#include <stdio.h>
#include <string.h>
const int NumOfNodes = 4;

char *msg = "hello";
int MsgSize = 5;

main(char * argv[],int argc)
{
  void client(int,int,int);

  int pid,left[2], right[2];
  int i;
  int order;
  int n;
  char *newMsg;

  if (pipe(left) < 0 || pipe(right) < 0)
  {
     fprintf(stderr," pipe failed \n");
     exit(-1);
  }

printf("master receiving pipe id %d\n",left[0]);
  order = 0;
  if ((pid = fork()) < 0)
  {
     fprintf(stderr," fork failed \n");
     exit(-1);
  }
  else if (pid > 0)      /* parent process */
  {
      close(left[1]);
      close(right[0]);

      for (i = 0; i < NumOfNodes; i ++)
      {
	  /* push data into the pipe */
	  if (write(right[1],msg,MsgSize) != MsgSize)
	      fprintf(stderr,"write error in main\n");  
	  printf("msg wrote %d %s\n",i, msg);
      }

      while (wait((int *)0) != pid);


      newMsg = (char *)malloc(50);
      for (i = 0; i < NumOfNodes; i ++)
      {
	  n = 0;
	  newMsg[n] = 0;
	  if ((n = read(left[0],newMsg,MsgSize)) != MsgSize)
	      fprintf(stderr,"read error in main %d\n",n);
	  newMsg[n] = 0;
	  printf("msg read back %d  %s\n",i,newMsg);
      }

      if ((n = read(left[0],newMsg,50)) <= 0)
	  fprintf(stderr,"last read error in main %d\n",n);
      newMsg[n] = 0;
      printf("msg read back last :  %s\n",newMsg);
      close(left[0]);
      close(right[1]);
      exit(0);
  }
  else /* child process, pid == 0 */
  {
      client(left[1],right[0],order);     /* passing the read fd */
      /* The first one (left[1]) is used to write back to the master by the */
      /* very last node on the pipe line. All intermediate nodes should use */
      /* right[1] to pass information to its child */
      
      close(left[1]);
      close(right[0]);
      exit(0);
  }
}


void client(int toMaster, int fromLeft, int level)
{
  int pid, right[2];
  char *item;
  int i;
  int n;

  printf("at level %d with toMaster %d\n",level,toMaster);
  item = (char *)malloc(30);
  if (level < NumOfNodes)     /* keep expanding */
  {
      if (pipe(right) < 0)
      {
	  fprintf(stderr," pipe failed \n");
	  exit(-1);
      }
      level ++;

      if ((pid = fork()) < 0)
      {
	  fprintf(stderr," fork failed in client\n");
	  exit(-1);
      }
      else if (pid > 0)      /* parent process */
      {
	  close(right[0]);

	  printf("before read at level %d \n",level);
	  for (i = 0; i < NumOfNodes; i ++)
	  {
	      n = 0;
	      if ((n = read(fromLeft,item,MsgSize)) != MsgSize)
		  fprintf(stderr,"read error in client %d\n",level);
	      printf("read at level %d i %d == %s\n",level, i, item);
	      if (write(right[1],item,MsgSize) != MsgSize)
		    /* push data into the pipe */
		  fprintf(stderr,"write error in client %d\n",level);
	  }

	  while (wait((int *)0) != pid);

	  
	  close(right[1]);
	  exit(0);
      }
      else /* child process, pid == 0 */
      {
	  client(toMaster,right[0],level);
      
	  close(right[1]);
	  exit(0);
      }
  }      /* if level < NumOfNodes */
  else   /* level == NumOfNodes, last one on the pipe, write back to master */
  {
      printf("action in final client\n");
      for (i = 0; i < NumOfNodes; i ++)
      {
	  if ((n = read(fromLeft,item,MsgSize)) != MsgSize)
	      fprintf(stderr,"read error in last %d\n",level);
	  printf("last read at i %d == %s\n",i,item);
	  if (write(toMaster,item,MsgSize) != MsgSize)
	      /* push data into the pipe */
	      fprintf(stderr,"write error in last %d\n",level);
      }
      item[n] = 0;
      strcat(item,"greeting from last");
      printf("last msg in client : %s\n",item);
      n = strlen(item);
      printf("strlen %d\n",n);
      if (write(toMaster,item,n) <= 0)
	  fprintf(stderr,"final write error\n");

      exit(0);
  }
}