpectMsg<ApplyAck>(TimeSpan.FromSeconds(3)).FailureReason.ShouldBeNull();

        var blank = WellFormed();
        blank.FailureReason = "";
        await service.ReportApply(blank, new FakeServerCallContext());
        probe.ExpectMsg<ApplyAck>(TimeSpan.FromSeconds(3)).FailureReason.ShouldBe("");
    }

    [Fact]
    public async Task An_unregistered_actor_yields_Unavailable()
    {
        // The boot window: the listener answers before Akka.Hosting has spawned the actor. Unavailable
        // is the retryable status, so the node's next attempt lands instead of the deployment
        // recording a permanent failure against a node that applied fine.
        var ex = await Should.ThrowAsync<RpcException>(() =>
            Service(new ActorRegistry()).ReportApply(WellFormed(), new FakeServerCallContext()));

        ex.StatusCode.ShouldBe(StatusCode.Unavailable);
    }

    [Fact]
    public async Task An_unspecified_outcome_yields_InvalidArgument()
    {
        // proto3 decodes an absent enum as 0. Refusing is the whole point: the deploy path seals on
        // Applied, so guessing an outcome the node never sent would seal a deployment nobody applied.
        var probe = CreateTestProbe("central-comm");
        var registry = new ActorRegistry();
        registry.Register<CentralCommunicationActorKey>(probe.Ref);

        var request = WellFormed();
        request.Outcome = ApplyOutcome.Unspecified;

        var ex = await Should.ThrowAsync<RpcException>(() =>
            Service(registry).ReportApply(request, new FakeServerCallContext()));

        ex.StatusCode.ShouldBe(StatusCode.InvalidArgument);
        probe.ExpectNoMsg(TimeSpan.FromMilliseconds(300));
    }

    [Fact]
    public async Task A_malformed_id_yields_InvalidArgument()
    {
        var request = WellFormed();
        request.DeploymentId = "not-a-guid";

        var probe = CreateTestProbe("central-comm");
        var registry = new ActorRegistry();
        registry.Register<CentralCommunicationActorKey>(probe.Ref);

        var ex = await Should.ThrowAsync<RpcException>(() =>
            Service(registry).ReportApply(request, new FakeServerCallContext()));

        ex.StatusCode.ShouldBe(StatusCode.InvalidArgument);
        probe.ExpectNoMsg(TimeSpan.FromMilliseconds(300));
    }

    [Fact]
    public async Task A_blank_node_id_yields_InvalidArgument()
    {
        // NodeId.Parse refuses a blank name; an ack whose node cannot be named is uncountable at the
        // coordinator, so it must be refused here rather than forwarded as an anonymous ack.
        var request = WellFormed();
        request.NodeId = "";

        var probe = CreateTestProbe("central-comm");
        var registry = new ActorRegistry();
        registry.Register<CentralCommunicationActorKey>(probe.Ref);

        var ex = await Should.ThrowAsync<RpcException>(() =>
            Service(registry).ReportApply(request, new FakeServerCallContext()));

        ex.StatusCode.ShouldBe(StatusCode.InvalidArgument);
        probe.ExpectNoMsg(TimeSpan.FromMilliseconds(300));
    }

    [Fact]
    public async Task An_undecodable_message_is_graded_before_the_registry()
    {
        // Ordering pin. With NO actor registered AND an undecodable message, the answer is
        // InvalidArgument, not Unavailable: Unavailable invites a retry, and retrying a message that
        // can never decode is a loop. The caller's fault is reported as the caller's fault.
        var request = WellFormed();
        request.Outcome = ApplyOutcome.Unspecified;

        var ex = await Should.ThrowAsync<RpcException>(() =>
            Service(new ActorRegistry()).ReportApply(request, new FakeServerCallContext()));

        ex.StatusCode.ShouldBe(StatusCode.InvalidArgument);
    }

    [Fact]
    public async Task A_decode_failure_logs_the_raw_correlation_id()
    {
        // The correlation id is logged as the raw wire string precisely because the ids may be what
        // failed to parse — an operator correlating a rejection cannot be given a value that only
        // exists once decoding succeeded.
        var logger = new CapturingLogger<CentralCommandGrpcService>();
        var request = WellFormed();
        request.CorrelationId = "correlation-that-never-parses";
        request.DeploymentId = "not-a-guid";

        await Should.ThrowAsync<RpcException>(() =>
            new CentralCommandGrpcService(new ActorRegistry(), logger)
                .ReportApply(request, new FakeServerCallContext()));

        logger.Entries.Any(e => e.Message.Contains("correlation-that-never-parses", StringComparison.Ordinal))
            .ShouldBeTrue("the rejection log must carry the raw correlation id");
    }

