using Grpc.Core;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Cluster;
using ZB.MOM.WW.OtOpcUa.Host.Configuration;

namespace ZB.MOM.WW.OtOpcUa.Host.Tests.Configuration;

/// <summary>
///     mesh gRPC command plane, Phase 0 — the node-side command endpoint's inbound gate. Mapping
///     <c>NodeCommandService</c> onto the pipeline is a Phase 1 task; this test covers only the
///     interceptor's own authorization behavior.
/// </summary>
/// <remarks>
///     Same contract as <see cref="TelemetryStreamAuthInterceptor"/>, scoped to
///     <c>/mesh_transport.v1.NodeCommandService/</c> — fail-closed on an unconfigured key,
///     constant-time comparison, gated on every handler shape so scoping holds regardless of RPC
///     shape. Deliberately NO <c>x-otopcua-cluster</c> requirement: that header is a central-side
///     routing hint, and requiring it here would gate on a value the caller chooses.
/// </remarks>
public sealed class MeshCommandAuthInterceptorTests
{
    private const string ExecuteMethod = "/mesh_transport.v1.NodeCommandService/Execute";
    private const string OtherMethod = "/telemetry.v1.TelemetryStreamService/Subscribe";

    private static MeshCommandAuthInterceptor CreateInterceptor(string? psk)
        => new(
            Options.Create(new MeshTransportOptions { GrpcPsk = psk }),
            NullLogger<MeshCommandAuthInterceptor>.Instance);

    private static ServerCallContext CreateContext(string method, string? authorizationHeader)
        => CreateContext(method, authorizationHeader is null ? [] : [authorizationHeader]);

    private static ServerCallContext CreateContext(string method, string[] authorizationHeaders)
    {
        var headers = new Metadata();
        foreach (var value in authorizationHeaders)
            headers.Add("authorization", value);

        return new FakeServerCallContext(method, headers);
    }

    /// <summary>Invokes the interceptor's unary path (how <c>Execute</c> actually runs).</summary>
    private static Task Invoke(MeshCommandAuthInterceptor interceptor, ServerCallContext context)
        => interceptor.UnaryServerHandler<string, string>(
            "request", context, (_, _) => Task.FromResult("ok"));

    [Fact]
    public async Task NonMeshCommandMethod_PassesThrough_EvenWithNoPskConfigured()
    {
        // The interceptor shares the AddGrpc pipeline with the sync / config-serve / telemetry
        // services, so it sees every call. It must be scoped strictly to the node command service.
        var interceptor = CreateInterceptor(psk: null);
        var context = CreateContext(OtherMethod, authorizationHeader: null);

        await Invoke(interceptor, context); // no throw
    }

    [Fact]
    public async Task ExecuteMethod_WithNoPskConfigured_IsDenied_EvenWithABearerToken()
    {
        // Fail-closed. "No PSK configured" is the DEFAULT — treating it as "no auth required" would
        // let anything that can reach the port drive RestartDriver / AlarmCommand / deployment
        // dispatch on this node. A token must not help.
        var interceptor = CreateInterceptor(psk: null);
        var context = CreateContext(ExecuteMethod, "Bearer anything-at-all");

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ExecuteMethod_WithBlankPskConfigured_IsDenied()
    {
        // Blank is distinct from unset in the options (GrpcPsk is nullable on purpose) but must be
        // treated identically here: an empty expected token would be satisfied by an empty bearer.
        var interceptor = CreateInterceptor("   ");
        var context = CreateContext(ExecuteMethod, "Bearer    ");

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ExecuteMethod_WithNoBearerToken_IsDenied()
    {
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, authorizationHeader: null);

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ExecuteMethod_WithMalformedAuthorizationHeader_IsDenied()
    {
        // No "Bearer " prefix at all — must be treated the same as a missing header.
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "the-cluster-psk");

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ExecuteMethod_WithWrongBearerToken_IsDenied()
    {
        // This is also the isolation proof: a node holding SITE-A's PSK rejects a caller presenting
        // SITE-B's. Nothing about the cluster id is consulted — only whether the key matches.
        var interceptor = CreateInterceptor("dev-mesh-psk-SITE-A");
        var context = CreateContext(ExecuteMethod, "Bearer dev-mesh-psk-SITE-B");

