replace method

Delta replace(int index, int len, Object? data)

Replaces length of characters starting at index with data.

This method applies heuristic rules before modifying this document and produces a change event with its source set to ChangeSource.local.

Returns an instance of Delta actually composed into this document.

Implementation

Delta replace(int index, int len, Object? data) {
  assert(index >= 0);
  assert(data is String || data is Embeddable || data is Delta);

  var delta = Delta();

  if (data is Delta) {
    // move to insertion point and add the inserted content
    if (index > 0) {
      delta.retain(index);
    }

    // remove any text we are replacing
    if (len > 0) {
      delta.delete(len);
    }

    // add the pasted content
    for (final op in data.operations) {
      delta.push(op);
    }

    compose(delta, ChangeSource.local);
  } else {
    final dataIsNotEmpty = (data is String) ? data.isNotEmpty : true;

    assert(dataIsNotEmpty || len > 0);

    // We have to insert before applying delete rules
    // Otherwise delete would be operating on stale document snapshot.
    if (dataIsNotEmpty) {
      delta = insert(index, data, replaceLength: len);
    }

    if (len > 0) {
      final deleteDelta = delete(index, len);
      delta = delta.compose(deleteDelta);
    }
  }

  return delta;
}