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191 lines
4.8 KiB
Ruby
191 lines
4.8 KiB
Ruby
class PlainTextToMarkdown
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SIGNATURE_SEPARATOR ||= "-- ".freeze
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URL_REGEX ||= /((?:https?:(?:\/{1,3}|[a-z0-9%])|www\d{0,3}[.])(?:[^\s()<>]+|\([^\s()<>]+\))+(?:\([^\s()<>]+\)|[^`!()\[\]{};:'".,<>?«»“”‘’\s]))/i
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def initialize(plaintext, opts = {})
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@plaintext = plaintext
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@lines = []
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@format_flowed = opts[:format_flowed] || false
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@delete_flowed_space = opts[:delete_flowed_space] || false
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end
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def to_markdown
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prepare_lines
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classify_lines
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markdown = ""
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last_quote_level = 0
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last_line_blank = false
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@lines.each do |line|
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current_line_blank = line.text.blank?
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unless last_line_blank && current_line_blank
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if line.quote_level > 0
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quote_identifiers = ">" * line.quote_level
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markdown << quote_identifiers << "\n" unless line.quote_level >= last_quote_level || current_line_blank
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markdown << quote_identifiers
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markdown << " " unless current_line_blank
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else
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markdown << "\n" unless last_quote_level == 0 || current_line_blank
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end
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markdown << convert_text(line)
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markdown << "\n"
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end
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last_line_blank = current_line_blank
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last_quote_level = line.quote_level
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end
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markdown.rstrip!
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markdown
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end
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private
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class CodeBlock < Struct.new(:start_line, :end_line)
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def initialize(start_line, end_line = nil)
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super
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end
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def valid?
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start_line.present? && end_line.present?
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end
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end
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class Line < Struct.new(:text, :quote_level, :code_block)
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def initialize(text, quote_level = 0, code_block = nil)
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super
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end
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def valid_code_block?
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code_block&.valid?
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end
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end
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def prepare_lines
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previous_line = nil
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@plaintext.each_line do |text|
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text.chomp!
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line = Line.new(text)
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remove_quote_level_indicators!(line)
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if @format_flowed
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line = merge_lines(line, previous_line)
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@lines << line unless line == previous_line
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else
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@lines << line
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end
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previous_line = line
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end
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end
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def classify_lines
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previous_line = nil
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@lines.each do |line|
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classify_line_as_code!(line, previous_line)
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previous_line = line
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end
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end
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# @param line [Line]
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def remove_quote_level_indicators!(line)
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match_data = line.text.match(/^(?<indicators>>+)\s?(?<text>.*)/)
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if match_data
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line.text = match_data[:text]
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line.quote_level = match_data[:indicators].length
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end
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end
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# @param line [Line]
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# @param previous_line [Line]
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# @return [Line]
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def merge_lines(line, previous_line)
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return line if previous_line.nil? || line.text.blank?
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return line if line.text == SIGNATURE_SEPARATOR || previous_line.text == SIGNATURE_SEPARATOR
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return line unless line.quote_level == previous_line.quote_level && previous_line.text.end_with?(" ")
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previous_line.text = previous_line.text[0...-1] if @delete_flowed_space
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previous_line.text += line.text
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previous_line
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end
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# @param line [Line]
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# @param previous_line [Line]
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def classify_line_as_code!(line, previous_line)
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line.code_block = previous_line.code_block unless previous_line.nil? || previous_line.valid_code_block?
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return unless line.text =~ /^\s{0,3}```/
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if line.code_block.present?
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line.code_block.end_line = line
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else
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line.code_block = CodeBlock.new(line)
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end
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end
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# @param line [Line]
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# @return [string]
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def convert_text(line)
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text = line.text
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if line.valid_code_block?
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code_block = line.code_block
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return code_block.start_line == line || code_block.end_line == line ? text.lstrip : text
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end
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converted_text = replace_duplicate_links(text)
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converted_text = escape_special_characters(converted_text)
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converted_text = indent_with_non_breaking_spaces(converted_text)
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converted_text
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end
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def replace_duplicate_links(text)
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text.to_enum(:scan, URL_REGEX)
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.map { $& }
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.group_by { |url| url }
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.keep_if { |_, urls | urls.length > 1 }
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.keys.each do |url|
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text.gsub!(Regexp.new(%Q|#{url}(\s*[()\\[\\]<>«»'"“”‘’]?#{url}[()\\[\\]<>«»'"“”‘’]?)|, Regexp::IGNORECASE), url)
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end
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text
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end
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def indent_with_non_breaking_spaces(text)
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text.sub(/^\s+/) do |s|
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# replace tabs with 2 spaces
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s.gsub!("\t", " ")
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# replace indentation with non-breaking spaces
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s.length > 1 ? " " * s.length : s
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end
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end
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def escape_special_characters(text)
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escaped_text = ""
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text.split(URL_REGEX).each do |text_part|
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if text_part =~ URL_REGEX
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# no escaping withing URLs
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escaped_text << text_part
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else
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# escape Markdown and HTML
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text_part.gsub!(/[\\`*_{}\[\]()#+\-.!~]/) { |c| "\\#{c}" }
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escaped_text << CGI.escapeHTML(text_part)
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end
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end
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escaped_text
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end
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end
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