    [Fact]
    public async Task A_not_ready_rejection_logs_the_peer_and_the_correlation_id()
    {
        // Diagnostic symmetry with the decode-failure warning above. The two rejections are the only
        // two ways an ack fails to reach the coordinator, and an operator reading the central log has
        // to correlate BOTH against the node's own log — which needs the correlation id — and against
        // which node was calling, which needs the peer. Decoding has already succeeded on this path,
        // so the decoded correlation id costs nothing to include.
        var logger = new CapturingLogger<CentralCommandGrpcService>();
        var request = WellFormed();

        await Should.ThrowAsync<RpcException>(() =>
            new CentralCommandGrpcService(new ActorRegistry(), logger)
                .ReportApply(request, new FakeServerCallContext()));

        var warning = logger.Entries.Single(e => e.Level == LogLevel.Warning);
        warning.Message.ShouldContain("ipv4:127.0.0.1:0");
        warning.Message.ShouldContain(request.CorrelationId);
    }

    /// <summary>Test logger that captures all log entries.</summary>
    /// <typeparam name="T">The category type.</typeparam>
    private sealed class CapturingLogger<T> : ILogger<T>
    {
        /// <summary>Gets the captured log entries.</summary>
        public List<(LogLevel Level, string Message, Exception? Exception)> Entries { get; } = [];

        /// <summary>Begins a scope (stub implementation).</summary>
        /// <typeparam name="TState">The type of the scope state.</typeparam>
        /// <param name="state">The scope state.</param>
        /// <returns>A no-op scope.</returns>
        public IDisposable BeginScope<TState>(TState state) where TState : notnull => NullScope.Instance;

        /// <summary>Checks if logging is enabled (always true).</summary>
        /// <param name="logLevel">The log level to check.</param>
        /// <returns><c>true</c>.</returns>
        public bool IsEnabled(LogLevel logLevel) => true;

        /// <summary>Logs an entry and captures it.</summary>
        /// <typeparam name="TState">The type of the log state.</typeparam>
        /// <param name="logLevel">The log level.</param>
        /// <param name="eventId">The event ID.</param>
        /// <param name="state">The log state.</param>
        /// <param name="exception">The exception, if any.</param>
        /// <param name="formatter">The log message formatter.</param>
        public void Log<TState>(
            LogLevel logLevel, EventId eventId, TState state, Exception? exception,
            Func<TState, Exception?, string> formatter)
        {
            Entries.Add((logLevel, formatter(state, exception), exception));
        }

        private sealed class NullScope : IDisposable
        {
            /// <summary>Gets the singleton instance.</summary>
            public static NullScope Instance { get; } = new();

            /// <summary>No-op.</summary>
            public void Dispose() { }
        }
    }

    /// <summary>Minimal <see cref="ServerCallContext"/> — the service reads only the method path.</summary>
    private sealed class FakeServerCallContext : ServerCallContext
    {
        protected override string MethodCore => "/mesh_transport.v1.CentralCommandService/ReportApply";
        protected override string HostCore => "localhost";
        protected override string PeerCore => "ipv4:127.0.0.1:0";
        protected override DateTime DeadlineCore => DateTime.MaxValue;
        protected override Metadata RequestHeadersCore => [];
        protected override CancellationToken CancellationTokenCore => CancellationToken.None;
        protected override Metadata ResponseTrailersCore { get; } = [];
        protected override Status StatusCore { get; set; }
        protected override WriteOptions? WriteOptionsCore { get; set; }
        protected override AuthContext AuthContextCore => new(null, new Dictionary<string, List<AuthProperty>>());

        protected override ContextPropagationToken CreatePropagationTokenCore(ContextPropagationOptions? options) =>
            throw new NotSupportedException();

        protected override Task WriteResponseHeadersAsyncCore(Metadata responseHeaders) => Task.CompletedTask;
    }
}