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# frozen_string_literal: true
require 'uri'
# Generated HTML is transformed back to GFM by:
# - app/assets/javascripts/behaviors/markdown/marks/math.js
# - app/assets/javascripts/behaviors/markdown/nodes/code_block.js
module Banzai
module Filter
# HTML filter that adds class="code math" and removes the dollar sign in $`2+2`$.
#
class MathFilter < HTML::Pipeline::Filter
# Attribute indicating inline or display math.
STYLE_ATTRIBUTE = 'data-math-style'.freeze
# Class used for tagging elements that should be rendered
TAG_CLASS = 'js-render-math'.freeze
INLINE_CLASSES = "code math #{TAG_CLASS}".freeze
DOLLAR_SIGN = '$'.freeze
def call
doc.css('code').each do |code|
closing = code.next
opening = code.previous
# We need a sibling before and after.
# They should end and start with $ respectively.
if closing && opening &&
closing.text? && opening.text? &&
closing.content.first == DOLLAR_SIGN &&
opening.content.last == DOLLAR_SIGN
code[:class] = INLINE_CLASSES
code[STYLE_ATTRIBUTE] = 'inline'
closing.content = closing.content[1..-1]
opening.content = opening.content[0..-2]
end
end
doc.css('pre.code.math').each do |el|
el[STYLE_ATTRIBUTE] = 'display'
el[:class] += " #{TAG_CLASS}"
end
doc
end
end
end
end
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