123 lines
3.5 KiB
Ruby
123 lines
3.5 KiB
Ruby
# frozen_string_literal: true
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# Generated HTML is transformed back to GFM by app/assets/javascripts/behaviors/markdown/nodes/table_of_contents.js
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module Banzai
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module Filter
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# HTML filter that adds an anchor child element to all Headers in a
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# document, so that they can be linked to.
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#
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# Generates the Table of Contents with links to each header. See Results.
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#
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# Based on HTML::Pipeline::TableOfContentsFilter.
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#
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# Context options:
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# :no_header_anchors - Skips all processing done by this filter.
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#
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# Results:
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# :toc - String containing Table of Contents data as a `ul` element with
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# `li` child elements.
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class TableOfContentsFilter < HTML::Pipeline::Filter
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PUNCTUATION_REGEXP = /[^\p{Word}\- ]/u.freeze
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def call
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return doc if context[:no_header_anchors]
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result[:toc] = +""
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headers = Hash.new(0)
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header_root = current_header = HeaderNode.new
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doc.css('h1, h2, h3, h4, h5, h6').each do |node|
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if header_content = node.children.first
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id = node
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.text
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.strip
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.downcase
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.gsub(PUNCTUATION_REGEXP, '') # remove punctuation
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.tr(' ', '-') # replace spaces with dash
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.squeeze('-') # replace multiple dashes with one
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.gsub(/\A(\d+)\z/, 'anchor-\1') # digits-only hrefs conflict with issue refs
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uniq = headers[id] > 0 ? "-#{headers[id]}" : ''
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headers[id] += 1
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href = "#{id}#{uniq}"
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current_header = HeaderNode.new(node: node, href: href, previous_header: current_header)
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header_content.add_previous_sibling(anchor_tag(href))
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end
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end
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push_toc(header_root.children, root: true)
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doc
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end
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private
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def anchor_tag(href)
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escaped_href = CGI.escape(href) # account for non-ASCII characters
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%Q{<a id="user-content-#{href}" class="anchor" href="##{escaped_href}" aria-hidden="true"></a>}
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end
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def push_toc(children, root: false)
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return if children.empty?
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klass = ' class="section-nav"' if root
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result[:toc] << "<ul#{klass}>"
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children.each { |child| push_anchor(child) }
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result[:toc] << '</ul>'
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end
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def push_anchor(header_node)
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result[:toc] << %Q{<li><a href="##{header_node.href}">#{header_node.text}</a>}
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push_toc(header_node.children)
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result[:toc] << '</li>'
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end
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class HeaderNode
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attr_reader :node, :href, :parent, :children
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def initialize(node: nil, href: nil, previous_header: nil)
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@node = node
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@href = CGI.escape(href) if href
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@children = []
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@parent = find_parent(previous_header)
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@parent.children.push(self) if @parent
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end
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def level
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return 0 unless node
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@level ||= node.name[1].to_i
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end
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def text
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return '' unless node
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@text ||= EscapeUtils.escape_html(node.text)
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end
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private
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def find_parent(previous_header)
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return unless previous_header
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if level == previous_header.level
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parent = previous_header.parent
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elsif level > previous_header.level
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parent = previous_header
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else
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parent = previous_header
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parent = parent.parent while parent.level >= level
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end
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parent
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end
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end
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end
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end
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end
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