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
)

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

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

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"

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"

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

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