bound_policy.hpp

// Copyright 2021 Arnaud Becheler    <abechele@umich.edu>
 
 
#pragma once
 
#include "concepts.hpp"
#include <cassert>
 
namespace quetzal::geography
{
class mirror
{
  public:
    int constexpr inline num_extra_vertices() const { return 0; }
 
    template <class Graph>
    void operator()([[maybe_unused]] typename Graph::vertex_descriptor s, [[maybe_unused]] Graph &graph,
                    [[maybe_unused]] const two_dimensional auto &grid) const
    {
        // do nothing as by default bounding box is reflective
    }
};
 
class sink
{
  public:
 
    int constexpr inline num_extra_vertices() const { return 1; }
 
    template <class Graph>
    void operator()(typename Graph::vertex_descriptor s, Graph &graph, const two_dimensional auto &grid) const
    {
        using edge_property = typename Graph::edge_property;
        int num_land_vertices = grid.width() * grid.height();
        int sink = num_land_vertices;
        assert( graph.num_vertices() == sink + 1 );
        if ( s < sink )
            detail::edge_construction<edge_property>::delegate(s, sink, graph, grid); // one-way ticket :(
    }
};
 
class torus
{
  public:
    int constexpr inline num_extra_vertices() const { return 0; }
 
    template <class Graph>
    void operator()(typename Graph::vertex_descriptor s, Graph &graph, const two_dimensional auto &grid) const
    {
        using edge_property = typename Graph::edge_property;
        auto width = grid.width();
        auto height = grid.height();
        int symmetricIndex = 0;
 
        // top border
        if (s < width)
        {
            symmetricIndex = s + width * (height - 1);
        }
        // bottom border
        else if (s >= (height - 1) * width)
        {
            symmetricIndex = s - (height - 1) * width;
        }
        // left border
        else if (s % width == 0)
        {
            symmetricIndex = s + width - 1;
        }
        // right border
        else if ((s + 1) % width == 0)
        {
            symmetricIndex = s - width + 1;
        }
        detail::edge_construction<edge_property>::delegate(s, symmetricIndex, graph, grid);
    }
};
 
} // namespace quetzal::geography