using System;
using System.IO;

namespace Org.BouncyCastle.Tls
{
    /// <summary>RFC 6066 3. Server Name Indication</summary>
    /// <remarks>
    /// Current implementation uses this guidance: "For backward compatibility, all future data structures associated
    /// with new NameTypes MUST begin with a 16-bit length field. TLS MAY treat provided server names as opaque data
    /// and pass the names and types to the application.". RFC 6066 specifies ASCII encoding for host_name (possibly
    /// using A-labels for IDNs), but note that the previous version (RFC 4366) specified UTF-8 encoding (see RFC 6066
    /// Appendix A). For maximum compatibility, it is recommended that client code tolerate receiving UTF-8 from the
    /// peer, but only generate ASCII itself.
    /// </remarks>
    public sealed class ServerName
    {
        private readonly short nameType;
        private readonly byte[] nameData;

        public ServerName(short nameType, byte[] nameData)
        {
            if (!TlsUtilities.IsValidUint8(nameType))
                throw new ArgumentException("must be from 0 to 255", "nameType");
            if (null == nameData)
                throw new ArgumentNullException("nameData");
            if (nameData.Length < 1 || !TlsUtilities.IsValidUint16(nameData.Length))
                throw new ArgumentException("must have length from 1 to 65535", "nameData");

            this.nameType = nameType;
            this.nameData = nameData;
        }

        public byte[] NameData
        {
            get { return nameData; }
        }

        public short NameType
        {
            get { return nameType; }
        }

        /// <summary>Encode this <see cref="ServerName"/> to a <see cref="Stream"/>.</summary>
        /// <param name="output">the <see cref="Stream"/> to encode to.</param>
        /// <exception cref="IOException"/>
        public void Encode(Stream output)
        {
            TlsUtilities.WriteUint8(nameType, output);
            TlsUtilities.WriteOpaque16(nameData, output);
        }

        /// <summary>Parse a <see cref="ServerName"/> from a <see cref="Stream"/>.</summary>
        /// <param name="input">the <see cref="Stream"/> to parse from.</param>
        /// <returns>a <see cref="ServerName"/> object.</returns>
        /// <exception cref="IOException"/>
        public static ServerName Parse(Stream input)
        {
            short name_type = TlsUtilities.ReadUint8(input);
            byte[] nameData = TlsUtilities.ReadOpaque16(input, 1);
            return new ServerName(name_type, nameData);
        }
    }
}