// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Diagnostics;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.Extensions.Primitives;
 
namespace Microsoft.Extensions.ServiceDiscovery;
 
/// <summary>
/// Represents a collection of service endpoints.
/// </summary>
[DebuggerDisplay("{ToString(),nq}")]
[DebuggerTypeProxy(typeof(ServiceEndpointCollectionDebuggerView))]
public sealed class ServiceEndpointSource
{
    private readonly List<ServiceEndpoint>? _endpoints;
 
    /// <summary>
    /// Initializes a new <see cref="ServiceEndpointSource"/> instance.
    /// </summary>
    /// <param name="endpoints">The endpoints.</param>
    /// <param name="changeToken">The change token.</param>
    /// <param name="features">The feature collection.</param>
    public ServiceEndpointSource(List<ServiceEndpoint>? endpoints, IChangeToken changeToken, IFeatureCollection features)
    {
        ArgumentNullException.ThrowIfNull(changeToken);
        ArgumentNullException.ThrowIfNull(features);
 
        _endpoints = endpoints;
        Features = features;
        ChangeToken = changeToken;
    }
 
    /// <summary>
    /// Gets the endpoints.
    /// </summary>
    public IReadOnlyList<ServiceEndpoint> Endpoints => _endpoints ?? (IReadOnlyList<ServiceEndpoint>)[];
 
    /// <summary>
    /// Gets the change token which indicates when this collection should be refreshed.
    /// </summary>
    public IChangeToken ChangeToken { get; }
 
    /// <summary>
    /// Gets the feature collection.
    /// </summary>
    public IFeatureCollection Features { get; }
 
    /// <inheritdoc/>
    public override string ToString()
    {
        if (_endpoints is not { } eps)
        {
            return "[]";
        }
 
        return $"[{string.Join(", ", eps)}]";
    }
 
    private sealed class ServiceEndpointCollectionDebuggerView(ServiceEndpointSource value)
    {
        public IChangeToken ChangeToken => value.ChangeToken;
 
        public IFeatureCollection Features => value.Features;
 
        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
        public ServiceEndpoint[] Endpoints => value.Endpoints.ToArray();
    }
}