using System;
using System.Threading.Tasks;
using Emby.Server.Implementations.Configuration;
using MediaBrowser.Common.Configuration;
using Microsoft.Extensions.Logging.Abstractions;
using StackExchange.Redis;
using Testcontainers.Redis;
using Xunit;

namespace Jellyfin.Server.Implementations.Tests.Configuration;

/// <summary>
/// Round-trips <see cref="RedisConfigurationInvalidationBus"/> through a real Redis, the transport two
/// replicas actually use to tell each other that the shared configuration directory has changed.
/// </summary>
[Trait("Category", "RequiresDocker")]
public sealed class RedisConfigurationInvalidationBusTests : IAsyncLifetime
{
    private readonly RedisContainer _container;
    private IConnectionMultiplexer? _redis;

    /// <summary>
    /// Initializes a new instance of the <see cref="RedisConfigurationInvalidationBusTests"/> class.
    /// </summary>
    public RedisConfigurationInvalidationBusTests()
    {
        _container = new RedisBuilder("redis:7-alpine").Build();
    }

    /// <inheritdoc />
    public async ValueTask InitializeAsync()
    {
        await _container.StartAsync();
        _redis = await ConnectionMultiplexer.ConnectAsync(_container.GetConnectionString());
    }

    /// <inheritdoc />
    public async ValueTask DisposeAsync()
    {
        if (_redis is not null)
        {
            await _redis.DisposeAsync();
        }

        await _container.DisposeAsync();
    }

    /// <summary>
    /// A notice published by one replica reaches the other, carrying enough to invalidate one entry.
    /// </summary>
    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
    [Fact]
    public async Task Publish_ReachesTheOtherInstance()
    {
        var received = new TaskCompletionSource<ConfigurationInvalidation>();
        var instanceA = CreateBus("pod-a");
        var instanceB = CreateBus("pod-b");

        instanceB.Subscribe(invalidation => received.TrySetResult(invalidation));

        instanceA.Publish(ConfigurationInvalidationScope.LibraryOptions, "/media/movies");

        var invalidation = await received.Task.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);
        Assert.Equal(ConfigurationInvalidationScope.LibraryOptions, invalidation.Scope);
        Assert.Equal("/media/movies", invalidation.Target);
        Assert.Equal("pod-a", invalidation.OriginId);
    }

    /// <summary>
    /// The publishing replica has already applied the change to its own cache, so it must not act on its
    /// own notice and reload what it just wrote.
    /// </summary>
    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
    [Fact]
    public async Task Publish_IsNotDeliveredToThePublisher()
    {
        var ownNotice = new TaskCompletionSource<ConfigurationInvalidation>();
        var otherNotice = new TaskCompletionSource<ConfigurationInvalidation>();
        var instanceA = CreateBus("pod-a");
        var instanceB = CreateBus("pod-b");

        instanceA.Subscribe(invalidation => ownNotice.TrySetResult(invalidation));
        instanceB.Subscribe(invalidation => otherNotice.TrySetResult(invalidation));

        instanceA.Publish(ConfigurationInvalidationScope.SystemConfiguration, null);

        // Ordering is per channel, so B having the notice means A would have had it too.
        await otherNotice.Task.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);
        Assert.False(ownNotice.Task.IsCompleted);
    }

    private RedisConfigurationInvalidationBus CreateBus(string originId)
    {
        Environment.SetEnvironmentVariable("JELLYFIN_INSTANCE_ID", originId);
        try
        {
            return new RedisConfigurationInvalidationBus(_redis!, NullLogger<RedisConfigurationInvalidationBus>.Instance);
        }
        finally
        {
            Environment.SetEnvironmentVariable("JELLYFIN_INSTANCE_ID", null);
        }
    }
}