using System;
using System.Diagnostics;

namespace Zeroconf.DNS
{
    #region RR definitions
    /*
    3.2. RR definitions

    3.2.1. Format

    All RRs have the same top level format shown below:

                                        1  1  1  1  1  1
          0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                                               |
        /                                               /
        /                      NAME                     /
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                      TYPE                     |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                     CLASS                     |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                      TTL                      |
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                   RDLENGTH                    |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
        /                     RDATA                     /
        /                                               /
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+


    where:

    NAME            an owner name, i.e., the name of the node to which this
                    resource record pertains.

    TYPE            two octets containing one of the RR TYPE codes.

    CLASS           two octets containing one of the RR CLASS codes.

    TTL             a 32 bit signed integer that specifies the time interval
                    that the resource record may be cached before the source
                    of the information should again be consulted.  Zero
                    values are interpreted to mean that the RR can only be
                    used for the transaction in progress, and should not be
                    cached.  For example, SOA records are always distributed
                    with a zero TTL to prohibit caching.  Zero values can
                    also be used for extremely volatile data.

    RDLENGTH        an unsigned 16 bit integer that specifies the length in
                    octets of the RDATA field.

    RDATA           a variable length string of octets that describes the
                    resource.  The format of this information varies
                    according to the TYPE and CLASS of the resource record.
    */
    #endregion

    /// <summary>
    /// Resource Record (rfc1034 3.6.)
    /// </summary>
    [DebuggerDisplay("Name = {NAME} TTL={TTL} Class={Class} Type = {Type} Record={RECORD}")]
    internal class RR
    {
        /// <summary>
        /// The name of the node to which this resource record pertains
        /// </summary>
        public string NAME;

        /// <summary>
        /// Specifies type of resource record
        /// </summary>
        public Type Type;

        /// <summary>
        /// Specifies type class of resource record, mostly IN but can be CS, CH or HS 
        /// </summary>
        public Class Class;

        /// <summary>
        /// Time to live, the time interval that the resource record may be cached
        /// </summary>
        public uint TTL
        {
            get => (uint)Math.Max(0, m_TTL - TimeLived);
            set => m_TTL = value;
        }

        private uint m_TTL;

        /// <summary>
        /// 
        /// </summary>
        public ushort RDLENGTH;

        /// <summary>
        /// One of the Record* classes
        /// </summary>
        public Record RECORD;

        public int TimeLived;

        public RR(RecordReader rr)
        {
            TimeLived = 0;
            NAME = rr.ReadDomainName();
            Type = (Type)rr.ReadUInt16();
            Class = (Class)rr.ReadUInt16();
            TTL = rr.ReadUInt32();
            RDLENGTH = rr.ReadUInt16();
            RECORD = rr.ReadRecord(Type, RDLENGTH);
            RECORD.RR = this;
        }

        public override string ToString()
        {
            return string.Format("{0,-32} {1}\t{2}\t{3}\t{4}",
                NAME,
                TTL,
                Class,
                Type,
                RECORD);
        }
    }

    internal class AnswerRR : RR
    {
        public AnswerRR(RecordReader br)
            : base(br)
        {
        }
    }

    internal class AuthorityRR : RR
    {
        public AuthorityRR(RecordReader br)
            : base(br)
        {
        }
    }

    internal class AdditionalRR : RR
    {
        public AdditionalRR(RecordReader br)
            : base(br)
        {
        }
    }
}
