defmodule EarmarkParser.Parser do

  @moduledoc false
  alias EarmarkParser.{Block, Line, LineScanner, Options}

  import EarmarkParser.Helpers.{AttrParser, LineHelpers, ReparseHelpers}

  import EarmarkParser.Helpers.LookaheadHelpers,
    only: [opens_inline_code: 1, still_inline_code: 2]

  import EarmarkParser.Message, only: [add_message: 2, add_messages: 2]
  import EarmarkParser.Parser.FootnoteParser, only: [parse_fn_defs: 3]
  import EarmarkParser.Parser.ListParser, only: [parse_list: 3]

  @doc """
  Given a markdown document (as either a list of lines or
  a string containing newlines), return a parse tree and
  the context necessary to render the tree.

  The options are a `%EarmarkParser.Options{}` structure. See `as_html!`
  for more details.
  """
  def parse_markdown(lines, options)

  def parse_markdown(lines, options = %Options{}) when is_list(lines) do
    {blocks, links, footnotes, options1} = parse(lines, options, false)

    context =
      %EarmarkParser.Context{options: options1, links: links}
      |> EarmarkParser.Context.update_context()

    context = put_in(context.footnotes, footnotes)
    context = put_in(context.options, options1)
    {blocks, context}
  end

  def parse_markdown(lines, options) when is_binary(lines) do
    lines
    |> String.split(~r{\r\n?|\n})
    |> parse_markdown(options)
  end

  def parse_markdown(lines, _) do
    raise ArgumentError, "#{inspect lines} not a binary, nor a list of binaries"
  end

  def parse(text_lines, options = %Options{}, recursive) do
    ["" | text_lines ++ [""]]
    |> LineScanner.scan_lines(options, recursive)
    |> parse_lines(options, recursive)
  end

  @doc false
  # Given a list of `Line.xxx` structs, group them into related blocks.
  # Then extract any id definitions, and build a map from them. Not
  # for external consumption.

  def parse_lines(lines, options, recursive) do
    {blocks, footnotes, options} =
      lines |> remove_trailing_blank_lines() |> lines_to_blocks(options, recursive)


    links = links_from_blocks(blocks)
    {blocks, links, footnotes, options}
  end

  defp lines_to_blocks(lines, options, recursive) do
    {blocks, footnotes, options1} = _parse(lines, [], options, recursive)

    {blocks |> assign_attributes_to_blocks([]), footnotes, options1}
  end

  defp _parse(input, result, options, recursive)
  defp _parse([], result, options, _recursive), do: {result, %{}, options}

  ###################
  # setext headings #
  ###################

  # 1 step
  defp _parse(
         [
           %Line.Blank{},
           %Line.Text{content: heading, lnb: lnb},
           %Line.SetextUnderlineHeading{annotation: annotation, level: level}
           | rest
         ],
         result,
         options,
         recursive
       ) do
    _parse(
      rest,
      [%Block.Heading{annotation: annotation, content: heading, level: level, lnb: lnb} | result],
      options,
      recursive
    )
  end

  # 1 step
  defp _parse(
         [
           %Line.Blank{},
           %Line.Text{content: heading, lnb: lnb},
           %Line.Ruler{type: "-"}
           | rest
         ],
         result,
         options,
         recursive
       ) do
    _parse(
      rest,
      [%Block.Heading{content: heading, level: 2, lnb: lnb} | result],
      options,
      recursive
    )
  end

  #################
  # Other heading #
  #################

  # 1 step
  defp _parse(
         [%Line.Heading{content: content, ial: ial, level: level, lnb: lnb} | rest],
         result,
         options,
         recursive
       ) do
    {options1, result1} =
      prepend_ial(
        options,
        ial,
        lnb,
        [%Block.Heading{content: content, level: level, lnb: lnb} | result]
      )

    _parse(rest, result1, options1, recursive)
  end

  #########
  # Ruler #
  #########

  # 1 step
  defp _parse([%Line.Ruler{type: type, lnb: lnb} | rest], result, options, recursive) do
    _parse(rest, [%Block.Ruler{type: type, lnb: lnb} | result], options, recursive)
  end

