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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 the original GitLab math syntax, one of three filters:
# DollarMathPreFilter, DollarMathPostFilter, and MathFilter
#
class MathFilter < HTML::Pipeline::Filter
# Handle the $`...`$ and ```math syntax in this filter.
# Also add necessary classes any existing math blocks.
CSS_MATH = 'pre[lang="math"] > code'
XPATH_MATH = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_MATH).freeze
CSS_CODE = 'code'
XPATH_CODE = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_CODE).freeze
CSS_INLINE_CODE = 'code[data-math-style]'
XPATH_INLINE_CODE = Gitlab::Utils::Nokogiri.css_to_xpath(CSS_INLINE_CODE).freeze
# Attribute indicating inline or display math.
STYLE_ATTRIBUTE = 'data-math-style'
# Class used for tagging elements that should be rendered
TAG_CLASS = 'js-render-math'
MATH_CLASSES = "code math #{TAG_CLASS}"
DOLLAR_SIGN = '$'
# Limit to how many nodes can be marked as math elements.
# Prevents timeouts for large notes.
# For more information check: https://gitlab.com/gitlab-org/gitlab/-/issues/341832
RENDER_NODES_LIMIT = 50
def call
@nodes_count = 0
process_existing
process_dollar_backtick_inline
process_math_codeblock
doc
end
private
# Add necessary classes to any existing math blocks
def process_existing
doc.xpath(XPATH_INLINE_CODE).each do |code|
break if @nodes_count >= RENDER_NODES_LIMIT
code[:class] = MATH_CLASSES
@nodes_count += 1
end
end
# Corresponds to the "$`...`$" syntax
def process_dollar_backtick_inline
doc.xpath(XPATH_CODE).each do |code|
break if @nodes_count >= RENDER_NODES_LIMIT
closing = code.next
opening = code.previous
# We need a sibling before and after.
# They should end and start with $ respectively.
next unless closing && opening &&
closing.text? && opening.text? &&
closing.content.first == DOLLAR_SIGN &&
opening.content.last == DOLLAR_SIGN
code[STYLE_ATTRIBUTE] = 'inline'
code[:class] = MATH_CLASSES
closing.content = closing.content[1..]
opening.content = opening.content[0..-2]
@nodes_count += 1
end
end
# Corresponds to the "```math...```" syntax
def process_math_codeblock
doc.xpath(XPATH_MATH).each do |node|
pre_node = node.parent
pre_node[STYLE_ATTRIBUTE] = 'display'
pre_node[:class] = TAG_CLASS
end
end
end
end
end
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