/*      $OpenBSD: _get_locname.c,v 1.1 2017/09/05 03:16:13 schwarze Exp $ */
/*
 * Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <errno.h>
#include <locale.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "rune.h"
#include "rune_local.h"

/*
 * Supplement the input with locale(1) variables from the
 * environment, validate it, and initialize UTF-8 when needed.
 * Return NULL on error, "" if unset (for LC_ALL only),
 * or the name of the locale that takes effect.
 */
const char *
_get_locname(int category, const char *locname)
{
        static const char *const catname[_LC_LAST - 1] = {
                "LC_COLLATE",   "LC_CTYPE",     "LC_MONETARY",
                "LC_NUMERIC",   "LC_TIME",      "LC_MESSAGES"
        };

        FILE            *fp;
        const char      *cp;
        int              save_errno;

        /* For empty input, inspect the environment. */
        if (*locname == '\0')
                locname = getenv("LC_ALL");

        if (category != LC_ALL) {
                if (locname == NULL || *locname == '\0')
                        locname = getenv(catname[category - 1]);
                if (locname == NULL || *locname == '\0')
                        locname = getenv("LANG");
        }

        /*
         * If still empty, treat LC_ALL as unset, but
         * fall back to the default locale for other categories.
         */
        if (locname == NULL || *locname == '\0')
                locname = category == LC_ALL ? "" : "C";

        /* Accept and ignore all language and territory prefixes. */
        if ((cp = strrchr(locname, '.')) == NULL)
                return locname;

        /* Reject all encodings except ASCII and UTF-8. */
        if (strcmp(cp + 1, "UTF-8") != 0)
                return NULL;

        /* Initialize the UTF-8 character encoding locale, if needed. */
        if (_Utf8RuneLocale != NULL)
                return locname;
        save_errno = errno;
        if ((fp = fopen(_PATH_LOCALE "/UTF-8/LC_CTYPE", "re")) != NULL) {
                _Utf8RuneLocale = _Read_RuneMagi(fp);
                fclose(fp);
        }
        errno = save_errno;
        return _Utf8RuneLocale == NULL ? NULL : locname;
}