using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using ScadaLink.Communication.Grpc;

namespace ScadaLink.Communication.Tests.Grpc;

public class SiteStreamGrpcClientFactoryTests
{
    private readonly ILoggerFactory _loggerFactory = NullLoggerFactory.Instance;

    [Fact]
    public void GetOrCreate_ReturnsSameClientForSameSite()
    {
        using var factory = new SiteStreamGrpcClientFactory(_loggerFactory);

        var client1 = factory.GetOrCreate("site-a", "http://localhost:5100");
        var client2 = factory.GetOrCreate("site-a", "http://localhost:5100");

        Assert.Same(client1, client2);
    }

    [Fact]
    public void GetOrCreate_ReturnsDifferentClientsForDifferentSites()
    {
        using var factory = new SiteStreamGrpcClientFactory(_loggerFactory);

        var client1 = factory.GetOrCreate("site-a", "http://localhost:5100");
        var client2 = factory.GetOrCreate("site-b", "http://localhost:5200");

        Assert.NotSame(client1, client2);
    }

    [Fact]
    public async Task RemoveSite_DisposesClient()
    {
        var factory = new SiteStreamGrpcClientFactory(_loggerFactory);

        var client1 = factory.GetOrCreate("site-a", "http://localhost:5100");
        await factory.RemoveSiteAsync("site-a");

        // After removal, GetOrCreate should return a new instance
        var client2 = factory.GetOrCreate("site-a", "http://localhost:5100");
        Assert.NotSame(client1, client2);
    }

    [Fact]
    public async Task RemoveSite_NonExistent_DoesNotThrow()
    {
        var factory = new SiteStreamGrpcClientFactory(_loggerFactory);
        await factory.RemoveSiteAsync("does-not-exist"); // Should not throw
    }

    [Fact]
    public async Task DisposeAsync_DisposesAllClients()
    {
        var factory = new SiteStreamGrpcClientFactory(_loggerFactory);

        factory.GetOrCreate("site-a", "http://localhost:5100");
        factory.GetOrCreate("site-b", "http://localhost:5200");

        await factory.DisposeAsync();

        // After dispose, creating new clients should work (new instances)
        // This tests that Dispose doesn't throw
    }

    [Fact]
    public void GetOrCreate_EndpointChanged_ReturnsClientBoundToNewEndpoint()
    {
        // Communication-012 regression: when the same site is requested with a
        // *different* endpoint (the NodeA→NodeB failover flip), the factory must
        // hand back a client bound to the new endpoint, not the stale cached one.
        using var factory = new TrackingEndpointFactory();

        var nodeA = factory.GetOrCreate("site-a", "http://localhost:5100");
        var nodeB = factory.GetOrCreate("site-a", "http://localhost:5200");

        Assert.NotSame(nodeA, nodeB);
        Assert.Equal("http://localhost:5100", nodeA.Endpoint);
        Assert.Equal("http://localhost:5200", nodeB.Endpoint);
    }

    [Fact]
    public void GetOrCreate_EndpointChanged_DisposesPriorClient()
    {
        // Communication-013 regression: a later edit to a site's gRPC address must
        // invalidate (and dispose) the stale cached client, so the corrected
        // endpoint takes effect without a central restart.
        using var factory = new TrackingEndpointFactory();

        var first = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5100");
        var second = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5200");

        Assert.NotSame(first, second);
        Assert.True(first.Disposed, "stale client for the old endpoint should be disposed");
        Assert.False(second.Disposed, "fresh client for the new endpoint should still be live");
    }

    [Fact]
    public void GetOrCreate_SameEndpoint_DoesNotDisposeOrRecreate()
    {
        // Endpoint unchanged → the cached client is reused untouched.
        using var factory = new TrackingEndpointFactory();

        var first = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5100");
        var second = (TrackingEndpointClient)factory.GetOrCreate("site-a", "http://localhost:5100");

        Assert.Same(first, second);
        Assert.False(first.Disposed);
    }

    /// <summary>Test client that records its endpoint and disposal (no real channel).</summary>
    private sealed class TrackingEndpointClient : SiteStreamGrpcClient
    {
        public TrackingEndpointClient(string endpoint) : base(endpoint) { }
        public bool Disposed { get; private set; }
        public override void Dispose() => Disposed = true;
        public override ValueTask DisposeAsync()
        {
            Disposed = true;
            return ValueTask.CompletedTask;
        }
    }

    /// <summary>Factory that hands out endpoint-tracking clients.</summary>
    private sealed class TrackingEndpointFactory : SiteStreamGrpcClientFactory
    {
        public TrackingEndpointFactory() : base(NullLoggerFactory.Instance) { }
        protected override SiteStreamGrpcClient CreateClient(string grpcEndpoint)
            => new TrackingEndpointClient(grpcEndpoint);
    }
}