"Reverting 22561"

pkg/mdv_observe/lib/src/observable_list.dart

-// Copyright (c) 2013, 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.
-
-part of mdv_observe;
-
-/**
- * Represents an observable list of model values. If any items are added,
- * removed, or replaced, then observers that are listening to [changes]
- * will be notified.
- */
-// TODO(jmesserly): remove implements List<E> once we can extend ListBase<E>
-class ObservableList<E> extends _ListBaseWorkaround with ObservableMixin
-    implements List<E> {
-  List<ListChangeRecord> _records;
-
-  static const _LENGTH = const Symbol('length');
-
-  /** The inner [List<E>] with the actual storage. */
-  final List<E> _list;
-
-  /**
-   * Creates an observable list of the given [length].
-   *
-   * If no [length] argument is supplied an extendable list of
-   * length 0 is created.
-   *
-   * If a [length] argument is supplied, a fixed size list of that
-   * length is created.
-   */
-  ObservableList([int length])
-      : _list = length != null ? new List<E>(length) : <E>[];
-
-  /**
-   * Creates an observable list with the elements of [other]. The order in
-   * the list will be the order provided by the iterator of [other].
-   */
-  factory ObservableList.from(Iterable<E> other) =>
-      new ObservableList<E>()..addAll(other);
-
-  // TODO(jmesserly): remove once we have mirrors
-  getValueWorkaround(key) => key == _LENGTH ? length : null;
-
-  setValueWorkaround(key, value) {
-    if (key == _LENGTH) length = value;
-  }
-
-  int get length => _list.length;
-
-  set length(int value) {
-    int len = _list.length;
-    if (len == value) return;
-
-    // Produce notifications if needed
-    if (hasObservers) {
-      if (value < len) {
-        // Remove items, then adjust length. Note the reverse order.
-        _recordChange(new ListChangeRecord(value, removedCount: len - value));
-      } else {
-        // Adjust length then add items
-        _recordChange(new ListChangeRecord(len, addedCount: value - len));
-      }
-    }
-
-    _list.length = value;
-  }
-
-  E operator [](int index) => _list[index];
-
-  void operator []=(int index, E value) {
-    var oldValue = _list[index];
-    if (hasObservers) {
-      _recordChange(new ListChangeRecord(index, addedCount: 1, removedCount: 1));
-    }
-    _list[index] = value;
-  }
-
-  // The following methods are here so that we can provide nice change events.
-
-  void setAll(int index, Iterable<E> iterable) {
-    if (iterable is! List && iterable is! Set) {
-      iterable = iterable.toList();
-    }
-    var len = iterable.length;
-    _list.setAll(index, iterable);
-    if (hasObservers && len > 0) {
-      _recordChange(
-          new ListChangeRecord(index, addedCount: len, removedCount: len));
-    }
-  }
-
-  void add(E value) {
-    int len = _list.length;
-    if (hasObservers) {
-      _recordChange(new ListChangeRecord(len, addedCount: 1));
-    }
-
-    _list.add(value);
-  }
-
-  void addAll(Iterable<E> iterable) {
-    int len = _list.length;
-    _list.addAll(iterable);
-    int added = _list.length - len;
-    if (hasObservers && added > 0) {
-      _recordChange(new ListChangeRecord(len, addedCount: added));
-    }
-  }
-
-  bool remove(Object element) {
-    for (int i = 0; i < this.length; i++) {
-      if (this[i] == element) {
-        removeRange(i, 1);
-        return true;
-      }
-    }
-    return false;
-  }
-
-  void removeRange(int start, int end) {
-    _rangeCheck(start, end);
-    int length = end - start;
-    _list.setRange(start, this.length - length, this, end);
-
-    int len = _list.length;
-    _list.length -= length;
-    if (hasObservers && length > 0) {
-      _recordChange(new ListChangeRecord(start, removedCount: length));
-    }
-  }
-
-  void insertAll(int index, Iterable<E> iterable) {
-    if (index < 0 || index > length) {
-      throw new RangeError.range(index, 0, length);
-    }
-    // TODO(floitsch): we can probably detect more cases.
-    if (iterable is! List && iterable is! Set) {
-      iterable = iterable.toList();
-    }
-    int insertionLength = iterable.length;
-    // There might be errors after the length change, in which case the list
-    // will end up being modified but the operation not complete. Unless we
-    // always go through a "toList" we can't really avoid that.
