// /**
//  * File: CIDR.cs
//  * Author: haraldwolff
//  *
//  * This file and it's content is copyrighted by the Author and / or copyright holder.
//  * Any use wihtout proper permission is illegal and may lead to legal actions.
//  *
//  *
//  **/
using System;
using System.Net;
using System.Linq;
using System.Collections.Generic;
using System.Collections;
using Newtonsoft.Json;
using LiteDB;

namespace ln.types
{
    public class CIDR : IEnumerable<CIDR>
    {
        public static CIDR Parse(String source)
        {
            string[] toks = source.Split('/');
            IPAddress ip = IPAddress.Parse(toks[0]);
            if (toks.Length == 2)
            {
                if (toks[1].IndexOf('.') != -1)
                {
                    IPAddress mask = IPAddress.Parse(toks[1]);
                    return new CIDR(ip, mask);
                }
                else
                {
                    uint w = uint.Parse(toks[1]);
                    return new CIDR(ip, w);
                }
            }
            return new CIDR(ip, 32);
        }

        private readonly uint _ip;
        private readonly uint _netmask;

        public int MaskWidth => (int)getNetWidth(_netmask);
        public CIDR Network => new CIDR(_ip & _netmask, _netmask);
        public CIDR Host => new CIDR(_ip, 0xffffffff);

        public int Size => (1 << (32 - MaskWidth));

        public byte[] IPBytes
        {
            get => BitConverter.GetBytes(_ip).Reverse().ToArray();
            //set => _ip = BitConverter.ToUInt32(value.Reverse().ToArray(), 0);
        }

        public byte[] MaskBytes
        {
            get => BitConverter.GetBytes(_netmask).Reverse().ToArray();
            //set => _netmask = BitConverter.ToUInt32(value.Reverse().ToArray(), 0);
        }

        public CIDR()
        {
        }

        public CIDR(uint ip, uint netmask)
        {
            this._ip = ip;
            this._netmask = netmask;
        }

        public CIDR(CIDR ip)
        {
            this._ip = ip._ip;
            this._netmask = 0xFFFFFFFF;
        }

        public CIDR(CIDR ip, uint maskwidth)
        {
            this._ip = ip._ip;
            this._netmask = maskFromWidth(maskwidth);
        }

        //public CIDR(IPAddress ip, uint maskwidth)
        //{
        //    _ip = BitConverter.ToUInt32(ip.GetAddressBytes().Reverse().ToArray(), 0);
        //    _netmask = maskFromWidth(maskwidth);
        //}

        public CIDR(IPAddress ip, IPAddress mask)
        {
            _ip = BitConverter.ToUInt32(ip.GetAddressBytes().Reverse().ToArray(), 0);
            _netmask = BitConverter.ToUInt32(mask.GetAddressBytes().Reverse().ToArray(), 0);
            getNetWidth(_netmask);
        }

        private uint maskFromWidth(uint value)
        {
            uint nm = 0;
            if (value == 0)
                nm = 0;
            else if (value == 32)
                nm = 0xFFFFFFFF;
            else
            {
                nm = 0xFFFFFFFF;
                nm <<= (int)(32 - value);
            }
            return nm;
        }

        private uint getNetWidth(uint nm)
        {
            uint w = 0;

            for (w = 32; w > 0; w--)
            {
                if ((nm & (1 << (int)(32 - w))) != 0)
                    break;
            }
            for (uint n = w; n > 0; n--)
            {
                if ((nm & (1 << (int)(32 - n))) == 0)
                    throw new FormatException("Netmask with holes");
            }

            return w;
        }

        public CIDR[] Divide(int bits)
        {
            if (MaskWidth + bits > 32)
                throw new ArgumentException("Netmask would be > 32bits", nameof(bits));

            int count = (1 << bits);
            uint newmask = maskFromWidth((uint)(MaskWidth + bits));
            uint nip = _ip;
            CIDR[] result = new CIDR[count];
            for (int n = 0; n < count; n++)
            {
                nip += (uint)(1 << (32 - MaskWidth - bits));
                result[n] = new CIDR(nip, newmask);
            }
            return result;
        }


        public override string ToString()
        {
            if (_netmask == 0xFFFFFFFF)
                return String.Format("{0}", String.Join(".", IPBytes.Select((x) => x.ToString())));
            else
                return String.Format("{0}/{1}", String.Join(".", IPBytes.Select((x) => x.ToString())), getNetWidth(_netmask));
        }

        public static implicit operator IPAddress(CIDR cidr)
        {
            return new IPAddress(cidr.IPBytes);
        }
        public static implicit operator CIDR(IPAddress iPAddress)
        {
            return new CIDR(BitConverter.ToUInt32(iPAddress.GetAddressBytes().Reverse().ToArray(), 0), 0xFFFFFFFF);
        }

        public bool Contains(CIDR you)
        {
            return (you.MaskWidth >= MaskWidth) && ((you._ip & _netmask) == (_ip & _netmask));
        }

        public bool Contains(IEnumerable<CIDR> candidates)
        {
            foreach (CIDR ip in candidates)
                if (Contains(ip))
                    return true;
            return false;
        }


        public override int GetHashCode()
        {
            return (int)(_ip ^ _netmask);
        }
        public override bool Equals(object obj)
        {
            if (obj is IPAddress)
                obj = (CIDR)(obj as IPAddress);

            if (obj is CIDR)
            {
                CIDR you = obj as CIDR;
                return (you._ip == _ip) && (you._netmask == _netmask);
            }
            return false;
        }

        public IEnumerator<CIDR> GetEnumerator()
        {
            return new CIDREnumerator(this);
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        class CIDREnumerator : IEnumerator<CIDR>
        {
            CIDR network;
            CIDR curCIDR;

            public CIDR Current => curCIDR;
            object IEnumerator.Current => curCIDR;

            public CIDREnumerator(CIDR network)
            {
                this.network = network.Network;
                Reset();
            }

            public void Dispose()
            {
            }

            public bool MoveNext()
            {
                curCIDR = new CIDR(curCIDR._ip + 1, 0xFFFFFFFF);
                return network.Contains(curCIDR);
            }

            public void Reset()
            {
                curCIDR = network;
            }
        }


        static CIDR()
        {
            BsonMapper.Global.RegisterType<CIDR>(
                serialize: (ip) => ip.ToString(),
                deserialize: (bson) => CIDR.Parse(bson.AsString)
            );


            List<JsonConverter> converters = new List<JsonConverter>();
            converters.Add(new CIDRJsonConverter());
            JsonConvert.DefaultSettings = () => new JsonSerializerSettings { Converters = converters };
        }

    }

    public class CIDRJsonConverter : JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            return (objectType == typeof(CIDR));
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, Newtonsoft.Json.JsonSerializer serializer)
        {
            return CIDR.Parse(reader.ReadAsString());
        }

        public override void WriteJson(JsonWriter writer, object value, Newtonsoft.Json.JsonSerializer serializer)
        {
            writer.WriteValue((value as CIDR).ToString());
        }

    }

}