defmodule EarmarkParser.Parser.ListParser do
  alias EarmarkParser.{Block, Line, Options}
  alias EarmarkParser.Parser.ListInfo

  import EarmarkParser.Helpers.StringHelpers, only: [behead: 2]
  import EarmarkParser.Message, only: [add_message: 2]
  import ListInfo

  @moduledoc false

  @not_pending {nil, 0}

  def parse_list(lines, result, options \\ %Options{}) do
    {items, rest, options1} = _parse_list_items_init(lines, [], options)
    list                    = _make_list(items, _empty_list(items) )
    {[list|result], rest, options1}
  end

  defp _parse_list_items_init([item|rest], list_items, options) do
    options1 = %{options|line: item.lnb}
    _parse_list_items_start(rest, _make_and_prepend_list_item(item, list_items), new(item, options1))
  end

  defp _parse_list_items_spaced(input, items, list_info)
  defp _parse_list_items_spaced(input, items, %{pending: @not_pending}=list_info) do
    _parse_list_items_spaced_np(input, items, list_info)
  end
  defp _parse_list_items_spaced(input, items, list_info) do
    _parse_list_items_spaced_pdg(input, items, list_info)
  end

  defp _parse_list_items_spaced_np([%Line.Blank{}|rest], items, list_info) do
    list_info1 = %{list_info|lines: [""|list_info.lines], options: %{list_info.options|line: list_info.options.line + 1}}
    _parse_list_items_spaced_np(rest, items, list_info1)
  end
  defp _parse_list_items_spaced_np([%Line.Ruler{}|_]=lines, items, list_info) do
    _finish_list_items(lines, items, false, list_info)
  end
  defp _parse_list_items_spaced_np([%Line.ListItem{indent: ii}=item|_]=input, list_items, %{width: w}=list_info)
    when ii < w do
      if _starts_list?(item, list_items) do
        _finish_list_items(input, list_items, false, list_info)
      else
        {items1, options1} = _finish_list_item(list_items, false, _loose(list_info))
        _parse_list_items_init(input, items1, options1)
      end
  end
  defp _parse_list_items_spaced_np([%Line.Indent{indent: ii}=item|rest], list_items, %{width: w}=list_info)
    when ii >= w do
      indented = _behead_spaces(item.line, w)
      _parse_list_items_spaced(rest, list_items, update_list_info(list_info, indented, item, true))
  end
  defp _parse_list_items_spaced_np([%Line.ListItem{}=line|rest], items, list_info) do
    indented = _behead_spaces(line.line, list_info.width)
    _parse_list_items_start(rest, items, update_list_info(list_info, indented, line))
  end
  # BUG: Still do not know how much to indent here???
  defp _parse_list_items_spaced_np([%{indent: indent, line: str_line}=line|rest], items, %{width: width}=list_info) when
    indent >= width
  do
    _parse_list_items_spaced(rest, items, update_list_info(list_info, behead(str_line, width), line, true))
  end
  defp _parse_list_items_spaced_np(input, items, list_info) do
    _finish_list_items(input ,items, false, list_info)
  end

  defp _parse_list_items_spaced_pdg(input, items, list_info)
  defp _parse_list_items_spaced_pdg([], items, %{pending: {pending, lnb}}=list_info) do
    options1 =
      add_message(list_info.options, {:warning, lnb, "Closing unclosed backquotes #{pending} at end of input"})
    _finish_list_items([], items, false, %{list_info| options: options1})
  end
  defp _parse_list_items_spaced_pdg([line|rest], items, list_info) do
    indented = _behead_spaces(line.line, list_info.width)
    _parse_list_items_spaced(rest, items, update_list_info(list_info, indented, line, true))
  end


  defp _parse_list_items_start(input, list_items, list_info)
  defp _parse_list_items_start(input, list_items, %{pending: @not_pending}=list_info) do
    _parse_list_items_start_np(input, list_items, list_info)
  end
  defp _parse_list_items_start(input, list_items, list_info) do
    _parse_list_items_start_pdg(input, list_items, list_info)
  end

