# frozen_string_literal: true class DiscourseDiff MAX_DIFFERENCE = 200 def initialize(before, after) @before = before @after = after before_html = tokenize_html_blocks(@before) after_html = tokenize_html_blocks(@after) before_markdown = tokenize_line(CGI::escapeHTML(@before)) after_markdown = tokenize_line(CGI::escapeHTML(@after)) @block_by_block_diff = ONPDiff.new(before_html, after_html).paragraph_diff @line_by_line_diff = ONPDiff.new(before_markdown, after_markdown).short_diff end def inline_html i = 0 inline = [] while i < @block_by_block_diff.size op_code = @block_by_block_diff[i][1] if op_code == :common then inline << @block_by_block_diff[i][0] else if op_code == :delete opposite_op_code = :add klass = "del" first = i second = i + 1 else opposite_op_code = :delete klass = "ins" first = i + 1 second = i end if i + 1 < @block_by_block_diff.size && @block_by_block_diff[i + 1][1] == opposite_op_code diff = ONPDiff.new(tokenize_html(@block_by_block_diff[first][0]), tokenize_html(@block_by_block_diff[second][0])).diff inline << generate_inline_html(diff) i += 1 else inline << add_class_or_wrap_in_tags(@block_by_block_diff[i][0], klass) end end i += 1 end "
#{inline.join}
" end def side_by_side_html i = 0 left, right = [], [] while i < @block_by_block_diff.size op_code = @block_by_block_diff[i][1] if op_code == :common left << @block_by_block_diff[i][0] right << @block_by_block_diff[i][0] else if op_code == :delete opposite_op_code = :add side = left klass = "del" first = i second = i + 1 else opposite_op_code = :delete side = right klass = "ins" first = i + 1 second = i end if i + 1 < @block_by_block_diff.size && @block_by_block_diff[i + 1][1] == opposite_op_code diff = ONPDiff.new(tokenize_html(@block_by_block_diff[first][0]), tokenize_html(@block_by_block_diff[second][0])).diff deleted, inserted = generate_side_by_side_html(diff) left << deleted right << inserted i += 1 else side << add_class_or_wrap_in_tags(@block_by_block_diff[i][0], klass) end end i += 1 end "
#{left.join}
#{right.join}
" end def side_by_side_markdown i = 0 table = [""] while i < @line_by_line_diff.size table << "" op_code = @line_by_line_diff[i][1] if op_code == :common table << "" table << "" else if op_code == :delete opposite_op_code = :add first = i second = i + 1 else opposite_op_code = :delete first = i + 1 second = i end if i + 1 < @line_by_line_diff.size && @line_by_line_diff[i + 1][1] == opposite_op_code before_tokens, after_tokens = tokenize_markdown(@line_by_line_diff[first][0]), tokenize_markdown(@line_by_line_diff[second][0]) if (before_tokens.size - after_tokens.size).abs > MAX_DIFFERENCE before_tokens, after_tokens = tokenize_line(@line_by_line_diff[first][0]), tokenize_line(@line_by_line_diff[second][0]) end diff = ONPDiff.new(before_tokens, after_tokens).short_diff deleted, inserted = generate_side_by_side_markdown(diff) table << "" table << "" i += 1 else if op_code == :delete table << "" table << "" else table << "" table << "" end end end table << "" i += 1 end table << "
#{@line_by_line_diff[i][0]}#{@line_by_line_diff[i][0]}#{deleted.join}#{inserted.join}#{@line_by_line_diff[i][0]}#{@line_by_line_diff[i][0]}
" table.join end private def tokenize_line(text) text.scan(/[^\r\n]+[\r\n]*/) end def tokenize_markdown(text) t, tokens = [], [] i = 0 while i < text.size if text[i] =~ /\w/ t << text[i] elsif text[i] =~ /[ \t]/ && t.join =~ /^\w+$/ begin t << text[i] i += 1 end while i < text.size && text[i] =~ /[ \t]/ i -= 1 tokens << t.join t = [] else tokens << t.join if t.size > 0 tokens << text[i] t = [] end i += 1 end tokens << t.join if t.size > 0 tokens end def tokenize_html_blocks(html) Nokogiri::HTML.fragment(html).search("./*").map(&:to_html) end def tokenize_html(html) HtmlTokenizer.tokenize(html) end def add_class_or_wrap_in_tags(html_or_text, klass) result = html_or_text.dup index_of_next_chevron = result.index(">") if result.size > 0 && result[0] == '<' && index_of_next_chevron index_of_class = result.index("class=") if index_of_class.nil? || index_of_class > index_of_next_chevron # we do not have a class for the current tag # add it right before the ">" result.insert(index_of_next_chevron, " class=\"diff-#{klass}\"") else # we have a class, insert it at the beginning if not already present classes = result[/class=(["'])([^\1]*)\1/, 2] if classes.include?("diff-#{klass}") result else result.insert(index_of_class + "class=".size + 1, "diff-#{klass} ") end end else "<#{klass}>#{result}" end end def generate_inline_html(diff) inline = [] diff.each do |d| case d[1] when :common then inline << d[0] when :delete then inline << add_class_or_wrap_in_tags(d[0], "del") when :add then inline << add_class_or_wrap_in_tags(d[0], "ins") end end inline end def generate_side_by_side_html(diff) deleted, inserted = [], [] diff.each do |d| case d[1] when :common deleted << d[0] inserted << d[0] when :delete then deleted << add_class_or_wrap_in_tags(d[0], "del") when :add then inserted << add_class_or_wrap_in_tags(d[0], "ins") end end [deleted, inserted] end def generate_side_by_side_markdown(diff) deleted, inserted = [], [] diff.each do |d| case d[1] when :common deleted << d[0] inserted << d[0] when :delete then deleted << "#{d[0]}" when :add then inserted << "#{d[0]}" end end [deleted, inserted] end class HtmlTokenizer < Nokogiri::XML::SAX::Document attr_accessor :tokens def initialize @tokens = [] end def self.tokenize(html) me = new parser = Nokogiri::HTML::SAX::Parser.new(me) parser.parse("#{html}") me.tokens end USELESS_TAGS = %w{html body} def start_element(name, attributes = []) return if USELESS_TAGS.include?(name) attrs = attributes.map { |a| " #{a[0]}=\"#{a[1]}\"" }.join @tokens << "<#{name}#{attrs}>" end AUTOCLOSING_TAGS = %w{area base br col embed hr img input meta} def end_element(name) return if USELESS_TAGS.include?(name) || AUTOCLOSING_TAGS.include?(name) @tokens << "" end def characters(string) @tokens.concat string.scan(/\W|\w+[ \t]*/).map { |x| CGI::escapeHTML(x) } end end end