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collection/lib/src/canonicalized_map.dart

-// Copyright (c) 2014, 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 dart.pkg.collection.canonicalized_map;
-
-import 'dart:collection';
-
-import 'utils.dart';
-
-/**
- * A map whose keys are converted to canonical values of type `C`.
- *
- * This is useful for using case-insensitive String keys, for example. It's more
- * efficient than a [LinkedHashMap] with a custom equality operator because it
- * only canonicalizes each key once, rather than doing so for each comparison.
- *
- * By default, `null` is allowed as a key. It can be forbidden via the
- * `isValidKey` parameter.
- */
-class CanonicalizedMap<C, K, V> implements Map<K, V> {
-  final Function _canonicalize;
-
-  final Function _isValidKeyFn;
-
-  final _base = new Map<C, Pair<K, V>>();
-
-  /**
-   * Creates an empty canonicalized map.
-   *
-   * The [canonicalize] function should return the canonical value for the given
-   * key. Keys with the same canonical value are considered equivalent.
-   *
-   * The [isValidKey] function is called before calling [canonicalize] for
-   * methods that take arbitrary objects. It can be used to filter out keys that
-   * can't be canonicalized.
-   */
-  CanonicalizedMap(C canonicalize(K key), {bool isValidKey(Object key)})
-      : _canonicalize = canonicalize,
-        _isValidKeyFn = isValidKey;
-
-  /**
-   * Creates a canonicalized map that is initialized with the key/value pairs of
-   * [other].
-   *
-   * The [canonicalize] function should return the canonical value for the given
-   * key. Keys with the same canonical value are considered equivalent.
-   *
-   * The [isValidKey] function is called before calling [canonicalize] for
-   * methods that take arbitrary objects. It can be used to filter out keys that
-   * can't be canonicalized.
-   */
-  CanonicalizedMap.from(Map<K, V> other, C canonicalize(K key),
-                        {bool isValidKey(Object key)})
-      : _canonicalize = canonicalize,
-        _isValidKeyFn = isValidKey {
-    addAll(other);
-  }
-
-  V operator [](Object key) {
-    if (!_isValidKey(key)) return null;
-    var pair = _base[_canonicalize(key)];
-    return pair == null ? null : pair.last;
-  }
-
-  void operator []=(K key, V value) {
-    _base[_canonicalize(key)] = new Pair(key, value);
-  }
-
-  void addAll(Map<K, V> other) {
-    other.forEach((key, value) => this[key] = value);
-  }
-
-  void clear() {
-    _base.clear();
-  }
-
-  bool containsKey(Object key) {
-    if (!_isValidKey(key)) return false;
-    return _base.containsKey(_canonicalize(key));
-  }
-
-  bool containsValue(Object value) =>
-      _base.values.any((pair) => pair.last == value);
-
-  void forEach(void f(K key, V value)) {
-    _base.forEach((key, pair) => f(pair.first, pair.last));
-  }
-
-  bool get isEmpty => _base.isEmpty;
-
-  bool get isNotEmpty => _base.isNotEmpty;
-
-  Iterable<K> get keys => _base.values.map((pair) => pair.first);
-
-  int get length => _base.length;
-
-  V putIfAbsent(K key, V ifAbsent()) {
-    return _base.putIfAbsent(_canonicalize(key),
-        () => new Pair(key, ifAbsent())).last;
-  }
-
-  V remove(Object key) {
-    if (!_isValidKey(key)) return null;
-    var pair = _base.remove(_canonicalize(key));
-    return pair == null ? null : pair.last;
-  }
-
-  Iterable<V> get values => _base.values.map((pair) => pair.last);
-
-  String toString() => Maps.mapToString(this);
-
-  bool _isValidKey(Object key) => (key == null || key is K) &&
-      (_isValidKeyFn == null || _isValidKeyFn(key));
-}