bidirectional links

_plugins/bidirectional_links_generator.rb

@@ -0,0 +1,106 @@
+# frozen_string_literal: true
+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
+
+        # 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,
+          "<a class='internal-link' href='.#{note_potentially_linked_to.url}#{link_extension}'>\\1</a>"
+        )
+
+        # 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,
+          "<a class='internal-link' href='.#{note_potentially_linked_to.url}#{link_extension}'>\\1</a>"
+        )
+
+        # 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,
+          "<a class='internal-link' href='.#{note_potentially_linked_to.url}#{link_extension}'>\\1</a>"
+        )
+
+        # Replace double-bracketed links using note filename
+        # [[cats]]
+        current_note.content = current_note.content.gsub(
+          /\[\[(#{title_from_filename})\]\]/i,
+          "<a class='internal-link' href='.#{note_potentially_linked_to.url}#{link_extension}'>\\1</a>"
+        )
+      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?(current_note.url)
+      end
+
+      # Nodes: Graph
+      graph_nodes << {
+        id: note_id_from_note(current_note),
+        path: "#{current_note.url}#{link_extension}",
+        label: current_note.data['title'],
+      } unless current_note.path.include?('_notes/index.html')
+
+      # 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