using System.Net.Http;
using System.Net.Sockets;
using Grpc.Core;
using ZB.MOM.WW.ScadaBridge.Communication.Grpc;

namespace ZB.MOM.WW.ScadaBridge.Communication.Tests.Grpc;

/// <summary>
/// ScadaBridge#136: <see cref="GrpcRetrySafety.WasNeverSent"/> admits only connect-phase failures
/// (the request provably never left the client) and rejects every shape that may have delivered it.
/// </summary>
public sealed class GrpcRetrySafetyNeverSentTests
{
    private static RpcException Rpc(StatusCode code, string detail, Exception? debug)
        => new(new Status(code, detail, debug));

    private static SocketException Sock(SocketError error) => new((int)error);

    /// <summary>The balancer's subchannel connect failure is pre-send, whatever the socket error.</summary>
    /// <param name="error">The socket error the subchannel connect saw.</param>
    [Theory]
    [InlineData(SocketError.ConnectionRefused)]
    [InlineData(SocketError.HostNotFound)]
    [InlineData(SocketError.TryAgain)]
    [InlineData(SocketError.HostUnreachable)]
    [InlineData(SocketError.TimedOut)]
    public void SubchannelConnectFailure_IsNeverSent(SocketError error)
    {
        var ex = Rpc(StatusCode.Unavailable, GrpcRetrySafety.SubchannelConnectFailureDetail, Sock(error));

        Assert.True(GrpcRetrySafety.WasNeverSent(ex));
        Assert.True(GrpcRetrySafety.ProvablyNotApplied(ex));
    }

    /// <summary>An HttpRequestException connect error with a connect-only socket error is pre-send.</summary>
    /// <param name="kind">The HTTP request error classification.</param>
    /// <param name="error">The socket error.</param>
    [Theory]
    [InlineData(HttpRequestError.ConnectionError, SocketError.ConnectionRefused)]
    [InlineData(HttpRequestError.NameResolutionError, SocketError.HostNotFound)]
    [InlineData(HttpRequestError.NameResolutionError, SocketError.TryAgain)]
    public void HttpConnectError_WithConnectOnlySocketError_IsNeverSent(HttpRequestError kind, SocketError error)
    {
        var ex = Rpc(StatusCode.Unavailable, "Error starting gRPC call.",
            new HttpRequestException(kind, "connect failed", Sock(error)));

        Assert.True(GrpcRetrySafety.WasNeverSent(ex));
    }

    /// <summary>Shapes that may follow delivery stay ambiguous.</summary>
    [Fact]
    public void FailuresThatMayFollowDelivery_AreNotNeverSent()
    {
        // Premature end / reset on an established connection.
        Assert.False(GrpcRetrySafety.WasNeverSent(Rpc(StatusCode.Unavailable, "Error starting gRPC call.",
            new HttpRequestException(HttpRequestError.ResponseEnded, "ended",
                new IOException("reset", Sock(SocketError.ConnectionReset))))));
        // A ConnectionError classification with a post-connect socket error.
        Assert.False(GrpcRetrySafety.WasNeverSent(Rpc(StatusCode.Unavailable, "Error starting gRPC call.",
            new HttpRequestException(HttpRequestError.ConnectionError, "x", Sock(SocketError.ConnectionReset)))));
        // A server-sent Unavailable (no transport exception at all).
        Assert.False(GrpcRetrySafety.WasNeverSent(Rpc(StatusCode.Unavailable, "modelled fault", null)));
        // A bare socket error outside the subchannel-pick path.
        Assert.False(GrpcRetrySafety.WasNeverSent(Rpc(StatusCode.Unavailable, "Error starting gRPC call.",
            Sock(SocketError.ConnectionRefused))));
        // Subchannel detail without a socket cause.
        Assert.False(GrpcRetrySafety.WasNeverSent(Rpc(StatusCode.Unavailable,
            GrpcRetrySafety.SubchannelConnectFailureDetail, new InvalidOperationException())));
        // Not Unavailable.
        Assert.False(GrpcRetrySafety.WasNeverSent(Rpc(StatusCode.DeadlineExceeded,
            GrpcRetrySafety.SubchannelConnectFailureDetail, Sock(SocketError.ConnectionRefused))));
    }
}