  ###############
  # Block Quote #
  ###############

  # split and parse
  defp _parse(lines = [%Line.BlockQuote{lnb: lnb} | _], result, options, recursive) do
    {quote_lines, rest} = Enum.split_while(lines, &blockquote_or_text?/1)
    lines = for line <- quote_lines, do: line.content
    {blocks, _, _, options1} = parse(lines, %{options | line: lnb}, true)
    _parse(rest, [%Block.BlockQuote{blocks: blocks, lnb: lnb} | result], options1, recursive)
  end

  #########
  # Table #
  #########

  # read and add verbatim
  defp _parse(
         lines = [
           %Line.TableLine{columns: cols1, lnb: lnb1, needs_header: false},
           %Line.TableLine{columns: cols2}
           | _rest
         ],
         result,
         options,
         recursive
       )
       when length(cols1) == length(cols2) do
    columns = length(cols1)
    {table, rest} = read_table(lines, columns, [])
    table1 = %{table | lnb: lnb1}
    _parse(rest, [table1 | result], options, recursive)
  end

  defp _parse(
         lines = [
           %Line.TableLine{columns: cols1, lnb: lnb1, needs_header: true},
           %Line.TableLine{columns: cols2, is_header: true}
           | _rest
         ],
         result,
         options,
         recursive
       )
       when length(cols1) == length(cols2) do
    columns = length(cols1)
    {table, rest} = read_table(lines, columns, [])
    table1 = %{table | lnb: lnb1}
    _parse(rest, [table1 | result], options, recursive)
  end

  #############
  # Paragraph #
  #############

  # split and add verbatim
  defp _parse(lines = [%Line.TableLine{lnb: lnb} | _], result, options, recursive) do
    {para_lines, rest} = Enum.split_while(lines, &text?/1)
    line_text = for line <- para_lines, do: line.line
    _parse(rest, [%Block.Para{lines: line_text, lnb: lnb + 1} | result], options, recursive)
  end

  # read and parse
  defp _parse(lines = [%Line.Text{lnb: lnb} | _], result, options, recursive) do
    {reversed_para_lines, rest, pending, annotation} = consolidate_para(lines)

    options1 =
      case pending do
        {nil, _} ->
          options

        {pending, lnb1} ->
          add_message(
            options,
            {:warning, lnb1, "Closing unclosed backquotes #{pending} at end of input"}
          )
      end

    line_text = for line <- reversed_para_lines |> Enum.reverse(), do: line.line

    if recursive == :list do
      _parse(rest, [%Block.Text{line: line_text, lnb: lnb} | result], options1, recursive)
    else
      _parse(
        rest,
        [%Block.Para{annotation: annotation, lines: line_text, lnb: lnb} | result],
        options1,
        recursive
      )
    end
  end

  defp _parse(
         [%Line.SetextUnderlineHeading{line: line, lnb: lnb, level: 2} | rest],
         result,
         options,
         recursive
       ) do
    _parse([%Line.Text{line: line, lnb: lnb} | rest], result, options, recursive)
  end

  #########
  # Lists #
  #########
  # We handle lists in two passes. In the first, we build list items,
  # in the second we combine adjacent items into lists. This is pass one

  defp _parse([%Line.ListItem{} | _] = input, result, options, recursive) do
    {with_prepended_lists, rest, options1} = parse_list(input, result, options)
    _parse([%Line.Blank{lnb: 0} | rest], with_prepended_lists, options1, recursive)
  end

  #################
  # Indented code #
  #################

  defp _parse(list = [%Line.Indent{lnb: lnb} | _], result, options, recursive) do
    {code_lines, rest} = Enum.split_while(list, &indent_or_blank?/1)
    code_lines = remove_trailing_blank_lines(code_lines)
    code = for line <- code_lines, do: properly_indent(line, 1)
    _parse([%Line.Blank{}|rest], [%Block.Code{lines: code, lnb: lnb} | result], options, recursive)
  end

