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