// /**
//  * 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.Linq;
using System.Collections.Generic;
using System.Collections;

namespace ln.types.net
{
    public class Network4 : IEnumerable<IPv4>
    {
        public static Network4 Parse(String source)
        {
            string[] toks = source.Split('/');
            IPv4 ipv4 = IPv4.Parse(toks[0]);

            if (toks.Length == 2)
            {
                if (toks[1].IndexOf('.') != -1)
                {
                    IPv4 mask = IPv4.Parse(toks[1]);
                    return new Network4(ipv4, mask);
                }
                else
                {
                    uint w = uint.Parse(toks[1]);
                    return new Network4(ipv4, w);
                }
            }
            return ipv4;
        }

        private readonly IPv4 network;
        public IPv4 Network => network;

        private readonly IPv4 netmask;
        public IPv4 Netmask => netmask;

        public uint Width => getNetWidth(netmask.AsUInt);
        public int Size => 1 << (int)(32-Width);

        /* Erste IP dieses Netzbereich */
        public IPv4 First => network;                                 
        /* Letzte IP in diesem Netzbereich */  
        public IPv4 Last => new IPv4(network.AsUInt + (uint)Size - 1);
        /* Erste IP folgend diesem Netzbereich */
        public IPv4 Next => new IPv4(network.AsUInt + (uint)Size);

        public Network4()
        {
        }

        public Network4(uint ip, uint mask)
        {
            network = new IPv4(ip & mask);
            netmask = new IPv4(mask);
            getNetWidth(netmask.AsUInt);
        }
        public Network4(IPv4 ip, IPv4 mask)
            :this(ip.AsUInt,mask.AsUInt)
        {}
        public Network4(IPv4 ip, uint mask)
            :this(ip.AsUInt, maskFromWidth(mask))
        {}

        private static 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 static 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 Network4[] Divide(int bits)
        {
            if (Width + bits > 32)
                throw new ArgumentException("Netmask would be > 32bits", nameof(bits));

            int count = (1 << bits);
            uint newmask = maskFromWidth((uint)(Width + bits));
            uint nip = network.AsUInt;

            Network4[] result = new Network4[count];
            for (int n = 0; n < count; n++)
            {
                result[n] = new Network4(nip, newmask);
                nip += (uint)(1 << (int)(32 - Width - bits));
            }
            return result;
        }

        public override string ToString()
        {
            return String.Format("{0}/{1}", String.Join(".", Network.IPBytes.Select((x) => x.ToString())), Width);
        }

        public static implicit operator Network4(IPv4 ip)
        {
            return new Network4(ip, 32);
        }


        public bool Contains(IPv4 ip)
        {
            return ((ip.AsUInt & netmask.AsUInt) == (network.AsUInt));
        }
        public bool Contains(Network4 other)
        {
            return (other.First >= First) && (other.Last <= Last);
        }

        public bool Contains(IEnumerable<IPv4> candidates)
        {
            foreach (IPv4 ip in candidates)
                if (Contains(ip))
                    return true;
            return false;
        }


        public override int GetHashCode()
        {
            return (int)(Network.GetHashCode() ^ Netmask.GetHashCode());
        }
        public override bool Equals(object obj)
        {
            if (obj is IPv4)
            {
                IPv4 you = obj as IPv4;
                return (Width == 32) && network.Equals(you);
            }
            else if (obj is Network4)
            {
                Network4 you = obj as Network4;
                return (network.Equals(you.network) && netmask.Equals(you.netmask));
            }
            return false;
        }

        public IEnumerator<IPv4> GetEnumerator()
        {
            return new Network4Enumerator(this);
        }

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

        class Network4Enumerator : IEnumerator<IPv4>
        {
            Network4 net4;
            IPv4 currentIP;

            public IPv4 Current => currentIP;
            object IEnumerator.Current => currentIP;

            public Network4Enumerator(Network4 network)
            {
                this.net4 = network;
                Reset();
            }

            public void Dispose()
            {
            }

            public bool MoveNext()
            {
                if (currentIP == null)
                    currentIP = net4.network;
                else
                    currentIP++;

                return net4.Contains(currentIP);
            }

            public void Reset()
            {
                currentIP = null;
            }
        }
    }
}