//
//      aegis - project change supervisor
//      Copyright (C) 2004-2006, 2008, 2009, 2012 Peter Miller
//
//      This program is free software; you can redistribute it and/or modify
//      it under the terms of the GNU General Public License as published by
//      the Free Software Foundation; either version 3 of the License, or
//      (at your option) any later version.
//
//      This program is distributed in the hope that it will be useful,
//      but WITHOUT ANY WARRANTY; without even the implied warranty of
//      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//      GNU General Public License for more details.
//
//      You should have received a copy of the GNU General Public License
//      along with this program. If not, see
//      <http://www.gnu.org/licenses/>.
//

#include <common/ac/string.h>

#include <libaegis/file.h>
#include <libaegis/os.h>
#include <libaegis/os/domain_name.h>
#include <libaegis/uname.h>


static bool
is_a_valid_domain_string(const nstring &candidate)
{
    if (candidate.empty())
        return false;
    const char *s = candidate.c_str();
    int numdots = 0;
    unsigned char state = '.';
    for (;;)
    {
        unsigned char c = *s++;
        switch (c)
        {
        case 0:
            return (state == 0 && numdots != 0);

        case '.':
            if (state == '.')
                return false;
            state = '.';
            ++numdots;
            break;

        case '0': case '1': case '2': case '3': case '4': case '5':
        case '6': case '7': case '8': case '9':
        case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
        case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
        case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u':
        case 'v': case 'w': case 'x': case 'y': case 'z':
        case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
        case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
        case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
        case 'V': case 'W': case 'X': case 'Y': case 'Z':
        case '=':
            state = 0;
            break;

        default:
            return false;
        }
    }
}


static bool
try_etc_mailname(nstring &result)
{
    bool ok = false;
    nstring mailname("/etc/mailname");
    os_become_orig();
    if (os_exists(mailname.get_ref()))
    {
        result = read_whole_file(mailname);
        ok = is_a_valid_domain_string(result);
    }
    os_become_undo();
    return ok;
}


static nstring
run_a_command(const char *cmd)
{
    nstring temp_file_name(os_edit_filename(0));
    nstring command(nstring(cmd) + " > " + temp_file_name + " 2> /dev/null");
    os_become_orig();
    nstring dir(os_curdir());
    int exit_status =
        os_execute_retcode
        (
            command.get_ref(),
            OS_EXEC_FLAG_SILENT,
            dir.get_ref()
        );
    nstring result;
    if (exit_status == 0)
        result = read_whole_file(temp_file_name);
    os_unlink_errok(temp_file_name);
    os_become_undo();
    return result;
}


static bool
try_a_command(const char *cmd, nstring &result)
{
    result = run_a_command(cmd);
    return is_a_valid_domain_string(result);
}


static bool
try_hostname_d(nstring &result)
{
     return try_a_command("hostname -d", result);
}


static bool
try_hostname_fqdn(nstring &result)
{
    result = run_a_command("hostname");
    const char *dot = strchr(result.c_str(), '.');
    if (!dot)
        return false;
    result = nstring(dot + 1);
    return is_a_valid_domain_string(result);
}


static bool
try_dnsdomainname(nstring &result)
{
    return try_a_command("dnsdomainname", result);
}


static bool
try_domainname(nstring &result)
{
    return try_a_command("domainname", result);
}


nstring
os_domain_name(void)
{
    static nstring cached_answer;
    if (cached_answer.size() == 0)
    {
        if
        (
            !try_etc_mailname(cached_answer)
        &&
            !try_hostname_d(cached_answer)
        &&
            !try_hostname_fqdn(cached_answer)
        &&
            !try_dnsdomainname(cached_answer)
        &&
            !try_domainname(cached_answer)
        )
            cached_answer = nstring(uname_node_get());
    }
    return cached_answer;
}


// vim: set ts=8 sw=4 et :