/*
 * Converter.cpp -- iconv based converter
 *
 * Copyright (c) 2013-2015 David Demelier <markand@malikania.fr>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <cerrno>
#include <cstring>
#include <string>
#include <iterator>
#include <memory>
#include <string>
#include <stdexcept>
#include <vector>

#include <iconv.h>

#include "converter.h"

struct Deleter {
    void operator()(iconv_t desc)
    {
        iconv_close(desc);
    }
};

using Iconv = std::unique_ptr<std::remove_pointer<iconv_t>::type, Deleter>;

std::string Converter::convert(const char *from, const char *to, const std::string &input)
{
    // No conversion if from and to are identical
    if (std::strcmp(from, to) == 0)
        return input;

    // Try to open the conversion descriptor
    auto cd = iconv_open(to, from);

    if (cd == (iconv_t)-1)
        throw std::invalid_argument(std::strerror(errno));

    Iconv cv(cd);
    std::size_t insize(input.size());
    std::size_t outsize(insize);
    std::vector<char> result(insize + 1);

    auto *b = &input[0];
    auto *p = &result[0];

    while (insize > 0) {
        /* Convert */
        auto r = iconv(cv.get(), &b, &insize, &p, &outsize);

        if (r == (size_t)-1) {
            switch (errno) {
            case EBADF:
            case EILSEQ:
            case EINVAL:
                throw std::invalid_argument(std::strerror(errno));
            case E2BIG:
                /*
                 * Here, we need to reallocate more data because the output
                 * string may need more space.
                 *
                 * We use 16 as an optimistic value.
                 */

                result.reserve(result.size() + 16 + 1);
                p = &result[result.size()];
                outsize += 16;
            default:
                break;
            }
        }

    }

    return std::string(&result[0], (p - &result[0]));
}