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ExecuteMethod_WithCorrectBearerToken_PassesThrough()
    {
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "Bearer the-cluster-psk");

        await Invoke(interceptor, context); // no throw
    }

    [Fact]
    public async Task ExecuteMethod_WithCorrectBearerToken_AndNoClusterHeader_PassesThrough()
    {
        // x-otopcua-cluster is a central-side routing hint. Requiring it here would gate on a value
        // the caller supplies about itself, which proves nothing the PSK has not already proven.
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "Bearer the-cluster-psk");

        await Invoke(interceptor, context); // no throw
    }

    [Fact]
    public async Task ExecuteMethod_WithAJunkAuthorizationHeaderBeforeTheRealOne_IsDenied()
    {
        // First entry wins, and it must parse. This interceptor originally scanned past a non-Bearer
        // header for a later Bearer one while its central-side clone took the first entry, so the
        // two clones gave OPPOSITE answers to this exact request. Both now share
        // GrpcRequestHeaders and both deny it; pinned identically on CentralCommandAuthInterceptor.
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, ["junk", "Bearer the-cluster-psk"]);

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ExecuteMethod_TokenComparison_IsNotAPrefixMatch()
    {
        // A prefix/StartsWith comparison would accept a truncated key and make the secret
        // recoverable one character at a time.
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "Bearer the-cluster-ps");

        var ex = await Should.ThrowAsync<RpcException>(() => Invoke(interceptor, context));
        ex.StatusCode.ShouldBe(StatusCode.PermissionDenied);
    }

    [Fact]
    public async Task ServerStreamingPath_IsAlsoGated()
    {
        // Execute is unary today, but gating only that path would leave any future streaming method
        // on the same service open. Gate every handler shape.
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "Bearer the-wrong-psk");

        var ex = await Should.ThrowAsync<RpcException>(() =>
            interceptor.ServerStreamingServerHandler<string, string>(
                "request", responseStream: null!, context, (_, _, _) => Task.CompletedTask));

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

    [Fact]
    public async Task ClientStreamingPath_IsAlsoGated()
    {
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "Bearer the-wrong-psk");

        var ex = await Should.ThrowAsync<RpcException>(() =>
            interceptor.ClientStreamingServerHandler<string, string>(
                requestStream: null!, context, (_, _) => Task.FromResult("ok")));

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

    [Fact]
    public async Task DuplexStreamingPath_IsAlsoGated()
    {
        var interceptor = CreateInterceptor("the-cluster-psk");
        var context = CreateContext(ExecuteMethod, "Bearer the-wrong-psk");

        var ex = await Should.ThrowAsync<RpcException>(() =>
            interceptor.DuplexStreamingServerHandler<string, string>(
                requestStream: null!, responseStream: null!, context, (_, _, _) => Task.CompletedTask));

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

    [Fact]
    public void HasExactlyOnePublicConstructor()
    {
        // Grpc.AspNetCore silently stops invoking an interceptor with more than one public ctor —
        // this pins the shape so a well-meaning overload doesn't quietly disable auth in production.
        var publicCtors = typeof(MeshCommandAuthInterceptor).GetConstructors();

        publicCtors.Length.ShouldBe(1);
    }

    /// <summary>
    ///     Minimal <see cref="ServerCallContext"/> carrying just a method name and request headers —
    ///     the only two things the interceptor reads. Hand-rolled because
    ///     <c>Grpc.Core.Testing.TestServerCallContext</c> ships only in the retired native package.
    /// </summary>
    private sealed class FakeServerCallContext(string method, Metadata requestHeaders)
        : ServerCallContext
    {
        protected override string MethodCore => method;
        protected override string HostCore => "localhost";
        protected override string PeerCore => "ipv4:127.0.0.1:12345";
        protected override DateTime DeadlineCore => DateTime.UtcNow.AddMinutes(1);
        protected override Metadata RequestHeadersCore => requestHeaders;
        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 { get; } =
            new(null, new Dictionary<string, List<AuthProperty>>());

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

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