  ###############
  # Fenced code #
  ###############

  defp _parse(
         [%Line.Fence{delimiter: delimiter, language: language, lnb: lnb} | rest],
         result,
         options,
         recursive
       ) do
    {code_lines, rest} =
      Enum.split_while(rest, fn line ->
        !match?(%Line.Fence{delimiter: ^delimiter, language: _}, line)
      end)

    {rest1, options1} = _check_closing_fence(rest, lnb, delimiter, options)
    code = for line <- code_lines, do: line.line

    _parse(
      rest1,
      [%Block.Code{lines: code, language: language, lnb: lnb} | result],
      options1,
      recursive
    )
  end

  ##############
  # HTML block #
  ##############
  defp _parse(
         [opener = %Line.HtmlOpenTag{annotation: annotation, tag: tag, lnb: lnb} | rest],
         result,
         options,
         recursive
       ) do
    {html_lines, rest1, unclosed, annotation} = _html_match_to_closing(opener, rest, annotation)

    options1 =
      add_messages(
        options,
        unclosed
        |> Enum.map(fn %{lnb: lnb1, tag: tag} ->
          {:warning, lnb1, "Failed to find closing <#{tag}>"}
        end)
      )

    html = Enum.reverse(html_lines)

    _parse(
      rest1,
      [%Block.Html{tag: tag, html: html, lnb: lnb, annotation: annotation} | result],
      options1,
      recursive
    )
  end

  ####################
  # HTML on one line #
  ####################

  defp _parse(
         [%Line.HtmlOneLine{annotation: annotation, line: line, lnb: lnb} | rest],
         result,
         options,
         recursive
       ) do
    _parse(
      rest,
      [%Block.HtmlOneline{annotation: annotation, html: [line], lnb: lnb} | result],
      options,
      recursive
    )
  end

  ################
  # HTML Comment #
  ################

  defp _parse(
         [line = %Line.HtmlComment{complete: true, lnb: lnb} | rest],
         result,
         options,
         recursive
       ) do
    _parse(rest, [%Block.HtmlComment{lines: [line.line], lnb: lnb} | result], options, recursive)
  end

  defp _parse(
         lines = [%Line.HtmlComment{complete: false, lnb: lnb} | _],
         result,
         options,
         recursive
       ) do
    {html_lines, rest} =
      Enum.split_while(lines, fn line ->
        !(line.line =~ ~r/-->/)
      end)

    {html_lines, rest} =
      if rest == [] do
        {html_lines, rest}
      else
        {html_lines ++ [hd(rest)], tl(rest)}
      end

    html = for line <- html_lines, do: line.line
    _parse(rest, [%Block.HtmlComment{lines: html, lnb: lnb} | result], options, recursive)
  end

  #################
  # ID definition #
  #################

  defp _parse([defn = %Line.IdDef{lnb: lnb} | rest], result, options, recursive) do
    _parse(
      rest,
      [%Block.IdDef{id: defn.id, url: defn.url, title: defn.title, lnb: lnb} | result],
      options,
      recursive
    )
  end

  #######################
  # Footnote Definition #
  #######################

  # Starting from 1.5.0 Footnote Definitions are always at the end of the document (GFM) meaning that the
  # `_parse` iteration can now end and we will trigger `_parse_fn_defs`
  # this has the advantage that we can make the assumption that the top of the `result`
  # list contains a `Block.FnList` element
  defp _parse([%Line.FnDef{} | _] = input, result, options, _recursive) do
    parse_fn_defs(input, result, options)
  end

  ####################
  # IAL (attributes) #
  ####################

  defp _parse(
         [%Line.Ial{attrs: attrs, lnb: lnb, verbatim: verbatim} | rest],
         result,
         options,
         recursive
       ) do
    {options1, attributes} = parse_attrs(options, attrs, lnb)

    _parse(
      rest,
      [%Block.Ial{attrs: attributes, content: attrs, lnb: lnb, verbatim: verbatim} | result],
      options1,
      recursive
    )
  end

  ###############
  # Blank Lines #
  ###############
  # We've reached the point where empty lines are no longer significant

  defp _parse([%Line.Blank{} | rest], result, options, recursive) do
    _parse(rest, result, options, recursive)
  end

