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# frozen_string_literal: true
# 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 implements our dollar math syntax, one of three filters:
# DollarMathPreFilter, DollarMathPostFilter, and MathFilter
#
class DollarMathPreFilter < HTML::Pipeline::TextFilter
# Based on the Pandoc heuristics,
# https://pandoc.org/MANUAL.html#extension-tex_math_dollars
#
# Handle the $$\n...\n$$ syntax in this filter, before markdown processing,
# by converting it into the ```math syntax. In this way, we can ensure
# that it's considered a code block and will not have any markdown processed inside it.
# Corresponds to the "$$\n...\n$$" syntax
REGEX = %r{
#{::Gitlab::Regex.markdown_code_or_html_blocks}
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(?=(?<=^\n|\A)\$\$\ *\n.*\n\$\$\ *(?=\n$|\z))(?:
# Display math block:
# $$
# latex math
# $$
(?<=^\n|\A)\$\$\ *\n
(?<display_math>
(?:.)+?
)
\n\$\$\ *(?=\n$|\z)
)
}mx.freeze
def call
@text.gsub(REGEX) do
if $~[:display_math]
# change from $$ to ```math
"```math\n#{$~[:display_math]}\n```"
else
$~[0]
end
end
end
end
end
end
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