class Bundler::Molinillo::DependencyGraph::DetachVertexNamed

def self.action_name
  :add_vertex
end

def down(graph)
  return unless @vertex
  graph.vertices[@vertex.name] = @vertex
  @vertex.outgoing_edges.each do |e|
    e.destination.incoming_edges << e
  end
  @vertex.incoming_edges.each do |e|
    e.origin.outgoing_edges << e
  end
end

def initialize(name)
  @name = name
end

def up(graph)
  return [] unless @vertex = graph.vertices.delete(name)
  removed_vertices = [@vertex]
  @vertex.outgoing_edges.each do |e|
    v = e.destination
    v.incoming_edges.delete(e)
    if !v.root? && v.incoming_edges.empty?
      removed_vertices.concat graph.detach_vertex_named(v.name)
    end
  end
  @vertex.incoming_edges.each do |e|
    v = e.origin
    v.outgoing_edges.delete(e)
  end
  removed_vertices
end