/* Copyright (C) 2014 InfiniDB, Inc.

   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; version 2 of
   the License.

   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., 51 Franklin Street, Fifth Floor, Boston,
   MA 02110-1301, USA. */

/*
 * InfiniDB FOSS License Exception
 * We want free and open source software applications under certain
 * licenses to be able to use the GPL-licensed InfiniDB idbhdfs
 * libraries despite the fact that not all such FOSS licenses are
 * compatible with version 2 of the GNU General Public License.
 * Therefore there are special exceptions to the terms and conditions
 * of the GPLv2 as applied to idbhdfs libraries, which are
 * identified and described in more detail in the FOSS License
 * Exception in the file utils/idbhdfs/FOSS-EXCEPTION.txt
 */

#include "HdfsRdwrFileBuffer.h"
#include "HdfsRdwrMemBuffer.h"
#include <stdlib.h>
#include <iostream>
#include <string>
#include <sstream>
#include <boost/filesystem/path.hpp>
#include <boost/filesystem/convenience.hpp>
#include <boost/scoped_array.hpp>

#include "IDBPolicy.h"
#include "BufferedFile.h"
#include "HdfsFile.h"
#include "IDBLogger.h"
using namespace std;

namespace idbdatafile
{

const size_t BUFSIZE = 1 * 1024 * 1024; // 1MB

HdfsRdwrFileBuffer::HdfsRdwrFileBuffer(const char* fname, const char* mode, unsigned opts) :
    IDBDataFile(fname),
    m_buffer(NULL),
    m_dirty(false),
    m_new(false)
{
    // we have been asked to support rw operations on a file that currently
    // exists in HDFS by using a local file buffer.

    IDBFileSystem& fs = IDBFactory::getFs( HDFS );

    // append an extra tmp extension if USE_TMPFILE extension is set.
    string input(fname);

    if (opts & USE_TMPFILE)
    {
        m_fname += ".tmp";   // use .tmp as working copy to replace the ".hdr/chk" backup.

        if (IDBPolicy::exists(m_fname.c_str()))
            input = m_fname; // get from .tmp if revisit
        else
            m_new = true;
    }

    // cache the size first - we will use this to determine if the
    // file already exists and needs to be read into the buffer
    off64_t size = fs.size(input.c_str());

    // first we will try to open the file for writing - if this fails
    // it means we can't actually open the file for writing and need
    // to throw exception anyway
    bool truncate = (mode != NULL && *mode == 'w');

    if ( size < 0 || truncate)
    {
        HdfsFile* trywrite = new HdfsFile(input.c_str(), "w", 0);
        delete trywrite;

        size = 0;
    }

    // if we get here, then will be ok to write later.  First we
    // we set up the local directory that we need to write to
    string bufname = IDBPolicy::hdfsRdwrScratch() + input;
    boost::filesystem::path pathDir(bufname);

    // this will create the directory we want to work in
    if ( IDBPolicy::mkdir(pathDir.parent_path().string().c_str()) != 0 )
    {
        ostringstream oss;
        oss << "Unable to create directory path: " << pathDir.parent_path();
        throw std::runtime_error(oss.str());
    }

    m_buffer = new BufferedFile( bufname.c_str(), "w+", IDBDataFile::USE_VBUF );

    // Now we need to
    // open one for reading if the file existed previously
    if ( size > 0 )
    {
        HdfsFile tryread(input.c_str(), "r", 0);

        boost::scoped_array<unsigned char> buffer(new unsigned char[BUFSIZE]);
        ssize_t bytesProcessed = 0;

        while (bytesProcessed < (ssize_t) size)
        {
            ssize_t tryToRead = ((ssize_t) BUFSIZE > size - bytesProcessed ? size - bytesProcessed : BUFSIZE);
            ssize_t bytesRead = tryread.read( buffer.get(), tryToRead );

            if (bytesRead < 0)
            {
                ostringstream oss;
                oss << "Unable to read file: " << input;
                throw std::runtime_error(oss.str());
            }
            else if (bytesRead == 0)   // the size changed since it was checked
                size = bytesProcessed;

            ssize_t err = m_buffer->write( buffer.get(), bytesRead );

            // write() will do the retrying
            if (err < 0)
            {
                ostringstream oss;
                oss << "Unable to write file: " << bufname;
                throw std::runtime_error(oss.str());
            }

            bytesProcessed += bytesRead;
        }

        m_buffer->seek(0, SEEK_SET);
    }
    else
    {
        // in this case there is no existing file to read and nothing else to do
        ;
    }
}

// This constructor is for use by HdfsRdwrMemBuffer to create a file buffer when we
// run out of memory.
HdfsRdwrFileBuffer::HdfsRdwrFileBuffer(HdfsRdwrMemBuffer* pMemBuffer) :
    IDBDataFile(pMemBuffer->name().c_str()),
    m_buffer(NULL),
    m_dirty(false)
{
    // we have been asked to replace memory buffered rw operations with file buffered
    // operations on a file that currently exists in HDFS.

