using Microsoft.Extensions.Primitives;
using Yarp.ReverseProxy.Configuration;

public sealed class InMemoryConfigProvider : IProxyConfigProvider
{
    private volatile InMemoryConfig _config;

    public InMemoryConfigProvider(IReadOnlyList<RouteConfig> routes,
                                  IReadOnlyList<ClusterConfig> clusters)
    {
        _config = new InMemoryConfig(routes, clusters);
    }

    public IProxyConfig GetConfig() => _config;

    public void Update(IReadOnlyList<RouteConfig> routes,
                       IReadOnlyList<ClusterConfig> clusters)
    {
        var old = _config;
        _config = new InMemoryConfig(routes, clusters);
        old.SignalChange();   // 触发 YARP 重新加载
    }

    private sealed class InMemoryConfig : IProxyConfig
    {
        private readonly CancellationTokenSource _cts = new();
        public InMemoryConfig(IReadOnlyList<RouteConfig> routes,
                              IReadOnlyList<ClusterConfig> clusters)
        {
            Routes  = routes;
            Clusters = clusters;
            ChangeToken = new CancellationChangeToken(_cts.Token);
        }
        public IReadOnlyList<RouteConfig>  Routes  { get; }
        public IReadOnlyList<ClusterConfig> Clusters { get; }
        public IChangeToken ChangeToken { get; }

        internal void SignalChange() => _cts.Cancel();
    }
}