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_FUNCS_NUM,
};

#define ENTER_MOUSE_SEQ "\x1b[?1000h\x1b[?1002h\x1b[?1015h\x1b[?1006h"
#define EXIT_MOUSE_SEQ "\x1b[?1006l\x1b[?1015l\x1b[?1002l\x1b[?1000l"

#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>", ENTER_MOUSE_SEQ, EXIT_MOUSE_SEQ,
};

// 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>", ENTER_MOUSE_SEQ, EXIT_MOUSE_SEQ,
};

// 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>", ENTER_MOUSE_SEQ, EXIT_MOUSE_SEQ,
};

// 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>", ENTER_MOUSE_SEQ, EXIT_MOUSE_SEQ,
};

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(tmp, sizeof(tmp), "%s/%c/%s", path, term[0], term);
	tmp[sizeof(tmp)-1] = '\0';
	char *data = read_file(tmp);
	if (data) {
		return data;
	}

	// fallback to darwin specific dirs structure
	snprintf(tmp, sizeof(tmp), "%s/%x/%s", path, term[0], term);
	tmp[sizeof(tmp)-1] = '\0';
	return read_file(tmp);
}

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(tmp, sizeof(tmp), "%s/.terminfo", home);
		tmp[sizeof(tmp)-1] = '\0';
		char *data = terminfo_try_path(tmp, term);
		if (data)
			return data;
	}

	// next, TERMINFO_DIRS
	const char *dirs = getenv("TERMINFO_DIRS");
	if (dirs) {
		snprintf(tmp, sizeof(tmp), "%s", dirs);
		tmp[sizeof(tmp)-1] = '\0';
		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_ALT_MAGIC 542
#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);
	strcpy(dst, src);
	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;

	const int number_sec_len = header[0] == TI_ALT_MAGIC ? 4 : 2;

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

	funcs[T_FUNCS_NUM-2] = ENTER_MOUSE_SEQ;
	funcs[T_FUNCS_NUM-1] = EXIT_MOUSE_SEQ;

	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 two entries are reserved for mouse. 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-2; i++) {
			free((void*)funcs[i]);
		}
		free(keys);
		free(funcs);
	}
}
