pure_html

defmodule PureHTML.TreeBuilder.Modes.Initial do
  @moduledoc """
  HTML5 "initial" insertion mode.

  This is the starting mode before any content is processed.

  Per HTML5 spec:
  - DOCTYPE token: Create DOCTYPE, switch to "before html"
  - Comment token: Insert as child of Document
  - Whitespace: Ignore
  - Anything else: Switch to "before html" and reprocess

  See: https://html.spec.whatwg.org/multipage/parsing.html#the-initial-insertion-mode
  """

  @behaviour PureHTML.TreeBuilder.InsertionMode

  @impl true
  def process({:character, text}, state) do
    # Whitespace is ignored in initial mode
    # Non-whitespace triggers mode switch and reprocess (quirks mode)
    case String.trim(text) do
      "" ->
        # All whitespace - ignore
        {:ok, state}

      _ ->
        # Has non-whitespace - no DOCTYPE seen, set quirks mode
        {:reprocess, %{state | mode: :before_html, quirks_mode: true}}
    end
  end

  def process({:comment, _text}, state) do
    # Comments in initial mode are inserted as children of the Document
    # This is handled at the document level in TreeBuilder.process_token
    # The mode module just needs to not change mode
    {:ok, state}
  end

  def process({:doctype, _name, _public, _system, _force_quirks}, state) do
    # DOCTYPE handling is done at process_token level
    # Valid DOCTYPE -> not quirks mode (quirks_mode stays false)
    {:ok, %{state | mode: :before_html}}
  end

  def process(_token, state) do
    # Any other token without DOCTYPE: set quirks mode
    {:reprocess, %{state | mode: :before_html, quirks_mode: true}}
  end
end