// * This file is part of the COLOBOT source code
// * Copyright (C) 2014 Polish Portal of Colobot (PPC)
// *
// * 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, either version 3 of the License, or
// * (at your option) any later version.
// *
// * 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, see  http://www.gnu.org/licenses/.

#include "common/resources/resourcestreambuffer.h"

#include <stdexcept>
#include <sstream>

CResourceStreamBuffer::CResourceStreamBuffer(size_t buffer_size) : m_buffer_size(buffer_size)
{
    if (buffer_size <= 0)
    {
        throw std::runtime_error("File buffer must be larger then 0 bytes");
    }

    m_buffer = new char[buffer_size];
    m_file = nullptr;
}


CResourceStreamBuffer::~CResourceStreamBuffer()
{
    close();
    delete m_buffer;
}


void CResourceStreamBuffer::open(const std::string &filename)
{
    if (PHYSFS_isInit())
    {
        m_file = PHYSFS_openRead(filename.c_str());
    }
}


void CResourceStreamBuffer::close()
{
    if (is_open())
    {
        PHYSFS_close(m_file);
    }
}


bool CResourceStreamBuffer::is_open()
{
    return m_file;
}


size_t CResourceStreamBuffer::size()
{
    return PHYSFS_fileLength(m_file);
}


std::streambuf::int_type CResourceStreamBuffer::underflow()
{
    if (PHYSFS_eof(m_file))
    {
        return traits_type::eof();
    }
    
    PHYSFS_sint64 read_count = PHYSFS_read(m_file, m_buffer, sizeof(char), m_buffer_size);
    if (read_count <= 0)
    {
        return traits_type::eof();
    }
    
    setg(m_buffer, m_buffer, m_buffer + read_count);

    return traits_type::to_int_type(*gptr());
}


std::streampos CResourceStreamBuffer::seekpos(std::streampos sp, std::ios_base::openmode which)
{
    return seekoff(off_type(sp), std::ios_base::beg, which);
}


std::streampos CResourceStreamBuffer::seekoff(std::streamoff off, std::ios_base::seekdir way, std::ios_base::openmode which)
{
    /* A bit of explanation:
       We are reading file by m_buffer_size parts so our 3 internal pointers will be
       * eback (not used here) - start of block
       * gptr - position of read cursor in block
       * egtpr - end of block
       off argument is relative to way */
    
    switch (way)
    {
        case std::ios_base::beg:
            return pos_type(off_type(off));

        case std::ios_base::cur:
            // tell will give cursor at begining of block so we have to add where in block we currently are
            return off + static_cast<off_type>(PHYSFS_tell(m_file)) - static_cast<off_type> (egptr() - gptr());

        case std::ios_base::end:
            return off + static_cast<off_type>(PHYSFS_fileLength(m_file));
            
        default:
            break;
    }

    return pos_type(off_type(-1));
}