/*
    Copyright 2007-2008 Christian Henning
    Use, modification and distribution are subject to the Boost Software License,
    Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
    http://www.boost.org/LICENSE_1_0.txt).
*/

/*************************************************************************************************/

#ifndef BOOST_GIL_EXTENSION_IO_DETAIL_READER_BASE_HPP_INCLUDED
#define BOOST_GIL_EXTENSION_IO_DETAIL_READER_BASE_HPP_INCLUDED

////////////////////////////////////////////////////////////////////////////////////////
/// \file
/// \brief
/// \author Christian Henning \n
///
/// \date   2007-2008 \n
///
////////////////////////////////////////////////////////////////////////////////////////

#include "base.hpp"

namespace boost { namespace gil { namespace detail {

/// Reader Base Class
/// 
/// It provides some basic functionality which is shared for all readers.
/// For instance, it recreates images when necessary. It checks whether
/// user supplied coordinates are valid.
///
/// @tparam FormatTag        A format tag, like jpeg_tag.
/// @tparam ConversionPolicy Conversion policy, see coversion_policies.hpp.
template< typename FormatTag
        , typename ConversionPolicy
        >
struct reader_base
{
public:

    /// Initializes an image. But also does some check ups.
    ///
    /// @tparam Image Image which implements boost::gil's ImageConcept.
    ///
    /// @param img  The image.
    /// @param info The image read info.
    template< typename Image >
    void init_image( Image&                              img
                   , const image_read_info< FormatTag >& info
                   )
    {
        _info = info;

        setup( _settings._dim );

        img.recreate( _settings._dim.x
                    , _settings._dim.y
                    );
    }

    template< typename View >
    void init_view( const View&                         view
                  , const image_read_info< FormatTag >& info
                  )
    {
        _info = info;

        setup( view.dimensions() );
    }

protected:

    reader_base( const image_read_settings< FormatTag >& settings )
    : _settings( settings )
    {}
    reader_base( const typename ConversionPolicy::color_converter_type& cc
               , const image_read_settings< FormatTag >&                settings
               )
    : _cc_policy( cc )
    , _settings( settings )
    {}

private:

    void setup( const point_t& dim )
    {
        check_coordinates( dim );

        if( dim == point_t( 0, 0 ))
        {
            _settings._dim.x = _info._width;
            _settings._dim.y = _info._height;
        }
        else
        {
            _settings._dim = dim;
        }
    }

    void check_coordinates( const point_t& dim )
    {
       typedef point_t::value_type int_t;

       int_t width  = static_cast< int_t >( _info._width  );
       int_t height = static_cast< int_t >( _info._height );

       io_error_if( (  _settings._top_left.x < 0
                    || _settings._top_left.y < 0
                    || dim.x < 0
                    || dim.y < 0
                    )
                 , "User provided view has incorrect size." );


       io_error_if( (  ( width  ) <  _settings._top_left.x
                    && ( width  ) <= dim.x
                    && ( height ) <  _settings._top_left.y
                    && ( height ) <= dim.y  )
                 , "User provided view has incorrect size."       );

       io_error_if( (  ( _settings._top_left.x + dim.x ) > width
                    || ( _settings._top_left.y + dim.y ) > height
                   )
                 , "User provided view has incorrect size." );

    }

protected:

    image_read_settings< FormatTag > _settings;
    image_read_info< FormatTag >     _info;

    ConversionPolicy _cc_policy;
};

} // namespace detail
} // namespace gil
} // namespace boost

#endif // BOOST_GIL_EXTENSION_IO_DETAIL_READER_BASE_HPP_INCLUDED