/*
 * Copyright (c) 2020, Peter Elliott <pelliott@ualberta.ca>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/LogStream.h>
#include <LibTar/TarStream.h>

namespace Tar {
TarFileStream::TarFileStream(TarStream& tar_stream)
    : m_tar_stream(tar_stream)
    , m_generation(tar_stream.m_generation)
{
}

size_t TarFileStream::read(Bytes bytes)
{
    // verify that the stream has not advanced
    VERIFY(m_tar_stream.m_generation == m_generation);

    if (has_any_error())
        return 0;

    auto to_read = min(bytes.size(), m_tar_stream.header().size() - m_tar_stream.m_file_offset);

    auto nread = m_tar_stream.m_stream.read(bytes.trim(to_read));
    m_tar_stream.m_file_offset += nread;
    return nread;
}

bool TarFileStream::unreliable_eof() const
{
    // verify that the stream has not advanced
    VERIFY(m_tar_stream.m_generation == m_generation);

    return m_tar_stream.m_stream.unreliable_eof()
        || m_tar_stream.m_file_offset >= m_tar_stream.header().size();
}

bool TarFileStream::read_or_error(Bytes bytes)
{
    // verify that the stream has not advanced
    VERIFY(m_tar_stream.m_generation == m_generation);

    if (read(bytes) < bytes.size()) {
        set_fatal_error();
        return false;
    }

    return true;
}

bool TarFileStream::discard_or_error(size_t count)
{
    // verify that the stream has not advanced
    VERIFY(m_tar_stream.m_generation == m_generation);

    if (count > m_tar_stream.header().size() - m_tar_stream.m_file_offset) {
        return false;
    }
    m_tar_stream.m_file_offset += count;
    return m_tar_stream.m_stream.discard_or_error(count);
}

TarStream::TarStream(InputStream& stream)
    : m_stream(stream)
{
    if (!m_stream.read_or_error(Bytes(&m_header, sizeof(m_header)))) {
        m_finished = true;
        return;
    }
    VERIFY(m_stream.discard_or_error(block_size - sizeof(Header)));
}

static constexpr unsigned long block_ceiling(unsigned long offset)
{
    return block_size * (1 + ((offset - 1) / block_size));
}

void TarStream::advance()
{
    if (m_finished)
        return;

    m_generation++;
    VERIFY(m_stream.discard_or_error(block_ceiling(m_header.size()) - m_file_offset));
    m_file_offset = 0;

    if (!m_stream.read_or_error(Bytes(&m_header, sizeof(m_header)))) {
        m_finished = true;
        return;
    }
    if (!valid()) {
        m_finished = true;
        return;
    }

    VERIFY(m_stream.discard_or_error(block_size - sizeof(Header)));
}

bool TarStream::valid() const
{
    return header().magic() == ustar_magic;
}

TarFileStream TarStream::file_contents()
{
    VERIFY(!m_finished);
    return TarFileStream(*this);
}

}