DHTSpider/Tancoder.Torrent/Nodes/Node.cs

#if !DISABLE_DHT
//
// Node.cs
//
// Authors:
//   Jérémie Laval <jeremie.laval@gmail.com>
//   Alan McGovern <alan.mcgovern@gmail.com>
//
// Copyright (C) 2008 Jérémie Laval, Alan McGovern
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//


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

using Tancoder.Torrent.BEncoding;
using System.Net;
using Tancoder.Torrent.Dht.Messages;
using System.Text;

namespace Tancoder.Torrent.Dht
{
    public class Node : IComparable<Node>, IEquatable<Node>
    {
        public static readonly int MaxFailures = 4;

        IPEndPoint endpoint;
        NodeId id;
        int failedCount;
        DateTime lastSeen;
        BEncodedString token;

        public IPEndPoint EndPoint
        {
            get { return endpoint; }
        }

        public int FailedCount
        {
            get { return failedCount; }
            set { failedCount = value; }
        }

        public NodeId Id
        {
            get { return id; }
        }

        public DateTime LastSeen
        {
            get { return lastSeen; }
            set { lastSeen = value; }
        }

        // FIXME: State should be set properly as per specification.
        // i.e. it needs to take into account the 'LastSeen' property.
        // and must take into account when a node does not send us messages etc
        public NodeState State
        {
            get
            {
                if (failedCount >= MaxFailures)
                    return NodeState.Bad;

                else if (lastSeen == DateTime.MinValue)
                    return NodeState.Unknown;

                return (DateTime.UtcNow - lastSeen).TotalMinutes < 15 ? NodeState.Good : NodeState.Questionable;
            }
        }

        public BEncodedString Token
        {
            get { return token; }
            set { token = value; }
        }

        public Node(NodeId id, IPEndPoint endpoint)
        {
            this.endpoint = endpoint;
            this.id = id;
        }

        public void Seen()
        {
            failedCount = 0;
            lastSeen = DateTime.UtcNow;
        }

        public BEncodedString CompactPort()
        {
            byte[] buffer = new byte[6];
            CompactPort(buffer, 0);
            return buffer;
        }

        public void CompactPort(byte[] buffer, int offset)
        {
            DhtMessage.Write(buffer, offset, endpoint.Address.GetAddressBytes());
            DhtMessage.Write(buffer, offset + 4, (ushort)endpoint.Port);
        }

        public static BEncodedString CompactPort(IList<Node> peers)
        {
            byte[] buffer = new byte[peers.Count * 6];
            for (int i = 0; i < peers.Count; i++)
                peers[i].CompactPort(buffer, i * 6);

            return new BEncodedString(buffer);
        }

        public BEncodedString CompactNode()
        {
            byte[] buffer = new byte[26];
            CompactNode(buffer, 0);
            return buffer;
        }

        private void CompactNode(byte[] buffer, int offset)
        {
            DhtMessage.Write(buffer, offset, id.Bytes);
            CompactPort(buffer, offset + 20);
        }

        public static BEncodedString CompactNode(IList<Node> nodes)
        {
            byte[] buffer = new byte[nodes.Count * 26];
            for (int i = 0; i < nodes.Count; i++)
                nodes[i].CompactNode(buffer, i * 26);

            return new BEncodedString(buffer);
        }

        public static Node FromCompactNode(byte[] buffer, int offset)
        {
            byte[] id = new byte[20];
            Buffer.BlockCopy(buffer, offset, id, 0, 20);
            IPAddress address = new IPAddress((uint)BitConverter.ToInt32(buffer, offset + 20));
            int port = (int)(ushort)IPAddress.NetworkToHostOrder((short)BitConverter.ToUInt16(buffer, offset + 24));
            return new Node(new NodeId(id), new IPEndPoint(address, port));
        }

        public static IEnumerable<Node> FromCompactNode(byte[] buffer)
        {
            for (int i = 0; (i + 26) <= buffer.Length; i += 26)
                yield return FromCompactNode(buffer, i);
        }

        public static IEnumerable<Node> FromCompactNode(BEncodedString nodes)
        {
            return FromCompactNode(nodes.TextBytes);
        }

        public static IEnumerable<Node> FromCompactNode(BEncodedList nodes)
        {
			foreach(BEncodedValue node in nodes)
	        {
                //bad format!
                if (!(node is BEncodedList))
                    continue;
                
	            string host = string.Empty;
	            long port = 0;
	            foreach (BEncodedValue val in (BEncodedList)node)
	            {
	                if(val is BEncodedString)
	                	host = ((BEncodedString)val).Text;
	                else if (val is BEncodedNumber)
	                    port = ((BEncodedNumber)val).Number;
	            }
	            IPAddress address;
	            IPAddress.TryParse(host, out address);
                
                //REM: bad design from bitcomet we do not have node id so create it...
                //or use torrent infohash?
                // Will messages from this node be discarded later on if the NodeId doesn't match?
                if (address != null)
	            	yield return new Node(NodeId.Create(), new IPEndPoint(address, (int)port));
	        }
        }

        //To order by last seen in bucket
        public int CompareTo(Node other)
        {
            if (other == null)
                return 1;
            
            return lastSeen.CompareTo(other.lastSeen);
        }

        public override bool Equals(object obj)
        {
            return Equals(obj as Node);
        }

        public bool Equals(Node other)
        {
            if (other == null)
                return false;

            return id.Equals(other.id);
        }

        public override int GetHashCode()
        {
            return id.GetHashCode();
        }

        public override string ToString()
        {
            StringBuilder sb = new StringBuilder(48);
            for (int i = 0; i < id.Bytes.Length; i++)
            {
                sb.Append(id.Bytes[i]);
                sb.Append("-");
            }
           return sb.ToString(0, sb.Length - 1);
        }

        public static IEnumerable<Node> CloserNodes(NodeId target, SortedList<NodeId, NodeId> currentNodes, IEnumerable<Node> newNodes, int maxNodes)
        {
            foreach (Node node in newNodes)
            {
                if (currentNodes.ContainsValue(node.Id))
                    continue;

                NodeId distance = node.Id.Xor(target);
                if (currentNodes.Count < maxNodes)
                {
                    currentNodes.Add(distance, node.Id);
                }
                else if (distance < currentNodes.Keys[currentNodes.Count - 1])
                {
                    currentNodes.RemoveAt(currentNodes.Count - 1);
                    currentNodes.Add(distance, node.Id);
                }
                else
                {
                    continue;
                }
                yield return node;
            }
        }
    }
}
#endif