Construct helpers

[AndrewDryga]

+defmodule Gateway.Helpers.Pagination do
 +  @moduledoc """
 +  Functions related to paging
 +  """
 +
 +  def page_info_from(params) do
 +    starting_after = extract_integer(params, "starting_after")
 +    ending_before = extract_integer(params, "ending_before")
 +    limit = extract_integer(params, "limit")
 +
 +    cursors = %Ecto.Paging.Cursors{starting_after: starting_after, ending_before: ending_before}
 +
 +    %Ecto.Paging{limit: limit, cursors: cursors}
 +  end
 +
 +  def extract_integer(map, key) do
 +    case Map.get(map, key) do
 +      nil ->
 +        nil
 +      string ->
 +        case Integer.parse(string) do
 +          {integer, ""} -> integer
 +          _ -> string
 +        end
 +    end
 +  end
 +end