import java.io.*;
   import java.util.ArrayList;
   import java.net.*;

    public class Server
   {
        int seqNum = 1;
      File readFile = null;
        DatagramSocket serverSocket;
        ObjectInputStream is;
        Boolean hasTimedOut=false;
        int portNum=43730;
        //check file
       public void openFile(String theFile)
      {
         try
         {
            readFile = new File(theFile);
         }
         catch(Exception e)
         {
            System.out.println("File error");
         }
      }

       public void runServer(int theplSize, String tHost, int toValue)
       {
         try
         {

            ObjectOutputStream out = null;
            ObjectInputStream in=null;

            DatagramPacket dPacket = null;
                DatagramPacket dPacketEnd=null;
            Packet packetAck=null;
                serverSocket=new DatagramSocket();
                byte[] fileContent=null;

                FileInputStream fin = new FileInputStream(readFile);
                while(true)
                {
            try
            {

                        //read from file

                    if(!hasTimedOut)
                    {

                        //determine if the file is shorter than the payload size
                    if(theplSize>readFile.length() && seqNum==1)
                    {
                        fileContent=new byte[(int)readFile.length()];
                    }
                    else if(theplSize<readFile.length())
                    {
                        fileContent=new byte[theplSize];
                    }
                    else
                    {
                        fileContent=new byte[fin.available()];
                    }
                        fin.read(fileContent);
                    }
               //System.out.println("available: "+fin.available());
                  //make packet
               Packet packetS = new Packet();
               packetS.setPayLoad(fileContent);

                        //print payload
               // for(int i=0;i<packetS.getLength();i++)
//                  {
//                      System.out.print(packetS.getPayLoad()[i]);
//                  }

                  //checksum payload
               packetS.setCheckSum(packetS.getLength());
                    System.out.println();
              // System.out.println("CheckSum: " + packetS.getCheckSum());
                //  System.out.println("lenth of packet: "+packetS.getPayLoad().length);

                  //increment seqNum
               packetS.setSeqNum(seqNum);
                    System.out.println("SeqNum: " + packetS.getSeqNum());


                  //make outputstream
               InetAddress address = InetAddress.getByName(tHost);
               ByteArrayOutputStream byteStream = new ByteArrayOutputStream(6400);
               ObjectOutputStream os = new ObjectOutputStream(new BufferedOutputStream(byteStream));
               os.flush();
               os.writeObject(packetS);
               os.flush();

               byte[] sendBuf = byteStream.toByteArray();
               dPacket = new DatagramPacket(sendBuf, sendBuf.length, address,portNum);
               serverSocket.send(dPacket);
               serverSocket.setSoTimeout(toValue);
               System.out.println("Object sent");


                    //recieve ack packet
               byte[] recvBuf = new byte[6400];
               DatagramPacket packet = new DatagramPacket(recvBuf,recvBuf.length);
               serverSocket.receive(packet);
               ByteArrayInputStream byteStreamIn = new ByteArrayInputStream(recvBuf);
               is = new ObjectInputStream(new BufferedInputStream(byteStreamIn));

                //read Packet
               packetAck =(Packet)is.readObject();
                    if (packetAck.getSeqNum()==seqNum)
               {
                   seqNum++;
               }

               System.out.println("Got ack packet for packet number: "+ packetAck.getSeqNum());
                    //check if payload was corrupted
               if(packetS.getCheckSum()==(packetAck.getCheckSum()))
               {
                  System.out.println("Packet "+packetS.getSeqNum()+" was not corrupted.");
                        hasTimedOut=false;
               }
               else
                    {
                  System.out.println("Packet "+packetS.getSeqNum()+" was corrupted.");
                        hasTimedOut=true;
                   }



                        //check if file is done being transfered
                    if(fin.available()==0)
                    {

                        Packet packetEnd = new Packet();
                        packetEnd.setSeqNum(-1);
                        ByteArrayOutputStream byteStreamEnd = new ByteArrayOutputStream(6400);
                     ObjectOutputStream osEnd = new ObjectOutputStream(new BufferedOutputStream(byteStreamEnd));
                osEnd.flush();
                osEnd.writeObject(packetEnd);
                osEnd.flush();

                         byte[] sendBufEnd = byteStreamEnd.toByteArray();
                 dPacketEnd = new DatagramPacket(sendBufEnd, sendBufEnd.length, address,43730);
                 serverSocket.send(dPacketEnd);
                    serverSocket.setSoTimeout(toValue);
                 System.out.println("End of File packet sent.");
                         System.out.println();
                        System.out.println("***Done transfering***");
                         break;
                    }


            }
            catch (SocketTimeoutException to)
            {

                    System.out.println("Time Out");
                    hasTimedOut=true;

            }
            catch (IOException ex)
            {
               ex.printStackTrace();
            }
                //close loop
                }
                is.close();

                serverSocket.close();

         }


         catch (Exception e)
         {
            e.printStackTrace();
         }


      }



   }