/****************************************************************************
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** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
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** This file is part of Qbs.
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** ensure the GNU Lesser General Public License version 3 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
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****************************************************************************/

#include "filesaver.h"
#include "stlutils.h"

#include <tools/iosutils.h>

#include <cerrno>
#include <fstream>

namespace qbs {
namespace Internal {

FileSaver::FileSaver(std::string filePath, bool overwriteIfUnchanged)
    : m_filePath(std::move(filePath)), m_overwriteIfUnchanged(overwriteIfUnchanged)
{
}

std::ostream *FileSaver::device()
{
    return m_memoryDevice.get();
}

bool FileSaver::open()
{
    if (!m_overwriteIfUnchanged) {
        std::ifstream file(utf8_to_native_path(m_filePath));
        if (file.is_open())
            m_oldFileContents.assign(std::istreambuf_iterator<std::ifstream::char_type>(file),
                                     std::istreambuf_iterator<std::ifstream::char_type>());
        else
            m_oldFileContents.clear();
    }

    m_memoryDevice = std::make_shared<std::stringstream>();
    return true;
}

bool FileSaver::commit()
{
    if (!device())
        return false;

    device()->flush();
    if (!device()->good())
        return false;

    const std::string newFileContents = m_memoryDevice->str();
    if (!m_overwriteIfUnchanged && m_oldFileContents == newFileContents)
        return true; // no need to write unchanged data

    const std::string tempFilePath = m_filePath + "~";
    std::ofstream tempFile(utf8_to_native_path(tempFilePath));
    if (!tempFile.is_open())
        return false;

    tempFile.write(newFileContents.data(), newFileContents.size());
    tempFile.close();
    if (!tempFile.good())
        return false;

    if (Internal::rename(tempFilePath, m_filePath) != 0) {
        if (errno != EEXIST)
            return false;
        if (Internal::unlink(m_filePath) != 0)
            return false;
        return Internal::rename(tempFilePath, m_filePath) == 0;
    }

    return true;
}

bool FileSaver::write(std::string_view data)
{
    return fwrite(data.data(), data.size(), device());
}

} // namespace Internal
} // namespace qbs