87 lines
2.9 KiB
Ruby
87 lines
2.9 KiB
Ruby
# frozen_string_literal: true
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module Banzai
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module Filter
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# HTML Filter for footnotes
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#
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# Footnotes are supported in CommonMark. However we were stripping
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# the ids during sanitization. Those are now allowed.
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#
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# Footnotes are numbered as an increasing integer starting at `1`.
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# The `id` associated with a footnote is based on the footnote reference
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# string. For example, `[^foot]` will generate `id="fn-foot"`.
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# In order to allow footnotes when rendering multiple markdown blocks
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# on a page, we need to make each footnote reference unique.
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# This filter adds a random number to each footnote (the same number
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# can be used for a single render). So you get `id=fn-1-4335` and `id=fn-foot-4335`.
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#
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class FootnoteFilter < HTML::Pipeline::Filter
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FOOTNOTE_ID_PREFIX = 'fn-'
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FOOTNOTE_LINK_ID_PREFIX = 'fnref-'
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FOOTNOTE_LI_REFERENCE_PATTERN = /\A#{FOOTNOTE_ID_PREFIX}.+\z/.freeze
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FOOTNOTE_LINK_REFERENCE_PATTERN = /\A#{FOOTNOTE_LINK_ID_PREFIX}.+\z/.freeze
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CSS_SECTION = "section[data-footnotes]"
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XPATH_SECTION = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_SECTION).freeze
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CSS_FOOTNOTE = 'sup > a[data-footnote-ref]'
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XPATH_FOOTNOTE = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_FOOTNOTE).freeze
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def call
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# Sanitization stripped off the section class - add it back in
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return doc unless section_node = doc.at_xpath(XPATH_SECTION)
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section_node.append_class('footnotes')
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rand_suffix = "-#{random_number}"
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modified_footnotes = {}
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doc.xpath(XPATH_FOOTNOTE).each do |link_node|
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ref_num = link_node[:id].delete_prefix(FOOTNOTE_LINK_ID_PREFIX)
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ref_num.gsub!(/[[:punct:]]/, '\\\\\&')
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css = "section[data-footnotes] li[id=#{fn_id(ref_num)}]"
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node_xpath = Gitlab::Utils::Nokogiri.css_to_xpath(css)
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footnote_node = doc.at_xpath(node_xpath)
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if footnote_node || modified_footnotes[ref_num]
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link_node[:href] += rand_suffix
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link_node[:id] += rand_suffix
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# Sanitization stripped off class - add it back in
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link_node.parent.append_class('footnote-ref')
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unless modified_footnotes[ref_num]
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footnote_node[:id] += rand_suffix
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backref_node = footnote_node.at_css("a[href=\"##{fnref_id(ref_num)}\"]")
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if backref_node
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backref_node[:href] += rand_suffix
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backref_node.append_class('footnote-backref')
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end
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modified_footnotes[ref_num] = true
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end
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end
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end
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doc
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end
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private
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def random_number
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@random_number ||= rand(10000)
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end
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def fn_id(num)
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"#{FOOTNOTE_ID_PREFIX}#{num}"
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end
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def fnref_id(num)
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"#{FOOTNOTE_LINK_ID_PREFIX}#{num}"
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end
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end
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end
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end
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