/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include "alloc-util.h"

#include "dns-def.h"

#include "dns-domain.h"

#include "hostname-setup.h"

#include "hostname-util.h"

#include "idn-util.h"

#include "log.h"

#include "resolved-util.h"

#include "utf8.h"

int resolve_system_hostname(char **full_hostname, char **first_label) {

        _cleanup_free_ char *h = NULL, *n = NULL;

#if HAVE_LIBIDN2

        _cleanup_free_ char *utf8 = NULL;

#elif HAVE_LIBIDN

        int k;

#endif

        char label[DNS_LABEL_MAX+1];

        const char *p, *decoded;

        int r;

        /* Return the full hostname in *full_hostname, if nonnull.

         *

         * Extract and normalize the first label of the locally configured hostname, check it's not

         * "localhost", and return it in *first_label, if nonnull. */

        r = gethostname_strict(&h);

        if (r < 0)

                return log_debug_errno(r, "Can't determine system hostname: %m");

        p = h;

        r = dns_label_unescape(&p, label, sizeof label, 0);

        if (r < 0)

                return log_debug_errno(r, "Failed to unescape hostname: %m");

        if (r == 0)

                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),

                                       "Couldn't find a single label in hostname.");

#if HAVE_LIBIDN || HAVE_LIBIDN2

        r = dlopen_idn();

        if (r < 0) {

                log_debug_errno(r, "Failed to initialize IDN support, ignoring: %m");

                decoded = label; /* no decoding */

        } else

#endif

        {

#if HAVE_LIBIDN2

                r = sym_idn2_to_unicode_8z8z(label, &utf8, 0);

                if (r != IDN2_OK)

                        return log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN),

                                               "Failed to undo IDNA: %s", sym_idn2_strerror(r));

                assert(utf8_is_valid(utf8));

                r = strlen(utf8);

                decoded = utf8;

#elif HAVE_LIBIDN

                k = dns_label_undo_idna(label, r, label, sizeof label);

                if (k < 0)

                        return log_debug_errno(k, "Failed to undo IDNA: %m");

                if (k > 0)

                        r = k;

                if (!utf8_is_valid(label))

                        return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),

                                               "System hostname is not UTF-8 clean.");

                decoded = label;

#else

                decoded = label; /* no decoding */

#endif

        }

        r = dns_label_escape_new(decoded, r, &n);

        if (r < 0)

                return log_debug_errno(r, "Failed to escape hostname: %m");

        if (is_localhost(n))

                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),

                                       "System hostname is 'localhost', ignoring.");

        if (full_hostname)

                *full_hostname = TAKE_PTR(h);

        if (first_label)

                *first_label = TAKE_PTR(n);

        return 0;

}