-    int len = _list.length;
-    _list.length += insertionLength;
-
-    _list.setRange(index + insertionLength, this.length, this, index);
-    _list.setAll(index, iterable);
-
-    if (hasObservers && insertionLength > 0) {
-      _recordChange(new ListChangeRecord(index, addedCount: insertionLength));
-    }
-  }
-
-  void insert(int index, E element) {
-    if (index < 0 || index > length) {
-      throw new RangeError.range(index, 0, length);
-    }
-    if (index == length) {
-      add(element);
-      return;
-    }
-    // We are modifying the length just below the is-check. Without the check
-    // Array.copy could throw an exception, leaving the list in a bad state
-    // (with a length that has been increased, but without a new element).
-    if (index is! int) throw new ArgumentError(index);
-    _list.length++;
-    _list.setRange(index + 1, length, this, index);
-    if (hasObservers) {
-      _recordChange(new ListChangeRecord(index, addedCount: 1));
-    }
-    _list[index] = element;
-  }
-
-
-  E removeAt(int index) {
-    E result = this[index];
-    removeRange(index, index + 1);
-    return result;
-  }
-
-  void _rangeCheck(int start, int end) {
-    if (start < 0 || start > this.length) {
-      throw new RangeError.range(start, 0, this.length);
-    }
-    if (end < start || end > this.length) {
-      throw new RangeError.range(end, start, this.length);
-    }
-  }
-
-  void _recordChange(ListChangeRecord record) {
-    if (_records == null) {
-      _records = [];
-      queueChangeRecords(_summarizeRecords);
-    }
-    _records.add(record);
-  }
-
-  /**
-   * We need to summarize change records. Consumers of these records want to
-   * apply the batch sequentially, and ensure that they can find inserted
-   * items by looking at that position in the list. This property does not
-   * hold in our record-as-you-go records. Consider:
-   *
-   *     var model = toObservable(['a', 'b']);
-   *     model.removeAt(1);
-   *     model.insertAll(0, ['c', 'd', 'e']);
-   *     model.removeRange(1, 3);
-   *     model.insert(1, 'f');
-   *
-   * Here, we inserted some records and then removed some of them.
-   * If someone processed these records naively, they would "play back" the
-   * insert incorrectly, because those items will be shifted.
-   *
-   * We summarize changes using a straightforward technique:
-   * Simulate the moves and use the final item positions to synthesize a
-   * new list of changes records. This has the advantage of not depending
-   * on the actual *values*, so we don't need to perform N^2 edit
-   */
-  // TODO(jmesserly): there's probably something smarter here, but this
-  // algorithm is pretty simple. It has complexity equivalent to the original
-  // list modifications.
-  // One simple idea: we can simply update the index map as we do the operations
-  // to the list, then produce the records at the end.
-  void _summarizeRecords() {
-    int oldLength = length;
-    for (var r in _records) {
-      oldLength += r.removedCount - r.addedCount;
-    }
-
-    if (length != oldLength) {
-      notifyPropertyChange(_LENGTH, oldLength, length);
-    }
-
-    if (_records.length == 1) {
-      notifyChange(_records[0]);
-      _records = null;
-      return;
-    }
-
-    var items = [];
-    for (int i = 0; i < oldLength; i++) items.add(i);
-    for (var r in _records) {
-      items.removeRange(r.index, r.index + r.removedCount);
-
-      // Represent inserts with -1.
-      items.insertAll(r.index, new List.filled(r.addedCount, -1));
-    }
-    assert(items.length == length);
-
-    _records = null;
-
-    int index = 0;
-    int offset = 0;
-    while (index < items.length) {
-      // Skip unchanged items.
-      while (index < items.length && items[index] == index + offset) {
-        index++;
-      }
-
-      // Find inserts
-      int startIndex = index;
-      while (index < items.length && items[index] == -1) {
-        index++;
-      }
-
-      int added = index - startIndex;
-
-      // Use the delta between our actual and expected position to determine
-      // how much was removed.
-      int actualItem = index < items.length ? items[index] : oldLength;
-      int expectedItem = startIndex + offset;
-
-      int removed = actualItem - expectedItem;
-
-      if (added > 0 || removed > 0) {
-        notifyChange(new ListChangeRecord(startIndex, addedCount: added,
-            removedCount: removed));
-      }
-
-      offset += removed - added;
-    }
-  }
-}
-
-// TODO(jmesserly): bogus type to workaround spurious VM bug with generic base
-// class and mixins.
-abstract class _ListBaseWorkaround extends ListBase<dynamic> {}