Mato

Mato, standing for Markdown Tooolkit, is an extensible, pipeline-based markdown processing toolkit, inspired by HTML::Pipeline.

This gem is built on commonmarker, a CommonMark implementation, which can parse markdown documents.

Usage

require 'mato'

# define a markdown-to-html processor:
mato = Mato.define do |config|
  # append pre-defined HTML filters:
  config.append_html_filter(Mato::HtmlFilters::SyntaxHighlight.new)
  config.append_html_filter(Mato::HtmlFilters::TaskList.new)
  config.append_html_filter(Mato::HtmlFilters::SectionAnchor.new)

  # append MentionLink, a customizable HTML filter:
  config.append_html_filter(Mato::HtmlFilters::MentionLink.new do |mention_candidate_map|
    candidate_accounts = mention_candidate_map.keys.map { |name| name.gsub(/^\@/, '') }
    User.where(account: candidate_accounts).each do |user|
      mention = "@#{user.account}"
      mention_candidate_map[mention].each do |node|
        node.replace("<a href='https://twitter.com/#{mention}' class='mention'>#{mention}</a>")
      end
    end
  end)
end

# Prosesses markdown into Mato::Document:
doc = mato.process(markdown_content)

# Renders doc as HTML:
html = doc.render_html

# Renders doc as HTML Table of Contents:
html_toc = doc.render_html_toc

# Extracts elements (e.g. mentions) with CSS selector:
doc.css('a').each do |element|
  # do something with element: Nokogiri::XML::Element
end

# Extracts nodes (e.g. mentions) with XPath selector:
doc.xpath('./text()').each do |node|
  # do something with node: Nokogiri::XML::Text
end

# Mato::Document can be cached with Rails.cache (i.e. Marshal.dump ready)
Rails.fetch(digest(markdown_content)) do
  mato.process(markdown_content)
end

# Applies extra filters and returns a new Mato::Document.
# Because Mato::Document is serializable, you can cache the base doc and then apply extra filters on demaond.
new_doc = doc.apply_html_filters(
  -> (fragment) { modify_fragment!(fragment) },
  SomeHtmlFilter.new(some_context), # anything that has #call(node) method
)

Filters

There are three kinds of filters to mutate input texts in Mato:

• Text Filters
• Markdown Filters
• HTML Filters

Text Filters

A text filter is a callable instance that takes a String and returns a mutated arg.

For example:

mato = Mato.define do |config|
  config.append_text_filter(->(text) {
    text.upcase
  })
end

mato.process("Hello!").render_html # "<p>HELLO!</p>\n"

Markdown Filters

A markdown filter is a callable instance that takes a `Commonmarker::Node and mutate it in the method. The return value is ignored.

For example:

mato = Mato.define do |config|
  config.append_markdown_filter(->(doc) {
    paragraph = doc.first_child
    text_node = paragraph.first_child
    text_node.string_content = text_node.string_content.upcase
  })
end

mato.process("Hello!").render_html # "<p>HELLO!</p>\n"

HTML Filters

An HTML filter is a callable object that takes a `Nokogiri::HTML4::DocumentFragment and mutate it in the method. The return value is ignored.

mato = Mato.define do |config|
  config.append_html_filter(->(doc) {
    text_node = doc.xpath('.//text()').first
    text_node.content = text_node.content.upcase
  })
end

mato.process("Hello!").render_html # "<p>HELLO!</p>\n"

Timeout

There is timeout option to kill filters in a specified time in seconds:

mato = Mato.define do |config|
  config.append_html_filter(FooFilter, timeout: timeout_in_sec, on_timeout: callback)
end

If you set on_error callback, you can omit on_timeout callback.

Errors in Filters

There is on_error callback to rescue errors in filters:

mato = Mato.define do |config|
  config.append_html_filter(FooFilter, on_error: callback)
end

Installation

Add this line to your application's Gemfile:

gem 'mato'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mato

Motivation

The original idea comes from qiita-markdown, a markdown processing tool like mato, based on html-pipeline.

html-pipeline is a great tool that invents the idea of "pipeline", to filter HTML node (or Nokogiri::XML::Node) in each filter. This is safe, fast, and easy to enhance.

However, html-pipeline is not suitable for cache, esp. context-aware caching.

(TBD)

Optional Dependencies

• rouge (>= 2.0) to use SyntaxHighlight
• sanitize (>= 4.0) to use Sanitization

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/bitjourney/mato.

License

The gem is available as open source under the terms of the MIT License.