const FOLD_FLOW = 'flow';
const FOLD_BLOCK = 'block';
const FOLD_QUOTED = 'quoted';
/**
 * 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`.
 */
function foldFlowLines(text, indent, mode = 'flow', {
  indentAtStart,
  lineWidth = 80,
  minContentWidth = 20,
  onFold,
  onOverflow
} = {}) {
  if (!lineWidth || lineWidth < 0) return text;
  const endStep = Math.max(1 + minContentWidth, 1 + lineWidth - indent.length);
  if (text.length <= endStep) return text;
  const folds = [];
  const escapedFolds = {};
  let end = lineWidth - indent.length;
  if (typeof indentAtStart === 'number') {
    if (indentAtStart > lineWidth - Math.max(2, minContentWidth)) folds.push(0);else end = lineWidth - indentAtStart;
  }
  let split = undefined;
  let prev = undefined;
  let overflow = false;
  let i = -1;
  let escStart = -1;
  let escEnd = -1;
  if (mode === FOLD_BLOCK) {
    i = consumeMoreIndentedLines(text, i);
    if (i !== -1) end = i + endStep;
  }
  for (let ch; ch = text[i += 1];) {
    if (mode === FOLD_QUOTED && ch === '\\') {
      escStart = i;
      switch (text[i + 1]) {
        case 'x':
          i += 3;
          break;
        case 'u':
          i += 5;
          break;
        case 'U':
          i += 9;
          break;
        default:
          i += 1;
      }
      escEnd = i;
    }
    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
        const 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;
          }
          // Account for newline escape, but don't break preceding escape
          const j = i > escEnd + 1 ? i - 2 : escStart - 1;
          // Bail out if lineWidth & minContentWidth are shorter than an escape string
          if (escapedFolds[j]) return text;
          folds.push(j);
          escapedFolds[j] = true;
          end = j + endStep;
          split = undefined;
        } else {
          overflow = true;
        }
      }
    }
    prev = ch;
  }
  if (overflow && onOverflow) onOverflow();
  if (folds.length === 0) return text;
  if (onFold) onFold();
  let res = text.slice(0, folds[0]);
  for (let i = 0; i < folds.length; ++i) {
    const fold = folds[i];
    const end = folds[i + 1] || text.length;
    if (fold === 0) res = `\n${indent}${text.slice(0, end)}`;else {
      if (mode === FOLD_QUOTED && escapedFolds[fold]) res += `${text[fold]}\\`;
      res += `\n${indent}${text.slice(fold + 1, end)}`;
    }
  }
  return res;
}
/**
 * Presumes `i + 1` is at the start of a line
 * @returns index of last newline in more-indented block
 */
function consumeMoreIndentedLines(text, i) {
  let ch = text[i + 1];
  while (ch === ' ' || ch === '\t') {
    do {
      ch = text[i += 1];
    } while (ch && ch !== '\n');
    ch = text[i + 1];
  }
  return i;
}

export { FOLD_BLOCK, FOLD_FLOW, FOLD_QUOTED, foldFlowLines };
