defmodule FrenzyWeb.FeedView do
  use FrenzyWeb, :view
  alias Frenzy.{Repo, Item}
  import Ecto.Query

  @spec next_page_path(Plug.Conn.t(), [Frenzy.Item.t()]) :: String.t() | nil
  def next_page_path(_conn, []), do: nil

  def next_page_path(conn, items) do
    %Item{id: id, date: date} = List.last(items)
    has_older = Repo.exists?(from i in Item, where: i.date < ^date)

    if has_older do
      Phoenix.Controller.current_path(conn, %{before: id})
    else
      nil
    end
  end

  @spec prev_page_path(Plug.Conn.t(), [Frenzy.Item.t()]) :: String.t() | nil
  def prev_page_path(_conn, []), do: nil

  def prev_page_path(conn, [%Item{id: id, date: date} | _]) do
    has_newer = Repo.exists?(from i in Item, where: i.date > ^date)

    if has_newer do
      Phoenix.Controller.current_path(conn, %{after: id})
    else
      nil
    end
  end
end