class AutoParagraph

# File lib/auto_paragraph.rb, line 7
def initialize(insert_line_breaks: true)
  @pre_tags = {}
  @insert_line_breaks = insert_line_breaks
end

# File lib/auto_paragraph.rb, line 12
def execute(input)
  return '' if input.strip.empty?

  @input = input.to_s

  setup_input_string

  add_placeholders
  add_p_tags
  remove_extraneous_p_tags
  insert_and_cleanup_br_tags

  replace_more_with_clear_both

  restore_placeholders

  @input
end

# File lib/auto_paragraph.rb, line 188
def add_closing_p_inside_div_address_form
  #Add a closing <p> inside <div>, <address>, or <form> tag if missing.
  @input.gsub!(%r{<p>([^<]+)</(div|address|form)>}, "<p>\\1</p></\\2>")
end

# File lib/auto_paragraph.rb, line 130
def add_double_break_below_block_level_closing_tags
# input = preg_replace('!(</' . $allblocks . '>)!', "$1\n\n", input);
  @input.gsub! %r{(</#{BLOCK_LEVEL_TAGS}>)}, "\\1\n\n"
end

# File lib/auto_paragraph.rb, line 61
def add_p_tags
  add_p_tags_at_doule_linebreaks
end

# File lib/auto_paragraph.rb, line 176
def add_p_tags_at_doule_linebreaks
  # Split up the contents into an array of strings, separated by double line breaks.
  @input = @input.split(/\n\s*\n/).map do |para|
      '<p>'+para.sub(/^\n+/,'').sub(/\n+$/,'')+"</p>\n"
  end.join("")
end

# File lib/auto_paragraph.rb, line 43
def add_placeholders
  pad_newline
  replace_pre_with_placeholders
end

# File lib/auto_paragraph.rb, line 126
def add_single_line_break_above_block_level_opening_tags
  @input.gsub! %r{(<#{BLOCK_LEVEL_TAGS}[^>]*>)}, "\n\\1"
end

# File lib/auto_paragraph.rb, line 145
def collapse_line_breaks_around_option_elements
  if @input.match("<option")
    @input.gsub!(/\s*<option/, '<option');
    @input.gsub!(/<\/option>\s*/, '</option>');
  end
end

# File lib/auto_paragraph.rb, line 161
def collapse_line_breaks_inside_audio_video_around_source_track
  # Collapse line breaks inside <audio> and <video> elements,
  # before and after <source> and <track> elements.
  if @input.match("<source") || @input.match("<track")
    @input.gsub!(%r{([<\[](?:audio|video)[^>\]]*[>\]])\s*}, "\\1")
    @input.gsub!(%r{\s*([<\[]/(?:audio|video)[>\]])}, "\\1")
    @input.gsub!(%r{\s*(<(?:source|track)[^>]*>)\s*}, "\\1")
  end
end

# File lib/auto_paragraph.rb, line 152
def collapse_line_breaks_inside_object_before_param_or_embed
  # Collapse line breaks inside <object> elements, before <param> and <embed> elements
  if @input.match("</object>")
    @input.gsub!(/(<object[^>]*>)\s*/, "\\1")
    @input.gsub!(/\s*<\/object>/, '</object>')
    @input.gsub!(/\s*(<\/?(?:param|embed)[^>]*>)\s*/, "\\1")
  end
end

# File lib/auto_paragraph.rb, line 313
def every_tag_only(source)
  # Returns every third element starting at 3:  ["","data","<tag>","","more data","</closetag>"] => ["<tag>","</closetag>"]
  source.drop(2).each_slice(3).map(&:first)
end

# File lib/auto_paragraph.rb, line 35
def input_hook
  @input
end

# File lib/auto_paragraph.rb, line 39
def input_hook=(input)
  @input = input
end

# File lib/auto_paragraph.rb, line 75
def insert_and_cleanup_br_tags
  insert_line_breaks
  remove_br_after_opening_closing_block_tag
  remove_br_before_some_block_tags
end

# File lib/auto_paragraph.rb, line 220
def insert_line_breaks
  # Optionally insert line breaks.
  if @insert_line_breaks
    # Replace newlines that shouldn't be touched with a placeholder.
    @input.gsub!(%r{<(script|style).*?</\1>}m) do |match|
      match.gsub("\n", "<WPPreserveNewline />")
    end

