#include <stdio.h>
#define MAX 10000
void extern exit(int);
typedef struct listnode {char *word; struct listnode *next;} List, *ListP;
extern List *malloc(size_t);

int strcomp(char *s, char *t) {
  for ( ; *s == *t++; s++ ) if (!*s) return 0;
  return (*s - *--t);
}

ListP construct(char *data, ListP n) {
  ListP new = malloc(sizeof(List));
  new->word = data;
  new->next = n;
  return new;
}

char *head(ListP lp) {
  return lp->word;
}

ListP rest(ListP lp) {
  return lp->next;
}

int length(ListP lp) {
  return (lp == NULL) ? 0 : 1 + length(rest(lp));
}

isMember(char *w, ListP lp) {
  if (lp == NULL) return 0;
  if (strcomp(w, lp->word)==0) return 1;
  return isMember(w, rest(lp));
}

ListP addLast(char *w, ListP lp) {
  return (lp == NULL) ? 
    construct(w, lp) : 
    construct (head(lp), addLast(w, rest(lp)));
}

/* For reading words from a file and storing them in wordsbuffer we need */
FILE *inFile;
char wordsbuffer[MAX];
char *previousword = wordsbuffer - 1;      // doesn't exist yet
char *thisword = wordsbuffer - 1;          // doesn't exist yet
char *nextword = wordsbuffer;              // next word will go here
int done = 0;

int alpha(char ch) {
  return  ((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'));
}

char lower(char c) {
  return (c >= 'A' && c <= 'Z') ? c + 'a' - 'A' : c;
}

char *getword() {
  if (done) return (char*) EOF;
  previousword = thisword;
  thisword = nextword;
  while (!alpha(*nextword = fgetc(inFile)) && (*nextword != EOF));
  if (*nextword == EOF) return (char*) EOF;
  *nextword = lower(*nextword);
  while (alpha(*++nextword = lower(fgetc(inFile))));
  if (*nextword == EOF) done = 1;
  *nextword++ = '\0';
  return thisword;
}

void ungetword() {  // ungets at most one word
  if (previousword < wordsbuffer) 
    printf("Attempt to unget what has not been got\n");
  else {
    nextword = thisword;
    thisword = previousword;
    previousword = wordsbuffer - 1;
  }
}

ListP reverse (ListP l) {
  /* You need to write this properly */
  return l;
}

main(int argc, char *argv[]) {
  char *this;
  ListP lp = NULL;
  int dup = 0;
  if (argc < 2) {
    fprintf(stderr, "Usage: fread <filename>\n");
    exit(-1);
  }
  inFile = fopen(argv[1], "r");
  while ((this = getword()) != (char*) EOF) {
    if (isMember(this, lp)) {
      dup++;
      ungetword();
    }
    else lp = addLast(this, lp);
  }
  printf("The list is\n");
  printlist(lp);
  printf("The list has length %d\n", length(lp));
  printf("The reversed list is\n");
  printlist(reverse(lp));
  printf("There were %d repeats\n", dup);
  printf("I needed %d bytes to store the words\n", (thisword - wordsbuffer));
}