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# frozen_string_literal: true
module Banzai
module Filter
# HTML Filter for footnotes
#
# Footnotes are supported in CommonMark. However we were stripping
# the ids during sanitization. Those are now allowed.
#
# Footnotes are numbered the same - the first one has `id=fn1`, the
# second is `id=fn2`, etc. In order to allow footnotes when rendering
# multiple markdown blocks on a page, we need to make each footnote
# reference unique.
#
# This filter adds a random number to each footnote (the same number
# can be used for a single render). So you get `id=fn1-4335` and `id=fn2-4335`.
#
class FootnoteFilter < HTML::Pipeline::Filter
FOOTNOTE_ID_PREFIX = 'fn-'
FOOTNOTE_LINK_ID_PREFIX = 'fnref-'
FOOTNOTE_LI_REFERENCE_PATTERN = /\A#{FOOTNOTE_ID_PREFIX}.+\z/.freeze
FOOTNOTE_LINK_REFERENCE_PATTERN = /\A#{FOOTNOTE_LINK_ID_PREFIX}.+\z/.freeze
CSS_SECTION = "ol > li a[href^=\"\##{FOOTNOTE_LINK_ID_PREFIX}\"]"
XPATH_SECTION = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_SECTION).freeze
CSS_FOOTNOTE = 'sup > a[id]'
XPATH_FOOTNOTE = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_FOOTNOTE).freeze
# only needed when feature flag use_cmark_renderer is turned off
INTEGER_PATTERN = /\A\d+\z/.freeze
FOOTNOTE_ID_PREFIX_OLD = 'fn'
FOOTNOTE_LINK_ID_PREFIX_OLD = 'fnref'
FOOTNOTE_LI_REFERENCE_PATTERN_OLD = /\A#{FOOTNOTE_ID_PREFIX_OLD}\d+\z/.freeze
FOOTNOTE_LINK_REFERENCE_PATTERN_OLD = /\A#{FOOTNOTE_LINK_ID_PREFIX_OLD}\d+\z/.freeze
FOOTNOTE_START_NUMBER = 1
CSS_SECTION_OLD = "ol > li[id=#{FOOTNOTE_ID_PREFIX_OLD}#{FOOTNOTE_START_NUMBER}]"
XPATH_SECTION_OLD = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_SECTION_OLD).freeze
def call
xpath_section = Feature.enabled?(:use_cmark_renderer) ? XPATH_SECTION : XPATH_SECTION_OLD
return doc unless first_footnote = doc.at_xpath(xpath_section)
# Sanitization stripped off the section wrapper - add it back in
if Feature.enabled?(:use_cmark_renderer)
first_footnote.parent.parent.parent.wrap('<section class="footnotes" data-footnotes>')
else
first_footnote.parent.wrap('<section class="footnotes">')
end
rand_suffix = "-#{random_number}"
modified_footnotes = {}
doc.xpath(XPATH_FOOTNOTE).each do |link_node|
if Feature.enabled?(:use_cmark_renderer)
ref_num = link_node[:id].delete_prefix(FOOTNOTE_LINK_ID_PREFIX)
ref_num.gsub!(/[[:punct:]]/, '\\\\\&')
else
ref_num = link_node[:id].delete_prefix(FOOTNOTE_LINK_ID_PREFIX_OLD)
end
node_xpath = Gitlab::Utils::Nokogiri.css_to_xpath("li[id=#{fn_id(ref_num)}]")
footnote_node = doc.at_xpath(node_xpath)
if footnote_node || modified_footnotes[ref_num]
next if Feature.disabled?(:use_cmark_renderer) && !INTEGER_PATTERN.match?(ref_num)
link_node[:href] += rand_suffix
link_node[:id] += rand_suffix
# Sanitization stripped off class - add it back in
link_node.parent.append_class('footnote-ref')
link_node['data-footnote-ref'] = nil if Feature.enabled?(:use_cmark_renderer)
unless modified_footnotes[ref_num]
footnote_node[:id] += rand_suffix
backref_node = footnote_node.at_css("a[href=\"##{fnref_id(ref_num)}\"]")
if backref_node
backref_node[:href] += rand_suffix
backref_node.append_class('footnote-backref')
backref_node['data-footnote-backref'] = nil if Feature.enabled?(:use_cmark_renderer)
end
modified_footnotes[ref_num] = true
end
end
end
doc
end
private
def random_number
@random_number ||= rand(10000)
end
def fn_id(num)
prefix = Feature.enabled?(:use_cmark_renderer) ? FOOTNOTE_ID_PREFIX : FOOTNOTE_ID_PREFIX_OLD
"#{prefix}#{num}"
end
def fnref_id(num)
prefix = Feature.enabled?(:use_cmark_renderer) ? FOOTNOTE_LINK_ID_PREFIX : FOOTNOTE_LINK_ID_PREFIX_OLD
"#{prefix}#{num}"
end
end
end
end
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