# frozen_string_literal: true class PlainTextToMarkdown SIGNATURE_SEPARATOR = "-- " def initialize(plaintext, opts = {}) @plaintext = plaintext @lines = [] @format_flowed = opts[:format_flowed] || false @delete_flowed_space = opts[:delete_flowed_space] || false end def to_markdown prepare_lines classify_lines markdown = +"" last_quote_level = 0 last_line_blank = false @lines.each do |line| current_line_blank = line.text.blank? unless last_line_blank && current_line_blank if line.quote_level > 0 quote_identifiers = ">" * line.quote_level unless line.quote_level >= last_quote_level || current_line_blank markdown << quote_identifiers << "\n" end markdown << quote_identifiers markdown << " " unless current_line_blank else markdown << "\n" unless last_quote_level == 0 || current_line_blank end markdown << convert_text(line) markdown << "\n" end last_line_blank = current_line_blank last_quote_level = line.quote_level end markdown.rstrip! markdown end private class CodeBlock < Struct.new(:start_line, :end_line) def initialize(start_line, end_line = nil) super end def valid? start_line.present? && end_line.present? end end class Line < Struct.new(:text, :quote_level, :code_block) def initialize(text, quote_level = 0, code_block = nil) super end def valid_code_block? code_block&.valid? end end def prepare_lines previous_line = nil @plaintext.each_line do |text| text.chomp! line = Line.new(text) remove_quote_level_indicators!(line) if @format_flowed line = merge_lines(line, previous_line) @lines << line unless line == previous_line else @lines << line end previous_line = line end end def classify_lines previous_line = nil @lines.each do |line| classify_line_as_code!(line, previous_line) previous_line = line end end # @param line [Line] def remove_quote_level_indicators!(line) match_data = line.text.match(/\A(?<indicators>>+)\s?(?<text>.*)/) if match_data line.text = match_data[:text] line.quote_level = match_data[:indicators].length end end # @param line [Line] # @param previous_line [Line] # @return [Line] def merge_lines(line, previous_line) return line if previous_line.nil? || line.text.blank? return line if line.text == SIGNATURE_SEPARATOR || previous_line.text == SIGNATURE_SEPARATOR unless line.quote_level == previous_line.quote_level && previous_line.text.end_with?(" ") return line end previous_line.text = previous_line.text[0...-1] if @delete_flowed_space previous_line.text += line.text previous_line end # @param line [Line] # @param previous_line [Line] def classify_line_as_code!(line, previous_line) line.code_block = previous_line.code_block unless previous_line.nil? || previous_line.valid_code_block? return unless line.text =~ /\A\s{0,3}```/ if line.code_block.present? line.code_block.end_line = line else line.code_block = CodeBlock.new(line) end end # @param line [Line] # @return [string] def convert_text(line) text = line.text if line.valid_code_block? code_block = line.code_block return code_block.start_line == line || code_block.end_line == line ? text.lstrip : text end converted_text = replace_duplicate_links(text) converted_text = escape_special_characters(converted_text) converted_text = indent_with_non_breaking_spaces(converted_text) converted_text end URL_REGEX = URI.regexp(%w[http https ftp mailto]) BEFORE = Regexp.escape(%Q|([<«"“'‘|) AFTER = Regexp.escape(%Q|)]>»"”'’|) def replace_duplicate_links(text) urls = Set.new text.scan(URL_REGEX) { urls << $& } urls.each do |url| escaped = Regexp.escape(url) text.gsub!( Regexp.new(%Q|#{escaped}\s*[#{BEFORE}]?#{escaped}[#{AFTER}]?|, Regexp::IGNORECASE), url, ) end text end def indent_with_non_breaking_spaces(text) text.sub(/\A\s+/) do |s| # replace tabs with 2 spaces s.gsub!("\t", " ") # replace indentation with non-breaking spaces s.length > 1 ? " " * s.length : s end end def escape_special_characters(text) urls = Set.new text.scan(URL_REGEX) { urls << $& } hoisted = urls.map { |url| [SecureRandom.hex, url] }.to_h hoisted.each { |h, url| text.gsub!(url, h) } text.gsub!(/[\\`*_{}\[\]()#+\-.!~]/) { |c| "\\#{c}" } text = CGI.escapeHTML(text) hoisted.each { |h, url| text.gsub!(h, url) } text end end