enum {
  T_ENTER_CA,
  T_EXIT_CA,
  T_SHOW_CURSOR,
  T_HIDE_CURSOR,
  T_CLEAR_SCREEN,
  T_SGR0,
  T_UNDERLINE,
  T_BOLD,
  T_BLINK,
  T_REVERSE,
  T_ENTER_KEYPAD,
  T_EXIT_KEYPAD,
  T_ENTER_MOUSE,
  T_EXIT_MOUSE,
  T_ENTER_BRACKETED_PASTE,
  T_EXIT_BRACKETED_PASTE,
  T_FUNCS_NUM,
};

#define EUNSUPPORTED_TERM -1

// rxvt-256color
static const char *rxvt_256color_keys[] = {
  "\033[11~", "\033[12~", "\033[13~", "\033[14~", "\033[15~", "\033[17~", "\033[18~", "\033[19~", "\033[20~", "\033[21~", "\033[23~", "\033[24~", "\033[2~", "\033[3~", "\033[7~", "\033[8~", "\033[5~", "\033[6~", "\033[A", "\033[B", "\033[D", "\033[C", 0
};
static const char *rxvt_256color_funcs[] = {
  "\0337\033[?47h", "\033[2J\033[?47l\0338", "\033[?25h", "\033[?25l", "\033[H\033[2J", "\033[m", "\033[4m", "\033[1m", "\033[5m", "\033[7m", "\033=", "\033>", "\033[?1000h", "\033[?1000l", "\033[?2004h", "\033[?2004l",
};

// Eterm
static const char *eterm_keys[] = {
  "\033[11~", "\033[12~", "\033[13~", "\033[14~", "\033[15~", "\033[17~", "\033[18~", "\033[19~", "\033[20~", "\033[21~", "\033[23~", "\033[24~", "\033[2~", "\033[3~", "\033[7~", "\033[8~", "\033[5~", "\033[6~", "\033[A", "\033[B", "\033[D", "\033[C", 0
};
static const char *eterm_funcs[] = {
  "\0337\033[?47h", "\033[2J\033[?47l\0338", "\033[?25h", "\033[?25l", "\033[H\033[2J", "\033[m", "\033[4m", "\033[1m", "\033[5m", "\033[7m", "", "", "", "", "", "",
};

// screen
static const char *screen_keys[] = {
  "\033OP", "\033OQ", "\033OR", "\033OS", "\033[15~", "\033[17~", "\033[18~", "\033[19~", "\033[20~", "\033[21~", "\033[23~", "\033[24~", "\033[2~", "\033[3~", "\033[1~", "\033[4~", "\033[5~", "\033[6~", "\033OA", "\033OB", "\033OD", "\033OC", 0
};
static const char *screen_funcs[] = {
  "\033[?1049h", "\033[?1049l", "\033[34h\033[?25h", "\033[?25l", "\033[H\033[J", "\033[m", "\033[4m", "\033[1m", "\033[5m", "\033[7m", "\033[?1h\033=", "\033[?1l\033>", "\033[?1000h", "\033[?1000l", "\033[?2004h", "\033[?2004l",
};

// rxvt-unicode
static const char *rxvt_unicode_keys[] = {
  "\033[11~", "\033[12~", "\033[13~", "\033[14~", "\033[15~", "\033[17~", "\033[18~", "\033[19~", "\033[20~", "\033[21~", "\033[23~", "\033[24~", "\033[2~", "\033[3~", "\033[7~", "\033[8~", "\033[5~", "\033[6~", "\033[A", "\033[B", "\033[D", "\033[C", 0
};
static const char *rxvt_unicode_funcs[] = {
  "\033[?1049h", "\033[r\033[?1049l", "\033[?25h", "\033[?25l", "\033[H\033[2J", "\033[m\033(B", "\033[4m", "\033[1m", "\033[5m", "\033[7m", "\033=", "\033>", "\033[?1000h", "\033[?1000l", "\033[?2004h", "\033[?2004l",
};

// linux
static const char *linux_keys[] = {
  "\033[[A", "\033[[B", "\033[[C", "\033[[D", "\033[[E", "\033[17~", "\033[18~", "\033[19~", "\033[20~", "\033[21~", "\033[23~", "\033[24~", "\033[2~", "\033[3~", "\033[1~", "\033[4~", "\033[5~", "\033[6~", "\033[A", "\033[B", "\033[D", "\033[C", 0
};
static const char *linux_funcs[] = {
  "", "", "\033[?25h\033[?0c", "\033[?25l\033[?1c", "\033[H\033[J", "\033[0;10m", "\033[4m", "\033[1m", "\033[5m", "\033[7m", "", "", "", "", "", "",
};

