defmodule Graphic do
  @dg :digraph
  
  # graph ops
  def bridge(g, a, b) do
    if !(g|>@dg.vertex(a)), do: g|>@dg.add_vertex(a)
    if !(g|>@dg.vertex(b)), do: g|>@dg.add_vertex(b)
    g|>@dg.add_edge(a, b)
  end

  def bridge(g, a, b, label) do
    if !(g|>@dg.vertex(a)), do: g|>@dg.add_vertex(a)
    if !(g|>@dg.vertex(b)), do: g|>@dg.add_vertex(b)
    g|>@dg.add_edge(a, b, label)
  end

  # graph reads
  def edges(g), do: g|>@dg.edges()|>Enum.map(& g|>@dg.edge(&1))
  def order(g), do: g|>:digraph_utils.topsort()

  # node reads
  def neighbors(g,n), do: g|>@dg.out_neighbours(n)
end