/*
 *      aegis - project change supervisor
 *      Copyright (C) 2003 Peter Miller;
 *      All rights reserved.
 *
 *      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 2 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, write to the Free Software
 *      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 *
 * MANIFEST: functions to manipulate substrs
 */

#include <sub.h>
#include <sub/substr.h>
#include <trace.h>
#include <wstr_list.h>


wstring_ty *
sub_substr(sub_context_ty *scp, wstring_list_ty *arg)
{
    wstring_ty      *result;
    string_ty       *s;
    long            n1;
    long            n2;
    wstring_ty      *ws;

    trace(("sub_substr()\n{\n"));
    if (arg->nitems != 4)
    {
        sub_context_error_set(scp, i18n("requires three arguments"));
        trace(("return NULL;\n"));
        trace(("}\n"));
        return 0;
    }
    s = wstr_to_str(arg->item[2]);
    n1 = atol(s->str_text);
    str_free(s);

    s = wstr_to_str(arg->item[3]);
    n2 = atol(s->str_text);
    str_free(s);

    if (n1 < 0)
    {
        n2 += n1;
        n1 = 0;
    }

    ws = arg->item[1];
    if (n2 <= 0 || n1 >= (long)ws->wstr_length)
        result = wstr_from_c("");
    else if (n1 + n2 > (long)ws->wstr_length)
        result = wstr_n_from_wc(ws->wstr_text + n1, ws->wstr_length - n1);
    else
        result = wstr_n_from_wc(ws->wstr_text + n1, (size_t)n2);
    trace(("return %8.8lX;\n", (long)result));
    trace(("}\n"));
    return result;
}
