defmodule ChunkySVG.Hills do
  def expand(attributes) do
    %{points: points} = attributes

    bez_points =
      [{0, 100} | points]
      |> ChunkySVG.Cons.each_cons()
      |> Enum.map(fn [{x1, y1}, {x2, y2}] ->
        [{x1 + (x2 - x1) / 2, Enum.min([y1, y2])}, {x2, y2}]
      end)

    bez_points = bez_points |> List.flatten() |> Enum.map(fn {x, y} -> "#{x},#{y}" end)
    bez_points = bez_points |> Enum.join(" ")
    path_spec = "M0,100 Q#{bez_points} L100,100 z"
    attributes = attributes |> Map.drop([:points]) |> Map.put(:d, path_spec)
    {:path, attributes, nil}
  end
end