Class: RandomWords::HTML2Markdown

Inherits:
Object
  • Object
show all
Defined in:
lib/random-words/html2markdown.rb

Overview

Convert HTML to Markdown

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(str, baseurl = nil, meta = {}) ⇒ HTML2Markdown

Initialize the HTML2Markdown converter

Parameters:

  • str (String) —

    The HTML string to convert

  • baseurl (String) (defaults to: nil) —

    The base URL for resolving relative links



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# File 'lib/random-words/html2markdown.rb', line 15

def initialize(str, baseurl = nil, meta = {})
  @links = []
  @footnotes = []
  @baseuri = (baseurl ? URI.parse(baseurl) : nil)
  @section_level = 0
  input = str.is_a?(String) ? str : str.output
  @encoding = input.encoding
  @markdown = output_for(Nokogiri::HTML(input, baseurl).root).gsub(/\n\n\n+/, "\n\n\n").strip
  @title = meta[:title] if meta[:title]
  @date = meta[:date] if meta[:date]
  @style = meta[:style] if meta[:style]
  @meta_type = meta[:type] if meta[:type]
end

Instance Attribute Details

#markdown ⇒ Object (readonly)

Returns the value of attribute markdown.



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# File 'lib/random-words/html2markdown.rb', line 10

def markdown
  @markdown
end

Instance Method Details

#add_footnote(counter, link) ⇒ Object

Add a footnote to the list of links

Parameters:

  • counter (String) —

    The footnote counter

  • link (Hash) —

    The link to add



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# File 'lib/random-words/html2markdown.rb', line 87

def add_footnote(counter, link)
  @footnotes << { counter: counter, title: link[:title] }
  @footnotes.length
end

#add_link(link) ⇒ Object

Add a link to the list of links

Parameters:

  • link (Hash) —

    The link to add



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# File 'lib/random-words/html2markdown.rb', line 94

def add_link(link)
  if @baseuri
    begin
      link[:href] = URI.parse(link[:href])
    rescue Exception
      link[:href] = URI.parse('')
    end
    link[:href].scheme = @baseuri.scheme unless link[:href].scheme
    unless link[:href].opaque
      link[:href].host = @baseuri.host unless link[:href].host
      link[:href].path = @baseuri.path.to_s + '/' + link[:href].path.to_s if link[:href].path.to_s[0] != '/'
    end
    link[:href] = link[:href].to_s
  end
  @links.each_with_index do |l, i|
    return i + 1 if l[:href] == link[:href]
  end
  @links << link
  @links.length
end

#output_for(node) ⇒ String

Convert a node to Markdown

Parameters:

  • node (Nokogiri::XML::Node) —

    The node to convert

Returns:

  • (String) —

    The converted Markdown string



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# File 'lib/random-words/html2markdown.rb', line 137

def output_for(node)
  case node.name
  when 'title'
    @title = node.content
    ''
  when 'head'
    output_for_children(node)
    ''
  when 'style', 'script'
    ''
  when 'br'
    "  \n"
  when 'p', 'div'
    "\n\n#{output_for_children(node)}\n\n"
  when 'section', 'article'
    @section_level += 1
    o = "\n\n----\n\n#{output_for_children(node)}\n\n"
    @section_level -= 1
    o
  when /h(\d+)/
    "\n\n" + (('#' * (::Regexp.last_match(1).to_i + @section_level)) + ' ' + output_for_children(node)) + "\n\n"
  when /mark/
    "==#{output_for_children(node)}=="
  when 'blockquote'
    @section_level += 1
    o = "\n\n> #{output_for_children(node).lstrip.gsub("\n", "\n> ")}\n\n".gsub(/> \n(> \n)+/, "> \n").sub(/> \n$/,
                                                                                                           "\n")
    @section_level -= 1
    o
  when 'cite'
    "*#{output_for_children(node)}*"
  when 'ul'
    "\n\n" + node.children.map { |el|
      next if el.name == 'text'

      "* #{output_for_children(el).gsub(/^(\t)|(    )/, "\t\t").gsub(/^>/, "\t>")}\n"
    }.join + "\n\n"
  when 'ol'
    i = 0
    "\n\n" + node.children.map { |el|
      next if el.name == 'text'

