work in progress: observable implementation using detailed change records

lib/observe/list.dart

Index: lib/observe/list.dart
diff --git a/lib/observe/list.dart b/lib/observe/list.dart
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+// Copyright (c) 2012, 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.
+
+library web_ui.observe.list;
+
+import 'dart:collection';
+import 'dart:collection-dev';
+import 'package:web_ui/observe.dart';
+
+// TODO(jmesserly): this should extend the real list implementation.
+// See http://dartbug.com/2600. The workaround was to copy+paste lots of code
+// from the VM.
+// TODO(jmesserly): also this shold extend Collection<E>, so we can delete
+// copy+paste code. Fix once we have mixins.
+/**
+ * Represents an observable list of model values. If any items are added,
+ * removed, or replaced, then observers that are registered with
+ * [observe] will be notified.
+ */
+class ObservableList<E> extends Observable implements List<E> {
+  /** 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 = 0]) : _list = new List<E>(length);
+
+  /**
+   * 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): This should be on List.
+  // See http://code.google.com/p/dart/issues/detail?id=947
+  bool remove(E item) {
+    int i = indexOf(item);
+    if (i == -1) return false;
+    removeAt(i);
+    return true;
+  }
+
+  // TODO(jmesserly): This should be on List, to match removeAt.
+  // See http://code.google.com/p/dart/issues/detail?id=5375
+  void insertAt(int index, E item) => insertRange(index, 1, item);
+
+  E get first => this[0];
+
+  Iterator<E> get iterator => new ListIterator<E>(this);
+
+  int get length {
+    if (observeReads) notifyRead(ChangeRecord.FIELD, 'length');
+    return _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
+        for (int i = len - 1; i >= value; i--) {
+          notifyChange(ChangeRecord.INDEX, i, null, null);
+        }
+        notifyChange(ChangeRecord.FIELD, 'length', len, value);
+      } else {
+        // Adjust length then add items
+        notifyChange(ChangeRecord.FIELD, 'length', len, value);
+        for (int i = len; i < value; i++) {
+          notifyChange(ChangeRecord.INDEX, i, null, null);
+        }
+      }
+    }
+
+    _list.length = value;
+  }
+
+  E operator [](int index) {
+    if (observeReads) notifyRead(ChangeRecord.INDEX, index);
+    return _list[index];
+  }
+
+  operator []=(int index, E value) {
+    var oldValue = _list[index];
+    if (hasObservers) notifyChange(ChangeRecord.INDEX, index, oldValue, value);
+    _list[index] = value;
+  }
+
+  void add(E value) {
+    int len = _list.length;
+    if (hasObservers) {
+      notifyChange(ChangeRecord.FIELD, 'length', len, len + 1);
+      notifyChange(ChangeRecord.INDEX, len, null, value);
+    }
+    _list.add(value);
+  }
+
+  // ---------------------------------------------------------------------------
+  // Note: below this comment, methods are either:
+  //   * redirect to Arrays
+  //   * copy+paste from VM GrowableObjectArray.
+  // The general idea is to have these methods operate in terms of our primitive
+  // methods above, so they correctly track reads/writes.
+  // ---------------------------------------------------------------------------
+
+  E removeLast() {
+    var len = length - 1;
+    var elem = this[len];
+    length = len;
+    return elem;
+  }
+
+  int indexOf(E element, [int start = 0]) =>
+      Arrays.indexOf(this, element, start, length);
+
+  int lastIndexOf(E element, [int start]) =>
+      Arrays.lastIndexOf(this, element, start);
+
+  ObservableList<E> getRange(int start, int length)  {
+    if (length == 0) return [];
+    Arrays.rangeCheck(this, start, length);
+    List list = new ObservableList<E>(length);
+    Arrays.copy(this, start, list, 0, length);
+    return list;
+  }
+
+  bool get isEmpty => length == 0;
+
+  E get last => this[length - 1];
+
+  void addLast(E value) => add(value);
+
+  void sort([compare = Comparable.compare]) =>
+      IterableMixinWorkaround.sortList(this, compare);
+
+  void clear() {
+    this.length = 0;
+  }
+
+  E removeAt(int index) {
+    if (index is! int) throw new ArgumentError(index);
+    E result = this[index];
+    int newLength = this.length - 1;
+    Arrays.copy(this,
+                index + 1,
+                this,
+                index,
+                newLength - index);
+    this.length = newLength;
+    return result;
+  }
+
+  void setRange(int start, int length, List<E> from, [int startFrom = 0]) {
+    Arrays.copy(from, startFrom, this, start, length);
+  }
+
+  void removeRange(int start, int length) {
+    if (length == 0) {
+      return;
+    }
+    Arrays.rangeCheck(this, start, length);
+    Arrays.copy(this,
+                start + length,
+                this,
+                start,
+                this.length - length - start);
+    this.length = this.length - length;
+  }
+
+  void insertRange(int start, int length, [E initialValue]) {
+    if (length == 0) {
+      return;
+    }
+    if ((length < 0) || (length is! int)) {
+      throw new ArgumentError("invalid length specified $length");
+    }
+    if (start < 0 || start > this.length) {
+      throw new RangeError.value(start);
+    }
+    var oldLength = this.length;
+    this.length = oldLength + length;  // Will expand if needed.
