using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Websockets.Managers
{
  public interface ISocketTokenManager
  {
    Guid GenerateToken(string s);
    string GetUsername(Guid g);
  }

  public class SocketTokenManager : ISocketTokenManager
  {
    /// <summary>
    /// Key is userName
    /// </summary>
    private readonly Dictionary<string, Guid> Tokens;

    public SocketTokenManager()
    {
      Tokens = new Dictionary<string, Guid>();
    }

    public Guid GenerateToken(string userName)
    {
      var guid = Guid.NewGuid();

      if (Tokens.ContainsKey(userName))
      {
        Tokens.Remove(userName);
      }
      Tokens.Add(userName, guid);

      _ = Task.Run(async () =>
      {
        await Task.Delay(TimeSpan.FromMinutes(1));
        Tokens.Remove(userName);
      });

      return guid;
    }

    /// <returns>User name associated to the guid or null.</returns>
    public string GetUsername(Guid guid)
    {
      if (Tokens.ContainsValue(guid))
      {
        var username = Tokens.First(kvp => kvp.Value == guid).Key;
        Tokens.Remove(username);
        return username;
      }
      return null;
    }
  }
}