defmodule LndClient.Tools.CommonPeers do
  @spec intersect(any, any) :: list
  def intersect node1_pub_key, node2_pub_key do
    node1_node_ids = node1_pub_key |> get_node_peer_ids
    node2_node_ids = node2_pub_key |> get_node_peer_ids

    node1_node_ids -- (node1_node_ids -- node2_node_ids)
  end

  defp get_node_peer_ids pub_key do
    { :ok, %Lnrpc.NodeInfo{ channels: channels } } = LndClient.get_node_info pub_key, true

    channels
    |> Enum.map(fn channel ->
      get_peer_pub_key channel, pub_key
    end)
  end

  defp get_peer_pub_key %{ node1_pub: local_pub_key } = channel, local_pub_key do
    channel.node2_pub
  end

  defp get_peer_pub_key %{ node2_pub: local_pub_key } = channel, local_pub_key do
    channel.node1_pub
  end
end