using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Emby.Server.Implementations;
using Emby.Server.Implementations.Configuration;
using Emby.Server.Implementations.Serialization;
using MediaBrowser.Common.Configuration;
using MediaBrowser.Common.Net;
using MediaBrowser.Controller.Configuration;
using Microsoft.Extensions.Logging.Abstractions;
using StackExchange.Redis;
using Xunit;

namespace Jellyfin.Server.Implementations.Tests.Configuration;

/// <summary>
/// Two independently constructed <see cref="ServerConfigurationManager"/> instances over one configuration
/// directory are the in-process stand-in for two replicas sharing one <c>/config</c> mount: what either of
/// them writes, the other has to pick up without being restarted.
/// </summary>
public sealed class SharedConfigurationPropagationTests : IDisposable
{
    private readonly string _root;

    /// <summary>
    /// Initializes a new instance of the <see cref="SharedConfigurationPropagationTests"/> class.
    /// </summary>
    public SharedConfigurationPropagationTests()
    {
        _root = Path.Combine(Path.GetTempPath(), "jf-config-prop-" + Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(_root);
    }

    /// <inheritdoc />
    public void Dispose()
    {
        try
        {
            Directory.Delete(_root, true);
        }
        catch (IOException)
        {
        }
    }

    /// <summary>
    /// A system configuration setting tightened on one replica has to hold on every other replica, not
    /// only on the one that served the admin's request.
    /// </summary>
    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
    [Fact]
    public async Task SystemConfigurationSavedOnOneInstance_IsSeenByAnotherWithoutRestart()
    {
        var fabric = new FakeInvalidationBusFabric();
        var instanceA = CreateInstance(fabric, "pod-a");
        var instanceB = await CreateSubscribedInstanceAsync(fabric, "pod-b");

        // B has the pre-change configuration in hand before A writes, as a running replica would.
        Assert.True(instanceB.Configuration.QuickConnectAvailable);

        instanceA.Configuration.QuickConnectAvailable = false;
        instanceA.SaveConfiguration();

        Assert.False(instanceB.Configuration.QuickConnectAvailable);
    }

    /// <summary>
    /// The same has to hold for the named configurations, which are cached per key and never reloaded.
    /// </summary>
    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
    [Fact]
    public async Task NamedConfigurationSavedOnOneInstance_IsSeenByAnotherWithoutRestart()
    {
        var fabric = new FakeInvalidationBusFabric();
        var instanceA = CreateInstance(fabric, "pod-a");
        var instanceB = await CreateSubscribedInstanceAsync(fabric, "pod-b");

        Assert.True(instanceB.GetNetworkConfiguration().EnableRemoteAccess);

        var updated = instanceA.GetNetworkConfiguration();
        updated.EnableRemoteAccess = false;
        instanceA.SaveConfiguration(NetworkConfigurationStore.StoreKey, updated);

        Assert.False(instanceB.GetNetworkConfiguration().EnableRemoteAccess);
    }

    /// <summary>
    /// A replica that cannot reach the bus keeps serving: the admin's save still lands on the shared
    /// directory, and the only loss is that the other replicas are not told about it.
    /// </summary>
    [Fact]
    public void SaveConfiguration_WithUnreachableBus_DoesNotThrow()
    {
        using var multiplexer = ConnectionMultiplexer.Connect("127.0.0.1:1,abortConnect=false,connectTimeout=200,connectRetry=1,syncTimeout=200");
        var bus = new RedisConfigurationInvalidationBus(multiplexer, NullLogger<RedisConfigurationInvalidationBus>.Instance);

        bus.Subscribe(_ => throw new InvalidOperationException("Nothing can be delivered by an unreachable bus."));

        var instance = CreateInstance(new FakeInvalidationBusFabric(), "pod-a");
        instance.InvalidationBus = bus;

        instance.Configuration.QuickConnectAvailable = false;
        instance.SaveConfiguration();
        instance.SaveConfiguration(NetworkConfigurationStore.StoreKey, instance.GetNetworkConfiguration());

        Assert.False(instance.Configuration.QuickConnectAvailable);
    }

    private async Task<ServerConfigurationManager> CreateSubscribedInstanceAsync(FakeInvalidationBusFabric fabric, string originId)
    {
        var instance = CreateInstance(fabric, originId);
        var subscriber = new ConfigurationInvalidationSubscriber(
            instance.InvalidationBus,
            instance,
            NullLogger<ConfigurationInvalidationSubscriber>.Instance);

        await subscriber.StartAsync(CancellationToken.None);
        return instance;
    }

    private ServerConfigurationManager CreateInstance(FakeInvalidationBusFabric fabric, string originId)
    {
        // Every instance has its own paths object, all of them pointing at the one shared directory.
        var paths = new ServerApplicationPaths(
            Ensure("data"),
            Ensure("log"),
            Ensure("config"),
            Ensure("cache"),
            Ensure("web"));

        var manager = new ServerConfigurationManager(paths, NullLoggerFactory.Instance, new MyXmlSerializer())
        {
            InvalidationBus = fabric.Connect(originId)
        };

        manager.AddParts([new NetworkConfigurationFactory()]);
        return manager;
    }

    private string Ensure(string name)
    {
        var path = Path.Combine(_root, name);
        Directory.CreateDirectory(path);
        return path;
    }
}