// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections;
using Microsoft.AspNetCore.Connections.Features;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Http.Features.Authentication;
 
namespace Microsoft.AspNetCore.Server.HttpSys;
 
internal sealed class StandardFeatureCollection : IFeatureCollection
{
    private static readonly Func<RequestContext, object> _identityFunc = ReturnIdentity;
    private static readonly Dictionary<Type, Func<RequestContext, object?>> _featureFuncLookup = new()
    {
        { typeof(IHttpRequestFeature), _identityFunc },
        { typeof(IHttpRequestBodyDetectionFeature), _identityFunc },
        { typeof(IHttpConnectionFeature), _identityFunc },
        { typeof(IHttpResponseFeature), _identityFunc },
        { typeof(IHttpResponseBodyFeature), _identityFunc },
        { typeof(ITlsConnectionFeature), ctx => ctx.GetTlsConnectionFeature() },
        { typeof(IHttpRequestLifetimeFeature), _identityFunc },
        { typeof(IHttpAuthenticationFeature), _identityFunc },
        { typeof(IHttpRequestIdentifierFeature), _identityFunc },
        { typeof(RequestContext), ctx => ctx },
        { typeof(IHttpMaxRequestBodySizeFeature), _identityFunc },
        { typeof(IHttpBodyControlFeature), _identityFunc },
        { typeof(IHttpSysRequestInfoFeature), _identityFunc },
        { typeof(IHttpSysRequestTimingFeature), _identityFunc },
        { typeof(IHttpResponseTrailersFeature), ctx => ctx.GetResponseTrailersFeature() },
        { typeof(IHttpResetFeature), ctx => ctx.GetResetFeature() },
        { typeof(IConnectionLifetimeNotificationFeature), ctx => ctx.GetConnectionLifetimeNotificationFeature() },
    };
 
    private readonly RequestContext _featureContext;
 
    static StandardFeatureCollection()
    {
        if (ComNetOS.IsWin8orLater)
        {
            // Only add the upgrade feature if it stands a chance of working.
            // SignalR uses the presence of the feature to detect feature support.
            // https://github.com/aspnet/HttpSysServer/issues/427
            _featureFuncLookup[typeof(IHttpUpgradeFeature)] = _identityFunc;
            // Win8+
            _featureFuncLookup[typeof(ITlsHandshakeFeature)] = ctx => ctx.GetTlsHandshakeFeature();
        }
 
        if (HttpApi.SupportsDelegation)
        {
            _featureFuncLookup[typeof(IHttpSysRequestDelegationFeature)] = _identityFunc;
        }
    }
 
    public StandardFeatureCollection(RequestContext featureContext)
    {
        _featureContext = featureContext;
    }
 
    public bool IsReadOnly
    {
        get { return true; }
    }
 
    public int Revision
    {
        get { return 0; }
    }
 
    public object? this[Type key]
    {
        get
        {
            Func<RequestContext, object?>? lookupFunc;
            _featureFuncLookup.TryGetValue(key, out lookupFunc);
            return lookupFunc?.Invoke(_featureContext);
        }
        set
        {
            throw new InvalidOperationException("The collection is read-only");
        }
    }
 
    private static object ReturnIdentity(RequestContext featureContext)
    {
        return featureContext;
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return ((IEnumerable<KeyValuePair<Type, object>>)this).GetEnumerator();
    }
 
    IEnumerator<KeyValuePair<Type, object>> IEnumerable<KeyValuePair<Type, object>>.GetEnumerator()
    {
        foreach (var featureFunc in _featureFuncLookup)
        {
            var feature = featureFunc.Value(_featureContext);
            if (feature != null)
            {
                yield return new KeyValuePair<Type, object>(featureFunc.Key, feature);
            }
        }
    }
 
    public TFeature? Get<TFeature>()
    {
        return (TFeature?)this[typeof(TFeature)];
    }
 
    public void Set<TFeature>(TFeature? instance)
    {
        this[typeof(TFeature)] = instance;
    }
}