defmodule Furlex.Parser.JsonLD do
  @behaviour Furlex.Parser

  @json_library Application.get_env(:furlex, :json_library, Jason)

  @spec parse(String.t) :: nil | {:ok, List.t}
  def parse(html) do
    meta = "script[type=\"application/ld+json\"]"

    case Floki.find(html, meta) do
      nil      ->
        {:ok, []}

      elements ->
        json_ld =
          elements
          |> Enum.map(&decode/1)
          |> List.flatten()

        {:ok, json_ld}
    end
  end

  defp decode(element) do
    element
    |> Floki.text(js: true)
    |> @json_library.decode!()
  end
end