require 'rouge/plugins/redcarpet' module Banzai module Filter # HTML Filter to highlight fenced code blocks # class SyntaxHighlightFilter < HTML::Pipeline::Filter include Rouge::Plugins::Redcarpet def call doc.search('pre > code').each do |node| highlight_node(node) end doc end def highlight_node(node) language = node.attr('class') code = node.text css_classes = "code highlight" lexer = lexer_for(language) begin code = format(lex(lexer, code)) css_classes << " js-syntax-highlight #{lexer.tag}" rescue # Gracefully handle syntax highlighter bugs/errors to ensure # users can still access an issue/comment/etc. end highlighted = %(
#{code}
)
# Extracted to a method to measure it
replace_parent_pre_element(node, highlighted)
end
private
# Separate method so it can be instrumented.
def lex(lexer, code)
lexer.lex(code)
end
def format(tokens)
rouge_formatter.format(tokens)
end
def lexer_for(language)
(Rouge::Lexer.find(language) || Rouge::Lexers::PlainText).new
end
def replace_parent_pre_element(node, highlighted)
# Replace the parent `pre` element with the entire highlighted block
node.parent.replace(highlighted)
end
# Override Rouge::Plugins::Redcarpet#rouge_formatter
def rouge_formatter(lexer = nil)
@rouge_formatter ||= Rouge::Formatters::HTML.new
end
end
end
end