//
// aegis - project change supervisor
// Copyright (C) 2014 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/time.h>

#include <libaegis/fix_tm_year.h>


static int
this_year(void)
{
    time_t now = 0;
    time(&now);
    struct tm *tmp = localtime(&now);
    return (tmp->tm_year + 1900);
}


static inline int
year_diff(int a, int b)
{
    int d = a - b;
    if (d < 0)
        d = -d;
    return d;
}


int
fix_tm_year(int n)
{
    if (n >= 1900)
        return (n - 1900);

    if (n >= 0 && n < 100)
    {
        int cccc = this_year();

        int this_century = (cccc / 100) * 100;
        int last_century = this_century - 100;
        int next_century = this_century + 100;

        int last_ccnn = last_century + n;
        int this_ccnn = this_century + n;
        int next_ccnn = next_century + n;

        // assume cvlosest century first
        int ccnn = this_ccnn;
        int d = year_diff(cccc, this_ccnn);

        // look for closer century
        int d2 = year_diff(cccc, last_ccnn);
        if (d2 < d)
        {
            ccnn = last_ccnn;
            d = d2;
        }

        // look for closer century
        int d3 = year_diff(cccc, next_ccnn);
        if (d3 < d)
        {
            ccnn = next_ccnn;
            d = d3;
        }
        return (ccnn - 1900);
    }

    return n;
}


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