defmodule IO.ANSI.Table.Spec.ColumnWidths do
  @moduledoc """
  Derives the column widths of a table.
  """

  alias IO.ANSI.Table.Spec.Rows
  alias IO.ANSI.Table.{Column, Spec}

  @spec derive(Spec.t()) :: Spec.t()
  def derive(%Spec{headings: headings, rows: rows, max_width: max} = spec) do
    widths = [headings | rows] |> Rows.transpose() |> Column.widths(max)
    put_in(spec.column_widths, widths)
  end
end