defmodule NLdoc.Validation.Rules.StyleItalicInHeading do
  @moduledoc """
  This rule validates that heading is not manually styled italic.

  Underlined is covered by the NoUnderline Rule
  """

  alias NLdoc.Spec.{Heading, Link, Paragraph, Text}
  alias NLdoc.Validation.{Severity, State}

  use NLdoc.Validation.Rule,
    severity: Severity.warning(),
    rule: "style-italic-in-heading",
    ruleset: "https://validation.spec.nldoc.nl/",
    # @TODO set `ruleset_version` to a real version
    ruleset_version: "unknown",
    validates: [Paragraph, Heading, Text, Link]

  @impl true
  def update_state(state = %State{}, %Heading{}),
    do: %State{state | parent_is_heading?: true}

  @impl true
  def update_state(state = %State{}, %{children: _children}),
    do: %State{state | parent_is_heading?: false}

  @impl true
  def valid?(%{styling: styling}, %State{parent_is_heading?: true}),
    do: !Enum.any?(styling, fn style -> style == :italic end)
end