  ##############################################################
  # Anything else... we warn, then treat it as if it were text #
  ##############################################################

  defp _parse([anything = %{lnb: lnb} | rest], result, options, recursive) do
    _parse(
      [%Line.Text{content: anything.line, lnb: lnb} | rest],
      result,
      add_message(options, {:warning, anything.lnb, "Unexpected line #{anything.line}"}),
      recursive
    )
  end


  #######################################################
  # Assign attributes that follow a block to that block #
  #######################################################

  defp assign_attributes_to_blocks([], result), do: result

  defp assign_attributes_to_blocks([%Block.Ial{attrs: attrs}, block | rest], result) do
    assign_attributes_to_blocks(rest, [%{block | attrs: attrs} | result])
  end

  defp assign_attributes_to_blocks([block | rest], result) do
    assign_attributes_to_blocks(rest, [block | result])
  end

  defp _check_closing_fence(rest, lnb, delimiter, options)
  defp _check_closing_fence([], lnb, delimiter, options) do
    {[], add_message(options, {:error, lnb, "Fenced Code Block opened with #{delimiter} not closed at end of input"})}
  end
  defp _check_closing_fence([_|rest], _lnb, _delimiter, options) do
    {rest, options}
  end

  ############################################################
  # Consolidate multiline inline code blocks into an element #
  ############################################################
  @not_pending {nil, 0}
  # ([#{},...]) -> {[#{}],[#{}],{'nil' | binary(),number()}}
  # @spec consolidate_para( ts ) :: { ts, ts, {nil | String.t, number} }
  defp consolidate_para(lines), do: _consolidate_para(lines, [], @not_pending, nil)

  defp _consolidate_para([], result, pending, annotation) do
    {result, [], pending, annotation}
  end

  defp _consolidate_para([line | rest] = lines, result, pending, annotation) do
    case _inline_or_text?(line, pending) do
      %{pending: still_pending, continue: true} ->
        _consolidate_para(rest, [line | result], still_pending, annotation || line.annotation)

      _ ->
        {result, lines, @not_pending, annotation}
    end
  end

  ##################################################
  # Read in a table (consecutive TableLines with
  # the same number of columns)

  defp read_table(lines, col_count, rows)

  defp read_table(
         [%Line.TableLine{columns: cols} | rest],
         col_count,
         rows
       )
       when length(cols) == col_count do
    read_table(rest, col_count, [cols | rows])
  end

  defp read_table(rest, col_count, rows) do
    rows = Enum.reverse(rows)
    table = Block.Table.new_for_columns(col_count)

    table =
      case look_for_alignments(rows) do
        nil -> %Block.Table{table | rows: rows}
        aligns -> %Block.Table{table | alignments: aligns, header: hd(rows), rows: tl(tl(rows))}
      end

    {table, [%Line.Blank{lnb: 0} | rest]}
  end

  defp look_for_alignments([_first, second | _rest]) do
    if Enum.all?(second, fn row -> row =~ ~r{^:?-+:?$} end) do
      second
      |> Enum.map(fn row -> Regex.replace(~r/-+/, row, "-") end)
      |> Enum.map(fn row ->
        case row do
          ":-:" -> :center
          ":-" -> :left
          "-" -> :left
          "-:" -> :right
        end
      end)
    else
      nil
    end
  end

  #####################################################
  # Traverse the block list and build a list of links #
  #####################################################

  defp links_from_blocks(blocks) do
    visit(blocks, Map.new(), &link_extractor/2)
  end

  defp link_extractor(item = %Block.IdDef{id: id}, result) do
    Map.put(result, String.downcase(id), item)
  end

  defp link_extractor(_, result), do: result

  ##################################
  # Visitor pattern for each block #
  ##################################

  defp visit([], result, _func), do: result

  # Structural node BlockQuote -> descend
  defp visit([item = %Block.BlockQuote{blocks: blocks} | rest], result, func) do
    result = func.(item, result)
    result = visit(blocks, result, func)
    visit(rest, result, func)
  end

