class Diffy::HtmlFormatter

def highlight(lines)
  "<strong>" +
    lines.
      # strip diff tokens (e.g. +,-,etc.)
      gsub(/(^|\\n)./, '').
      # mark line boundaries from higher level line diff
      # html is all escaped so using brackets should make this safe.
      gsub('\n', '<LINE_BOUNDARY>').
      # join characters back by stripping out newlines
      gsub("\n", '').
      # close and reopen strong tags.  we don't want inline elements
      # spanning block elements which get added later.
      gsub('<LINE_BOUNDARY>',"</strong>\n<strong>") + "</strong>"
end