terdle/wordle.c

#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <strings.h>
#include <stdlib.h>

#define WORD_LENGTH 5

/* represents a 5-bit letter */
typedef uint8_t let_t;

/* represents a 5-bit letter + 3-bit position */
typedef uint8_t lpos_t;

/* represents a set of possible letters (technically, 26-bits) */
typedef uint32_t let_set_t;

/* represents 5 5-bit letters, a word */
typedef uint32_t word_t;

#define let_from_char(c) (((c) - 'a') & 0x1F)

#define let_to_char(c) ((c) + 'a')

lpos_t cptolp(char c, uint8_t pos) {
  return (let_from_char(c) << 3) | pos;
}

let_set_t ls_add(let_set_t set, let_t letter) {
  return set | (1 << letter);
}

let_set_t ls_test(let_set_t set, let_t letter) {
  return (set & (1 << letter)) != 0;
}

uint8_t lp_pos(lpos_t lp) {
  return 0x07 & lp;
}

char lp_char(lpos_t lp) {
  return let_to_char(lp >> 3);
}

/* result is a 2-bit value: */
typedef enum result {
  RES_BLACK = 0x01,
  RES_YELLOW = 0x02,
  RES_GREEN = 0x03
} result_t;

/* represents a wordle result: 5 2-bit result codes */
typedef uint16_t result_set_t;

result_set_t rs_set(result_t res, size_t index, result_t value) {
  return res | ((value & 0x3) << (2 * index));
}

result_t rs_get(result_t res, size_t index) {
  return (res >> (2 * index)) & 0x3;
}

char word_charat(word_t word, size_t index) {
  return (char) ((word >> (index * 5)) & 0x1F) + 'a';
}

/* converts a 5-letter word to its compacted representation */
word_t strtoword(char *str) {
  word_t word = 0;
  for (size_t i = 0; i < WORD_LENGTH; ++i) {
    word |= (str[i] - 'a') << (5 * i);
  }
  return word;
}

void wordtostr(char *out, word_t word) {
  for (size_t i = 0; i < WORD_LENGTH; ++i) {
    out[i] = word_charat(word, i);
  }
}

result_set_t guess_match_werd(char *answer, char *guess) {
  bool guess_consumed[WORD_LENGTH] = {false};
  bool answer_consumed[WORD_LENGTH] = {false};
  result_set_t result_set = 0;
  for (size_t i = 0; i < WORD_LENGTH; ++i) {
    if (answer[i] == guess[i]) {
      answer_consumed[i] = true;
      guess_consumed[i] = true;
      result_set = rs_set(result_set, i, RES_GREEN);
    }
  }
  for (size_t i = 0; i < WORD_LENGTH; ++i) {
    if (guess_consumed[i]) { continue; }
    bool found = false;
    for (size_t j = 0; j < WORD_LENGTH; ++j) {
      if (answer_consumed[j]) { continue; }
      if (answer[j] == guess[i]) {
        answer_consumed[j] = true;
        found = true;
        break;
      }
    }
    if (found) {
      result_set = rs_set(result_set, i, RES_YELLOW);
    } else {
      result_set = rs_set(result_set, i, RES_BLACK);
    }
  }
  return result_set;
}

result_set_t guess_match(word_t answer_word, word_t guess_word) {
  char answer[6] = {0},
       guess[6] = {0};
  wordtostr(answer, answer_word);
  wordtostr(guess, guess_word);
  return guess_match_werd(answer, guess);
}

/* returns whether or not the game was won */
typedef struct wordle_game {
  word_t target;
  uint32_t turn_limit;
  int (*guess_fn)(word_t *, void *);
  void *guess_fn_data;
  void (*display_fn)(result_set_t, void *);
  void *display_fn_data;
} wordle_game_t;

bool play_game(wordle_game_t *game) {
  for (uint32_t turn = 1; turn <= game->turn_limit; ++turn) {
    word_t guess = 0;
    if (game->guess_fn(&guess, game->guess_fn_data) != 0) {
      printf("guesser failure\n");
    }
    result_set_t result_set = guess_match(game->target, guess);
    game->display_fn(result_set, game->display_fn_data);
    if (guess == game->target) {
      return true;
    }
  }
  return false;
}

struct linebuf {
  char *buffer;
  size_t capacity;
};

int term_guess(word_t *word, void *data) {
  struct linebuf *linebuf = data;
  while (true) {
    ssize_t bytes_read = getline(&(linebuf->buffer), &(linebuf->capacity), stdin);
    if (bytes_read == -1) {
      return -1;
    }
    char *buf_end = linebuf->buffer;
    strsep(&buf_end, "\n");
    if (strchr(linebuf->buffer, '\0') - linebuf->buffer == WORD_LENGTH) {
      *word = strtoword(linebuf->buffer);
      return 0;
    } else {
      continue;
    }
  }
}

void term_display(result_set_t result_set, void *ignored) {
  (void) ignored;
  for (size_t i = 0; i < WORD_LENGTH; ++i) {
    switch (rs_get(result_set, i)) {
      case RES_BLACK:
        fputc(' ', stdout);
        break;
      case RES_YELLOW:
        fputc('Y', stdout);
        break;
      case RES_GREEN:
        fputc('G', stdout);
        break;
      default:
        fputc('X', stdout);
        break;
    }
  }
  fputs(" result", stdout);
  fputc('\n', stdout);
}

int main(int argc, char *argv[]) {
  struct linebuf lb = {
    .capacity = 6,
    .buffer = (char *) malloc(lb.capacity),
  };
  wordle_game_t game = {
    .target = strtoword("total"),
    .turn_limit = 6,
    .guess_fn = term_guess,
    .guess_fn_data = &lb,
    .display_fn = term_display,
    .display_fn_data = NULL,
  };
  int x = play_game(&game);
  printf("endgame %d\n", x);
  return 0;
}