/*
 * Copyright © 2021-2024 Nick Bowler
 *
 * Helper functions for formatting --help program output.
 *
 * In order to support localized output, this depends on the Gnulib gettext-h
 * and mbswidth modules.  However, if ENABLE_NLS is not defined (or defined to
 * 0) then these modules are not required.
 *
 * License WTFPL2: Do What The Fuck You Want To Public License, version 2.
 * This is free software: you are free to do what the fuck you want to.
 * There is NO WARRANTY, to the extent permitted by law.
 */

#if HAVE_CONFIG_H
#	include <config.h>
#endif
#include <stdio.h>
#include <stddef.h>
#include <string.h>
#include <assert.h>
#include <limits.h>
#include <getopt.h>

#include "help.h"

#ifndef ENABLE_NLS
#	define ENABLE_NLS 0
#endif
#ifndef HELP_GETOPT_LONG_ONLY
#	define HELP_GETOPT_LONG_ONLY 0
#endif

#if ENABLE_NLS
#	include <locale.h>
#	include <gettext.h>
#	include <mbswidth.h>
#else
#	define gettext(s) (s)
#	define pgettext_expr(c, s) (s)
#	define mbsnwidth(a, b, c) (assert(0), 0)
#endif

#define STR_L10N_(x)
#define N_(s) s

/* Returns a single numeric value depending on the type of option:
 *
 *   6 - if the option has a short option character and an optional argument
 *   5 - if the option has a short option character and a mandatory argument
 *   4 - if the option has a short option charater and no argument
 *   3 - N/A
 *   2 - if the option has no short option character and an optional argument
 *   1 - if the option has no short option character and a mandatory argument
 *   0 - if the option has no short option character and no argument
 */
static int option_type(const struct option *opt)
{
	int ret = opt->has_arg & 3;

#if !HELP_GETOPT_LONG_ONLY
	if (!opt->flag)
		ret |= (opt->val <= CHAR_MAX) << 2;
#endif

	return ret;
}

enum {
	OPT_SHORT_WITH_OPTIONAL_ARG  = 6,
	OPT_SHORT_WITH_MANDATORY_ARG = 5,
	OPT_SHORT_WITHOUT_ARG        = 4,
	OPT_LONG_WITH_OPTIONAL_ARG   = 2,
	OPT_LONG_WITH_MANDATORY_ARG  = 1,
	OPT_LONG_WITHOUT_ARG         = 0
};

#if HELP_GETOPT_LONG_ONLY
/* String table generated by gen-strtab.awk from help-glo.str */
#define STRTAB_INITIALIZER \
	     N_(" -%s [%s]") \
	"\0" "%*s%.*s\n" \
	"\0" N_(" -%s %s") \
	"\0" N_(" -%s") \
	""
enum {
	fmt_long_optional_arg = 0,
	fmt_long_mandatory_arg = 19,
	fmt_long_without_arg = 27,
	fmt_desc = 10,
	fmt_nl = 17
};
#else
/* String table generated by gen-strtab.awk from help-std.str */
#define STRTAB_INITIALIZER \
	STR_L10N_(N_(" --%s[=%s]")) \
	STR_L10N_(N_(" --%s=%s")) \
	STR_L10N_(N_(" --%s")) \
	     N_(" -%c, --%s[=%s]") \
	"\0" N_(" -%c, --%s=%s") \
	"\0" N_(" -%c, --%s") \
	"\0" "%*s%.*s\n" \
	""
enum {
	fmt_short_optional_arg = 0,
	fmt_long_optional_arg = 5,
	fmt_short_mandatory_arg = 16,
	fmt_long_mandatory_arg = 21,
	fmt_short_without_arg = 30,
	fmt_long_without_arg = 35,
	fmt_desc = 41,
	fmt_nl = 48
};
#endif

static const struct optstr {
	unsigned char map[HELP_GETOPT_LONG_ONLY ? 3 : 7];
	char tab[sizeof (STRTAB_INITIALIZER)];
} optstr = {
	{
		offsetof(struct optstr, tab) + fmt_long_without_arg,
		offsetof(struct optstr, tab) + fmt_long_mandatory_arg,
		offsetof(struct optstr, tab) + fmt_long_optional_arg,
#if !HELP_GETOPT_LONG_ONLY
		0,
		offsetof(struct optstr, tab) + fmt_short_without_arg,
		offsetof(struct optstr, tab) + fmt_short_mandatory_arg,
		offsetof(struct optstr, tab) + fmt_short_optional_arg,
#endif
	},
	STRTAB_INITIALIZER
};

/*
 * When NLS is enabled, we assume snprintf is available.  The GNU libintl
 * library should provide a suitable fallback if necessary.
 */
#if ENABLE_NLS && !defined(help_do_snprintf)
#define help_do_snprintf snprintf
#elif !ENABLE_NLS
#define help_do_snprintf fake_snprintf
static inline int fake_snprintf(char *buf, size_t n, const char *fmt, ...)
{
	return -1;
}
#endif

#define has_short_char(type) (!HELP_GETOPT_LONG_ONLY && (type & 4))

int help_print_optstring(const struct option *opt, const char *argname, int l)
{
	int type = option_type(opt);
	const char *fmt, *nls_arg;
	char optstring[256];
	int w;

	fmt = (char *)&optstr + optstr.map[type];
	if (!ENABLE_NLS)
		goto no_translate;

	nls_arg = argname ? pgettext_expr(opt->name, argname) : argname;
	if (has_short_char(type)) {
		w = help_do_snprintf(optstring, sizeof optstring,
		                     gettext(fmt), opt->val, opt->name,
				     nls_arg);
	} else {
		w = help_do_snprintf(optstring, sizeof optstring,
		                     gettext(fmt), opt->name,
		                     nls_arg);
	}

	if (w < 0 || w >= sizeof optstring)
		goto no_translate;

	w = mbsnwidth(optstring, w, 0);
	printf("%s", optstring);
	goto out;

no_translate:
	if (has_short_char(type)) {
		w = printf(fmt, opt->val, opt->name, argname);
	} else {
		w = printf(fmt, opt->name, argname);
	}
out:
	if (w <= 0 || w > l) {
		putchar('\n');
		return 0;
	}

	return w;
}

void help_print_desc(const struct option *opt, const char *s, int i, int w)
{
	if (opt)
		s = pgettext_expr(opt->name, s);

	do {
		size_t n = strcspn(s, &optstr.tab[fmt_nl]);

		printf(&optstr.tab[fmt_desc], n ? i-w : 0, "", (int)n, s);
		s += n + (s[n] != '\0');
		w = 0;
	} while (*s);
}