  # Structural node List -> descend
  defp visit([item = %Block.List{blocks: blocks} | rest], result, func) do
    result = func.(item, result)
    result = visit(blocks, result, func)
    visit(rest, result, func)
  end

  # Structural node ListItem -> descend
  defp visit([item = %Block.ListItem{blocks: blocks} | rest], result, func) do
    result = func.(item, result)
    result = visit(blocks, result, func)
    visit(rest, result, func)
  end

  # Leaf, leaf it alone
  defp visit([item | rest], result, func) do
    result = func.(item, result)
    visit(rest, result, func)
  end

  ###################################################################
  # Consume HTML, taking care of nesting. Assumes one tag per line. #
  ###################################################################

  defp _html_match_to_closing(opener, rest, annotation),
    do: _find_closing_tags([opener], rest, [opener.line], [], annotation)

  defp _find_closing_tags(needed, input, html_lines, text_lines, annotation)

  # No more open tags, happy case
  defp _find_closing_tags([], rest, html_lines, [], annotation),
    do: {html_lines, rest, [], annotation}

  # run out of input, unhappy case
  defp _find_closing_tags(needed, [], html_lines, text_lines, annotation),
    do: {_add_text_lines(html_lines, text_lines), [], needed, annotation}

  # still more lines, still needed closing
  defp _find_closing_tags(
         needed = [needed_hd | needed_tl],
         [rest_hd | rest_tl],
         html_lines,
         text_lines,
         annotation
       ) do
    cond do
      _closes_tag?(rest_hd, needed_hd) ->
        _find_closing_tags(
          needed_tl,
          rest_tl,
          [rest_hd.line | _add_text_lines(html_lines, text_lines)],
          [],
          _override_annotation(annotation, rest_hd)
        )

      _opens_tag?(rest_hd) ->
        _find_closing_tags(
          [rest_hd | needed],
          rest_tl,
          [rest_hd.line | _add_text_lines(html_lines, text_lines)],
          [],
          annotation
        )

      true ->
        _find_closing_tags(needed, rest_tl, html_lines, [rest_hd.line | text_lines], annotation)
    end
  end

  defp _add_text_lines(html_lines, []),
    do: html_lines

  defp _add_text_lines(html_lines, text_lines),
    do: [text_lines |> Enum.reverse() |> Enum.join("\n") | html_lines]

  ###########
  # Helpers #
  ###########

  defp _closes_tag?(%Line.HtmlCloseTag{tag: ctag}, %Line.HtmlOpenTag{tag: otag}) do
    ctag == otag
  end

  defp _closes_tag?(_, _), do: false

  defp _opens_tag?(%Line.HtmlOpenTag{}), do: true
  defp _opens_tag?(_), do: false

  defp _inline_or_text?(line, pending)

  defp _inline_or_text?(line = %Line.Text{}, @not_pending) do
    pending = opens_inline_code(line)
    %{pending: pending, continue: true}
  end

  defp _inline_or_text?(line = %Line.TableLine{}, @not_pending) do
    pending = opens_inline_code(line)
    %{pending: pending, continue: true}
  end

  defp _inline_or_text?(_line, @not_pending), do: %{pending: @not_pending, continue: false}

  defp _inline_or_text?(line, pending) do
    pending = still_inline_code(line, pending)
    %{pending: pending, continue: true}
  end

  defp _override_annotation(annotation, line), do: annotation || line.annotation

  defp remove_trailing_blank_lines(lines) do
    lines
    |> Enum.reverse()
    |> Enum.drop_while(&blank?/1)
    |> Enum.reverse()
  end

  def prepend_ial(context, maybeatts, lnb, result)
  def prepend_ial(context, nil, _lnb, result), do: {context, result}

  def prepend_ial(context, ial, lnb, result) do
    {context1, attributes} = parse_attrs(context, ial, lnb)
    {context1, [%Block.Ial{attrs: attributes, content: ial, lnb: lnb, verbatim: ial} | result]}
  end
end

# SPDX-License-Identifier: Apache-2.0