using System;
using System.Collections.Generic;

sealed class Axfr : Task
{
  private uint NextRun;
  private uint Stage;
  private uint Refresh = 600;
  private uint Retry = 600;

  private void Finish( bool Ok )
  {
    Stage = 0;
    uint Wait = ( Ok ? Refresh : Retry ) + 1;
    Wait -= (uint)Random.Number( (int)Wait / 5 ); // Random 20% variation.
    NextRun = Cache.Clock + Wait;
    #if (Trace)
      Log( "Finished : Ok=" + Ok + " Wait=" + Wait + " seconds" );
    #endif
    TaskFinished();
  }

  public override void Go()
  {
    if ( Stage == 0 ) 
    {
      TaskInit();
      #if (Trace)
        LogX( "Running" );
      #endif
    }
    lock ( Cache.Workers )
    {
      if ( Stage == 0 )
      {
        Worker.Recurse( QName, QT.SOA, this ); // Forces update of cached SOA
        Stage = 1;
      }
      else if ( Stage == 1 )
      {
        RRset SOA = QName.Get( QT.ServerFail, DC.Wire ); // Make sure we detect ServerFail
        if ( SOA == null ) SOA = QName.Get( QT.SOA, DC.Wire );
        if ( SOA == null )
          Worker.Recurse( QName, QT.SOA, this );
        else if ( SOA.Type == QT.SOA )
        {
          Refresh = SOA_Help.GetRefresh(SOA);
          Retry = SOA_Help.GetRetry(SOA); 

          RRset Old = QName.Get( QT.SOA, DC.Zone );
          uint NewSerial = SOA_Help.GetSerial(SOA);
          bool Same = SOA_Help.GetSerial(Old) == NewSerial;
          #if (Trace)
            Log( "Got Serial " + NewSerial + " Same=" + Same );
          #endif
          if ( Same )        
            Finish( true );
          else
          {
            Worker.Recurse( QName, QT.AXFR, this );
            Stage = 2;
          }
        }
        else 
        {
          #if (Trace)
            Log( "Failed to fetch SOA for " + QName );
          #endif
          Finish( false );
        }
      }
      else // Stage == 2
      {
        bool Ok = false;
        RRset X = QName.Get( QT.AXFR );
        if ( X != null && X.Type == QT.AXFR )
        {
          NamedRRset[] L = X.Extra.ToArray();
          Loader.LoadZone( QName, L, ZoneSource.AXFR );
          Loader.SaveToFile( QName, L );
          Ok = true;
        }
        Finish( Ok );
      }
    }
  }

  private static List<Axfr> TaskList = new List<Axfr>();

  public Axfr( Domain Zone ) : base( Zone, QT.AXFR )
  {
    Zone.RefCount += 1;
    Cache.SetClock();
    NextRun = Cache.Clock + 5 + (uint)Random.Number(5); // Schedule to run in next 5-10 seconds
    TaskList.Add( this );
  }

  public static void Run()
  {
    Cache.SetClock();
    foreach ( Axfr A in TaskList )    
    {
      if ( !A.Running && Cache.Clock >= A.NextRun )
      {
        A.Go();
        return;
      }
    }
  }

}