defmodule NLdoc.Validation.Content do
  @moduledoc """
  This module provides helper functions for validating the content of NLdoc spec objects.
  """

  @doc """
  Returns true if the given text is visible, i.e. consists anything else than whitespace or invisible characters.
  If the given text is an `NLdoc.Spec` object, this function will recursively check whether any of its children
  contain visible text.
  """
  @spec visible_text?(NLdoc.Spec.object() | String.t() | nil) :: boolean()
  def visible_text?(text) when is_binary(text),
    # \s matches standard whitespace characters.
    # \b matches a backspace character.
    # \x{0085} matches Unicode character U+0085 (Next Line).
    # See the tests for this module for a complete list of all these Unicode characters and what they are.
    # See also https://en.wikipedia.org/wiki/Whitespace_character#Unicode
    do:
      String.replace(
        text,
        ~r/[\s\b\x{0085}\x{00A0}\x{1680}\x{180E}\x{2000}\x{2001}\x{2002}\x{2003}\x{2004}\x{2005}\x{2006}\x{2007}\x{2008}\x{2009}\x{200A}\x{200B}\x{200C}\x{200D}\x{2028}\x{2029}\x{202F}\x{205F}\x{2060}\x{3000}\x{FEFF}]/u,
        ""
      ) != ""

  def visible_text?(%{text: text}), do: visible_text?(text)
  def visible_text?(%{children: children}), do: Enum.any?(children, &visible_text?/1)
  def visible_text?(_), do: false
end