#include <stdio.h>
/*
  Part 1 of Project 1.

  Students: your job is to implement the eval_wff function.

  The eval_wff function takes as input three parameters:
    wff: a string of characters (a null-terminated array of characters)
         that represents a WFF.
    val: an array of integers (1 represents true, 0 represents false)
      that say whether a propositional variable is true or false.
      For example, val['p'] says whether p is true or false.
    start: is the position of the start of a WFF within the wff array.

  The eval_wff function returns a struct containing two data members.
  The first data member, named end, is the index for one-past the
    last character in the WFF that started at start.
  The second, named value, is 1 if the WFF starting at start
    is true and returns 0 if the WFF starting at start
    is false.

  Hint: implement eval_wff as a recursive function (it calls itself) that is
    similar to the check_wff function given below.

*/
struct eval_ret {
  int end;
  int value;
};

struct eval_ret eval_wff(char wff[], int val[], int start);


/*
  check_wff 
    inputs:
      wff: is an array of characters, possibly representing a WFF
      start: is the position of the start of a WFF within the wff array.
    output:
      -1 if wff is not a WFF, or
      a positive integer that is one past the end of the WFF
        that started at start
*/
int check_wff(char wff[], int start) {
  switch (wff[start]) {
  case 'N':
    return check_wff(wff, start + 1);
  case 'C':
    start = check_wff(wff, start + 1);
    if (start == -1) 
      return -1;
    return check_wff(wff, start);
  case 'A':
    start = check_wff(wff, start + 1);
    if (start == -1) 
      return -1;
    return check_wff(wff, start);
  case 'K':
    start = check_wff(wff, start + 1);
    if (start == -1) 
      return -1;
    return check_wff(wff, start);
  case 'E':
    start = check_wff(wff, start + 1);
    if (start == -1) 
      return -1;
    return check_wff(wff, start);
  case 'p':
  case 'q':
  case 'r':
  case 's':
    return start + 1;
  default:
    return -1;
  }
}

const int val_len = 128;

/*
  true_vars is a NULL terminated string
 */
void init_val(int* val, char* true_vars) {
  int i;
  for (i = 0; i != val_len; ++i)
    val[i] = 0;
  for (i = 0; true_vars[i] != 0; ++i)
    val[true_vars[i]] = 1;
}

int main(int argc, char* argv[])
{
  FILE* f;
  char true_vars[5];
  int val[val_len];
  char c, wff[10000];
  int result, i;

  f = fopen(argv[1], "r");
  i = 0;
  while ((c = fgetc(f)) != '\n')
    true_vars[i++] = c;
  true_vars[i] = 0;

  init_val(val, true_vars);
  
  fscanf(f, "%s", wff);
  fclose(f);

  result = check_wff(wff, 0);
  if (result == -1)
    printf("not a wff\n");

  if (eval_wff(wff, val, 0).value)
    printf("true\n");
  else
    printf("false\n");

  return 0;
}