require "nokogiri" class HtmlToMarkdown class Block < Struct.new(:name, :head, :body, :opened, :markdown) def initialize(name, head="", body="", opened=false, markdown=""); super; end end def initialize(html, opts={}) @opts = opts || {} @doc = fix_span_elements(Nokogiri::HTML(html)) remove_whitespaces! end # If a `
` is within a `` that's invalid, so let's hoist the `
` up def fix_span_elements(node) if node.name == 'span' && node.at('div') node.swap(node.children) end node.children.each {|c| fix_span_elements(c)} node end def remove_whitespaces! @doc.traverse do |node| if node.is_a? Nokogiri::XML::Text node.content = node.content.gsub(/\A[[:space:]]+/, "") if node.previous_element&.description&.block? node.content = node.content.gsub(/\A[[:space:]]+/, "") if node.previous_element.nil? && node.parent.description&.block? node.content = node.content.gsub(/[[:space:]]+\z/, "") if node.next_element&.description&.block? node.content = node.content.gsub(/[[:space:]]+\z/, "") if node.next_element.nil? && node.parent.description&.block? node.remove if node.content.empty? end end end def to_markdown @stack = [Block.new("root")] @markdown = "" traverse(@doc) @markdown << format_block @markdown.gsub(/\n{3,}/, "\n\n").strip end def traverse(node) node.children.each { |n| visit(n) } end def visit(node) return if node["style"] && node["style"][/display\s*:\s*none/] if node.description&.block? && node.parent&.description&.block? && @stack[-1].markdown.size > 0 block = @stack[-1].dup @markdown << format_block block.markdown = "" block.opened = true @stack << block end visitor = "visit_#{node.name}" respond_to?(visitor) ? send(visitor, node) : traverse(node) end BLACKLISTED ||= %w{button datalist fieldset form input label legend meter optgroup option output progress select textarea style script} BLACKLISTED.each do |tag| class_eval <<-RUBY def visit_#{tag}(node) "" end RUBY end def visit_pre(node) code = node.children.find { |c| c.name == "code" } code_class = code ? code["class"] : "" lang = code_class ? code_class[/lang-(\w+)/, 1] : "" @stack << Block.new("pre") @markdown << "```#{lang}\n" traverse(node) @markdown << format_block @markdown << "```\n" end def visit_blockquote(node) @stack << Block.new("blockquote", "> ", "> ") traverse(node) @markdown << format_block end BLOCK_WITH_NEWLINE ||= %w{div p} BLOCK_WITH_NEWLINE.each do |tag| class_eval <<-RUBY def visit_#{tag}(node) @stack << Block.new("#{tag}") traverse(node) @markdown << format_block @markdown << "\n" end RUBY end BLOCK_LIST ||= %w{menu ol ul} BLOCK_LIST.each do |tag| class_eval <<-RUBY def visit_#{tag}(node) @stack << Block.new("#{tag}") traverse(node) @markdown << format_block end RUBY end def visit_li(node) parent = @stack.reverse.find { |n| n.name[/ul|ol|menu/] } prefix = parent&.name == "ol" ? "1. " : "- " @stack << Block.new("li", prefix, " ") traverse(node) @markdown << format_block end (1..6).each do |n| class_eval <<-RUBY def visit_h#{n}(node) @stack << Block.new("h#{n}", "#" * #{n} + " ") traverse(node) @markdown << format_block end RUBY end WHITELISTED ||= %w{del ins kbd s small strike sub sup} WHITELISTED.each do |tag| class_eval <<-RUBY def visit_#{tag}(node) @stack[-1].markdown << "<#{tag}>" traverse(node) @stack[-1].markdown << "" end RUBY end def visit_abbr(node) @stack[-1].markdown << (node["title"].present? ? %Q[] : "") traverse(node) @stack[-1].markdown << "" end def visit_img(node) if is_valid_src?(node["src"]) && is_visible_img?(node) if @opts[:keep_img_tags] @stack[-1].markdown << node.to_html else title = node["alt"].presence || node["title"].presence @stack[-1].markdown << "![#{title}](#{node["src"]})" end end end def visit_a(node) if is_valid_href?(node["href"]) @stack[-1].markdown << "[" traverse(node) @stack[-1].markdown << "](#{node["href"]})" else traverse(node) end end def visit_tt(node) @stack[-1].markdown << "`" traverse(node) @stack[-1].markdown << "`" end def visit_code(node) @stack.reverse.find { |n| n.name["pre"] } ? traverse(node) : visit_tt(node) end def visit_br(node) @stack[-1].markdown << "\n" end def visit_hr(node) @stack[-1].markdown << "\n\n---\n\n" end def visit_strong(node) delimiter = node.text["*"] ? "__" : "**" @stack[-1].markdown << delimiter traverse(node) @stack[-1].markdown << delimiter end alias :visit_b :visit_strong def visit_em(node) delimiter = node.text["*"] ? "_" : "*" @stack[-1].markdown << delimiter traverse(node) @stack[-1].markdown << delimiter end alias :visit_i :visit_em def visit_text(node) @stack[-1].markdown << node.text.gsub(/\s{2,}/, " ") end def format_block lines = @stack[-1].markdown.each_line.map do |line| prefix = @stack.map { |b| b.opened ? b.body : b.head }.join @stack.each { |b| b.opened = true } prefix + line.rstrip end @stack.pop (lines + [""]).join("\n") end def is_valid_href?(href) href.present? && (href.start_with?("http") || href.start_with?("www.")) end def is_valid_src?(src) return false if src.blank? return true if @opts[:keep_cid_imgs] && src.start_with?("cid:") src.start_with?("http") || src.start_with?("www.") end def is_visible_img?(img) return false if img["width"].present? && img["width"].to_i == 0 return false if img["height"].present? && img["height"].to_i == 0 return false if img["style"].present? && img["style"][/(width|height)\s*:\s*0/] true end end