#include <assert.h>
#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>

#define BUFLEN 128

struct Entry {
   char buf[BUFLEN]; /* associated input line */
   char* hint; /* description or hint, points into buf */
   char* phrase; /* to be guessed phrase, points into buf */
};

unsigned int sample(char* filename,
      unsigned int nofentries, struct Entry selected[nofentries]) {
   FILE* fp = fopen(filename, "r");
   if (!fp) return 0;
   char buf[BUFLEN];
   unsigned int filled = 0;
   unsigned int number_of_records = 0;
   while (fgets(buf, sizeof buf, fp)) {
      char* sep = 0;
      for (char* cp = buf; *cp && cp < buf + sizeof buf; ++cp) {
	 if (*cp == '\t') {
	    sep = cp; break;
	 }
      }
      if (!sep) continue;
      ++number_of_records;
      unsigned int index = filled;
      if (filled < nofentries) {
	 ++filled;
      } else {
	 index = rand() % number_of_records;
      }
      if (index < nofentries) {
	 strncpy(selected[index].buf, buf, sizeof buf);
	 selected[index].hint = selected[index].buf;
	 unsigned int i = sep - buf;
	 selected[index].phrase = selected[index].buf + i + 1;
	 selected[index].buf[i] = 0; /* separate the two strings */
      }
   }
   fclose(fp);
   return filled;
}

unsigned long incl(unsigned long letterset, char ch) {
   assert(isalpha(ch));
   if (isupper(ch)) {
      ch = tolower(ch);
   }
   letterset |= 1 << (ch - 'a');
   return letterset;
}

bool inset(unsigned long letterset, char ch) {
   assert(isalpha(ch));
   if (isupper(ch)) {
      ch = tolower(ch);
   }
   return letterset & (1 << (ch - 'a'));
}

unsigned long init_set_from_phrase(char* phrase) {
   unsigned long letterset = 0;
   while (*phrase) {
      char ch = *phrase;
      if (isalpha(ch)) {
	 letterset = incl(letterset, ch);
      }
      ++phrase;
   }
   return letterset;
}

void print_status(unsigned int hangman_count,
      unsigned long guessed, char* phrase) {
   printf("%d ", hangman_count);
   unsigned int count = 0;
   for (char letter = 'a'; letter <= 'z'; ++letter) {
      if (inset(guessed, letter)) {
	 putchar(letter);
      } else {
	 ++count;
      }
   }
   while (count--) {
      putchar(' ');
   }
   putchar(' ');
   for (char* cp = phrase; *cp != '\n'; ++cp) {
      if (isalpha(*cp) && !inset(guessed, *cp)) {
	 putchar('_');
      } else {
	 putchar(*cp);
      }
   }
   putchar('\n'); fflush(stdout);
}

/* return value:
   > 0: number of points
   = 0: game lost
   -1:  end of input
*/
int run_game(struct Entry* entry) {
   // start the game by printing the description
   puts(entry->hint);

   // prepare the game
   unsigned long letterset = init_set_from_phrase(entry->phrase);
   unsigned long guessed = 0;
   unsigned int hangman_count = 7;
   while (hangman_count && ((guessed & letterset) != letterset)) {
      print_status(hangman_count, guessed, entry->phrase);
      int ch;
      while ((ch = getchar()) != EOF && !isalpha(ch)) {
	 if (!isspace(ch)) {
	    puts("Letter expected.");
	 }
      }
      if (ch == EOF) {
	 puts("End of input. Exiting."); return -1;
      }
      if (!inset(letterset, ch)) {
	 --hangman_count;
      }
      guessed = incl(guessed, ch);
   }
   print_status(hangman_count, guessed, entry->phrase);
   if (hangman_count > 0) {
      printf("Congratulations, you got %d points!\n", hangman_count);
   } else {
      fputs(entry->phrase, stdout); // use fputs to avoid a double LF
      puts("You lose!");
   }
   return hangman_count;
}

int main() {
   srand(getpid() ^ time(0));
   struct Entry entries[16];
   unsigned int nof_entries = sample("Ulm.hm",
      sizeof entries / sizeof(entries[0]), entries);
   if (nof_entries == 0) {
      puts("No valid input file found."); return 1;
   }

   unsigned int points = 0; unsigned int games;
   for (games = 0; games < sizeof(entries)/sizeof(entries[0]); ++games) {
      int result = run_game(entries + games);
      if (result < 0) break;
      points += result;
   }
   printf("You got %d points after %d games.\n", points, games);
}