#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "fields.h"
#include "sllist.h"

typedef struct {
  char *fname;
  char *lname;
  double score;
} Person;

/* Insert the new person into the list while maintaining a sorted order.
 * we need to traverse through the list until we find a node whose name
 * is alphabetically greater than the inserted name. We then need to
 * insert the new node *before* the node at which we stopped. This will
 * require us to keep a pointer to the previous node as well as the
 * current node, since with a singly linked list we cannot get back
 * to the previous node from the current node. 
 */
void insert_person(Person *p, Sllist *student_list) {
  Sllist_Node *prev_node = NULL;
  Sllist_Node *current_node;
  Person *current_person;

  if (sll_empty(student_list)) {
    sll_append(student_list, p);
    return;
  }
  for (current_node = sll_first(student_list);
       current_node != NULL;
       current_node = sll_next(current_node)) {
    current_person = (Person *)sll_val(current_node);
    if (p->score < current_person->score)
      break;
    else
      prev_node = current_node;
  }
  if (prev_node == NULL) 
    sll_prepend(student_list, p);
  else
    sll_insert_after(student_list, prev_node, p);
}

/* Return the average score in a list of people */

double return_avg(Sllist *d)
{
  Sllist_Node *tmp;
  double n, t;
  Person *p;

  t = 0.0;
  n = 0;
  for (tmp = sll_first(d); tmp != NULL; tmp = sll_next(tmp)) {
    p = (Person *) sll_val(tmp);
    t += p->score;
    n++;
  }
  if (n == 0) return (double) 0;
  return t/n;
}
  
/* Print a list of students, plus the difference between each student's 
   score and the average */

print_list(Sllist *d, double avg)
{
  Sllist_Node *tmp;
  double diff;
  Person *p;

  for (tmp = sll_first(d); tmp != NULL; tmp = sll_next(tmp)) {
    p = (Person *) sll_val(tmp);
    diff = p->score - avg;
    printf("  %-10s %-10s   %5.2lf  %6.2lf\n", 
           p->fname, p->lname, p->score, diff);
  }
}
  
/* The main -- read in the students, calculate the averages and print them */

main()
{
  IS is;
  Sllist *grad, *ugrad;
  double uavg, gavg;
  Person *p;

  /* Create a list of graduate students and a list of undergraduate students.
   */ 
  grad = new_sllist();
  ugrad = new_sllist();

  /* Read in the students and put them into either grad or ugrad */

  is = new_inputstruct(NULL);

  while (get_line(is) >= 0) {
    if (is->NF != 4) {
      fprintf(stderr, "Line %d: Bad format for grade file\n", is->line);
      exit(1);
    }
    p = (Person *) malloc(sizeof(Person));
    p->fname = strdup(is->fields[0]);
    p->lname = strdup(is->fields[1]);
    if (sscanf(is->fields[3], "%lf", &p->score) != 1) {
      fprintf(stderr, "Line %d: Bad format for grade file\n", is->line);
      exit(1);
    }
    if (strcmp(is->fields[2], "U") == 0) {
      insert_person(p, ugrad);
    } else if (strcmp(is->fields[2], "G") == 0) {
      insert_person(p, grad);
    } else {
      fprintf(stderr, "Line %d: Bad format for grade file\n", is->line);
      exit(1);
    }
  }

  /* Print out the undergraduate average and students */

  if (!sll_empty(ugrad)) {
    uavg = return_avg(ugrad);
    printf("Undergraduates: Average = %5.2lf\n", uavg);
    print_list(ugrad, uavg);
    printf("\n");
  }

  /* Print out the graduate average and students */

  if (!sll_empty(grad)) {
    gavg = return_avg(grad);
    printf("Graduates: Average = %5.2lf\n", gavg);
    print_list(grad, gavg);
    printf("\n");
  }

  /* free the lists */
  free_sllist(ugrad);
  free_sllist(grad);
}