+    Arrays.copy(this,
+                start,
+                this,
+                start + length,
+                oldLength - start);
+    for (int i = start; i < start + length; i++) {
+      this[i] = initialValue;
+    }
+  }
+
+  String toString() => Collections.collectionToString(this);
+
+  // ---------------------------------------------------------------------------
+  // Note: below this comment, methods are copy+paste from Collection<E> and
+  // Iterable<E>. Remove when we have mixins.
+  // ---------------------------------------------------------------------------
+
+  void addAll(Iterable<E> elements) {
+    for (E element in elements) add(element);
+  }
+
+  List<E> get reversed => new ReversedListView<E>(this, 0, length);
+
+  void removeAll(Iterable elements) =>
+    IterableMixinWorkaround.removeAll(this, elements);
+  void retainAll(Iterable elements) =>
+      IterableMixinWorkaround.retainAll(this, elements);
+  void removeMatching(bool test(E element)) =>
+      IterableMixinWorkaround.removeMatching(this, test);
+  void retainMatching(bool test(E element)) =>
+    IterableMixinWorkaround.retainMatching(this, test);
+  Iterable mappedBy(f(E element)) =>
+      IterableMixinWorkaround.mappedByList(this, f);
+  Iterable<E> where(bool f(E element)) =>
+      IterableMixinWorkaround.where(this, f);
+  bool contains(E element) => IterableMixinWorkaround.contains(this, element);
+  void forEach(void f(E element)) => IterableMixinWorkaround.forEach(this, f);
+  dynamic reduce(var initialValue,
+                 dynamic combine(var previousValue, E element)) =>
+      IterableMixinWorkaround.reduce(this, initialValue, combine);
+  bool every(bool f(E element)) => IterableMixinWorkaround.every(this, f);
+  String join([String separator]) =>
+      IterableMixinWorkaround.join(this, separator);
+  bool any(bool f(E element)) => IterableMixinWorkaround.any(this, f);
+  List<E> toList() => new List<E>.from(this);
+  Set<E> toSet() => new Set<E>.from(this);
+  E min([int compare(E a, E b)]) => IterableMixinWorkaround.min(this, compare);
+  E max([int compare(E a, E b)]) => IterableMixinWorkaround.max(this, compare);
+  Iterable<E> take(int n) => IterableMixinWorkaround.takeList(this, n);
+  Iterable<E> takeWhile(bool test(E value))
+      => IterableMixinWorkaround.takeWhile(this, test);
+  Iterable<E> skip(int n) => IterableMixinWorkaround.skipList(this, n);
+  Iterable<E> skipWhile(bool test(E value)) =>
+      IterableMixinWorkaround.skipWhile(this, test);
+  E get single => IterableMixinWorkaround.single(this);
+  E firstMatching(bool test(E value), { E orElse() }) =>
+      IterableMixinWorkaround.firstMatching(this, test, orElse);
+  E lastMatching(bool test(E value), {E orElse()}) =>
+      IterableMixinWorkaround.lastMatching(this, test, orElse);
+  E singleMatching(bool test(E value)) =>
+      IterableMixinWorkaround.singleMatching(this, test);
+  E elementAt(int index) => IterableMixinWorkaround.elementAt(this, index);
+}