comment + refactor renumber

bin/renumber

@@ -6,33 +6,40 @@ files = Array(ARGV.shift || Dir.glob("./**/*.md"))
 files.each do |file|
   content = File.read(file)
 
+  # First, scan for all references ([#]: at beginning of line)
+  # and look for duplicates
   refs = content.scan(/^\[\d+\]:/)
+  dups = refs.combination(2).filter_map { |i, j| i if i == j }
 
-  unless refs == refs.uniq
-    warn "Error in #{file}: duplicate refs detected"
+  # If duplicate refs detected, this won't work, so bail out
+  if dups.any?
+    warn "Duplicate refs detected in #{file} (#{dups * ", "})"
     exit 1
   end
 
   idx = 0
   code_block = false
-  refs = {}
+  cache = {}
 
-  updated = content.gsub(/\[\d+\]|```|`/) do |token|
+  # Find all numbered links (in text + references) + code delimeters
+  # (for fenced code blocks, "`" suffices because "```" is an odd number)
+  updated = content.gsub(/\[\d+\]|`/) do |token|
     case token
-    when "```", "`"
+    when "`"
+      # We don't want to do substitution inside code blocks
+      # (where `[#]` sometimes occurs) but we do want to toggle
+      # whether or not we're in a code block
       code_block = !code_block
       token
     else
-      if code_block
-        token
-      else
-        refs[token] ||= "[$$#{idx += 1}]"
-      end
+      # If we're in a code block, just return the token
+      # Otherwise, check if the reference has already been assigned
+      # - If so, return the cached value
+      # - If not, bump the index, cache the value, and return it
+      code_block ? token : cache[token] ||= "[#{idx += 1}]"
     end
   end
 
-  updated.gsub!("$$", "")
-
   if fix
     File.write(file, updated)
   elsif content != updated