#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#define DICTIONARY "/usr/share/dict/words"

struct trie {
  struct trie *children[26];
  uint8_t terminal;
};

void new_trie(struct trie *tree) {
  uint8_t idx = 0;

  for(; idx < 26; idx += 1) {
    tree->children[idx] = NULL;
  }

  tree->terminal = 0;
}

void trie_insert(struct trie *tree, const char *str, uint8_t len) {
  struct trie *node = tree;
  uint8_t idx = 0;

  for(; idx < len; idx += 1) {
    uint8_t pos = tolower(str[idx]) - 'a';

    if(node->children[pos] == NULL) {
      void *mem = malloc(sizeof(struct trie));

      if(mem == NULL) {
        fprintf(stderr, "could not allocate memory: %s\n", strerror(errno));
        exit(1);
      }

      node->children[pos] = mem;
      new_trie(node->children[pos]);
    }

    node = node->children[pos];
  }

  node->terminal = 1;
}

uint8_t trie_has(struct trie *tree, const char *str, uint8_t len) {
  struct trie *node = tree;
  uint8_t idx = 0;

  for(; idx < len; idx += 1) {
    uint8_t pos = tolower(str[idx]) - 'a';

    if(node->children[pos] == NULL) {
      return 0;
    }

    node = node->children[pos];
  }

  return node->terminal;
}

int main(int argc, char **argv) {
  struct trie dict;
  new_trie(&dict);

  int fd = open(DICTIONARY, O_RDONLY);

  if(fd < 0) {
    fprintf(stderr, "could not open %s: %s\n", DICTIONARY, strerror(errno));
    return 1;
  }

  ssize_t bytes = 0;
  char buf[1024] = { 0 };
  char word[128] = { 0 };
  uint8_t len = 0;

  while((bytes = read(fd, buf, sizeof(buf))) > 0) {
    ssize_t idx = 0;

    for(; idx < bytes; idx += 1) {
      if(buf[idx] == '\n') {
        trie_insert(&dict, word, len);
        len = 0;
        bzero(word, sizeof(word));
      } else if(len < sizeof(word)) {
        word[len] = buf[idx];
        len += 1;
      }
    }
  }

  if(bytes < 0) {
    fprintf(stderr, "could not read from %s: %s\n", DICTIONARY, strerror(errno));
    return 1;
  }

  const char *check = "paladin";

  if(argc > 1) {
    check = argv[1];
  }

  return !trie_has(&dict, check, strlen(check));
}