/* This file is part of Libspectre.
 *
 * Copyright (C) 2007, 2012 Albert Astals Cid <aacid@kde.org>
 * Copyright (C) 2007 Carlos Garcia Campos <carlosgc@gnome.org>
 *
 * Libspectre 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, or (at your option)
 * any later version.
 *
 * Libspectre 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

/* This function comes from spectre-utils from libspectre */

#include "gstrtod.h"

#include <clocale>
#include <cerrno>
#include <cstdlib>
#include <cstring>

#define ascii_isspace(c) ((c) == ' ' || (c) == '\f' || (c) == '\n' || (c) == '\r' || (c) == '\t' || (c) == '\v')
#define ascii_isdigit(c) ((c) >= '0' && (c) <= '9')

double gatof(const char *nptr)
{
    return gstrtod(nptr, nullptr);
}

double gstrtod(const char *nptr, char **endptr)
{
    char *fail_pos;
    double val;
    struct lconv *locale_data;
    const char *decimal_point;
    int decimal_point_len;
    const char *p, *decimal_point_pos;
    const char *end = nullptr; /* Silence gcc */
    int strtod_errno;

    fail_pos = nullptr;

    locale_data = localeconv();
    decimal_point = locale_data->decimal_point;
    decimal_point_len = strlen(decimal_point);

    decimal_point_pos = nullptr;
    end = nullptr;

    if (decimal_point[0] != '.' || decimal_point[1] != 0) {
        p = nptr;
        /* Skip leading space */
        while (ascii_isspace(*p)) {
            p++;
        }

        /* Skip leading optional sign */
        if (*p == '+' || *p == '-') {
            p++;
        }

        if (ascii_isdigit(*p) || *p == '.') {
            while (ascii_isdigit(*p)) {
                p++;
            }

            if (*p == '.') {
                decimal_point_pos = p++;
            }

            while (ascii_isdigit(*p)) {
                p++;
            }

            if (*p == 'e' || *p == 'E') {
                p++;
            }
            if (*p == '+' || *p == '-') {
                p++;
            }
            while (ascii_isdigit(*p)) {
                p++;
            }

            end = p;
        }
        /* For the other cases, we need not convert the decimal point */
    }

    if (decimal_point_pos) {
        char *copy, *c;

        /* We need to convert the '.' to the locale specific decimal point */
        copy = static_cast<char *>(malloc(end - nptr + 1 + decimal_point_len));

        c = copy;
        memcpy(c, nptr, decimal_point_pos - nptr);
        c += decimal_point_pos - nptr;
        memcpy(c, decimal_point, decimal_point_len);
        c += decimal_point_len;
        memcpy(c, decimal_point_pos + 1, end - (decimal_point_pos + 1));
        c += end - (decimal_point_pos + 1);
        *c = 0;

        errno = 0;
        val = strtod(copy, &fail_pos);
        strtod_errno = errno;

        if (fail_pos) {
            if (fail_pos - copy > decimal_point_pos - nptr) {
                fail_pos = const_cast<char *>(nptr) + (fail_pos - copy) - (decimal_point_len - 1);
            } else {
                fail_pos = const_cast<char *>(nptr) + (fail_pos - copy);
            }
        }

        free(copy);
    } else if (end) {
        char *copy;

        copy = static_cast<char *>(malloc(end - const_cast<char *>(nptr) + 1));
        memcpy(copy, nptr, end - nptr);
        *(copy + (end - const_cast<char *>(nptr))) = 0;

        errno = 0;
        val = strtod(copy, &fail_pos);
        strtod_errno = errno;

        if (fail_pos) {
            fail_pos = const_cast<char *>(nptr) + (fail_pos - copy);
        }

        free(copy);
    } else {
        errno = 0;
        val = strtod(nptr, &fail_pos);
        strtod_errno = errno;
    }

    if (endptr) {
        *endptr = fail_pos;
    }

    errno = strtod_errno;

    return val;
}
