using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;

namespace UdPunching
{
    public class ExchangeMessage
    {
        // [0....] Flags
        // [1....] Section count
        // [2....] Section Type
        // [3...N] Section Content
        // [N+1..] Next Section Type

        public ExchangeMessageFlags Flags { get; set; }

        public DateTime? PeerTimeStamp { get; set; }

        public IPEndPoint PeerEndPoint { get; set; }

        public Guid? PeerId { get; set; }

        //TODO: more properties

        public ExchangeMessage()
        {
        }

        public ExchangeMessage(byte[] data)
        {
            var ptr = -1;
            Flags = (ExchangeMessageFlags)data[++ptr];

            var count = data[++ptr];
            for (var i = 0; i < count; i++)
            {
                var section = (ExchangeMessageSection)data[++ptr];
                switch (section)
                {
                    case ExchangeMessageSection.TimeStamp:
                        ptr += data.ReadUnixTimeStamp(++ptr, out var timeStamp);
                        PeerTimeStamp = timeStamp;
                        break;

                    case ExchangeMessageSection.PeerEndPoint:
                        ptr += data.ReadIpEndPoint(++ptr, out var ipEndPoint);
                        PeerEndPoint = ipEndPoint;
                        break;

                    case ExchangeMessageSection.PeerId:
                        PeerId = new Guid(data.Skip(++ptr).Take(16).ToArray());
                        ptr += 16;
                        break;

                    default:
                        //TODO: handle more sections
                        throw new ArgumentOutOfRangeException();
                }
            }
        }

        private Dictionary<ExchangeMessageSection, byte[]> CreateSectionDictionary()
        {
            var dic = new Dictionary<ExchangeMessageSection, byte[]>();

            if (PeerTimeStamp.HasValue)
            {
                dic[ExchangeMessageSection.TimeStamp] = PeerTimeStamp.Value.ToUnixTimeStamp().ToLeBytes();
            }

            if (null != PeerEndPoint)
            {
                var buf = new byte[17];
                PeerEndPoint.Address.ToPaddingString().ToAsciiBytes(buf);
                PeerEndPoint.Port.ToLe16Bytes(buf, 15);
                dic[ExchangeMessageSection.PeerEndPoint] = buf;
            }

            if (PeerId.HasValue)
            {
                dic[ExchangeMessageSection.PeerId] = PeerId.Value.ToByteArray();
            }

            //TODO: add more sections from properties

            return dic;
        }

        public byte[] ToBytes()
        {
            var dic = CreateSectionDictionary();

            var lst = new List<byte>(1 + 1 + dic.Count + dic.Sum(p => p.Value.Length))
            {
                (byte)Flags,
                (byte)dic.Count
            };

            foreach (var kvp in dic)
            {
                lst.Add((byte)kvp.Key);
                lst.AddRange(kvp.Value);
            }

            return lst.ToArray();
        }

        public void WriteToBuffer(byte[] buffer)
        {
            var dic = CreateSectionDictionary();

            var ptr = -1;
            buffer[++ptr] = (byte)Flags;
            buffer[++ptr] = (byte)dic.Count;

            foreach (var item in dic)
            {
                buffer[++ptr] = (byte)item.Key;
                item.Value.CopyTo(buffer, ++ptr);
            }
        }
    }
}