/* checks to make sure the server can work when a client leaves it 
   hanging... */

#include <stdio.h>      /* standard C i/o facilities */
#include <stdlib.h>     /* needed for atoi() */
#include <unistd.h>  	/* defines STDIN_FILENO, system calls,etc */
#include <sys/types.h>  /* system data type definitions */
#include <sys/socket.h> /* socket specific definitions */
#include <netinet/in.h> /* INET constants and stuff */
#include <arpa/inet.h>  /* IP address conversion stuff */
#include <netdb.h>	/* gethostbyname */
#include <sys/time.h>
#include "support.h"


int waitandack(int sk, struct sockaddr_in *s,int bnum) {
  char buff[1000];
  int len;
  int opcode,block;

  if ((len=wait_for_response(sk,s,buff,1000))==0) {
    printf("No Response from server\n");
    return(0);
  }
  opcode = get_opcode(buff);
  block = get_blocknum(buff);
  if ((opcode != DATA) || (block != bnum)) {
    printf("Invalid (not what I expected!)\n");
    print_msg(buff,len);
    return(-1);
  }
  printf("Got block %d (%d)\n",block,len);

  build_ack(buff,block);
  if (sendto(sk,buff,4,NULL,(struct sockaddr*)s,sizeof(*s))<0) {
    perror("Error sending");
    return(0);
  }
  printf("Sending ACK for block %d: ",block);
  print_msg(buff,4);
  return(len);
}



int waitforresend(int sk, struct sockaddr_in *s,int bnum) {
  char buff[1000];
  int len;
  int opcode,block;
  int waits=0;

  while (waits<4) {
    if ((len=wait_for_response(sk,s,buff,1000))==0) {
      if (waits<4) {
	waits++;
	continue;
      } else {
	printf("No resend of block received %d\n",bnum);
	return(0);
      }
    } 
    opcode = get_opcode(buff);
    block = get_blocknum(buff);
    if ((opcode != DATA) || (block != bnum)) {
      printf("Invalid (not what I expected!) waiting for resend \n");
      return(0);
    }
    break;
  }
  printf("Get a restransmission from server: block %d\n",bnum);
  return(1);
}

int partialfiletransfer(int sk, struct sockaddr_in *sorig, char *filename) {
  int sent;
  char buff[1000];
  int len;
  int bnum=1;
  struct sockaddr_in s;

  memcpy(&s,sorig,sizeof(s));
  len = build_request(buff,RRQ,filename,"octet");
  printf("Sending RRQ:  ");
  print_msg(buff,len);
  sent = sendto(sk,buff,len,NULL,(struct sockaddr*)&s,sizeof(s));

  while (bnum<4) {

    if ( (len=waitandack(sk,&s,bnum))==0) {
      printf("Error with client\n");
      return(0);
    }

    if (len!=516) {
      printf("Premature completion!\n");
      break;
    }
    bnum++;
  }
  printf("Leaving server hanging after block %d\n",bnum);
  if (! waitforresend(sk,&s,bnum)) {
    printf("ERROR: NO RETRANSMISSION\n");
    return(0);
  }
  if (! waitforresend(sk,&s,bnum)) {
    printf("ERROR: NO RETRANSMISSION\n");
    return(0);
  }
  return(1);
}



int filetransfer(int sk, struct sockaddr_in *sorig, char *filename) {
  int sent;
  char buff[1000];
  int len;
  int bnum=1;
  struct sockaddr_in s;

  memcpy(&s,sorig,sizeof(s));

  len = build_request(buff,RRQ,filename,"octet");
  printf("Sending RRQ:  ");
  print_msg(buff,len);
  sent = sendto(sk,buff,len,NULL,(struct sockaddr*)&s,sizeof(s));

  while (1) {

    if ( (len=waitandack(sk,&s,bnum))==0) {
      printf("Error with client\n");
      return(0);
    }

    if (len!=516) {
      return(1);
    }
    bnum++;
  }
  return(0);
}


/* client program:

   The following must passed in on the command line:
      hostname of the server (argv[1])
      port number of the server (argv[2])
      file name (argv[3])

*/



int main( int argc, char **argv ) {
  int sk,sk2;
  struct sockaddr_in server;
  struct hostent *hp;

  /* Make sure we have the right number of command line args */

  if (argc!=4) {
    printf("Usage: %s <server name> <port number> <filename>\n",argv[0]);
    exit(0);
  }

  /* create a socket 
     IP protocol family (PF_INET) 
     UDP (SOCK_DGRAM)
  */
  
  if ((sk = socket( PF_INET, SOCK_DGRAM, 0 )) < 0)
    {
      printf("Problem creating socket\n");
      exit(1);
    }

  if ((sk2 = socket( PF_INET, SOCK_DGRAM, 0 )) < 0)
    {
      printf("Problem creating socket\n");
      exit(1);
    }

  server.sin_family = AF_INET;
  if ((hp = gethostbyname(argv[1]))==0) {
    printf("Invalid or unknown host\n");
    exit(1);
  }

  /* copy the IP address into the sockaddr 
     It is already in network byte order 
  */

  memcpy( &server.sin_addr.s_addr, hp->h_addr, hp->h_length);

  /* establish the server port number - we must use network byte order! */
  server.sin_port = htons(atoi(argv[2]));

  partialfiletransfer(sk,&server,argv[3]);
  if (!filetransfer(sk2,&server,argv[3])) {
    printf("TIMEOUT: ERROR Server not responding\n");
  } else {
    printf("TIMEOUT: OK\n");
  }
  return(0);
}