      i += 1
      "#{i}. #{output_for_children(el).gsub(/^(\t)|(    )/, "\t\t").gsub(/^>/, "\t>")}\n"
    }.join + "\n\n"
  when 'code'
    if @in_pre
      @in_pre = false
      node.text.strip
    else
      "`#{output_for_children(node).tr("\n", ' ')}`"
    end
  when 'pre'
    @in_pre = true
    lang = node['lang'] || node['language']
    lang = '' if lang.nil? || lang.empty?
    "\n\n```#{lang}\n" + output_for_children(node).lstrip + "\n```\n\n"
  when 'hr'
    "\n\n* * * *\n\n"
  when 'a', 'link'
    link = { href: node['href'], title: node['title'] }
    if link[:href] =~ /^#fn:(\d+)/
      counter = Regexp.last_match[1]
      add_footnote(counter, link)
      "[^fn#{counter}]"
    else
      "[#{output_for_children(node).tr("\n", ' ')}][#{add_link(link)}]"
    end
  when 'img'
    link = { href: node['src'], title: node['title'] }
    "![#{node['alt']}][#{add_link(link)}]"
  when 'video', 'audio', 'embed'
    link = { href: node['src'], title: node['title'] }
    "[#{output_for_children(node).tr("\n", ' ')}][#{add_link(link)}]"
  when 'object'
    link = { href: node['data'], title: node['title'] }
    "[#{output_for_children(node).tr("\n", ' ')}][#{add_link(link)}]"
  when 'i', 'em', 'u'
    "_#{output_for_children(node)}_"
  when 'b', 'strong'
    "**#{output_for_children(node)}**"
  when 'dl'
    "\n\n" + node.children.map do |el|
      case el.name
      when 'dt'
        "#{output_for_children(el)}\n"
      when 'dd'
        ": #{output_for_children(el)}\n\n"
      end
    end.join + "\n\n"
  # Tables are not part of Markdown, so we output WikiCreole
  when 'table'
    @table_header = true
    node.children.select do |c|
      %w[tr tbody thead].include?(c.name)
    end.map do |c|
      output_for(c)
    end.join
  when 'tr'
    header = "\n"
    if @table_header
      @table_header = false
      cells = node.children.count do |c|
        %w[th td].include?(c.name)
      end
      header = "\n|#{Array.new(cells) { '-------' }.join('|')}|\n"
    end
    node.children.select do |c|
      %w[th td].include?(c.name)
    end.map do |c|
      output_for(c)
    end.join.gsub('||', '|') + header
  when 'th', 'td'
    "| #{output_for_children(node)} |"
  when 'text'
    # Sometimes Nokogiri lies. Force the encoding back to what we know it is
    if /\S/.match?((c = node.content.force_encoding(@encoding)))
      c.gsub!(/\n\n+/, '<$PreserveDouble$>')
      c.gsub!(/\s+/, ' ')
      c.gsub('<$PreserveDouble$>', "\n\n")
    else
      c
    end
  else
    output_for_children(node)
  end
end

#output_for_children(node) ⇒ Object

Recursively convert child nodes

Parameters:

  • node (Nokogiri::XML::Node) —

    The parent node



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# File 'lib/random-words/html2markdown.rb', line 78

def output_for_children(node)
  node.children.map do |el|
    output_for(el)
  end.join
end

#to_s ⇒ String

Convert the HTML to Markdown

Examples:

converter = HTML2Markdown.new('<p>Hello world</p>')
puts converter.to_s

Returns:

  • (String) —

    The converted Markdown string



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# File 'lib/random-words/html2markdown.rb', line 34

def to_s
  meta = ''

  if @meta_type
    meta = "      title: \#{@title}\n      date: \#{@date}\n      css: \#{@style}\n    EOMETA\n    case @meta_type\n    when :multimarkdown\n      meta = <<~EOMMD\n        \#{meta.strip}\n\n      EOMMD\n    when :yaml\n      meta = <<~EOYAML\n        ---\n        \#{meta.strip}\n        ---\n      EOYAML\n    end\n  end\n  i = 0\n  @markdown = TableCleanup.new(@markdown).clean\n  out = \"\#{meta}\#{@markdown}\"\n\n  if @links.any?\n    out += \"\\n\\n\" + @links.map do |link|\n      i += 1\n      \"[\#{i}]: \#{link[:href]}\" + (link[:title] ? %( \"\#{link[:title]}\") : '')\n    end.join(\"\\n\")\n  end\n\n  if @footnotes.any?\n    out += \"\\n\\n\" + @footnotes.map { |link|\n      \"[^fn\#{link[:counter]}]: \#{link[:title]}\"\n    }.join(\"\\n\\n\")\n  end\n  out\nend\n"

#wrap(str) ⇒ String

Wrap a string to 74 characters

Parameters:

  • str (String) —

    The string to wrap

Returns:

  • (String) —

    The wrapped string



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# File 'lib/random-words/html2markdown.rb', line 118

def wrap(str)
  return str if str.include?("\n")

  out = []
  line = []
  str.split(/[ \t]+/).each do |word|
    line << word
    if line.join(' ').length >= 74
      out << line.join(' ')
      line = []
    end
  end
  out << (line.join(' ') + (/[ \t\n]/.match?(str[-1..-1]) ? str[-1..-1] : ''))
  out.join("\n")
end