red

defmodule Red.Edge do
  alias Red.{Entity, Relation}
  defstruct relation: nil, target: nil

  @type t :: %Red.Edge{relation: Relation.t, target: Entity.t}

  @spec ops(t, atom) :: [...]
  def ops(%__MODULE__{} = edge, :add) do
    [origin, target] =
      [edge.relation.entity, edge.target]
      |> Enum.map(&Red.key/1)
      |> conform_to_direction(edge)

    [
      ["ZADD", "#{origin}:#{edge.relation.name}:in",  0, target],
      ["ZADD", "#{target}:#{edge.relation.name}:out", 0, origin]
    ]
  end

  @out %{relation: %{direction: :out}}
  defp conform_to_direction([origin, target], @out), do: [target, origin]
  defp conform_to_direction([origin, target], _in),  do: [origin, target]
end