antl_utils

if Code.ensure_loaded?(Ecto) do
  defmodule AntlUtils.Ecto.Paginator do
    @moduledoc """
    Documentation for Paginator.
    """

    import Ecto.Query
    @per_page 100

    @doc """
    Paginate.

    ## Examples

      iex> queryable = from u in "products"
      #Ecto.Query<from p0 in "products">
      iex> Paginator.paginate(queryable, 1)
      #Ecto.Query<from p0 in "products", limit: ^100, offset: ^0>
      iex> Paginator.paginate(queryable, 2)
      #Ecto.Query<from p0 in "products", limit: ^100, offset: ^100>
      iex> Paginator.paginate(queryable, 3)
      #Ecto.Query<from p0 in "products", limit: ^100, offset: ^200>
      iex> Paginator.paginate(queryable, 3, [per_page: 10])
      #Ecto.Query<from p0 in "products", limit: ^10, offset: ^20>

    """
    @spec paginate(any, number, keyword) :: Ecto.Query.t()
    def paginate(queryable, page, opts \\ []) when page > 0 do
      per_page = Keyword.get(opts, :per_page, @per_page)

      offset = per_page * (page - 1)

      queryable
      |> limit(^per_page)
      |> offset(^offset)
    end
  end
end