// xterm
static const char *xterm_keys[] = {
  "\033OP", "\033OQ", "\033OR", "\033OS", "\033[15~", "\033[17~", "\033[18~", "\033[19~", "\033[20~", "\033[21~", "\033[23~", "\033[24~", "\033[2~", "\033[3~", "\033OH", "\033OF", "\033[5~", "\033[6~", "\033OA", "\033OB", "\033OD", "\033OC", 0
};
static const char *xterm_funcs[] = {
  "\033[?1049h", "\033[?1049l", "\033[?12l\033[?25h", "\033[?25l", "\033[H\033[2J", "\033(B\033[m", "\033[4m", "\033[1m", "\033[5m", "\033[7m", "\033[?1h\033=", "\033[?1l\033>", "\033[?1000h", "\033[?1000l", "\033[?2004h", "\033[?2004l",
};

static struct term {
  const char *name;
  const char **keys;
  const char **funcs;
} terms[] = {
  {"rxvt-256color", rxvt_256color_keys, rxvt_256color_funcs},
  {"Eterm", eterm_keys, eterm_funcs},
  {"screen", screen_keys, screen_funcs},
  {"rxvt-unicode", rxvt_unicode_keys, rxvt_unicode_funcs},
  {"linux", linux_keys, linux_funcs},
  {"xterm", xterm_keys, xterm_funcs},
  {0, 0, 0},
};

static bool init_from_terminfo = false;
static const char **keys;
static const char **funcs;

static int try_compatible(const char *term, const char *name,
        const char **tkeys, const char **tfuncs)
{
  if (strstr(term, name)) {
    keys = tkeys;
    funcs = tfuncs;
    return 0;
  }

  return EUNSUPPORTED_TERM;
}

static int init_term_builtin(void)
{
  int i;
  const char *term = getenv("TERM");

  if (term) {
    for (i = 0; terms[i].name; i++) {
      if (!strcmp(terms[i].name, term)) {
        keys = terms[i].keys;
        funcs = terms[i].funcs;
        return 0;
      }
    }

    /* let's do some heuristic, maybe it's a compatible terminal */
    if (try_compatible(term, "xterm", xterm_keys, xterm_funcs) == 0)
      return 0;
    if (try_compatible(term, "rxvt", rxvt_unicode_keys, rxvt_unicode_funcs) == 0)
      return 0;
    if (try_compatible(term, "linux", linux_keys, linux_funcs) == 0)
      return 0;
    if (try_compatible(term, "Eterm", eterm_keys, eterm_funcs) == 0)
      return 0;
    if (try_compatible(term, "screen", screen_keys, screen_funcs) == 0)
      return 0;
    /* let's assume that 'cygwin' is xterm compatible */
    if (try_compatible(term, "cygwin", xterm_keys, xterm_funcs) == 0)
      return 0;
  }

  return EUNSUPPORTED_TERM;
}

//----------------------------------------------------------------------
// terminfo
//----------------------------------------------------------------------

static char *read_file(const char *file) {
  FILE *f = fopen(file, "rb");
  if (!f)
    return 0;

  struct stat st;
  if (fstat(fileno(f), &st) != 0) {
    fclose(f);
    return 0;
  }

  char *data = malloc(st.st_size);
  if (!data) {
    fclose(f);
    return 0;
  }

  if (fread(data, 1, st.st_size, f) != (size_t)st.st_size) {
    fclose(f);
    free(data);
    return 0;
  }

  fclose(f);
  return data;
}

static char *terminfo_try_path(const char *path, const char *term) {
  char tmp[4096];
  // snprintf guarantee for older compilers
  assert(sizeof(tmp) > sizeof(path)+sizeof("/x/")+sizeof(term)+1);
  snprintf(tmp, sizeof(tmp), "%s/%c/%s", path, term[0], term);
  char *data = read_file(tmp);
  if (data) {
    return data;
  }

  // fallback to darwin specific dirs structure
  // snprintf guarantee above still applies
  snprintf(tmp, sizeof(tmp), "%s/%x/%s", path, term[0], term);
  return read_file(tmp);
}

void string_copy(char* dest, const char* src, int dest_capacity) {
  strncpy(dest, src, dest_capacity);
  dest[dest_capacity-1] = '\0';
}

void string_append(char* dest, const char* src, int dest_capacity) {
  strncat(dest, src, dest_capacity);
  dest[dest_capacity-1] = '\0';
}

static char *load_terminfo(void) {
  char tmp[4096];
  const char *term = getenv("TERM");
  if (!term) {
    return 0;
  }

