// 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 System.Diagnostics.CodeAnalysis;
using System.Text;

namespace System.Net.Http
{
    internal sealed class HttpAuthority : IEquatable<HttpAuthority>
    {
        // ALPN Protocol Name should also be part of an authority, but we are special-casing for HTTP/3, so this can be assumed to be "H3".
        // public string AlpnProtocolName { get; }

        public string IdnHost { get; }
        public string HostValue { get; }
        public int Port { get; }

        public HttpAuthority(string host, int port)
        {
            Debug.Assert(host != null);

            // This is very rarely called, but could be optimized to avoid the URI-specific stuff by bringing in DomainNameHelpers from System.Private.Uri.
            var builder = new UriBuilder(Uri.UriSchemeHttp, host, port);
            Uri uri = builder.Uri;

            if (uri.HostNameType == UriHostNameType.IPv6)
            {
                // This includes brackets for IPv6 and ScopeId for IPv6 LLA so Connect works.
                IdnHost = $"[{uri.IdnHost}]";
                // This is bracket enclosed IPv6 without ScopeID for LLA
                HostValue = uri.Host;
            }
            else
            {
                // IPv4 address, dns or puny encoded name
                HostValue = IdnHost = uri.IdnHost;
            }

            if (!Ascii.IsValid(HostValue))
            {
                Debug.Assert(uri.HostNameType == UriHostNameType.Basic);

                // This is not a DNS host and it contains non-ASCII characters.
                // Uri failed to Punycode encode it, likely because one of the labels was too long for DNS.
                throw new HttpRequestException(SR.net_http_request_invalid_host_punycode);
            }

            Port = port;
        }

        public bool Equals([NotNullWhen(true)] HttpAuthority? other)
        {
            return other != null && string.Equals(IdnHost, other.IdnHost) && Port == other.Port;
        }

        public override bool Equals([NotNullWhen(true)] object? obj)
        {
            return obj is HttpAuthority other && Equals(other);
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(IdnHost, Port);
        }

        // For diagnostics
        public override string ToString()
        {
            return IdnHost != null ? $"{IdnHost}:{Port}" : "<empty>";
        }

        public static bool operator ==(HttpAuthority? left, HttpAuthority? right)
        {
            return left is null ? right is null : left.Equals(right);
        }
        public static bool operator !=(HttpAuthority? left, HttpAuthority? right)
            => !(left == right);
    }
}