export default function(argString) {
  if (Array.isArray(argString)) return argString;

  argString = argString.trim();

  var i = 0;
  var prevC = null;
  var c = null;
  var opening = null;
  var args = [];

  for (var ii = 0; ii < argString.length; ii++) {
    prevC = c;
    c = argString.charAt(ii);

    // split on spaces unless we're in quotes.
    if (c === ' ' && !opening) {
      if (!(prevC === ' ')) {
        i++;
      }
      continue;
    }

    // don't split the string if we're in matching
    // opening or closing single and double quotes.
    if (c === opening) {
      if (!args[i]) args[i] = '';
      opening = null;
    } else if ((c === "'" || c === '"') && argString.indexOf(c, ii + 1) > 0 && !opening) {
      opening = c;
    }

    if (!args[i]) args[i] = '';
    args[i] += c;
  }

  return args;
}