using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.ServiceModel;
using System.Timers;
using DistributedGA.Core.Domain;

namespace DistributedGA.ContactServer {

  [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
  public class ContactServiceImpl : IContactService, IDisposable {

    private ConcurrentDictionary<PeerInfo, DateTime> allPeers = null;

    private Timer timer = null;

    private Object logLock = new Object();

    private Object timerLock = new Object();//if elapsed takes too long, another thread also enters the method

    public ContactServiceImpl() {
      allPeers = new ConcurrentDictionary<PeerInfo, DateTime>();

      timer = new Timer(1000 * 60 * 2); //each minute
      timer.Elapsed += CleanUpContactTable;
      timer.Start();
    }

    public void RegisterPeer(PeerInfo source) {
      try {
        UpdateHeartbeat(source);
      }
      catch (Exception ex) {
        AddError("ContactServiceImpl.RegisterPeer", ex);
      }
    }

    public List<PeerInfo> GetPeerList(PeerInfo source) {
      try {
        UpdateHeartbeat(source);
        //only return peers of the same work group and not the sender itself
        return allPeers.Keys.Where(x => {
          if (source.ProblemInstance.Equals(x.ProblemInstance) &&
              (!(x.IpAddress.Equals(source.IpAddress) && (x.Port.Equals(source.Port)))))
            return true;
          else
            return false;
        }).ToList();
      }
      catch (Exception ex) {
        AddError("ContactServiceImpl.GetPeerList", ex);
        return null;
      }
    }

    public void UpdateHeartbeat(PeerInfo source) {
      try {
        Console.WriteLine("hb from {0}:{1}", source.IpAddress, source.Port);
        DateTime now = DateTime.Now;
        allPeers.AddOrUpdate(source, now, (k, v) => v = now);
      }
      catch (Exception ex) {
        AddError("ContactServiceImpl.UpdateHeartbeat", ex);
      }
    }

    private void CleanUpContactTable(object sender, ElapsedEventArgs e) {
      lock (timerLock) {
        DateTime deadline = DateTime.Now;
        //collect items to remove
        List<PeerInfo> itemsToDelete = new List<PeerInfo>();
        foreach (PeerInfo pi in allPeers.Keys) {
          DateTime tmp;
          if (allPeers.TryGetValue(pi, out tmp)) {
            if (tmp.AddMinutes(2) < deadline) {
              itemsToDelete.Add(pi);
            }
          }
        }
        //remove items
        foreach (PeerInfo pi in itemsToDelete) {
          DateTime tmp;
          allPeers.TryRemove(pi, out tmp);
          Console.WriteLine(string.Format("Removed peer {0}:{1} from dictionary because last access was: {2}", pi.IpAddress, pi.Port, tmp));
        }
      }
    }

    private void AddError(string source, Exception ex) {

    }

    public void Dispose() {
      timer.Stop();
      timer.Dispose();
      timer = null;
    }

  }
}