truncateMiddle.lua

-- via https://stackoverflow.com/questions/5723154/truncate-a-string-in-the-middle-with-javascript
--     https://stackoverflow.com/questions/831552/ellipsis-in-the-middle-of-a-text-mac-style/36470401#36470401
function truncateMiddle (str, maxLength, separator)
  maxLength = maxLength or 30
  separator = separator or "…"

  if (maxLength < 1) then return str end
  if (string.len(str) <= maxLength) then return str end
  if (maxLength == 1) then return string.sub(str, 0, 1) .. separator end

  midpoint = math.ceil(string.len(str) / 2)
  toremove = string.len(str) - maxLength
  lstrip = math.ceil(toremove / 2)
  rstrip = toremove - lstrip

  return string.sub(str, 1, midpoint - lstrip) .. separator .. string.sub(str, 1 + midpoint + rstrip)
end