kcl-digital-humanities-garden/_plugins/bidirectional_links_generator.rb

# frozen_string_literal: true

# Generate bi-directional links from a given collection and the nodes graph.
class BidirectionalLinksGenerator < Jekyll::Generator
  def generate(site)
    graph_nodes = []
    graph_edges = []

    all_notes = site.collections['notes'].docs
    all_pages = site.pages

    all_docs = all_notes + all_pages

    link_extension = site.config['use_html_extension'] ? '.html' : ''

    # Convert all Wiki/Roam-style double-bracket link syntax to plain HTML
    # anchor tag elements (<a>) with "internal-link" CSS class
    all_docs.each do |current_note|
      all_docs.each do |note_potentially_linked_to|
        title_from_filename = File.basename(
          note_potentially_linked_to.basename,
          File.extname(note_potentially_linked_to.basename)
        ).gsub('_', ' ').gsub('-', ' ').capitalize

        new_href = "#{site.baseurl}#{note_potentially_linked_to.url}#{link_extension}"
        anchor_tag = "<a class='internal-link' href='#{new_href}'>\\1</a>"

        # Replace double-bracketed links with label using note title
        # [[A note about cats|this is a link to the note about cats]]
        current_note.content = current_note.content.gsub(
          /\[\[#{title_from_filename}\|(.+?)(?=\])\]\]/i,
          anchor_tag
        )

        # Replace double-bracketed links with label using note filename
        # [[cats|this is a link to the note about cats]]
        current_note.content = current_note.content.gsub(
          /\[\[#{note_potentially_linked_to.data['title']}\|(.+?)(?=\])\]\]/i,
          anchor_tag
        )

        # Replace double-bracketed links using note title
        # [[a note about cats]]
        current_note.content = current_note.content.gsub(
          /\[\[(#{note_potentially_linked_to.data['title']})\]\]/i,
          anchor_tag
        )

        # Replace double-bracketed links using note filename
        # [[cats]]
        current_note.content = current_note.content.gsub(
          /\[\[(#{title_from_filename})\]\]/i,
          anchor_tag
        )
      end

      # At this point, all remaining double-bracket-wrapped words are
      # pointing to non-existing pages, so let's turn them into disabled
      # links by greying them out and changing the cursor
      current_note.content = current_note.content.gsub(
        /\[\[(.*)\]\]/i, # match on the remaining double-bracket links
        <<~HTML.chomp    # replace with this HTML (\\1 is what was inside the brackets)
          <span title='There is no note that matches this link.' class='invalid-link'>
            <span class='invalid-link-brackets'>[[</span>
            \\1
            <span class='invalid-link-brackets'>]]</span></span>
        HTML
      )
    end

    # Identify note backlinks and add them to each note
    all_notes.each do |current_note|
      # Nodes: Jekyll
      notes_linking_to_current_note = all_notes.filter do |e|
        e.content.include?("href='#{current_note.url}'")
      end

      # Nodes: Graph
      unless current_note.path.include?('_notes/index.html')
        graph_nodes << {
          id: note_id_from_note(current_note),
          path: "#{site.baseurl}#{current_note.url}#{link_extension}",
          label: current_note.data['title'],
          status: current_note.data['status'],
          type: current_note.data['type']
        }
      end

      # Edges: Jekyll
      current_note.data['backlinks'] = notes_linking_to_current_note

      # Edges: Graph
      notes_linking_to_current_note.each do |n|
        graph_edges << {
          source: note_id_from_note(n),
          target: note_id_from_note(current_note)
        }
      end
    end

    File.write('_includes/notes_graph.json', JSON.dump({
                                                         edges: graph_edges,
                                                         nodes: graph_nodes
                                                       }))
  end

  def note_id_from_note(note)
    note.data['title']
        .dup
        .gsub(/\W+/, ' ')
        .delete(' ')
        .to_i(36)
        .to_s
  end
end