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

namespace IP_Filtering
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(IsInStringContext("192.168.0.1")); //Should return true
            Console.WriteLine(IsInStringContext("192.168.0.2")); //Should return true
            Console.WriteLine(IsInStringContext("192.168.0.3")); //Should return false
            Console.WriteLine(IsInStringContext("192.168.1.133")); //Should return true (in range)
            Console.WriteLine(IsInStringContext("192.168.4.54")); //Should return true (in range)
            Console.WriteLine(IsInStringContext("192.168.4.53")); //Should return false (not in range)
            Console.WriteLine(IsInStringContext("192.168.2.34")); //Should return true (in CIDR range)
            Console.WriteLine(IsInStringContext("192.168.3.34")); //Should return false (not in CIDR range)
            Console.WriteLine(IsInStringContext("192.168.3.212")); //Should return true (in CIDR range) !!
        }

        private static readonly List<string> StringDataContext = new List<string>{
            "192.168.0.1", "192.168.0.2", "192.168.1.0 - 192.168.1.255", "192.168.2.0/24", "192.168.3.128/25", "192.168.4.54 - 192.168.4.62"
        };

        public static bool IsInStringContext(string ip)
        {
            //Check if it's explicitly in the data context
            if (StringDataContext.Exists(d => d == ip))
                return true;

            var givenIPOctets = ip.Split('.');

            //Next, check if it's in range
            //For this, I am going to assume IP ranges can only be a range of the last octet
            foreach (string address in StringDataContext.Where(sdc => sdc.Contains('-')))
            {
                string[] addresses = address.Replace(" ", "").Split('-');
                string[] firstAddressOctets = addresses[0].Split('.');
                string[] secondAddressOctets = addresses[1].Split('.');

                //Make sure first three octets are the same
                if (givenIPOctets[0] != firstAddressOctets[0] ||
                    givenIPOctets[1] != firstAddressOctets[1] ||
                    givenIPOctets[2] != firstAddressOctets[2])
                {
                    continue;
                }

                int ipAddressLastOctet = int.Parse(givenIPOctets[3]);
                int firstAddressLastOctet = int.Parse(firstAddressOctets[3]);
                int secondAddressLastOctet = int.Parse(secondAddressOctets[3]);

                if (ipAddressLastOctet >= firstAddressLastOctet && ipAddressLastOctet <= secondAddressLastOctet)
                    return true;
            }

            //Lastly, check if it's in CIDR range.
            //Again, I'm going to assume IP ranges can only be part of the last octet.
            foreach (string address in StringDataContext.Where(sdc => sdc.Contains('/')))
            {
                string[] ipAddress = address.Split('/');
                string[] octets = ipAddress[0].Split('.');

                if (givenIPOctets[0] != octets[0] ||
                    givenIPOctets[1] != octets[1] ||
                    givenIPOctets[2] != octets[2])
                {
                    continue;
                }

                int maxOctet = (int)Math.Pow(2, 32 - int.Parse(ipAddress[1])) + int.Parse(octets[3]);
                if (int.Parse(givenIPOctets[3]) >= int.Parse(octets[3]) && int.Parse(givenIPOctets[3]) <= maxOctet)
                    return true;
            }
            return false;
        }
    }
}