// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// @assertion ListBase<E> class
/// Implements ListMixin<E>
/// Abstract implementation of a list.
/// All operations are defined in terms of length, operator[], operator[]= and
/// length=, which need to be implemented.
/// @description Implementation of length, operator[], operator[]= and length=
/// @author sgrekhov@unipro.ru

library list_base_lib;
import "dart:collection";

class ListBaseImpl<E> extends ListBase<E> {
  List<E> _list;

  ListBaseImpl.empty(): _list = new List<E>.empty(growable: true);
  ListBaseImpl(int length, E fill): _list = new List.filled(length, fill);
  
  E operator [](int index) => _list[index];

  void operator []=(int index, E value) {
    _list[index] = value;
  }

  int get length => _list.length;

  void set length(int newLength) {
    _list.length = newLength;
  }
}

ListBase<E> create<E>([int? length, E? fill]) {
  if (length == null) {
    return new ListBaseImpl<E>.empty();
  }
  if (fill != null) {
    return new ListBaseImpl(length, fill);
  }
  throw new Exception("List length specified but fill is null");
}