/*  Copyright 2013 IST Austria
    Contributed by: Ulrich Bauer, Michael Kerber, Jan Reininghaus

    This file is part of PHAT.

    PHAT is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    PHAT 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with PHAT.  If not, see <http://www.gnu.org/licenses/>. */

#pragma once

#include <phat/helpers/misc.h>
#include <phat/boundary_matrix.h>

namespace phat {
    class twist_reduction {
    public:
        template< typename Representation >
        void operator () ( boundary_matrix< Representation >& boundary_matrix ) {

            const index nr_columns = boundary_matrix.get_num_cols();
            std::vector< index > lowest_one_lookup( nr_columns, -1 );
            
            for( index cur_dim = boundary_matrix.get_max_dim(); cur_dim >= 1 ; cur_dim-- ) {
                for( index cur_col = 0; cur_col < nr_columns; cur_col++ ) {
                    if( boundary_matrix.get_dim( cur_col ) == cur_dim ) {
                        index lowest_one = boundary_matrix.get_max_index( cur_col );
                        while( lowest_one != -1 && lowest_one_lookup[ lowest_one ] != -1 ) {
                            boundary_matrix.add_to( lowest_one_lookup[ lowest_one ], cur_col );
                            lowest_one = boundary_matrix.get_max_index( cur_col );
                        }
                        if( lowest_one != -1 ) {
                            lowest_one_lookup[ lowest_one ] = cur_col;
                            boundary_matrix.clear( lowest_one );
                        }
                        boundary_matrix.finalize( cur_col );
                    }
                }
            }
        }
    };
}