    # Normalize <br>
    @input.gsub!(Regexp.union('<br>', '<br/>'), '<br />')

    # Replace any new line characters that aren't preceded by a <br /> with a <br />.
    @input.gsub!(%r{(?<!<br />)\s*\n}, "<br />\n")

    # Replace newline placeholders with newlines.
    @input.gsub!('<WPPreserveNewline />', "\n")
  end
end

# File lib/auto_paragraph.rb, line 121
def multiple_brs_into_two_line_breaks
  @input.gsub! %r{<br\s*/?>\s*<br\s*/?>}, "\n\n"
end

# File lib/auto_paragraph.rb, line 86
def pad_newline
  @input += "\n"
end

# File lib/auto_paragraph.rb, line 239
def remove_br_after_opening_closing_block_tag
  # If a <br /> tag is after an opening or closing block tag, remove it.
  @input.gsub!(%r{(</?#{BLOCK_LEVEL_TAGS}[^>]*>)\s*<br />}, "\\1")
end

# File lib/auto_paragraph.rb, line 244
def remove_br_before_some_block_tags
  # If a <br /> tag is before a subset of opening or closing block tags, remove it.
  @input.gsub!(%r{<br />(\s*</?(?:p|li|div|dl|dd|dt|th|pre|td|ul|ol)[^>]*>)}, "\\1")
  @input.gsub!(%r{\n</p>$}, "</p>")
end

# File lib/auto_paragraph.rb, line 65
def remove_extraneous_p_tags
  remove_p_with_only_whitespace
  add_closing_p_inside_div_address_form
  unwrap_opening_closing_element_from_p
  unwrap_li_from_p
  unwrap_blockquote_from_p
  remove_preceeding_p_from_block_element_tag
  remove_following_p_from_block_element_tag
end

# File lib/auto_paragraph.rb, line 215
def remove_following_p_from_block_element_tag
  # If an opening or closing block element tag is followed by a closing <p> tag, remove it.
  @input.gsub!(%r{(</?#{BLOCK_LEVEL_TAGS}[^>]*>)\s*</p>}, "\\1")
end

# File lib/auto_paragraph.rb, line 172
def remove_more_than_two_contiguous_line_breaks
  @input.gsub!(/\n\n+/, "\n\n")
end

# File lib/auto_paragraph.rb, line 183
def remove_p_with_only_whitespace
  # Under certain strange conditions it could create a P of entirely whitespace.
  @input.gsub!(%r{<p>\s*</p>}, '')
end

# File lib/auto_paragraph.rb, line 210
def remove_preceeding_p_from_block_element_tag
  # If an opening or closing block element tag is preceded by an opening <p> tag, remove it.
  @input.gsub!(%r{<p>\s*(</?#{BLOCK_LEVEL_TAGS}[^>]*>)}, "\\1")
end

# File lib/auto_paragraph.rb, line 318
def replace_in_html_tags(haystack, replace_pairs)
  # find all elements
  tags_split = split_html_elements(haystack)
  changed = false

  # Loop through every third element (html tags only)
  keys = Regexp.new(replace_pairs.keys.join("|"))
  every_tag_only(tags_split).each do |tag|
    # Changes existing string, so replaces inside tags_split array
    changed = true if tag.gsub!(keys, replace_pairs)
  end

  haystack = tags_split.join("") if changed

  haystack
end

# File lib/auto_paragraph.rb, line 250
def replace_more_with_clear_both
  @input.gsub! %r{<!--more(.*?)?-->}, '<div class="clear-both"></div>'
end

# File lib/auto_paragraph.rb, line 141
def replace_newlines_in_elements_with_placeholders
  @input = replace_in_html_tags(@input, { "\n" => " <!-- wpnl --> " })
end

# File lib/auto_paragraph.rb, line 90
def replace_pre_with_placeholders
  # Pre tags shouldn't be touched by autop.
  # Replace pre tags with placeholders and bring them back after autop.
  if @input.match("<pre")
    @pre_tags = {}

    input_parts = @input.split '</pre>'
    last_input_part = input_parts.pop

    input = ''
    input_parts.each_with_index do |input_part,i|

      start_position = input_part.index('<pre')

