function foldFlowLines(text, indent, mode, _ref) {
  var indentAtStart = _ref.indentAtStart,
      _ref$lineWidth = _ref.lineWidth,
      lineWidth = _ref$lineWidth === void 0 ? 80 : _ref$lineWidth,
      _ref$minContentWidth = _ref.minContentWidth,
      minContentWidth = _ref$minContentWidth === void 0 ? 20 : _ref$minContentWidth,
      onFold = _ref.onFold,
      onOverflow = _ref.onOverflow;
  if (!lineWidth || lineWidth < 0) return text;
  var endStep = Math.max(1 + minContentWidth, 1 + lineWidth - indent.length);
  if (text.length <= endStep) return text;
  var folds = [];
  var escapedFolds = {};
  var end = lineWidth - (typeof indentAtStart === 'number' ? indentAtStart : indent.length);
  var split = undefined;
  var prev = undefined;
  var overflow = false;
  var i = -1;

  if (mode === FOLD_BLOCK) {
    i = consumeMoreIndentedLines(text, i);
    if (i !== -1) end = i + endStep;
  }

  for (var ch; ch = text[i += 1];) {
    if (mode === FOLD_QUOTED && ch === '\\') {
      switch (text[i + 1]) {
        case 'x':
          i += 3;
          break;

        case 'u':
          i += 5;
          break;

        case 'U':
          i += 9;
          break;

        default:
          i += 1;
      }
    }

    if (ch === '\n') {
      if (mode === FOLD_BLOCK) i = consumeMoreIndentedLines(text, i);
      end = i + endStep;
      split = undefined;
    } else {
      if (ch === ' ' && prev && prev !== ' ' && prev !== '\n' && prev !== '\t') {
        // space surrounded by non-space can be replaced with newline + indent
        var next = text[i + 1];
        if (next && next !== ' ' && next !== '\n' && next !== '\t') split = i;
      }

      if (i >= end) {
        if (split) {
          folds.push(split);
          end = split + endStep;
          split = undefined;
        } else if (mode === FOLD_QUOTED) {
          // white-space collected at end may stretch past lineWidth
          while (prev === ' ' || prev === '\t') {
            prev = ch;
            ch = text[i += 1];
            overflow = true;
          } // i - 2 accounts for not-dropped last char + newline-escaping \


          folds.push(i - 2);
          escapedFolds[i - 2] = true;
          end = i - 2 + endStep;
          split = undefined;
        } else {
          overflow = true;
        }
      }
    }

    prev = ch;
  }

  if (overflow && onOverflow) onOverflow();
  if (folds.length === 0) return text;
  if (onFold) onFold();
  var res = text.slice(0, folds[0]);

  for (var _i = 0; _i < folds.length; ++_i) {
    var fold = folds[_i];

    var _end = folds[_i + 1] || text.length;

    if (mode === FOLD_QUOTED && escapedFolds[fold]) res += "".concat(text[fold], "\\");
    res += "\n".concat(indent).concat(text.slice(fold + 1, _end));
  }

  return res;
}
Tries to keep input at up to `lineWidth` characters, splitting only on spaces
not followed by newlines or spaces unless `mode` is `'quoted'`. Lines are
terminated with `\n` and started with `indent`.

@param {string} text
@param {string} indent
@param {string} [mode='flow'] `'block'` prevents more-indented lines
  from being folded; `'quoted'` allows for `\` escapes, including escaped
  newlines
@param {Object} options
@param {number} [options.indentAtStart] Accounts for leading contents on
  the first line, defaulting to `indent.length`
@param {number} [options.lineWidth=80]
@param {number} [options.minContentWidth=20] Allow highly indented lines to
  stretch the line width
@param {function} options.onFold Called once if the text is folded
@param {function} options.onFold Called once if any line of text exceeds
  lineWidth characters