commit 5ed51b7e9cbb76b4c50bce09eea87fa38f7de221
Author: Shanti Chellaram <shanti@shanti.im>
Date:   Mon Jan 31 20:50:07 2022 -0500

    makin me a wordle clone

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..62bb9ea
--- /dev/null
+++ b/README.md
@@ -0,0 +1 @@
+Proof that wordle is solvable in 6 moves.
diff --git a/wordle.c b/wordle.c
new file mode 100644
index 0000000..bf4c3a0
--- /dev/null
+++ b/wordle.c
@@ -0,0 +1,207 @@
+#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;
+}