    // Set up the local directory that we need to write to
    string bufname = IDBPolicy::hdfsRdwrScratch() + name();
    boost::filesystem::path pathDir(bufname);

    // this will create the directory we want to work in
    if ( IDBPolicy::mkdir(pathDir.parent_path().string().c_str()) != 0 )
    {
        ostringstream oss;
        oss << "MemBuffer overflow. Unable to create directory path: " << pathDir.parent_path();
        throw std::runtime_error(oss.str());
    }

    m_buffer = new BufferedFile( bufname.c_str(), "w+", IDBDataFile::USE_VBUF );

    // Dump the contents of the memory buffer into the file
    const unsigned char* membuffer = pMemBuffer->getbuffer();
    ssize_t bytesToProcess = pMemBuffer->size();
    ssize_t bytesProcessed = 0;

    while (bytesToProcess > 0)
    {
        bytesProcessed = m_buffer->write( membuffer, bytesToProcess );

        if ((bytesProcessed < 0 && errno != EINTR) || bytesProcessed == 0)  // write() does a lot of retrying
        {
            ostringstream oss;
            oss << "MemBuffer overflow. Error while writing: " << pathDir << " " << strerror(errno);
            throw std::runtime_error(oss.str());
        }

        if (bytesProcessed > 0)
        {
            membuffer += bytesProcessed;
            bytesToProcess -= bytesProcessed;
        }
    }
}

HdfsRdwrFileBuffer::~HdfsRdwrFileBuffer()
{
    close();
}

ssize_t HdfsRdwrFileBuffer::pread(void* ptr, off64_t offset, size_t count)
{
    return m_buffer->pread(ptr, offset, count);
}

ssize_t HdfsRdwrFileBuffer::read(void* ptr, size_t count)
{
    return m_buffer->read(ptr, count);
}

ssize_t HdfsRdwrFileBuffer::write(const void* ptr, size_t count)
{
    m_dirty = true;
    return m_buffer->write(ptr, count);
}

int HdfsRdwrFileBuffer::seek(off64_t offset, int whence)
{
    return m_buffer->seek(offset, whence);
}

int HdfsRdwrFileBuffer::truncate(off64_t length)
{
    m_dirty = true;
    return m_buffer->truncate(length);
}

off64_t HdfsRdwrFileBuffer::size()
{
    return m_buffer->size();
}

off64_t HdfsRdwrFileBuffer::tell()
{
    return m_buffer->tell();
}

int HdfsRdwrFileBuffer::flush()
{
    int ret = 0;
    int err;

    if (m_dirty || m_new)
    {
        // no need to flush the tmp file:
        //     this the owner and the file is not for others to read.
        //     BufferedFile::size() uses ftell get the file current size.
        // ret =  m_buffer->flush();

        size_t size = m_buffer->size();

        HdfsFile writer(m_fname.c_str(), "w", 0);

        boost::scoped_array<unsigned char> buffer(new unsigned char[BUFSIZE]);

        ssize_t bytesProcessed = 0;
        err = m_buffer->seek(0, SEEK_SET);

        if (err)
            return err;

        /* If this operation doesn't complete successfully, something bad happened.
            Is there anything we can do about cleanup in this case?
         */
        while (bytesProcessed < (ssize_t) size)
        {
            ssize_t bytesToRead = min( BUFSIZE, size - bytesProcessed );
            ssize_t bytesRead = m_buffer->read( buffer.get(), bytesToRead );

            if (bytesRead < 0)
                return -1;
            else if (bytesRead == 0)  // early EOF.  File must have changed size.
                size = bytesProcessed;

            ssize_t bytesWritten = writer.write( buffer.get(), bytesRead );

            if (bytesWritten < bytesRead)   // a fatal error happened during the write
                return -1;

            bytesProcessed += bytesRead;
        }

        m_dirty = false;
        m_new = false;
    }

    return ret;
}

time_t HdfsRdwrFileBuffer::mtime()
{
    return m_buffer->mtime();
}

int HdfsRdwrFileBuffer::close()
{
    // on close, flush data from tmp file back to hdfs
    flush();

    string buffile = m_buffer->name();

    // now cleanup our buffer
    if ( IDBPolicy::remove(buffile.c_str()) != 0 )
    {
        ostringstream oss;
        oss << "Unable to remove HdfsRdwr buffer file: " << buffile;
        throw std::runtime_error(oss.str());
    }

    // delete will close the BufferedFile
    delete m_buffer;
    m_buffer = 0;
    return 0;
}

}