  defp _parse_list_items_start_np(input, list_items, list_info)
  defp _parse_list_items_start_np([%Line.Blank{}|input], items, list_info) do
    _parse_list_items_spaced(input, items, prepend_line(list_info, ""))
  end
  defp _parse_list_items_start_np([], list_items, list_info) do
    _finish_list_items([], list_items, true, list_info)
  end
  defp _parse_list_items_start_np([%Line.Ruler{}|_]=input, list_items, list_info) do
    _finish_list_items(input, list_items, true, list_info)
  end
  defp _parse_list_items_start_np([%Line.Heading{}|_]=input, list_items, list_info) do
    _finish_list_items(input, list_items, true, list_info)
  end
  defp _parse_list_items_start_np([%Line.ListItem{indent: ii}=item|_]=input, list_items, %{width: w}=list_info)
    when ii < w do
      if _starts_list?(item, list_items) do
        _finish_list_items(input, list_items, true, list_info)
      else
        {items1, options1} = _finish_list_item(list_items, true, list_info)
        _parse_list_items_init(input, items1, options1)
      end
  end
  # Slurp in everything else before a first blank line
  defp _parse_list_items_start_np([%{line: str_line}=line|rest], items, list_info) do
    indented = _behead_spaces(str_line, list_info.width)
    _parse_list_items_start(rest, items, update_list_info(list_info, indented, line))
  end

  defp _parse_list_items_start_pdg(input, items, list_info)
  defp _parse_list_items_start_pdg([], items, list_info) do
    _finish_list_items([], items, true, list_info)
  end
  defp _parse_list_items_start_pdg([%{line: str_line}=line|rest], items, list_info) do
    indented = _behead_spaces(str_line, list_info.width)
    _parse_list_items_start(rest, items, update_list_info(list_info, indented, line))
  end

  defp _behead_spaces(str, len) do
    Regex.replace(~r/\A\s{1,#{len}}/, str, "")
  end

  # INLINE CANDIDATE
  defp _empty_list([%Block.ListItem{loose?: loose?, type: type}|_]) do
    %Block.List{loose?: loose?, type: type}
  end

  defp _extract_start(%{bullet: bullet}) do
    start_number_rgx = ~r{\A0*(\d+)\.}

    case Regex.run(start_number_rgx, bullet) do
      nil -> ""
      [_, "1"] -> ""
      [_, start] -> ~s{ start="#{start}"}
    end
  end

  defp _finish_list_item([%Block.ListItem{}=item|items], _at_start?, list_info) do
    {blocks, _, _, options1} = list_info.lines
                            |> Enum.reverse
                            |> EarmarkParser.Parser.parse(%{list_info.options|line: item.lnb}, :list)
    loose1? = _already_loose?(items) || list_info.loose?
    {[%{item | blocks: blocks, loose?: loose1?}|items], options1}
  end

  defp _finish_list_items(input, items, at_start?, list_info) do
    {items1, options1} = _finish_list_item(items, at_start?, list_info)
    {items1, input, options1}
  end

  defp _make_and_prepend_list_item(%Line.ListItem{bullet: bullet, lnb: lnb, type: type}, list_items) do
    [%Block.ListItem{bullet: bullet, lnb: lnb, spaced?: false, type: type}|list_items]
  end

  defp _make_list(items, list)
  defp _make_list([%Block.ListItem{bullet: bullet, lnb: lnb}=item], %Block.List{loose?: loose?}=list) do
    %{list | blocks: [%{item | loose?: loose?}|list.blocks],
      bullet: bullet,
      lnb: lnb,
      start: _extract_start(item)}
  end
  defp _make_list([%Block.ListItem{}=item|rest], %Block.List{loose?: loose?}=list) do
   _make_list(rest, %{list | blocks: [%{item | loose?: loose?}|list.blocks]})
  end

  defp _already_loose?(items)
  defp _already_loose?([]), do: false
  defp _already_loose?([%{loose?: loose?}|_]), do: loose?

  defp _loose(list_info), do: %{list_info|loose?: true}

  defp _starts_list?(%{bullet: bullet1}, [%Block.ListItem{bullet: bullet2}|_]) do
    String.last(bullet1) != String.last(bullet2)
  end

end
# SPDX-License-Identifier: Apache-2.0
