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

namespace TorControlLibrary
{
    public class ExitPolicy
    {
        public ExitPolicy() { }
        public ExitPolicy(String policy)
        {
            ParsePolicy(policy);
        }
        public void ParsePolicy(String policy)
        {
            int count = 0;
            StringReader sr = new StringReader(policy);
            while (true)
            {
                String line = sr.ReadLine();
                if (String.IsNullOrEmpty(line))
                    break;
                Policy.Add(count++, new PolicyLine(line));
            }
        }
        public Boolean IsAcceptableDestination(IPEndPoint destination)
        {
            return checkAddress((UInt32)System.Net.IPAddress.HostToNetworkOrder(BitConverter.ToInt32(destination.Address.GetAddressBytes(), 0)), (UInt16)destination.Port);
        }

        public Boolean IsAcceptableDestination(IPAddress address, UInt16 port)
        {
            return checkAddress((UInt32)System.Net.IPAddress.HostToNetworkOrder(BitConverter.ToInt32(address.GetAddressBytes(), 0)), port);
        }
        private Boolean checkAddress(UInt32 address, UInt16 port)
        {
            //the first match dictates the appropriate action
            for (int i = 0; i < Policy.Count; i++)
            {
                if (Policy[i].AddressRangeStart <= address &&
                   Policy[i].AddressRangeEnd >= address)
                    if (Policy[i].PortRangeStart <= port &&
                       Policy[i].PortRangeEnd >= port)
                        return Policy[i].Action.Equals("accept");
            }
            return false;
        }
        private SortedList<Int32, PolicyLine> Policy = new SortedList<int,PolicyLine>();

        class PolicyLine
        {
            public PolicyLine(String line)
            {
                Int32 ptr = line.IndexOf(' ');
                Action = line.Substring(0, ptr);
                ptr++;
                //Address
                String address = line.Substring(ptr, line.IndexOf(':') - ptr);
                if (address.Equals("*"))
                {
                    AddressRangeStart = UInt32.MinValue;
                    AddressRangeEnd = UInt32.MaxValue;
                }
                else
                {
                    if (address.Contains("/"))
                    { //range
                        String[] rangeParts = address.Split('/');
                        System.Net.IPAddress ipAddress = System.Net.IPAddress.Parse(rangeParts[0]);
                        
                        UInt32 mask = ((UInt32)0xFFFFFFFF << (32 - Int32.Parse(rangeParts[1])));
                        AddressRangeStart = BitConverter.ToUInt32(ipAddress.GetAddressBytes(), 0);
                        //Cast to int to avoid long overload
                        AddressRangeStart = (UInt32)System.Net.IPAddress.HostToNetworkOrder((int)AddressRangeStart);

                        AddressRangeEnd = AddressRangeStart | ~(UInt32)mask;
                    }
                    else
                    { //Single IP
                        System.Net.IPAddress ipAddress = System.Net.IPAddress.Parse(address);
                        AddressRangeStart = BitConverter.ToUInt32(ipAddress.GetAddressBytes(),0);
                        AddressRangeEnd = BitConverter.ToUInt32(ipAddress.GetAddressBytes(), 0);
                    }
                }
                //Port
                ptr = line.IndexOf(':') + 1;
                String port = line.Substring(ptr);
                if (port.Equals("*"))
                {
                    PortRangeStart = UInt16.MinValue;
                    PortRangeEnd = UInt16.MaxValue;
                }
                else
                {
                    if (port.Contains("-"))
                    { //range
                        String[] portParts = port.Split('-');
                        PortRangeStart = UInt16.Parse(portParts[0]);
                        PortRangeEnd = UInt16.Parse(portParts[1]);
                    }
                    else
                    {
                        PortRangeStart = UInt16.Parse(port);
                        PortRangeEnd = UInt16.Parse(port);
                    }
                }
            }
            public String Action { get; set; }
            public UInt32 AddressRangeStart { get; set; }
            public UInt32 AddressRangeEnd { get; set; }
            public UInt16 PortRangeStart { get; set; }
            public UInt16 PortRangeEnd { get; set; }
        }
    }
}