/*
   This code can be used to test your layer 5 implementation
   (which in turn should use your layer 4 implementation, etc.)

 Included is a set of functions that can be used as a layer 1
   implementation, and a main program.

 Question, suggestions, etc. should be sent to netprog@cs.rpi.edu
*/

#include <stdio.h>	/* printf, fprintf, etc */
#include <unistd.h>   	/* need this for read(), write() */
#include <stdlib.h>	/* needed for exit()  */
#include <string.h>	/* strlen, etc */


/*------------------------------------------------------------------
   Sample layer 1 implementation - this can be used to
   provide half-duplex communication by using the shell to
   create a pipe between a sender process and a receiver process.
*/

/* sample l1_read just calls read on stdin */
int l1_read( char *b) {
  return(read(0,b,1));
}

/* sample l1_write just calls write to stdout */
int l1_write(char b) {
  return(write(1,&b,1));
}

/* definition of student_rec */

typedef struct {
  char *firstname;
  char *lastname;
  int id;
} student_rec;



/* layer 5 prototypes */

int l5_write(student_rec *stu);
int l5_read(student_rec *stu);

/*------------------------------------------------------------------
   Main program. This program can be a sender or a receiver,
    it depends on how many command line arguments are supplied
    when the program is run. 
*/

int main(int argc,char **argv) {

  student_rec x;

  /* If there are 3 command line arguments then this program will send
     the first (argv[1]) as the "firstname" and the second as the "lastname"
     and the third as the id.
     It uses l5_write to send the structure.

     If there are not 3 command line arguments, the program assumes it should
     be a reader, so it calls l5_read to get the named value.
  */

  if (argc!=4) {

    /* I'm a reader - read the structure */

    if (l5_read(&x)==-1) {
      fprintf(stderr,"Reading error\n");
      exit(1);
    } 

    /* print out the record */

    printf("Name: %s %s\n",x.firstname, x.lastname);
    printf("ID: %d\n",x.id);

  } else {

    /* I'm a writer (argv == 4) */

    /* make sure strings are not too large */

    if (strlen(argv[1])>80) {
      fprintf(stderr,"Error - first name is too long\n");
      return(0);
    }

    if (strlen(argv[2])>80) {
      fprintf(stderr,"Error - last name is too long\n");
      return(0);
    }


    /*  the first command line argument is the firstname, the second
	is the lastname. */

    x.firstname = argv[1];
    x.lastname = argv[2];

    /* argv[3] is the id */

    x.id = atoi(argv[3]);

    /* send the struct */

    if (l5_write(&x)==-1) {
      /* something went wrong when sending */
      fprintf(stderr,"Error sending record\n");
      exit(1);
    }

  }
  return(1);
}