      # Malformed html?
      if !start_position
        input += input_part
        next
      end

      placeholder_name = "<pre wp-pre-tag-#{i}></pre>";
      @pre_tags[placeholder_name] = input_part[start_position..-1]+'</pre>'

      input += input_part[0..start_position-1] + placeholder_name
    end
    @input = input + last_input_part
  end
  @input
end

# File lib/auto_paragraph.rb, line 261
def restore_newlines_in_elements_with_placeholders
  # Restore newlines in all elements.
  @input.gsub!(Regexp.union(' <!-- wpnl --> ', '<!-- wpnl -->'), "\n")
end

# File lib/auto_paragraph.rb, line 81
def restore_placeholders
  restore_pre_with_placeholders
  restore_newlines_in_elements_with_placeholders
end

# File lib/auto_paragraph.rb, line 254
def restore_pre_with_placeholders
  # Replace placeholder <pre> tags with their original content.
  @pre_tags.each do |key, val|
    @input.gsub!(key, val)
  end
end

# File lib/auto_paragraph.rb, line 49
def setup_input_string
  multiple_brs_into_two_line_breaks
  add_single_line_break_above_block_level_opening_tags
  add_double_break_below_block_level_closing_tags
  standardize_newline_to_backslash_n
  replace_newlines_in_elements_with_placeholders
  collapse_line_breaks_around_option_elements
  collapse_line_breaks_inside_object_before_param_or_embed
  collapse_line_breaks_inside_audio_video_around_source_track
  remove_more_than_two_contiguous_line_breaks
end

# File lib/auto_paragraph.rb, line 309
def split_html_elements(text)
  text.split(split_html_elements_regex)
end

# File lib/auto_paragraph.rb, line 267
def split_html_elements_regex

  comments =
        '!'          + # Start of comment, after the <.
       '(?:'         + # Unroll the loop: Consume everything until --> is found.
           '-(?!->)' + # Dash not followed by end of comment.
           '[^\-]*+' + # Consume non-dashes.
       ')*+'         + # Loop possessively.
       '(?:-->)?'      # End of comment. If not found, match all input.

  cdata =
        '!\[CDATA\['  + # Start of comment, after the <.
       '[^\]]*+'      + # Consume non-].
       '(?:'          + # Unroll the loop: Consume everything until ]]> is found.
           '\](?!\]>)'  + # One ] not followed by end of comment.
           '[^\]]*+'  + # Consume non-].
       ')*+'          + # Loop possessively.
       '(?:\]\]>)?'       # End of comment. If not found, match all input.

  regex =
        '([^<]*)'                  + # Find from the start of the string
        '('                        + # Capture the tag
           '<'                     + # Find start of element.
           '(?:'                   + # (non-matching group)
              '(?=!--)'            + # Is this a comment?
              comments             + # Find end of comment
           ')'                     +
           '|'                     + # OR
           '(?:'                   + # (non-matching group)
             '(?=!\[CDATA\[)'      + # Is this a comment?
             cdata                 + # Find end of comment
           ')'                     +
           '|'                     + # OR
           '(?:'                   + # (non-matching group)
             '[^>]*'               + # Find end of element.
           ')'                     + #
           '>?'                    + # If not found, match all input.
       ')'

  Regexp.new(regex, Regexp::MULTILINE)
end

# File lib/auto_paragraph.rb, line 135
def standardize_newline_to_backslash_n
  ["\r\n","\r"].each do |from|
    @input.gsub! from, "\n"
  end
end

# File lib/auto_paragraph.rb, line 204
def unwrap_blockquote_from_p
  # If a <blockquote> is wrapped with a <p>, move it inside the <blockquote>.
  @input.gsub!(%r{<p><blockquote([^>]*)>}i, "<blockquote\\1><p>")
  @input.gsub!("</blockquote></p>", "</p></blockquote>")
end

# File lib/auto_paragraph.rb, line 198
def unwrap_li_from_p
  # In some cases <li> may get wrapped in <p>, fix them.
  @input.gsub!(%r{<p>(<li.+?)</p>}, "\\1")
end

# File lib/auto_paragraph.rb, line 193
def unwrap_opening_closing_element_from_p
  #  If an opening or closing block element tag is wrapped in a <p>, unwrap it.
  @input.gsub!(%r{<p>\s*(</?#{BLOCK_LEVEL_TAGS}[^>]*>)\s*</p>}, "\\1")
end