// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// Mobius Forensic Toolkit
// Copyright (C) 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2020,2021,2022 Eduardo Aguiar
//
// 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 2, 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 "reader_impl.h"
#include "imagefile_impl.h"
#include <mobius/exception.inc>
#include <mobius/string_functions.h>
#include <stdexcept>

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Constructor
//! \param imagefile_impl imagefile_impl object
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
reader_impl::reader_impl (const imagefile_impl& imagefile_impl)
  : size_ (imagefile_impl.get_size ()),
    segments_ (imagefile_impl.get_segment_array ())
{
  segment_idx_ = std::int64_t (imagefile_impl.get_attribute ("segments"));

  if (segment_idx_ == 0)
    throw std::runtime_error (mobius::MOBIUS_EXCEPTION_MSG ("segment files not found"));

  segment_size_ = std::int64_t (imagefile_impl.get_attribute ("segment_size"));
  
  _set_stream ();
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Set read position
//! \param offset offset in bytes
//! \param w either beginning, current or end
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
reader_impl::seek (offset_type offset, whence_type w)
{
  // calculate offset from the beginning of data
  offset_type abs_offset;

  if (w == whence_type::beginning)
    abs_offset = offset;

  else if (w == whence_type::current)
    abs_offset = pos_ + offset;

  else if (w == whence_type::end)
    abs_offset = size_ - 1 + offset;

  else
    throw std::invalid_argument (mobius::MOBIUS_EXCEPTION_MSG ("invalid whence_type"));

  // update current pos, if possible
  if (abs_offset < 0)
    throw std::invalid_argument (mobius::MOBIUS_EXCEPTION_MSG ("invalid offset"));
  
  else if (size_type (abs_offset) <= size_)  
    {
      pos_ = abs_offset;
      _set_stream ();
    }
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Read bytes from reader
//! \param size size in bytes
//! \return bytearray containing data
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
mobius::bytearray
reader_impl::read (size_type size)
{
  if (!stream_)
    _set_stream ();

  mobius::bytearray data = stream_.read (size);
  pos_ += data.size ();
  size -= data.size ();

  while (size > 0 && pos_ < size_)
    {
      _set_stream ();
      mobius::bytearray tmp = stream_.read (size);
      pos_ += tmp.size ();
      size -= tmp.size ();
      data += tmp;
    }

  return data;
}

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//! \brief Set read stream according to current position
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
void
reader_impl::_set_stream ()
{
  if (pos_ >= size_)
    return;

  size_type segment_idx = pos_ / segment_size_;
  size_type pos = pos_ % segment_size_;

  if (segment_idx != segment_idx_)
    {
      stream_ = segments_.new_reader (segment_idx);
      segment_idx_ = segment_idx;
    }

  stream_.seek (pos);
}