  // if TERMINFO is set, no other directory should be searched
  const char *terminfo = getenv("TERMINFO");
  if (terminfo) {
    return terminfo_try_path(terminfo, term);
  }

  // next, consider ~/.terminfo
  const char *home = getenv("HOME");
  if (home) {
    // snprintf guarantee for older compilers
    assert(sizeof(tmp) > sizeof(home)+sizeof("/.terminfo")+1);
    string_copy(tmp, home, sizeof(tmp));
    string_append(tmp, "/.terminfo", sizeof(tmp));
    char *data = terminfo_try_path(tmp, term);
    if (data)
      return data;
  }

  // next, TERMINFO_DIRS
  const char *dirs = getenv("TERMINFO_DIRS");
  if (dirs) {
    // snprintf guarantee for older compilers
    assert(sizeof(tmp) > sizeof(dirs));
    strncpy(tmp, dirs, sizeof(tmp));
    char *dir = strtok(tmp, ":");
    while (dir) {
      const char *cdir = dir;
      if (strcmp(cdir, "") == 0) {
        cdir = "/usr/share/terminfo";
      }
      char *data = terminfo_try_path(cdir, term);
      if (data)
        return data;
      dir = strtok(0, ":");
    }
  }

  // fallback to /usr/share/terminfo
  return terminfo_try_path("/usr/share/terminfo", term);
}

#define TI_MAGIC 0432
#define TI_HEADER_LENGTH 12
#define TB_KEYS_NUM 22

static const char *terminfo_copy_string(char *data, int str, int table) {
  const int16_t off = *(int16_t*)(data + str);
  const char *src = data + table + off;
  int len = strlen(src);
  char *dst = malloc(len+1);
  string_copy(dst, src, len+1);
  return dst;
}

static const int16_t ti_funcs[] = {
  28, 40, 16, 13, 5, 39, 36, 27, 26, 34, 89, 88,
};

static const int16_t ti_keys[] = {
  66, 68 /* apparently not a typo; 67 is F10 for whatever reason */, 69,
  70, 71, 72, 73, 74, 75, 67, 216, 217, 77, 59, 76, 164, 82, 81, 87, 61,
  79, 83,
};

static int init_term(void) {
  int i;
  char *data = load_terminfo();
  if (!data) {
    init_from_terminfo = false;
    return init_term_builtin();
  }

  int16_t *header = (int16_t*)data;
  if ((header[1] + header[2]) % 2) {
    // old quirk to align everything on word boundaries
    header[2] += 1;
  }

  const int str_offset = TI_HEADER_LENGTH +
    header[1] + header[2] + 2 * header[3];
  const int table_offset = str_offset + 2 * header[4];

  keys = malloc(sizeof(const char*) * (TB_KEYS_NUM+1));
  for (i = 0; i < TB_KEYS_NUM; i++) {
    keys[i] = terminfo_copy_string(data,
      str_offset + 2 * ti_keys[i], table_offset);
  }
  keys[TB_KEYS_NUM] = 0;

  funcs = malloc(sizeof(const char*) * T_FUNCS_NUM);
  // the last four entries are reserved for mouse, bracketed paste. because the table offset is
  // not there, the two entries have to fill in manually
  for (i = 0; i < T_FUNCS_NUM-4; i++) {
    funcs[i] = terminfo_copy_string(data,
      str_offset + 2 * ti_funcs[i], table_offset);
  }

  funcs[T_FUNCS_NUM-4] = "\033[?1000h";
  funcs[T_FUNCS_NUM-3] = "\033[?1000l";
  funcs[T_FUNCS_NUM-2] = "\033[?2004h";
  funcs[T_FUNCS_NUM-1] = "\033[?2004l";

  init_from_terminfo = true;
  free(data);
  return 0;
}

static void shutdown_term(void) {
  if (init_from_terminfo) {
    int i;
    for (i = 0; i < TB_KEYS_NUM; i++) {
      free((void*)keys[i]);
    }
    // the last four entries are reserved for mouse, bracketed paste. because the table offset
    // is not there, the two entries have to fill in manually and do not
    // need to be freed.
    for (i = 0; i < T_FUNCS_NUM-4; i++) {
      free((void*)funcs[i]);
    }
    free(keys);
    free(funcs);
  }
}
