jellyfin-ha-src/tests/Jellyfin.Server.Implementations.Tests/Configuration/FakeInvalidationBusFabric.cs

using System;
using System.Collections.Generic;
using System.Linq;
using MediaBrowser.Common.Configuration;

namespace Jellyfin.Server.Implementations.Tests.Configuration;

/// <summary>
/// An in-process stand-in for the Redis pub/sub bus: every endpoint connected to one fabric receives
/// what the others publish, and never its own notices.
/// </summary>
internal sealed class FakeInvalidationBusFabric
{
    private readonly List<Endpoint> _endpoints = new();

    /// <summary>
    /// Connects a new instance to the fabric.
    /// </summary>
    /// <param name="originId">The identity of the connecting instance.</param>
    /// <returns>The bus of that instance.</returns>
    public IConfigurationInvalidationBus Connect(string originId)
    {
        var endpoint = new Endpoint(this, originId);
        lock (_endpoints)
        {
            _endpoints.Add(endpoint);
        }

        return endpoint;
    }

    private void Broadcast(ConfigurationInvalidation invalidation)
    {
        Endpoint[] endpoints;
        lock (_endpoints)
        {
            endpoints = _endpoints.ToArray();
        }

        foreach (var endpoint in endpoints.Where(e => !string.Equals(e.OriginId, invalidation.OriginId, StringComparison.Ordinal)))
        {
            endpoint.Deliver(invalidation);
        }
    }

    private sealed class Endpoint : IConfigurationInvalidationBus
    {
        private readonly FakeInvalidationBusFabric _fabric;
        private readonly List<Action<ConfigurationInvalidation>> _handlers = new();

        public Endpoint(FakeInvalidationBusFabric fabric, string originId)
        {
            _fabric = fabric;
            OriginId = originId;
        }

        public string OriginId { get; }

        public void Publish(ConfigurationInvalidationScope scope, string? target)
            => _fabric.Broadcast(new ConfigurationInvalidation { Scope = scope, Target = target, OriginId = OriginId });

        public void Subscribe(Action<ConfigurationInvalidation> handler)
            => _handlers.Add(handler);

        public void Deliver(ConfigurationInvalidation invalidation)
        {
            foreach (var handler in _handlers)
            {
                handler(invalidation);
            }
        }
    }
}