utils.js

// helper functions to convert old string ops to and from subtype ops
function convertFromText(c) {
  c.t = 'text0';
  var o = {p: c.p.pop()};
  if (c.si != null) o.i = c.si;
  if (c.sd != null) o.d = c.sd;
  c.o = [o];
}

function convertToText(c) {
  c.p.push(c.o[0].p);
  if (c.o[0].i != null) c.si = c.o[0].i;
  if (c.o[0].d != null) c.sd = c.o[0].d;
  delete c.t;
  delete c.o;
}

// Returns the common length of the paths of ops a and b
function commonLengthForOps(a, b) {
  var alen = a.p.length;
  var blen = b.p.length;
  if (a.na != null || a.t)
    alen++;

  if (b.na != null || b.t)
    blen++;

  if (alen === 0) return -1;
  if (blen === 0) return null;

  alen--;
  blen--;

  for (var i = 0; i < alen; i++) {
    var p = a.p[i];
    if (i >= blen || p !== b.p[i])
      return null;
  }

  return alen;
};

// Returns true if an op can affect the given path
function canOpAffectPath(op, path) {
  return commonLengthForOps({p:path}, op) != null;
};

module.exports = { convertFromText, convertToText, commonLengthForOps, canOpAffectPath };