Function checkRep

src/static/js/Changeset.ts:245–291

(cs: string)

 * @returns {string} the checked Changeset
 */
export const checkRep = (cs: string) => {
  const unpacked = unpack(cs);
  const oldLen = unpacked.oldLen;
  const newLen = unpacked.newLen;
  const ops = unpacked.ops;
  let charBank = unpacked.charBank;

  const assem = new SmartOpAssembler();
  let oldPos = 0;
  let calcNewLen = 0;
  for (const o of deserializeOps(ops)) {
    switch (o.opcode) {
      case '=':
        oldPos += o.chars;
        calcNewLen += o.chars;
        break;
      case '-':
        oldPos += o.chars;
        assert(oldPos <= oldLen, `${oldPos} > ${oldLen} in ${cs}`);
        break;
      case '+':
      {
        assert(charBank.length >= o.chars, 'Invalid changeset: not enough chars in charBank');
        const chars = charBank.slice(0, o.chars);
        const nlines = (chars.match(/\n/g) || []).length;
        assert(nlines === o.lines,
          'Invalid changeset: number of newlines in insert op does not match the charBank');
        assert(o.lines === 0 || chars.endsWith('\n'),
          'Invalid changeset: multiline insert op does not end with a newline');
        charBank = charBank.slice(o.chars);
        calcNewLen += o.chars;
        assert(calcNewLen <= newLen, `${calcNewLen} > ${newLen} in ${cs}`);
        break;
      }
      default:
        assert(false, `Invalid changeset: Unknown opcode: ${JSON.stringify(o.opcode)}`);
    }
    assem.append(o);
  }
  calcNewLen += oldLen - oldPos;
  assert(calcNewLen === newLen, 'Invalid changeset: claimed length does not match actual length');
  assert(charBank === '', 'Invalid changeset: excess characters in the charBank');
  assem.endDocument();
  const normalized = pack(oldLen, calcNewLen, assem.toString(), unpacked.charBank);
  assert(normalized === cs, 'Invalid changeset: not in canonical form');
  return cs;
};

/**
 * A custom made StringBuffer